[llvm-branch-commits] [llvm] release/22.x: [LoopVectorize] Fix nondeterminism in loop-vectorize (#200833) (PR #203850)
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Mon Jun 15 02:03:15 PDT 2026
llvmorg-github-actions[bot] wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-vectorizers
Author: llvmbot
<details>
<summary>Changes</summary>
Backport 7ff58e4747dcece251d3e5cf2e5d8de4670c5252
Requested by: @<!-- -->OCHyams
---
Full diff: https://github.com/llvm/llvm-project/pull/203850.diff
2 Files Affected:
- (modified) llvm/lib/Transforms/Vectorize/LoopVectorize.cpp (+2-2)
- (added) llvm/test/Transforms/LoopVectorize/X86/nondetermisitic-widening-cost.ll (+147)
``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 77589e06d9c33..08adc5a80d2c1 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -5799,7 +5799,7 @@ void LoopVectorizationCostModel::setCostBasedWideningDecision(ElementCount VF) {
return;
// Start with all scalar pointer uses.
- SmallPtrSet<Instruction *, 8> AddrDefs;
+ SmallSetVector<Instruction *, 8> AddrDefs;
for (BasicBlock *BB : TheLoop->blocks())
for (Instruction &I : *BB) {
Instruction *PtrDef =
@@ -5817,7 +5817,7 @@ void LoopVectorizationCostModel::setCostBasedWideningDecision(ElementCount VF) {
for (auto &Op : I->operands())
if (auto *InstOp = dyn_cast<Instruction>(Op))
if (TheLoop->contains(InstOp) && !isa<PHINode>(InstOp) &&
- AddrDefs.insert(InstOp).second)
+ AddrDefs.insert(InstOp))
Worklist.push_back(InstOp);
}
diff --git a/llvm/test/Transforms/LoopVectorize/X86/nondetermisitic-widening-cost.ll b/llvm/test/Transforms/LoopVectorize/X86/nondetermisitic-widening-cost.ll
new file mode 100644
index 0000000000000..b99322c0ce924
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/X86/nondetermisitic-widening-cost.ll
@@ -0,0 +1,147 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals none --version 6
+; RUN: opt --passes=loop-vectorize %s -S | FileCheck %s
+
+; Check that we see expected deterministic (over multiple test runs) output.
+; NOTE: Beware, if this test fails it may be due to non-determinism.
+
+target triple = "x86_64-unknown-linux"
+
+define float @fun(i64 %0, float %1, ptr noalias %a, ptr noalias %b, i64 %len) #0 {
+; CHECK-LABEL: define float @fun(
+; CHECK-SAME: i64 [[TMP0:%.*]], float [[TMP1:%.*]], ptr noalias [[A:%.*]], ptr noalias [[B:%.*]], i64 [[LEN:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[VLA:%.*]] = alloca float, i64 [[LEN]], align 16
+; CHECK-NEXT: br label %[[VECTOR_MEMCHECK:.*]]
+; CHECK: [[VECTOR_MEMCHECK]]:
+; CHECK-NEXT: [[TMP3:%.*]] = shl i64 [[TMP0]], 2
+; CHECK-NEXT: [[DIFF_CHECK:%.*]] = icmp ult i64 [[TMP3]], 32
+; CHECK-NEXT: br i1 [[DIFF_CHECK]], label %[[SCALAR_PH:.*]], label %[[VECTOR_PH:.*]]
