[llvm] [VPlan] Set correct VPIRFlags for FP selects when sinking stores. (PR #212973)
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Thu Jul 30 04:41:58 PDT 2026
https://github.com/fhahn updated https://github.com/llvm/llvm-project/pull/212973
>From 2addbc35eb333adae5e26e6688b47215424200fa Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Thu, 30 Jul 2026 09:57:14 +0100
Subject: [PATCH 1/2] [VPlan] Set correct VPIRFlags for FP selects when sinking
stores.
Selects of floats carry fast-math flags. Update getDefaultFlags to take
the result type and use it to handle selects.
Then update sinkPredicatedStores to pass through the correct default
flags.
This fixes a crash in cse when intersecting common metadata.
Fixes https://github.com/llvm/llvm-project/issues/212811.
---
llvm/lib/Transforms/Vectorize/VPlan.h | 7 +-
.../lib/Transforms/Vectorize/VPlanRecipes.cpp | 9 +-
.../Transforms/Vectorize/VPlanTransforms.cpp | 6 +-
...predicated-loads-with-predicated-stores.ll | 85 +++++++++++++++++++
4 files changed, 100 insertions(+), 7 deletions(-)
diff --git a/llvm/lib/Transforms/Vectorize/VPlan.h b/llvm/lib/Transforms/Vectorize/VPlan.h
index 1aeed394d7482..7085338467578 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.h
+++ b/llvm/lib/Transforms/Vectorize/VPlan.h
@@ -1098,10 +1098,9 @@ class VPIRFlags {
}
public:
- /// Returns default flags for \p Opcode for opcodes that support it, asserts
- /// otherwise. Opcodes not supporting default flags include compares and
- /// ComputeReductionResult.
- static VPIRFlags getDefaultFlags(unsigned Opcode);
+ /// Returns default flags for \p Opcode and scalar \p ResultTy for opcodes
+ /// that support it, asserts
+ static VPIRFlags getDefaultFlags(unsigned Opcode, Type *ResultTy = nullptr);
#if !defined(NDEBUG)
/// Returns true if the set flags are valid for \p Opcode.
diff --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
index 5d692ea89ac2e..449568c148542 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -2493,7 +2493,7 @@ VPIRFlags::FastMathFlagsTy::FastMathFlagsTy(const FastMathFlags &FMF) {
ApproxFunc = FMF.approxFunc();
}
-VPIRFlags VPIRFlags::getDefaultFlags(unsigned Opcode) {
+VPIRFlags VPIRFlags::getDefaultFlags(unsigned Opcode, Type *ResultTy) {
switch (Opcode) {
case Instruction::Add:
case Instruction::Sub:
@@ -2526,6 +2526,13 @@ VPIRFlags VPIRFlags::getDefaultFlags(unsigned Opcode) {
case Instruction::FPExt:
case Instruction::FPTrunc:
return FastMathFlags();
+ case Instruction::Select:
+ case Instruction::PHI:
+ case Instruction::Call:
+ // Selects only have fast-math flags if they produce a floating-point value.
+ if (ResultTy && FPMathOperator::isSupportedFloatingPointType(ResultTy))
+ return FastMathFlags();
+ return VPIRFlags();
case Instruction::ICmp:
case Instruction::FCmp:
case VPInstruction::ComputeReductionResult:
diff --git a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
index 3311a9711cb3f..9d2490aceedc1 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
@@ -3892,8 +3892,10 @@ void VPlanTransforms::sinkPredicatedStores(VPlan &Plan,
"all members in group must agree on IsSingleScalar");
VPValue *Mask = Group[I]->getMask();
VPValue *Value = Group[I]->getOperand(0);
- SelectedValue = Builder.createSelect(Mask, Value, SelectedValue,
- Group[I]->getDebugLoc());
+ SelectedValue = Builder.createSelect(
+ Mask, Value, SelectedValue, Group[I]->getDebugLoc(), "",
+ VPIRFlags::getDefaultFlags(Instruction::Select,
+ Value->getScalarType()));
}
// Find the store with minimum alignment to use.
diff --git a/llvm/test/Transforms/LoopVectorize/hoist-predicated-loads-with-predicated-stores.ll b/llvm/test/Transforms/LoopVectorize/hoist-predicated-loads-with-predicated-stores.ll
index e11c8d08f7e3f..4e2d9717d0764 100644
--- a/llvm/test/Transforms/LoopVectorize/hoist-predicated-loads-with-predicated-stores.ll
+++ b/llvm/test/Transforms/LoopVectorize/hoist-predicated-loads-with-predicated-stores.ll
@@ -1661,3 +1661,88 @@ loop.latch:
exit:
ret void
}
+
+; Make sure fast-math flags are dropped correctly on selects created when sinking
+; stores.
