[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Matt Arsenault via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Matt Arsenault via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );

arsenm wrote:

const always to the left. East const is weird 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

@@ -992,6 +993,8 @@ void AMDGPUPassConfig::addIRPasses() {
   if (isPassEnabled(EnableImageIntrinsicOptimizer))
 addPass(createAMDGPUImageIntrinsicOptimizerPass());
 
+  addPass(createExpandVariadicsPass(ExpandVariadicsMode::Lowering));

JonChesterfield wrote:

I'm also paranoid enough to want that, it's 
'--expand-variadics-override=disable' from the command line or changing the 
::Lowering in that line to ::Disable. Commenting out the addPass also kills it, 
but would cause the lit pipeline tests to fail. I'll put a comment above that 
pass saying this.

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

https://github.com/Pierre-vh approved this pull request.

LGTM if a kill switch is added, I would wait a day more before landing in case 
anyone else has concerns

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -992,6 +993,8 @@ void AMDGPUPassConfig::addIRPasses() {
   if (isPassEnabled(EnableImageIntrinsicOptimizer))
 addPass(createAMDGPUImageIntrinsicOptimizerPass());
 
+  addPass(createExpandVariadicsPass(ExpandVariadicsMode::Lowering));

Pierre-vh wrote:

Please add a kill switch `cl::opt` for the pass in the AMDGPUTargetMachine 
before landing, in case it has unforeseen issues. It'd be easier to 
default-disable while fixing, rather than revert a big patch :)

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

https://github.com/Pierre-vh edited 
https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Joseph Huber via cfe-commits]

@@ -8,10 +8,15 @@ add_custom_target(libc-long-running-tests)
 
 add_subdirectory(UnitTest)
 
-if(LIBC_TARGET_OS_IS_GPU AND

jhuber6 wrote:

Done

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

JonChesterfield wrote:

If there's no va_start and we're optimising there's no work to do. Otherwise 
when lowering we still transform declarations (which have no basic blocks) and 
calls to unknown pointers, so that separate compilation works. That's why 
knowing it's the whole program would be useful.

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> Early exit on lack of va_start will be incorrect in the lowering case, which 
> is the only one enabled by default. I believe existing comments are all 
> addressed.

Figured if there's no `va_start` there's nothing for the pass to do anyway.

> Precommit the cmake diagnostic tweak sounds good, would you like to land that?

Sure

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

@@ -8,10 +8,15 @@ add_custom_target(libc-long-running-tests)
 
 add_subdirectory(UnitTest)
 
-if(LIBC_TARGET_OS_IS_GPU AND

JonChesterfield wrote:

This is helpful for me working out why libc isn't running tests but otherwise 
unrelated to this PR, I'll drop it from the change and you can apply or discard 
it separately as you prefer.

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

JonChesterfield wrote:

Early exit on lack of va_start will be incorrect in the lowering case, which is 
the only one enabled by default. I believe existing comments are all addressed. 
Precommit the cmake diagnostic tweak sounds good, would you like to land that?

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Joseph Huber via cfe-commits]

@@ -8,10 +8,15 @@ add_custom_target(libc-long-running-tests)
 
 add_subdirectory(UnitTest)
 
-if(LIBC_TARGET_OS_IS_GPU AND

jhuber6 wrote:

Can we precommit or move this to a separate patch

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Joseph Huber via cfe-commits]

https://github.com/jhuber6 edited 
https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Joseph Huber via cfe-commits]

https://github.com/jhuber6 commented:

Overall I think this is good. Address the existing comments and I think we 
should be able to land it. Potentially we should be able to check for the 
existence of `va_start` in the module to early-exit like you said, which will 
keep functional changes to a minimum.

FWIW if you use `clangd` with `clang-tidy` it should let you automatically fix 
the LLVM style issues.

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

JonChesterfield wrote:

We can check for the va_start which is a good approximation, but there can be a 
variadic function pointer from another module and the only place that would 
show up is a call instruction, and the only way to find that is enumeration. 
Amdgpu can somewhat cheat using the whole.program assumption but it's sketchy.

