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Attempt to enable MemCpyOpt unconditionally in D104801
<https://reviews.llvm.org/D104801> uncovered the fact that
there are users that do not expect LLVM to materialize `memset` intrinsic.
While other passes can do that, too, MemCpyOpt triggers it more frequently and
breaks sanitizers and
some downstream users.
For now introduce a flag to force-enable the flag and opt-in only CUDA
compilation with NVPTX back-end.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D106401
Files:
clang/lib/Driver/ToolChains/Cuda.cpp
llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
Index: llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -67,6 +67,10 @@
#define DEBUG_TYPE "memcpyopt"
+static cl::opt<bool> EnableMemCpyOptWithoutLibcalls(
+ "-enable-memcpyopt-without-libcalls", cl::init(false), cl::Hidden,
+ cl::desc("Enable memcpyopt even when libcalls are disabled"));
+
static cl::opt<bool>
EnableMemorySSA("enable-memcpyopt-memoryssa", cl::init(true), cl::Hidden,
cl::desc("Use MemorySSA-backed MemCpyOpt."));
@@ -1757,7 +1761,16 @@
// If we don't have at least memset and memcpy, there is little point of
doing
// anything here. These are required by a freestanding implementation, so if
// even they are disabled, there is no point in trying hard.
- if (!TLI->has(LibFunc_memset) || !TLI->has(LibFunc_memcpy))
+ bool ShoudRunMemCpyOpt =
+ (TLI->has(LibFunc_memset) && TLI->has(LibFunc_memcpy))
+ // Some targets have libcalls disabled, but still want to run the pass.
+ // TODO: the pass should not depend on libcall availability as the
targets
+ // should provide alternative ways of lowering standard LLVM
+ // intrinsics. Alas, there are existing users that can't currently handle
+ // `memset` intrinsic materialized by this pass. See
+ // https://reviews.llvm.org/D104801 for the details.
+ || EnableMemCpyOptWithoutLibcalls;
+ if (!ShoudRunMemCpyOpt)
return false;
while (true) {
Index: clang/lib/Driver/ToolChains/Cuda.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Cuda.cpp
+++ clang/lib/Driver/ToolChains/Cuda.cpp
@@ -686,7 +686,8 @@
"Only OpenMP or CUDA offloading kinds are supported for NVIDIA
GPUs.");
if (DeviceOffloadingKind == Action::OFK_Cuda) {
- CC1Args.push_back("-fcuda-is-device");
+ CC1Args.append(
+ {"-fcuda-is-device", "-mllvm", "-enable-memcpyopt-without-libcalls"});
if (DriverArgs.hasFlag(options::OPT_fcuda_approx_transcendentals,
options::OPT_fno_cuda_approx_transcendentals,
false))
Index: llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -67,6 +67,10 @@
#define DEBUG_TYPE "memcpyopt"
+static cl::opt<bool> EnableMemCpyOptWithoutLibcalls(
+ "-enable-memcpyopt-without-libcalls", cl::init(false), cl::Hidden,
+ cl::desc("Enable memcpyopt even when libcalls are disabled"));
+
static cl::opt<bool>
EnableMemorySSA("enable-memcpyopt-memoryssa", cl::init(true), cl::Hidden,
cl::desc("Use MemorySSA-backed MemCpyOpt."));
@@ -1757,7 +1761,16 @@
// If we don't have at least memset and memcpy, there is little point of doing
// anything here. These are required by a freestanding implementation, so if
// even they are disabled, there is no point in trying hard.
- if (!TLI->has(LibFunc_memset) || !TLI->has(LibFunc_memcpy))
+ bool ShoudRunMemCpyOpt =
+ (TLI->has(LibFunc_memset) && TLI->has(LibFunc_memcpy))
+ // Some targets have libcalls disabled, but still want to run the pass.
+ // TODO: the pass should not depend on libcall availability as the targets
+ // should provide alternative ways of lowering standard LLVM
+ // intrinsics. Alas, there are existing users that can't currently handle
+ // `memset` intrinsic materialized by this pass. See
+ // https://reviews.llvm.org/D104801 for the details.
+ || EnableMemCpyOptWithoutLibcalls;
+ if (!ShoudRunMemCpyOpt)
return false;
while (true) {
Index: clang/lib/Driver/ToolChains/Cuda.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Cuda.cpp
+++ clang/lib/Driver/ToolChains/Cuda.cpp
@@ -686,7 +686,8 @@
"Only OpenMP or CUDA offloading kinds are supported for NVIDIA GPUs.");
if (DeviceOffloadingKind == Action::OFK_Cuda) {
- CC1Args.push_back("-fcuda-is-device");
+ CC1Args.append(
+ {"-fcuda-is-device", "-mllvm", "-enable-memcpyopt-without-libcalls"});
if (DriverArgs.hasFlag(options::OPT_fcuda_approx_transcendentals,
options::OPT_fno_cuda_approx_transcendentals, false))
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