[llvm] [ConstFold] Fold fixed-vectors in simplifyIntrinsic (PR #213625)
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Mon Aug 3 02:07:45 PDT 2026
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<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: Ramkumar Ramachandra (artagnon)
<details>
<summary>Changes</summary>
This exposes an underlying bug in wasm.dot-folding, which we fix. The motivation for this patch is to enable folding of get.active.lane.mask in VPlan in a follow-up.
---
Full diff: https://github.com/llvm/llvm-project/pull/213625.diff
6 Files Affected:
- (modified) llvm/include/llvm/Analysis/ConstantFolding.h (+1)
- (modified) llvm/include/llvm/Analysis/TargetFolder.h (+2-1)
- (modified) llvm/lib/Analysis/ConstantFolding.cpp (+9-4)
- (modified) llvm/lib/Analysis/InstructionSimplify.cpp (+1-1)
- (modified) llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp (+1-1)
- (modified) llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll (+9)
``````````diff
diff --git a/llvm/include/llvm/Analysis/ConstantFolding.h b/llvm/include/llvm/Analysis/ConstantFolding.h
index 4ea0a6f69e81b..87867d6f5303e 100644
--- a/llvm/include/llvm/Analysis/ConstantFolding.h
+++ b/llvm/include/llvm/Analysis/ConstantFolding.h
@@ -171,6 +171,7 @@ LLVM_ABI Constant *ConstantFoldCall(const CallBase *Call, Function *F,
LLVM_ABI Constant *ConstantFoldIntrinsic(Intrinsic::ID ID,
ArrayRef<Constant *> Ops, Type *Ty,
+ const DataLayout &DL,
Function *CxtF = nullptr);
/// ConstantFoldLoadThroughBitcast - try to cast constant to destination type
diff --git a/llvm/include/llvm/Analysis/TargetFolder.h b/llvm/include/llvm/Analysis/TargetFolder.h
index 9bae2e4d5c974..80d798ee64356 100644
--- a/llvm/include/llvm/Analysis/TargetFolder.h
+++ b/llvm/include/llvm/Analysis/TargetFolder.h
@@ -196,7 +196,8 @@ class LLVM_ABI TargetFolder final : public IRBuilderFolder {
Function *CxtF = nullptr) const override {
if (all_of(Ops, IsaPred<Constant>))
return ConstantFoldIntrinsic(
- ID, ArrayRef((Constant *const *)Ops.data(), Ops.size()), Ty, CxtF);
+ ID, ArrayRef((Constant *const *)Ops.data(), Ops.size()), Ty, DL,
+ CxtF);
return nullptr;
}
diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index e5d52ece939c2..c7347aebbd2e3 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -4300,7 +4300,7 @@ static Constant *ConstantFoldScalarCall(StringRef Name,
static Constant *ConstantFoldFixedVectorCall(
StringRef Name, Intrinsic::ID IntrinsicID, FixedVectorType *FVTy,
ArrayRef<Constant *> Operands, const DataLayout &DL,
- const TargetLibraryInfo *TLI, const CallBase *Call) {
+ const TargetLibraryInfo *TLI = nullptr, const CallBase *Call = nullptr) {
SmallVector<Constant *, 4> Result(FVTy->getNumElements());
SmallVector<Constant *, 4> Lane(Operands.size());
Type *Ty = FVTy->getElementType();
@@ -4466,9 +4466,12 @@ static Constant *ConstantFoldFixedVectorCall(
for (unsigned I = 0; I < NumElements; ++I) {
ConstantInt *Elt0 =
- cast<ConstantInt>(Operands[0]->getAggregateElement(I));
+ dyn_cast<ConstantInt>(Operands[0]->getAggregateElement(I));
ConstantInt *Elt1 =
- cast<ConstantInt>(Operands[1]->getAggregateElement(I));
+ dyn_cast<ConstantInt>(Operands[1]->getAggregateElement(I));
+
+ if (!Elt0 || !Elt1)
+ return nullptr;
MulVector[I] = Elt0->getSExtValue() * Elt1->getSExtValue();
}
@@ -4713,13 +4716,15 @@ ConstantFoldStructCall(StringRef Name, Intrinsic::ID IntrinsicID,
Constant *llvm::ConstantFoldIntrinsic(Intrinsic::ID ID,
ArrayRef<Constant *> Ops, Type *Ty,
- Function *CxtF) {
+ const DataLayout &DL, Function *CxtF) {
// In the absence of CxtF, assume strictfp conservatively.
if (!canConstantFoldIntrinsic(ID, CxtF ? CxtF->isStrictFP() : true) ||
(DisableFPCallFolding &&
anyTypeContainsFP(
Ty, ArrayRef<Value *>((Value *const *)Ops.data(), Ops.size()))))
return nullptr;
+ if (auto *FVTy = dyn_cast<FixedVectorType>(Ty))
+ return ConstantFoldFixedVectorCall("", ID, FVTy, Ops, DL);
return ConstantFoldScalarCall("", ID, Ty, Ops);
}
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index ec044be705ab0..10b159192c4be 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -7352,7 +7352,7 @@ Value *llvm::simplifyIntrinsic(Intrinsic::ID IID, Type *ReturnType,
if (all_of(Args, IsaPred<Constant>))
if (Constant *C = ConstantFoldIntrinsic(
IID, ArrayRef((Constant *const *)Args.data(), Args.size()),
- ReturnType, CxtF))
+ ReturnType, Q.DL, CxtF))
return C;
// Most of the intrinsics with no operands have some kind of side effect.
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 460024f607858..f109d3fd61640 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -2301,7 +2301,7 @@ Value *InstCombinerImpl::foldSelectWithConstOpToBinOp(ICmpInst *Cmp,
auto FoldBinaryOpOrIntrinsic = [&](Constant *LHS, Constant *RHS) {
return IsIntrinsic
- ? ConstantFoldIntrinsic(Opcode, {LHS, RHS}, LHS->getType())
+ ? ConstantFoldIntrinsic(Opcode, {LHS, RHS}, LHS->getType(), DL)
: ConstantFoldBinaryOpOperands(Opcode, LHS, RHS, DL);
};
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll b/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll
index d44437bd518af..dcb4b32152e8e 100644
--- a/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll
@@ -28,6 +28,15 @@ define <4 x i32> @dot_nonzero() {
ret <4 x i32> %res
}
+define <4 x i32> @dot_poison() {
+; CHECK-LABEL: define <4 x i32> @dot_poison() {
+; CHECK-NEXT: [[RES:%.*]] = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> <i16 1, i16 poison, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>, <8 x i16> <i16 1, i16 2, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>)
+; CHECK-NEXT: ret <4 x i32> [[RES]]
+;
+ %res = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> <i16 1, i16 poison, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>, <8 x i16> <i16 1, i16 2, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>)
+ ret <4 x i32> %res
+}
+
define <4 x i32> @dot_one_negative() {
; CHECK-LABEL: define <4 x i32> @dot_one_negative() {
; CHECK-NEXT: ret <4 x i32> splat (i32 -2)
``````````
</details>
https://github.com/llvm/llvm-project/pull/213625
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