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> An offline suggestion from Pierre is that this should early-exit if there are 
> no variadic functions in the module. That's a good thing, I'd like to 
> consider it another of the increase-complexity-for-decreased-compile-time to 
> implement after something has landed.

I thought any use of varargs would introduce LLVM intrinsics. Shouldn't it be 
trivial to look if any of those exist in the module?

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

JonChesterfield wrote:

An offline suggestion from Pierre is that this should early-exit if there are 
no variadic functions in the module. That's a good thing, I'd like to consider 
it another of the increase-complexity-for-decreased-compile-time to implement 
after something has landed.

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

JonChesterfield wrote:

Thanks @Pierre-vh, I think those are all applied. Also removed llvm:: from some 
other places, and remembered that llvm doesn't like the if () {braces} which 
are so useful for git merge not introducing bugs so removed the majority of 
those as well. Feel confident enough after reading through to mark it green? 
All it can do is take variadic functions from hard errors to probably working.

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

https://github.com/JonChesterfield edited 
https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

https://github.com/JonChesterfield edited 
https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );

JonChesterfield wrote:

I'm pretty sure I've been told to move const to the other side by other 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );

Pierre-vh wrote:

```suggestion
  static std::unique_ptr create(const llvm::Triple );
```
(style more 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}

Pierre-vh wrote:

```suggestion
  VariadicABIInfo() = default;
```


https://github.com/llvm/llvm-project/pull/93362
___

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Pierre van Houtryve via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

JonChesterfield wrote:

Majority of review comments applied. Merged 94083 (with apologies to Matt) and 
rebased.

I claim the top level strategy of "turn ... into va_list then fix up known call 
sites" is a reasonable strategy for optimising variadic functions. The target 
specific quirks being abstracted over by the existing va_list interface is 
pleasing.

The target abstraction here is not totally what I want it to be and there are 
some simplifying assumptions (e.g. the C calling conv check probably needs to 
be under target-specific, variadic invokes exist in libc++) that won't survive 
for long.

Still, I think this is a worthwhile step forward. It's the machinery needed to 
render variadic functions zero cost at compile time, and gives back ends with 
freedom over their ABI the option to totally ignore variadic functions. 
@bigboze this is the pass I looked for during the IPU bring up - it would have 
been great to say "a void *, four byte alignment seems fine" and cross 
"implement varargs" off the backlog in half an hour, instead of hand 
implementing the thing in sdag. Shipping this would also mean successfully 
avoiding implementing varargs in sdag and globalisel for amdgpu, and whatever 
nvptx codegen uses, so there's a definite code reuse theme from the IR strategy.

My near immediate future involves trying to work out what the 
addrspace/struct/memory-error weirdness on amdgpu is but I'm also looking 
forward to the variadic wrapper functions in my headers on x64 disappearing at 
O1 time.

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

https://github.com/JonChesterfield edited 
https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

@@ -33,6 +33,7 @@ static_library("IPO") {
 "DeadArgumentElimination.cpp",
 "ElimAvailExtern.cpp",
 "EmbedBitcodePass.cpp",
+"ExpandVariadics.cpp",

JonChesterfield wrote:

Nice, I did not know what. I am indeed not a BUILD.gn user.

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Eli Friedman via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Eli Friedman via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Eli Friedman via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Eli Friedman via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Eli Friedman via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Eli Friedman via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Eli Friedman via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Eli Friedman via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Eli Friedman via cfe-commits]

