[llvm] [ScalarizeMaskedMemIntrin][ProfCheck] Correctly annotate branch weights (part 2) (PR #219286)
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Thu Aug 27 13:47:10 PDT 2026
llvmorg-github-actions[bot] wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: Yonah Goldberg (YonahGoldberg)
<details>
<summary>Changes</summary>
https://github.com/llvm/llvm-project/pull/218753 broke LLVM CI because it added a new test in `ScalarizeMaskedMemIntrin` that was not opted out of during profcheck. Profcheck failed because this pass creates new branches that did not attach branch weight metadata. We don't have any information on the distribution of masks at runtime, so we have to mark branch weights as explicitly unknown.
This basically extends https://github.com/llvm/llvm-project/pull/181568, Aiden am I missing something for why you didn't add the branch weight metadata for all branch creation before?
Tested the `ScalarizeMaskedMemIntrin` tests with profcheck locally and they all pass.
---
Full diff: https://github.com/llvm/llvm-project/pull/219286.diff
2 Files Affected:
- (modified) llvm/lib/Transforms/Scalar/ScalarizeMaskedMemIntrin.cpp (+35-7)
- (modified) llvm/utils/profcheck-xfail.txt (-7)
``````````diff
diff --git a/llvm/lib/Transforms/Scalar/ScalarizeMaskedMemIntrin.cpp b/llvm/lib/Transforms/Scalar/ScalarizeMaskedMemIntrin.cpp
index be5e58125081f..432b079051d80 100644
--- a/llvm/lib/Transforms/Scalar/ScalarizeMaskedMemIntrin.cpp
+++ b/llvm/lib/Transforms/Scalar/ScalarizeMaskedMemIntrin.cpp
@@ -277,9 +277,13 @@ static void scalarizeMaskedLoad(const DataLayout &DL, bool HasBranchDivergence,
if (isSplatValue(Mask, /*Index=*/0)) {
Value *Predicate = Builder.CreateExtractElement(Mask, uint64_t(0ull),
Mask->getName() + ".first");
+ // We mark the branch weights as explicitly unknown given they would only
+ // be derivable from the mask which we do not have VP information for.
Instruction *ThenTerm =
SplitBlockAndInsertIfThen(Predicate, InsertPt, /*Unreachable=*/false,
- /*BranchWeights=*/nullptr, DTU);
+ getExplicitlyUnknownBranchWeightsIfProfiled(
+ *CI->getFunction(), DEBUG_TYPE),
+ DTU);
BasicBlock *CondBlock = ThenTerm->getParent();
CondBlock->setName("cond.load");
@@ -336,9 +340,13 @@ static void scalarizeMaskedLoad(const DataLayout &DL, bool HasBranchDivergence,
// %Elt = load i32* %EltAddr
// VResult = insertelement <16 x i32> VResult, i32 %Elt, i32 Idx
//
+ // We mark the branch weights as explicitly unknown given they would only
+ // be derivable from the mask which we do not have VP information for.
Instruction *ThenTerm =
SplitBlockAndInsertIfThen(Predicate, InsertPt, /*Unreachable=*/false,
- /*BranchWeights=*/nullptr, DTU);
+ getExplicitlyUnknownBranchWeightsIfProfiled(
+ *CI->getFunction(), DEBUG_TYPE),
+ DTU);
BasicBlock *CondBlock = ThenTerm->getParent();
CondBlock->setName("cond.load");
@@ -453,9 +461,13 @@ static void scalarizeMaskedStore(const DataLayout &DL, bool HasBranchDivergence,
if (isSplatValue(Mask, /*Index=*/0)) {
Value *Predicate = Builder.CreateExtractElement(Mask, uint64_t(0ull),
Mask->getName() + ".first");
+ // We mark the branch weights as explicitly unknown given they would only
+ // be derivable from the mask which we do not have VP information for.
Instruction *ThenTerm =
SplitBlockAndInsertIfThen(Predicate, InsertPt, /*Unreachable=*/false,
- /*BranchWeights=*/nullptr, DTU);
+ getExplicitlyUnknownBranchWeightsIfProfiled(
+ *CI->getFunction(), DEBUG_TYPE),
+ DTU);
BasicBlock *CondBlock = ThenTerm->getParent();
CondBlock->setName("cond.store");
Builder.SetInsertPoint(CondBlock->getTerminator());
@@ -507,9 +519,13 @@ static void scalarizeMaskedStore(const DataLayout &DL, bool HasBranchDivergence,
// %EltAddr = getelementptr i32* %1, i32 0
// %store i32 %OneElt, i32* %EltAddr
//
+ // We mark the branch weights as explicitly unknown given they would only
+ // be derivable from the mask which we do not have VP information for.