+; CHECK: [[VECTOR_PH]]:
+; CHECK-NEXT: [[TMP4:%.*]] = getelementptr [4 x i8], ptr [[VLA]], i64 [[TMP0]]
+; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x float> poison, float [[TMP1]], i64 0
+; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x float> [[BROADCAST_SPLATINSERT]], <4 x float> poison, <4 x i32> zeroinitializer
+; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
+; CHECK: [[VECTOR_BODY]]:
+; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT: [[TMP6:%.*]] = add i64 [[INDEX]], 1
+; CHECK-NEXT: [[TMP7:%.*]] = add i64 [[INDEX]], 2
+; CHECK-NEXT: [[TMP8:%.*]] = add i64 [[INDEX]], 3
+; CHECK-NEXT: [[TMP11:%.*]] = add i64 [[INDEX]], 4
+; CHECK-NEXT: [[TMP12:%.*]] = add i64 [[INDEX]], 5
+; CHECK-NEXT: [[TMP9:%.*]] = add i64 [[INDEX]], 6
+; CHECK-NEXT: [[TMP10:%.*]] = add i64 [[INDEX]], 7
+; CHECK-NEXT: [[TMP48:%.*]] = getelementptr [8 x i8], ptr [[A]], i64 [[INDEX]]
+; CHECK-NEXT: [[TMP49:%.*]] = getelementptr [8 x i8], ptr [[A]], i64 [[TMP6]]
+; CHECK-NEXT: [[TMP50:%.*]] = getelementptr [8 x i8], ptr [[A]], i64 [[TMP7]]
+; CHECK-NEXT: [[TMP51:%.*]] = getelementptr [8 x i8], ptr [[A]], i64 [[TMP8]]
+; CHECK-NEXT: [[TMP15:%.*]] = getelementptr [8 x i8], ptr [[A]], i64 [[TMP11]]
+; CHECK-NEXT: [[TMP16:%.*]] = getelementptr [8 x i8], ptr [[A]], i64 [[TMP12]]
+; CHECK-NEXT: [[TMP17:%.*]] = getelementptr [8 x i8], ptr [[A]], i64 [[TMP9]]
+; CHECK-NEXT: [[TMP18:%.*]] = getelementptr [8 x i8], ptr [[A]], i64 [[TMP10]]
+; CHECK-NEXT: [[TMP60:%.*]] = load ptr, ptr [[TMP48]], align 8
+; CHECK-NEXT: [[TMP62:%.*]] = load ptr, ptr [[TMP49]], align 8
+; CHECK-NEXT: [[TMP64:%.*]] = load ptr, ptr [[TMP50]], align 8
+; CHECK-NEXT: [[TMP65:%.*]] = load ptr, ptr [[TMP51]], align 8
+; CHECK-NEXT: [[TMP23:%.*]] = load ptr, ptr [[TMP15]], align 8
+; CHECK-NEXT: [[TMP24:%.*]] = load ptr, ptr [[TMP16]], align 8
+; CHECK-NEXT: [[TMP25:%.*]] = load ptr, ptr [[TMP17]], align 8
+; CHECK-NEXT: [[TMP26:%.*]] = load ptr, ptr [[TMP18]], align 8
+; CHECK-NEXT: [[TMP66:%.*]] = load i64, ptr [[TMP60]], align 8
+; CHECK-NEXT: [[TMP33:%.*]] = load i64, ptr [[TMP62]], align 8
+; CHECK-NEXT: [[TMP67:%.*]] = load i64, ptr [[TMP64]], align 8
+; CHECK-NEXT: [[TMP35:%.*]] = load i64, ptr [[TMP65]], align 8
+; CHECK-NEXT: [[TMP31:%.*]] = load i64, ptr [[TMP23]], align 8
+; CHECK-NEXT: [[TMP32:%.*]] = load i64, ptr [[TMP24]], align 8
+; CHECK-NEXT: [[TMP36:%.*]] = load i64, ptr [[TMP25]], align 8
+; CHECK-NEXT: [[TMP34:%.*]] = load i64, ptr [[TMP26]], align 8
+; CHECK-NEXT: [[TMP68:%.*]] = getelementptr [4 x i8], ptr [[A]], i64 [[TMP66]]
+; CHECK-NEXT: [[TMP69:%.*]] = getelementptr [4 x i8], ptr [[A]], i64 [[TMP33]]