@@ -0,0 +1,1037 @@
+//===-- ExpandVariadicsPass.cpp *- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===--===//
+//
+// This is an optimization pass for variadic functions. If called from codegen,
+// it can serve as the implementation of variadic functions for a given target.
+//
+// The strategy is to turn the ... part of a variadic function into a va_list
+// and fix up the call sites. The majority of the pass is target independent.
+// The exceptions are the va_list type itself and the rules for where to store
+// variables in memory such that va_arg can iterate over them given a va_list.
+//
+// The majority of the plumbing is splitting the variadic function into a
+// single basic block that packs the variadic arguments into a va_list and
+// a second function that does the work of the original. That packing is
+// exactly what is done by va_start. Further, the transform from ... to va_list
+// replaced va_start with an operation to copy a va_list from the new argument,
+// which is exactly a va_copy. This is useful for reducing target-dependence.
+//
+// A va_list instance is a forward iterator, where the primary operation va_arg
+// is dereference-then-increment. This interface forces significant convergent
+// evolution between target specific implementations. The variation in runtime
+// data layout is limited to that representable by the iterator, parameterised
+// by the type passed to the va_arg instruction.
+//
+// Therefore the majority of the target specific subtlety is packing arguments
+// into a stack allocated buffer such that a va_list can be initialised with it
+// and the va_arg expansion for the target will find the arguments at runtime.
+//
+// The aggregate effect is to unblock other transforms, most critically the
+// general purpose inliner. Known calls to variadic functions become zero cost.
+//
+// Consistency with clang is primarily tested by emitting va_arg using clang
+// then expanding the variadic functions using this pass, followed by trying
+// to constant fold the functions to no-ops.
+//
+// Target specific behaviour is tested in IR - mainly checking that values are
+// put into positions in call frames that make sense for that particular 
target.
+//
+// There is one "clever" invariant in use. va_start intrinsics that are not
+// within a varidic functions are an error in the IR verifier. When this
+// transform moves blocks from a variadic function into a fixed arity one, it
+// moves va_start intrinsics along with everything else. That means that the
+// va_start intrinsics that need to be rewritten to use the trailing argument
+// are exactly those that are in non-variadic functions so no further state
+// is needed to distinguish those that need to be rewritten.
+//
+//===--===//
+
+#include "llvm/Transforms/IPO/ExpandVariadics.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Passes/OptimizationLevel.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#define DEBUG_TYPE "expand-variadics"
+
+using namespace llvm;
+
+namespace {
+
+cl::opt ExpandVariadicsModeOption(
+DEBUG_TYPE "-override", cl::desc("Override the behaviour of " DEBUG_TYPE),
+cl::init(ExpandVariadicsMode::Unspecified),
+cl::values(clEnumValN(ExpandVariadicsMode::Unspecified, "unspecified",
+  "Use the implementation defaults"),
+   clEnumValN(ExpandVariadicsMode::Disable, "disable",
+  "Disable the pass entirely"),
+   clEnumValN(ExpandVariadicsMode::Optimize, "optimize",
+  "Optimise without changing ABI"),
+   clEnumValN(ExpandVariadicsMode::Lowering, "lowering",
+  "Change variadic calling convention")));
+
+bool commandLineOverride() {
+  return ExpandVariadicsModeOption != ExpandVariadicsMode::Unspecified;
+}
+
+// Instances of this class encapsulate the target-dependant behaviour as a
+// function of triple. Implementing a new ABI is adding a case to the switch
+// in create(llvm::Triple) at the end of this file.
+class VariadicABIInfo {
+protected:
+  VariadicABIInfo() {}
+
+public:
+  static std::unique_ptr create(llvm::Triple const );
+
+  // Allow overriding whether the pass runs on a per-target basis
+  virtual bool enableForTarget() = 0;
+
+  // 

[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Eli Friedman via cfe-commits]

@@ -33,6 +33,7 @@ static_library("IPO") {
 "DeadArgumentElimination.cpp",
 "ElimAvailExtern.cpp",
 "EmbedBitcodePass.cpp",
+"ExpandVariadics.cpp",

efriedma-quic wrote:

There's a bot that updates the gn files automatically... so unless you're 
building this way, I'd suggest not touching this file.

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Eli Friedman via cfe-commits]

https://github.com/efriedma-quic commented:

Left some review comments.  Please land 
https://github.com/llvm/llvm-project/pull/94083 first.

I agree it makes sense to land this in essentially its current form; it seems 
to be the right algorithm.

