zequanwu updated this revision to Diff 262933.
zequanwu marked an inline comment as done.
zequanwu added a comment.
update comment.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D78659/new/
https://reviews.llvm.org/D78659
Files:
llvm/docs/LangRef.rst
llvm/include/llvm/Bitcode/LLVMBitCodes.h
llvm/include/llvm/IR/Attributes.td
llvm/include/llvm/IR/InstrTypes.h
llvm/lib/AsmParser/LLLexer.cpp
llvm/lib/AsmParser/LLParser.cpp
llvm/lib/AsmParser/LLToken.h
llvm/lib/Bitcode/Reader/BitcodeReader.cpp
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
llvm/lib/IR/Attributes.cpp
llvm/lib/IR/Verifier.cpp
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/test/Transforms/SimplifyCFG/nomerge.ll
Index: llvm/test/Transforms/SimplifyCFG/nomerge.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/SimplifyCFG/nomerge.ll
@@ -0,0 +1,71 @@
+; RUN: opt < %s -O1 -S | FileCheck %s
+
+; The attribute nomerge prevents the 3 bar() calls from being sunk/hoisted into
+; one inside a function. Check that there are still 3 tail calls.
+
+; Test case for preventing sinking
+; CHECK-LABEL: define void @sink
+; CHECK: if.then:
+; CHECK-NEXT: tail call void @bar()
+; CHECK: if.then2:
+; CHECK-NEXT: tail call void @bar()
+; CHECK: if.end3:
+; CHECK-NEXT: tail call void @bar()
+define void @sink(i32 %i) {
+entry:
+ switch i32 %i, label %if.end3 [
+ i32 5, label %if.then
+ i32 7, label %if.then2
+ ]
+
+if.then:
+ tail call void @bar() #0
+ br label %if.end3
+
+if.then2:
+ tail call void @bar() #0
+ br label %if.end3
+
+if.end3:
+ tail call void @bar() #0
+ ret void
+}
+
+; Test case for preventing hoisting
+; CHECK-LABEL: define void @hoist
+; CHECK: if.then:
+; CHECK-NEXT: tail call void @bar()
+; CHECK: if.then2:
+; CHECK-NEXT: tail call void @bar()
+; CHECK: if.end:
+; CHECK-NEXT: tail call void @bar()
+define void @hoist(i32 %i) {
+entry:
+ %i.addr = alloca i32, align 4
+ store i32 %i, i32* %i.addr, align 4
+ %0 = load i32, i32* %i.addr, align 4
+ %cmp = icmp eq i32 %0, 5
+ br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+ tail call void @bar() #1
+ unreachable
+
+if.else:
+ %1 = load i32, i32* %i.addr, align 4
+ %cmp1 = icmp eq i32 %i, 7
+ br i1 %cmp1, label %if.then2, label %if.end
+
+if.then2:
+ tail call void @bar() #1
+ unreachable
+
+if.end:
+ tail call void @bar() #1
+ unreachable
+}
+
+declare void @bar()
+
+attributes #0 = { nomerge }
+attributes #1 = { noreturn nomerge }
Index: llvm/lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1300,6 +1300,14 @@
if (!TTI.isProfitableToHoist(I1) || !TTI.isProfitableToHoist(I2))
return Changed;
+ // If any of the two call sites has nomerge attribute, stop hoisting.
+ if (const auto *CB1 = dyn_cast<CallBase>(I1))
+ if (CB1->cannotMerge())
+ return Changed;
+ if (const auto *CB2 = dyn_cast<CallBase>(I2))
+ if (CB2->cannotMerge())
+ return Changed;
+
if (isa<DbgInfoIntrinsic>(I1) || isa<DbgInfoIntrinsic>(I2)) {
assert (isa<DbgInfoIntrinsic>(I1) && isa<DbgInfoIntrinsic>(I2));
// The debug location is an integral part of a debug info intrinsic
@@ -1485,8 +1493,9 @@
// Conservatively return false if I is an inline-asm instruction. Sinking
// and merging inline-asm instructions can potentially create arguments
// that cannot satisfy the inline-asm constraints.