+; CHECK-NEXT: [[TMP70:%.*]] = getelementptr [4 x i8], ptr [[A]], i64 [[TMP67]]
+; CHECK-NEXT: [[TMP43:%.*]] = getelementptr [4 x i8], ptr [[A]], i64 [[TMP35]]
+; CHECK-NEXT: [[TMP44:%.*]] = getelementptr [4 x i8], ptr [[A]], i64 [[TMP31]]
+; CHECK-NEXT: [[TMP45:%.*]] = getelementptr [4 x i8], ptr [[A]], i64 [[TMP32]]
+; CHECK-NEXT: [[TMP46:%.*]] = getelementptr [4 x i8], ptr [[A]], i64 [[TMP36]]
+; CHECK-NEXT: [[TMP47:%.*]] = getelementptr [4 x i8], ptr [[A]], i64 [[TMP34]]
+; CHECK-NEXT: [[TMP52:%.*]] = load float, ptr [[TMP68]], align 4
+; CHECK-NEXT: [[TMP53:%.*]] = load float, ptr [[TMP69]], align 4
+; CHECK-NEXT: [[TMP54:%.*]] = load float, ptr [[TMP70]], align 4
+; CHECK-NEXT: [[TMP55:%.*]] = load float, ptr [[TMP43]], align 4
+; CHECK-NEXT: [[TMP56:%.*]] = insertelement <4 x float> poison, float [[TMP52]], i32 0
+; CHECK-NEXT: [[TMP57:%.*]] = insertelement <4 x float> [[TMP56]], float [[TMP53]], i32 1
+; CHECK-NEXT: [[TMP58:%.*]] = insertelement <4 x float> [[TMP57]], float [[TMP54]], i32 2
+; CHECK-NEXT: [[TMP59:%.*]] = insertelement <4 x float> [[TMP58]], float [[TMP55]], i32 3
+; CHECK-NEXT: [[TMP71:%.*]] = load float, ptr [[TMP44]], align 4
+; CHECK-NEXT: [[TMP72:%.*]] = load float, ptr [[TMP45]], align 4
+; CHECK-NEXT: [[TMP73:%.*]] = load float, ptr [[TMP46]], align 4
+; CHECK-NEXT: [[TMP74:%.*]] = load float, ptr [[TMP47]], align 4
+; CHECK-NEXT: [[TMP75:%.*]] = insertelement <4 x float> poison, float [[TMP71]], i32 0
+; CHECK-NEXT: [[TMP76:%.*]] = insertelement <4 x float> [[TMP75]], float [[TMP72]], i32 1
+; CHECK-NEXT: [[TMP77:%.*]] = insertelement <4 x float> [[TMP76]], float [[TMP73]], i32 2
+; CHECK-NEXT: [[TMP78:%.*]] = insertelement <4 x float> [[TMP77]], float [[TMP74]], i32 3
+; CHECK-NEXT: [[TMP61:%.*]] = getelementptr [4 x i8], ptr [[VLA]], i64 [[INDEX]]
+; CHECK-NEXT: [[TMP79:%.*]] = getelementptr float, ptr [[TMP61]], i64 4
+; CHECK-NEXT: store <4 x float> [[TMP59]], ptr [[TMP61]], align 4
+; CHECK-NEXT: store <4 x float> [[TMP78]], ptr [[TMP79]], align 4
+; CHECK-NEXT: [[TMP63:%.*]] = getelementptr [4 x i8], ptr [[TMP4]], i64 [[INDEX]]
+; CHECK-NEXT: [[TMP80:%.*]] = getelementptr float, ptr [[TMP63]], i64 4
+; CHECK-NEXT: store <4 x float> [[BROADCAST_SPLAT]], ptr [[TMP63]], align 4
+; CHECK-NEXT: store <4 x float> [[BROADCAST_SPLAT]], ptr [[TMP80]], align 4
+; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 8
+; CHECK-NEXT: [[TMP37:%.*]] = icmp eq i64 [[INDEX_NEXT]], 128
+; CHECK-NEXT: br i1 [[TMP37]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
+; CHECK: [[MIDDLE_BLOCK]]:
+; CHECK-NEXT: br label %[[SCALAR_PH]]
+; CHECK: [[SCALAR_PH]]:
+; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i64 [ 128, %[[MIDDLE_BLOCK]] ], [ 0, %[[VECTOR_MEMCHECK]] ]
