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[MemProf] Add ambigous memprof attribute #157204

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merged 2 commits into from
Sep 6, 2025
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[MemProf] Add ambigous memprof attribute #157204

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[MemProf] Add ambigous memprof attribute
teresajohnson Sep 5, 2025
b75e224
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teresajohnson Sep 6, 2025
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8 changes: 8 additions & 0 deletions llvm/include/llvm/Analysis/MemoryProfileInfo.h
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,14 @@ LLVM_ABI std::string getAllocTypeAttributeString(AllocationType Type);
/// True if the AllocTypes bitmask contains just a single type.
LLVM_ABI bool hasSingleAllocType(uint8_t AllocTypes);

/// Removes any existing "ambiguous" memprof attribute. Called before we apply a
/// specific allocation type such as "cold", "notcold", or "hot".
LLVM_ABI void removeAnyExistingAmbiguousAttribute(CallBase *CB);

/// Adds an "ambiguous" memprof attribute to call with a matched allocation
/// profile but that we haven't yet been able to disambiguate.
LLVM_ABI void addAmbiguousAttribute(CallBase *CB);

/// Class to build a trie of call stack contexts for a particular profiled
/// allocation call, along with their associated allocation types.
/// The allocation will be at the root of the trie, which is then used to
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22 changes: 22 additions & 0 deletions llvm/lib/Analysis/MemoryProfileInfo.cpp
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Expand Up @@ -121,6 +121,24 @@ bool llvm::memprof::hasSingleAllocType(uint8_t AllocTypes) {
return NumAllocTypes == 1;
}

void llvm::memprof::removeAnyExistingAmbiguousAttribute(CallBase *CB) {
if (CB->hasFnAttr("memprof")) {
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@snehasish snehasish Sep 6, 2025

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nit: if(!CB->hasFnAttr ....) return

to avoid nesting.

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@teresajohnson teresajohnson Sep 6, 2025

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done

assert(CB->getFnAttr("memprof").getValueAsString() == "ambiguous");
CB->removeFnAttr("memprof");
}
}

void llvm::memprof::addAmbiguousAttribute(CallBase *CB) {
// We may have an existing ambiguous attribute if we are reanalyzing
// after inlining.
if (CB->hasFnAttr("memprof")) {
assert(CB->getFnAttr("memprof").getValueAsString() == "ambiguous");
} else {
auto A = llvm::Attribute::get(CB->getContext(), "memprof", "ambiguous");
CB->addFnAttr(A);
}
}

void CallStackTrie::addCallStack(
AllocationType AllocType, ArrayRef<uint64_t> StackIds,
std::vector<ContextTotalSize> ContextSizeInfo) {
Expand Down Expand Up @@ -466,6 +484,9 @@ void CallStackTrie::addSingleAllocTypeAttribute(CallBase *CI, AllocationType AT,
StringRef Descriptor) {
auto AllocTypeString = getAllocTypeAttributeString(AT);
auto A = llvm::Attribute::get(CI->getContext(), "memprof", AllocTypeString);
// After inlining we may be able to convert an existing ambiguous allocation
// to an unambiguous one.
removeAnyExistingAmbiguousAttribute(CI);
CI->addFnAttr(A);
if (MemProfReportHintedSizes) {
std::vector<ContextTotalSize> ContextSizeInfo;
Expand Down Expand Up @@ -525,6 +546,7 @@ bool CallStackTrie::buildAndAttachMIBMetadata(CallBase *CI) {
assert(MIBCallStack.size() == 1 &&
"Should only be left with Alloc's location in stack");
CI->setMetadata(LLVMContext::MD_memprof, MDNode::get(Ctx, MIBNodes));
addAmbiguousAttribute(CI);
return true;
}
// If there exists corner case that CallStackTrie has one chain to leaf
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2 changes: 2 additions & 0 deletions llvm/lib/Transforms/IPO/MemProfContextDisambiguation.cpp
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Expand Up @@ -3965,6 +3965,7 @@ void CallsiteContextGraph<DerivedCCG, FuncTy, CallTy>::identifyClones(
void ModuleCallsiteContextGraph::updateAllocationCall(
CallInfo &Call, AllocationType AllocType) {
std::string AllocTypeString = getAllocTypeAttributeString(AllocType);
removeAnyExistingAmbiguousAttribute(cast<CallBase>(Call.call()));
auto A = llvm::Attribute::get(Call.call()->getFunction()->getContext(),
"memprof", AllocTypeString);
cast<CallBase>(Call.call())->addFnAttr(A);
Expand Down Expand Up @@ -5501,6 +5502,7 @@ bool MemProfContextDisambiguation::applyImport(Module &M) {
// clone J-1 (J==0 is the original clone and does not have a VMaps
// entry).
CBClone = cast<CallBase>((*VMaps[J - 1])[CB]);
removeAnyExistingAmbiguousAttribute(CBClone);
CBClone->addFnAttr(A);
ORE.emit(OptimizationRemark(DEBUG_TYPE, "MemprofAttribute", CBClone)
<< ore::NV("AllocationCall", CBClone) << " in clone "
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21 changes: 14 additions & 7 deletions llvm/unittests/Analysis/MemoryProfileInfoTest.cpp
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@snehasish snehasish Sep 6, 2025

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Is it worth testing that the attribute is only added to the allocation calls and not other callinsts which are part of the allocation context?