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Eli Friedman via cfe-commits]

https://github.com/efriedma-quic edited 
https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

I can confirm that it passes the tests against the `libc` targets, namely basic 
`stdarg.h` implementations and `sprintf`.

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

JonChesterfield wrote:

I wish to ship this as-is. This patch is carefully constructed to be zero risk 
and landing it significantly improves the chances of zero-overhead varargs 
shipping. This revision passes the amdgpu libc tests. The tests are fragile to 
seemingly trivial changes to the IR generated which is obstructive to emitting 
nicer IR and some changes to the target abstraction I wish to make.

I have approximately isolated the libc / amdgpu memory error. I believe the 
amdgpu backend miscompiles constructs involving addrspacecast and passing 
structs to functions in a fashion which interacts badly with the lowering this 
pass chooses to do. That would explain why the transform has been easy and 
robust when implemented on x86, x64, nvptx, aarch64 and webassembly - and very 
prone to confusing memory errors and strange action at a distance on amdgpu. I 
note that this pass was originally made target-independent because I failed to 
get it running robustly on amdgpu alone.

Various previous revisions of this pass have passed the amdgpu libc tests and 
other similar revisions failed, I'd guess it's about 1/3 are "good" and 2/3 are 
"bad". I want to land this now, on a "good" revision, so we have something in 
tree that I can iterate on and feed into the ROCm dev branches, where I may 
have other colleagues or a working debugger available.

The pass core is straightforward and likely to be functionally correct. It 
isn't in the default pass pipeline so the only non-test time it'll run to begin 
with is for amdgpu. The lowering is exactly what webassembly does already and 
very close to nvptx. I'll implement x64 and aarch64 in parallel with chasing 
amdgpu oddities, both are mechanical exercises in case analysis and test 
coverage. I believe wasm needs no further changes.

Various things are suboptimal on amdgpu. Passing some things byref is better 
than the current everything inline layout. The extra parameter should be in 
(5), not (0). Codegen is noisier than it should be. Most permutations to the 
current scheme win "memory error" from HSA. I think these should be part of 
ongoing work after this lands and not a prereq.

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

@@ -10,6 +10,50 @@
 
 #include "test/UnitTest/Test.h"
 
+#include "src/__support/OSUtil/io.h"
+#include "src/__support/integer_to_string.h"
+using namespace LIBC_NAMESPACE;
+
+namespace {
+
+void nl() { write_to_stderr("\n"); }
+void dump(const char *s) {
+  write_to_stderr(s);
+  nl();
+}
+
+void dump(int32_t s) {

JonChesterfield wrote:

Ah rubbish, the libc commit isn't supposed to be in this PR. That's a 
collection of local hacks trying to get libc to build and tell me useful 
things, which I've uploaded in error while patching Matt's comments. I'll work 
out how to remove that

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[via cfe-commits]

@@ -10,6 +10,50 @@
 
 #include "test/UnitTest/Test.h"
 
+#include "src/__support/OSUtil/io.h"
+#include "src/__support/integer_to_string.h"
+using namespace LIBC_NAMESPACE;
+
+namespace {
+
+void nl() { write_to_stderr("\n"); }
+void dump(const char *s) {
+  write_to_stderr(s);
+  nl();
+}
+
+void dump(int32_t s) {

lntue wrote:

Probably it's better to do:
```
template 
cpp::enable_if_t, void> dump(T s) {
  auto x = IntegerToString(s);
  write_to_stderr(x.view());
  nl();
}
```
Then all the usages below could be changed to `dump(s.*);`

https://github.com/llvm/llvm-project/pull/93362
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[clang] [libc] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

JonChesterfield wrote:

I've spawned #93974 in case we can land the target independent part in parallel 
with me trying to debug the amdgpu/libc error. Maintaining different branches 
with different variations on what subset is implemented is confusing me quite a 
lot and leads to reviewers seeing essentially the same code repeatedly - I 
haven't found a way to represent base + N extensions in github without landing 
the base commit first.

https://github.com/llvm/llvm-project/pull/93362
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