+define void @sink_stores_cse_select_dropping_fmf(ptr %dst, ptr %src, ptr %invar.dst, i64 %n, i1 %c) {
+; CHECK-LABEL: define void @sink_stores_cse_select_dropping_fmf(
+; CHECK-SAME: ptr [[DST:%.*]], ptr [[SRC:%.*]], ptr [[INVAR_DST:%.*]], i64 [[N:%.*]], i1 [[C:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[N]], 2
+; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label %[[SCALAR_PH:.*]], label %[[VECTOR_MEMCHECK:.*]]
+; CHECK: [[VECTOR_MEMCHECK]]:
+; CHECK-NEXT: [[TMP0:%.*]] = shl i64 [[N]], 2
+; CHECK-NEXT: [[SCEVGEP:%.*]] = getelementptr i8, ptr [[DST]], i64 [[TMP0]]
+; CHECK-NEXT: [[SCEVGEP1:%.*]] = getelementptr i8, ptr [[INVAR_DST]], i64 4
+; CHECK-NEXT: [[SCEVGEP2:%.*]] = getelementptr i8, ptr [[SRC]], i64 4
+; CHECK-NEXT: [[BOUND0:%.*]] = icmp ult ptr [[DST]], [[SCEVGEP1]]
+; CHECK-NEXT: [[BOUND1:%.*]] = icmp ult ptr [[INVAR_DST]], [[SCEVGEP]]
+; CHECK-NEXT: [[FOUND_CONFLICT:%.*]] = and i1 [[BOUND0]], [[BOUND1]]
+; CHECK-NEXT: [[BOUND03:%.*]] = icmp ult ptr [[DST]], [[SCEVGEP2]]
+; CHECK-NEXT: [[BOUND14:%.*]] = icmp ult ptr [[SRC]], [[SCEVGEP]]
+; CHECK-NEXT: [[FOUND_CONFLICT5:%.*]] = and i1 [[BOUND03]], [[BOUND14]]
+; CHECK-NEXT: [[CONFLICT_RDX:%.*]] = or i1 [[FOUND_CONFLICT]], [[FOUND_CONFLICT5]]
+; CHECK-NEXT: [[BOUND06:%.*]] = icmp ult ptr [[INVAR_DST]], [[SCEVGEP2]]
+; CHECK-NEXT: [[BOUND17:%.*]] = icmp ult ptr [[SRC]], [[SCEVGEP1]]
+; CHECK-NEXT: [[FOUND_CONFLICT8:%.*]] = and i1 [[BOUND06]], [[BOUND17]]
+; CHECK-NEXT: [[CONFLICT_RDX9:%.*]] = or i1 [[CONFLICT_RDX]], [[FOUND_CONFLICT8]]
+; CHECK-NEXT: br i1 [[CONFLICT_RDX9]], label %[[SCALAR_PH]], label %[[VECTOR_PH:.*]]
+; CHECK: [[VECTOR_PH]]:
+; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[N]], 2
+; CHECK-NEXT: [[N_VEC:%.*]] = sub i64 [[N]], [[N_MOD_VF]]
+; CHECK-NEXT: [[TMP1:%.*]] = load float, ptr [[SRC]], align 4, !alias.scope [[META133:![0-9]+]]
+; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <2 x float> poison, float [[TMP1]], i64 0
+; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <2 x float> [[BROADCAST_SPLATINSERT]], <2 x float> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT: [[TMP2:%.*]] = fmul <2 x float> [[BROADCAST_SPLAT]], splat (float 3.000000e+00)
+; CHECK-NEXT: [[TMP3:%.*]] = fmul nnan <2 x float> [[BROADCAST_SPLAT]], splat (float 2.000000e+00)
+; CHECK-NEXT: [[TMP4:%.*]] = extractelement <2 x float> [[TMP3]], i64 0
+; CHECK-NEXT: [[TMP5:%.*]] = extractelement <2 x float> [[TMP2]], i64 0
+; CHECK-NEXT: [[TMP6:%.*]] = select i1 [[C]], float [[TMP4]], float [[TMP5]]
+; CHECK-NEXT: [[TMP7:%.*]] = fmul nnan float [[TMP6]], 5.000000e+00
+; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
+; CHECK: [[VECTOR_BODY]]:
+; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT: [[TMP8:%.*]] = add i64 [[INDEX]], 1
+; CHECK-NEXT: [[TMP9:%.*]] = getelementptr inbounds float, ptr [[DST]], i64 [[INDEX]]
+; CHECK-NEXT: [[TMP10:%.*]] = getelementptr inbounds float, ptr [[DST]], i64 [[TMP8]]
+; CHECK-NEXT: store float [[TMP6]], ptr [[TMP9]], align 4, !alias.scope [[META136:![0-9]+]], !noalias [[META138:![0-9]+]]