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@teresajohnson teresajohnson Sep 6, 2025

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I don't think so - we are only adding these new attributes to the same calls where we currently add memprof attributes. This unittest in particular doesn't have any non-alloc calls in any case - it's only checking what we add to the allocations.

Original file line number Diff line number Diff line change
Expand Up @@ -228,7 +228,8 @@ declare dso_local noalias noundef i8* @malloc(i64 noundef)
CallBase *Call = findCall(*Func, "call");
Trie.buildAndAttachMIBMetadata(Call);

EXPECT_FALSE(Call->hasFnAttr("memprof"));
EXPECT_TRUE(Call->hasFnAttr("memprof"));
EXPECT_EQ(Call->getFnAttr("memprof").getValueAsString(), "ambiguous");
EXPECT_TRUE(Call->hasMetadata(LLVMContext::MD_memprof));
MDNode *MemProfMD = Call->getMetadata(LLVMContext::MD_memprof);
ASSERT_EQ(MemProfMD->getNumOperands(), 2u);
Expand Down Expand Up @@ -277,7 +278,8 @@ declare dso_local noalias noundef i8* @malloc(i64 noundef)
CallBase *Call = findCall(*Func, "call");
Trie.buildAndAttachMIBMetadata(Call);

EXPECT_FALSE(Call->hasFnAttr("memprof"));
EXPECT_TRUE(Call->hasFnAttr("memprof"));
EXPECT_EQ(Call->getFnAttr("memprof").getValueAsString(), "ambiguous");
EXPECT_TRUE(Call->hasMetadata(LLVMContext::MD_memprof));
MDNode *MemProfMD = Call->getMetadata(LLVMContext::MD_memprof);
ASSERT_EQ(MemProfMD->getNumOperands(), 2u);
Expand Down Expand Up @@ -331,7 +333,8 @@ declare dso_local noalias noundef i8* @malloc(i64 noundef)
CallBase *Call = findCall(*Func, "call");
Trie.buildAndAttachMIBMetadata(Call);

EXPECT_FALSE(Call->hasFnAttr("memprof"));
EXPECT_TRUE(Call->hasFnAttr("memprof"));
EXPECT_EQ(Call->getFnAttr("memprof").getValueAsString(), "ambiguous");
EXPECT_TRUE(Call->hasMetadata(LLVMContext::MD_memprof));
MDNode *MemProfMD = Call->getMetadata(LLVMContext::MD_memprof);
ASSERT_EQ(MemProfMD->getNumOperands(), 2u);
Expand Down Expand Up @@ -390,7 +393,8 @@ declare dso_local noalias noundef i8* @malloc(i64 noundef)
CallBase *Call = findCall(*Func, "call");
Trie.buildAndAttachMIBMetadata(Call);

EXPECT_FALSE(Call->hasFnAttr("memprof"));
EXPECT_TRUE(Call->hasFnAttr("memprof"));
EXPECT_EQ(Call->getFnAttr("memprof").getValueAsString(), "ambiguous");
EXPECT_TRUE(Call->hasMetadata(LLVMContext::MD_memprof));
MDNode *MemProfMD = Call->getMetadata(LLVMContext::MD_memprof);
ASSERT_EQ(MemProfMD->getNumOperands(), 2u);
Expand Down Expand Up @@ -461,7 +465,8 @@ declare dso_local noalias noundef i8* @malloc(i64 noundef)
ASSERT_NE(Call, nullptr);
Trie.buildAndAttachMIBMetadata(Call);

EXPECT_FALSE(Call->hasFnAttr("memprof"));
EXPECT_TRUE(Call->hasFnAttr("memprof"));
EXPECT_EQ(Call->getFnAttr("memprof").getValueAsString(), "ambiguous");
EXPECT_TRUE(Call->hasMetadata(LLVMContext::MD_memprof));
MDNode *MemProfMD = Call->getMetadata(LLVMContext::MD_memprof);
EXPECT_THAT(MemProfMD, MemprofMetadataEquals(ExpectedVals));
Expand Down Expand Up @@ -534,7 +539,8 @@ declare dso_local noalias noundef i8* @malloc(i64 noundef)
// Restore original option value.
MemProfKeepAllNotColdContexts = OrigMemProfKeepAllNotColdContexts;

EXPECT_FALSE(Call->hasFnAttr("memprof"));
EXPECT_TRUE(Call->hasFnAttr("memprof"));
EXPECT_EQ(Call->getFnAttr("memprof").getValueAsString(), "ambiguous");
EXPECT_TRUE(Call->hasMetadata(LLVMContext::MD_memprof));
MDNode *MemProfMD = Call->getMetadata(LLVMContext::MD_memprof);
EXPECT_THAT(MemProfMD, MemprofMetadataEquals(ExpectedVals));
Expand Down Expand Up @@ -662,7 +668,8 @@ declare dso_local noalias noundef i8* @malloc(i64 noundef)
// The hot allocations will be converted to NotCold and pruned as they
// are unnecessary to determine how to clone the cold allocation.

EXPECT_FALSE(Call->hasFnAttr("memprof"));
EXPECT_TRUE(Call->hasFnAttr("memprof"));
EXPECT_EQ(Call->getFnAttr("memprof").getValueAsString(), "ambiguous");
EXPECT_TRUE(Call->hasMetadata(LLVMContext::MD_memprof));
MemProfMD = Call->getMetadata(LLVMContext::MD_memprof);
ASSERT_EQ(MemProfMD->getNumOperands(), 2u);
Expand Down