+ // If the instruction has nomerge attribute, return false.
if (const auto *C = dyn_cast<CallBase>(I))
- if (C->isInlineAsm())
+ if (C->cannotMerge())
return false;
// Each instruction must have zero or one use.
Index: llvm/lib/IR/Verifier.cpp
===================================================================
--- llvm/lib/IR/Verifier.cpp
+++ llvm/lib/IR/Verifier.cpp
@@ -1509,6 +1509,7 @@
/// Return true if this attribute kind only applies to functions.
static bool isFuncOnlyAttr(Attribute::AttrKind Kind) {
switch (Kind) {
+ case Attribute::NoMerge:
case Attribute::NoReturn:
case Attribute::NoSync:
case Attribute::WillReturn:
Index: llvm/lib/IR/Attributes.cpp
===================================================================
--- llvm/lib/IR/Attributes.cpp
+++ llvm/lib/IR/Attributes.cpp
@@ -372,6 +372,8 @@
return "noinline";
if (hasAttribute(Attribute::NonLazyBind))
return "nonlazybind";
+ if (hasAttribute(Attribute::NoMerge))
+ return "nomerge";
if (hasAttribute(Attribute::NonNull))
return "nonnull";
if (hasAttribute(Attribute::NoRedZone))
Index: llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
===================================================================
--- llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -647,6 +647,8 @@
return bitc::ATTR_KIND_NO_INLINE;
case Attribute::NoRecurse:
return bitc::ATTR_KIND_NO_RECURSE;
+ case Attribute::NoMerge:
+ return bitc::ATTR_KIND_NO_MERGE;
case Attribute::NonLazyBind:
return bitc::ATTR_KIND_NON_LAZY_BIND;
case Attribute::NonNull:
Index: llvm/lib/Bitcode/Reader/BitcodeReader.cpp
===================================================================
--- llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -1306,6 +1306,9 @@
case Attribute::Preallocated:
llvm_unreachable("preallocated attribute not supported in raw format");
break;
+ case Attribute::NoMerge:
+ llvm_unreachable("nomerge attribute not supported in raw format");
+ break;
}
llvm_unreachable("Unsupported attribute type");
}
@@ -1318,7 +1321,7 @@
if (I == Attribute::SanitizeMemTag || I == Attribute::Dereferenceable ||
I == Attribute::DereferenceableOrNull || I == Attribute::ArgMemOnly ||
I == Attribute::AllocSize || I == Attribute::NoSync ||
- I == Attribute::Preallocated)
+ I == Attribute::Preallocated || I == Attribute::NoMerge)
continue;
if (uint64_t A = (Val & getRawAttributeMask(I))) {
if (I == Attribute::Alignment)
@@ -1465,6 +1468,8 @@
return Attribute::NoInline;
case bitc::ATTR_KIND_NO_RECURSE:
return Attribute::NoRecurse;
+ case bitc::ATTR_KIND_NO_MERGE:
+ return Attribute::NoMerge;
case bitc::ATTR_KIND_NON_LAZY_BIND:
return Attribute::NonLazyBind;
case bitc::ATTR_KIND_NON_NULL:
Index: llvm/lib/AsmParser/LLToken.h
===================================================================
--- llvm/lib/AsmParser/LLToken.h
+++ llvm/lib/AsmParser/LLToken.h
@@ -204,6 +204,7 @@
kw_noinline,
kw_norecurse,
kw_nonlazybind,
+ kw_nomerge,
kw_nonnull,
kw_noredzone,
kw_noreturn,
Index: llvm/lib/AsmParser/LLParser.cpp
===================================================================
--- llvm/lib/AsmParser/LLParser.cpp
+++ llvm/lib/AsmParser/LLParser.cpp
@@ -1306,6 +1306,7 @@
B.addAttribute(Attribute::NoImplicitFloat); break;
case lltok::kw_noinline: B.addAttribute(Attribute::NoInline); break;
case lltok::kw_nonlazybind: B.addAttribute(Attribute::NonLazyBind); break;