+; CHECK-NEXT: br label %[[FOR_BODY:.*]]
+; CHECK: [[FOR_BODY]]:
+; CHECK-NEXT: [[INDVARS_IV:%.*]] = phi i64 [ [[BC_RESUME_VAL]], %[[SCALAR_PH]] ], [ [[INDVARS_IV_NEXT:%.*]], %[[FOR_BODY]] ]
+; CHECK-NEXT: [[ARRAYIDX16:%.*]] = getelementptr [8 x i8], ptr [[A]], i64 [[INDVARS_IV]]
+; CHECK-NEXT: [[TMP38:%.*]] = load ptr, ptr [[ARRAYIDX16]], align 8
+; CHECK-NEXT: [[TMP39:%.*]] = load i64, ptr [[TMP38]], align 8
+; CHECK-NEXT: [[ARRAYIDX18:%.*]] = getelementptr [4 x i8], ptr [[A]], i64 [[TMP39]]
+; CHECK-NEXT: [[TMP40:%.*]] = load float, ptr [[ARRAYIDX18]], align 4
+; CHECK-NEXT: [[ARRAYIDX21:%.*]] = getelementptr [4 x i8], ptr [[VLA]], i64 [[INDVARS_IV]]
+; CHECK-NEXT: store float [[TMP40]], ptr [[ARRAYIDX21]], align 4
+; CHECK-NEXT: [[TMP41:%.*]] = load i64, ptr [[B]], align 8
+; CHECK-NEXT: [[ARRAYIDX27:%.*]] = getelementptr [4 x i8], ptr [[A]], i64 [[TMP41]]
+; CHECK-NEXT: [[TMP42:%.*]] = load float, ptr [[ARRAYIDX27]], align 4
+; CHECK-NEXT: [[ARRAYIDX28:%.*]] = getelementptr [4 x i8], ptr [[VLA]], i64 [[TMP0]]
+; CHECK-NEXT: [[ARRAYIDX30:%.*]] = getelementptr [4 x i8], ptr [[ARRAYIDX28]], i64 [[INDVARS_IV]]
+; CHECK-NEXT: store float [[TMP1]], ptr [[ARRAYIDX30]], align 4
+; CHECK-NEXT: [[INDVARS_IV_NEXT]] = add i64 [[INDVARS_IV]], 1
+; CHECK-NEXT: [[EXITCOND_NOT:%.*]] = icmp eq i64 [[INDVARS_IV]], 128
+; CHECK-NEXT: br i1 [[EXITCOND_NOT]], label %[[FOR_END_LOOPEXIT:.*]], label %[[FOR_BODY]], !llvm.loop [[LOOP3:![0-9]+]]
+; CHECK: [[FOR_END_LOOPEXIT]]:
+; CHECK-NEXT: [[R:%.*]] = load float, ptr [[VLA]], align 4
+; CHECK-NEXT: ret float [[R]]
+;
+entry:
+ %vla = alloca float, i64 %len, align 16
+ br label %loop
+
+loop:
+ %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+ %arrayidx16 = getelementptr [8 x i8], ptr %a, i64 %iv
+ %2 = load ptr, ptr %arrayidx16, align 8
+ %3 = load i64, ptr %2, align 8
+ %arrayidx18 = getelementptr [4 x i8], ptr %a, i64 %3
+ %4 = load float, ptr %arrayidx18, align 4
+ %arrayidx21 = getelementptr [4 x i8], ptr %vla, i64 %iv
+ store float %4, ptr %arrayidx21, align 4
+ %5 = load i64, ptr %b, align 8
+ %arrayidx27 = getelementptr [4 x i8], ptr %a, i64 %5
+ %6 = load float, ptr %arrayidx27, align 4
+ %arrayidx28 = getelementptr [4 x i8], ptr %vla, i64 %0
+ %arrayidx30 = getelementptr [4 x i8], ptr %arrayidx28, i64 %iv
+ store float %1, ptr %arrayidx30, align 4
+ %iv.next = add i64 %iv, 1
+ %exitcond.not = icmp eq i64 %iv, 128
+ br i1 %exitcond.not, label %for.end.loopexit, label %loop
+
+for.end.loopexit:
+ %r = load float, ptr %vla
+ ret float %r
+}
+
+attributes #0 = { "target-features"="+avx2" }
``````````
</details>
https://github.com/llvm/llvm-project/pull/203850
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