+; CHECK-NEXT: store float [[TMP6]], ptr [[TMP10]], align 4, !alias.scope [[META136]], !noalias [[META138]]
+; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 2
+; CHECK-NEXT: [[TMP11:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
+; CHECK-NEXT: br i1 [[TMP11]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP140:![0-9]+]]
+; CHECK: [[MIDDLE_BLOCK]]:
+; CHECK-NEXT: store float [[TMP7]], ptr [[INVAR_DST]], align 4, !alias.scope [[META141:![0-9]+]], !noalias [[META133]]
+; CHECK-NEXT: [[CMP_N:%.*]] = icmp eq i64 [[N]], [[N_VEC]]
+; CHECK-NEXT: br i1 [[CMP_N]], [[EXIT:label %.*]], label %[[SCALAR_PH]]
+; CHECK: [[SCALAR_PH]]:
+;
+entry:
+ br label %loop.header
+
+loop.header:
+ %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop.latch ]
+ %l = load float, ptr %src, align 4
+ %gep.dst = getelementptr inbounds float, ptr %dst, i64 %iv
+ br i1 %c, label %then, label %else
+
+then:
+ %mul.then = fmul nnan float %l, 2.000000e+00
+ store float %mul.then, ptr %gep.dst, align 4
+ br label %loop.latch
+
+else:
+ %mul.else = fmul float %l, 3.000000e+00
+ store float %mul.else, ptr %gep.dst, align 4
+ br label %loop.latch
+
+loop.latch:
+ %merge = phi float [ %mul.then, %then ], [ %mul.else, %else ]
+ %mul.merge = fmul nnan float %merge, 5.000000e+00
+ store float %mul.merge, ptr %invar.dst, align 4
+ %iv.next = add i64 %iv, 1
+ %ec = icmp eq i64 %iv.next, %n
+ br i1 %ec, label %exit, label %loop.header
+
+exit:
+ ret void
+}
>From b8005f0ab03dbf4dd15d6e695e2880e7e52f4dd9 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Thu, 30 Jul 2026 12:35:35 +0100
Subject: [PATCH 2/2] !fixup restore comment
---
llvm/lib/Transforms/Vectorize/VPlan.h | 3 ++-
llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp | 2 --
2 files changed, 2 insertions(+), 3 deletions(-)
diff --git a/llvm/lib/Transforms/Vectorize/VPlan.h b/llvm/lib/Transforms/Vectorize/VPlan.h
index 7085338467578..814b77a96e825 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.h
+++ b/llvm/lib/Transforms/Vectorize/VPlan.h
@@ -1099,7 +1099,8 @@ class VPIRFlags {
public:
/// Returns default flags for \p Opcode and scalar \p ResultTy for opcodes
- /// that support it, asserts
+ /// that support it, asserts otherwise. Opcodes not supporting default flags
+ /// include compares and ComputeReductionResult.
static VPIRFlags getDefaultFlags(unsigned Opcode, Type *ResultTy = nullptr);
#if !defined(NDEBUG)
diff --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
index 22811696d7b0d..ca63d1498316b 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -2528,8 +2528,6 @@ VPIRFlags VPIRFlags::getDefaultFlags(unsigned Opcode, Type *ResultTy) {
case Instruction::FPTrunc:
return FastMathFlags();
case Instruction::Select:
- case Instruction::PHI:
- case Instruction::Call:
// Selects only have fast-math flags if they produce a floating-point value.
if (ResultTy && FPMathOperator::isSupportedFloatingPointType(ResultTy))
return FastMathFlags();
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