+ case lltok::kw_nomerge: B.addAttribute(Attribute::NoMerge); break;
case lltok::kw_noredzone: B.addAttribute(Attribute::NoRedZone); break;
case lltok::kw_noreturn: B.addAttribute(Attribute::NoReturn); break;
case lltok::kw_nosync: B.addAttribute(Attribute::NoSync); break;
@@ -1698,6 +1699,7 @@
case lltok::kw_noimplicitfloat:
case lltok::kw_noinline:
case lltok::kw_nonlazybind:
+ case lltok::kw_nomerge:
case lltok::kw_noredzone:
case lltok::kw_noreturn:
case lltok::kw_nocf_check:
@@ -1797,6 +1799,7 @@
case lltok::kw_noimplicitfloat:
case lltok::kw_noinline:
case lltok::kw_nonlazybind:
+ case lltok::kw_nomerge:
case lltok::kw_noredzone:
case lltok::kw_noreturn:
case lltok::kw_nocf_check:
Index: llvm/lib/AsmParser/LLLexer.cpp
===================================================================
--- llvm/lib/AsmParser/LLLexer.cpp
+++ llvm/lib/AsmParser/LLLexer.cpp
@@ -658,6 +658,7 @@
KEYWORD(noinline);
KEYWORD(norecurse);
KEYWORD(nonlazybind);
+ KEYWORD(nomerge);
KEYWORD(nonnull);
KEYWORD(noredzone);
KEYWORD(noreturn);
Index: llvm/include/llvm/IR/InstrTypes.h
===================================================================
--- llvm/include/llvm/IR/InstrTypes.h
+++ llvm/include/llvm/IR/InstrTypes.h
@@ -1717,6 +1717,9 @@
addAttribute(AttributeList::FunctionIndex, Attribute::NoDuplicate);
}
+ /// Determine if the call cannot be tail merged.
+ bool cannotMerge() const { return isInlineAsm() || hasFnAttr(Attribute::NoMerge); }
+
/// Determine if the invoke is convergent
bool isConvergent() const { return hasFnAttr(Attribute::Convergent); }
void setConvergent() {
Index: llvm/include/llvm/IR/Attributes.td
===================================================================
--- llvm/include/llvm/IR/Attributes.td
+++ llvm/include/llvm/IR/Attributes.td
@@ -103,6 +103,9 @@
/// Function is called early and/or often, so lazy binding isn't worthwhile.
def NonLazyBind : EnumAttr<"nonlazybind">;
+/// Disable merging for call sites
+def NoMerge : EnumAttr<"nomerge">;
+
/// Pointer is known to be not null.
def NonNull : EnumAttr<"nonnull">;
Index: llvm/include/llvm/Bitcode/LLVMBitCodes.h
===================================================================
--- llvm/include/llvm/Bitcode/LLVMBitCodes.h
+++ llvm/include/llvm/Bitcode/LLVMBitCodes.h
@@ -634,6 +634,7 @@
ATTR_KIND_NOSYNC = 63,
ATTR_KIND_SANITIZE_MEMTAG = 64,
ATTR_KIND_PREALLOCATED = 65,
+ ATTR_KIND_NO_MERGE = 66,
};
enum ComdatSelectionKindCodes {
Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -1519,6 +1519,14 @@
This attribute indicates that the inliner should never inline this
function in any situation. This attribute may not be used together
with the ``alwaysinline`` attribute.
+``nomerge``
+ This attribute indicates that calls to this function should never be merged
+ during optimization. For example, it will prevent tail merging otherwise
+ identical code sequences that raise an exception or terminate the program.
+ Tail merging normally reduces the precision of source location information,
+ making stack traces less useful for debugging. This attribute gives the
+ user control over the tradeoff between code size and debug information
+ precision.
``nonlazybind``
This attribute suppresses lazy symbol binding for the function. This
may make calls to the function faster, at the cost of extra program
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