Instruction *ThenTerm =
SplitBlockAndInsertIfThen(Predicate, InsertPt, /*Unreachable=*/false,
- /*BranchWeights=*/nullptr, DTU);
+ getExplicitlyUnknownBranchWeightsIfProfiled(
+ *CI->getFunction(), DEBUG_TYPE),
+ DTU);
BasicBlock *CondBlock = ThenTerm->getParent();
CondBlock->setName("cond.store");
@@ -905,9 +921,13 @@ static void scalarizeMaskedExpandLoad(const DataLayout &DL,
// %Elt = load i32* %EltAddr
// VResult = insertelement <16 x i32> VResult, i32 %Elt, i32 Idx
//
+ // We mark the branch weights as explicitly unknown given they would only
+ // be derivable from the mask which we do not have VP information for.
Instruction *ThenTerm =
SplitBlockAndInsertIfThen(Predicate, InsertPt, /*Unreachable=*/false,
- /*BranchWeights=*/nullptr, DTU);
+ getExplicitlyUnknownBranchWeightsIfProfiled(
+ *CI->getFunction(), DEBUG_TYPE),
+ DTU);
BasicBlock *CondBlock = ThenTerm->getParent();
CondBlock->setName("cond.load");
@@ -1031,9 +1051,13 @@ static void scalarizeMaskedCompressStore(const DataLayout &DL,
// %EltAddr = getelementptr i32* %1, i32 0
// %store i32 %OneElt, i32* %EltAddr
//
+ // We mark the branch weights as explicitly unknown given they would only
+ // be derivable from the mask which we do not have VP information for.
Instruction *ThenTerm =
SplitBlockAndInsertIfThen(Predicate, InsertPt, /*Unreachable=*/false,
- /*BranchWeights=*/nullptr, DTU);
+ getExplicitlyUnknownBranchWeightsIfProfiled(
+ *CI->getFunction(), DEBUG_TYPE),
+ DTU);
BasicBlock *CondBlock = ThenTerm->getParent();
CondBlock->setName("cond.store");
@@ -1140,9 +1164,13 @@ static void scalarizeMaskedVectorHistogram(const DataLayout &DL, CallInst *CI,
Value *Predicate =
Builder.CreateExtractElement(Mask, Idx, "Mask" + Twine(Idx));
+ // We mark the branch weights as explicitly unknown given they would only
+ // be derivable from the mask which we do not have VP information for.
Instruction *ThenTerm =
SplitBlockAndInsertIfThen(Predicate, InsertPt, /*Unreachable=*/false,
- /*BranchWeights=*/nullptr, DTU);
+ getExplicitlyUnknownBranchWeightsIfProfiled(
+ *CI->getFunction(), DEBUG_TYPE),
+ DTU);
BasicBlock *CondBlock = ThenTerm->getParent();
CondBlock->setName("cond.histogram.update");
diff --git a/llvm/utils/profcheck-xfail.txt b/llvm/utils/profcheck-xfail.txt
index f058bcd329380..abf169d7f39ff 100644
--- a/llvm/utils/profcheck-xfail.txt
+++ b/llvm/utils/profcheck-xfail.txt
@@ -109,13 +109,6 @@ Transforms/PreISelIntrinsicLowering/AArch64/expand-exp.ll
Transforms/PreISelIntrinsicLowering/AArch64/expand-fp-math.ll
Transforms/PreISelIntrinsicLowering/AArch64/expand-fp-math-binary.ll
Transforms/PreISelIntrinsicLowering/AArch64/expand-log.ll
-Transforms/ScalarizeMaskedMemIntrin/AArch64/expand-masked-load.ll
-Transforms/ScalarizeMaskedMemIntrin/AArch64/expand-masked-store.ll
-Transforms/ScalarizeMaskedMemIntrin/X86/expand-masked-compressstore.ll
-Transforms/ScalarizeMaskedMemIntrin/X86/expand-masked-expandload.ll
-Transforms/ScalarizeMaskedMemIntrin/X86/expand-masked-load.ll
-Transforms/ScalarizeMaskedMemIntrin/X86/expand-masked-store.ll
-Transforms/ScalarizeMaskedMemIntrin/X86/metadata.ll
Transforms/StackProtector/cross-dso-cfi-stack-chk-fail.ll
Transforms/TailCallElim/2010-06-26-MultipleReturnValues.ll
Transforms/TailCallElim/accum_recursion.ll
``````````
</details>
https://github.com/llvm/llvm-project/pull/219286
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