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[SLP] Fix isCommutative to check uses of the original instruction instead of the converted instruction. #143094

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Merged
merged 6 commits into from
Jun 17, 2025
Merged

[SLP] Fix isCommutative to check uses of the original instruction instead of the converted instruction. #143094

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[SLP] Pre-commit test.
HanKuanChen Jun 6, 2025
0b666c7
[SLP] Fix isCommutative to check uses of the original instruction
HanKuanChen Jun 6, 2025
ed476d6
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HanKuanChen Jun 7, 2025
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HanKuanChen Jun 7, 2025
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HanKuanChen Jun 17, 2025
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rename file and better function name
HanKuanChen Jun 17, 2025
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18 changes: 12 additions & 6 deletions llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -511,15 +511,15 @@ static bool isSplat(ArrayRef<Value *> VL) {
}

/// \returns True if \p I is commutative, handles CmpInst and BinaryOperator.
static bool isCommutative(Instruction *I) {
static bool isCommutative(Instruction *I, Instruction *InstWithUses) {
if (auto *Cmp = dyn_cast<CmpInst>(I))
return Cmp->isCommutative();
if (auto *BO = dyn_cast<BinaryOperator>(I))
return BO->isCommutative() ||
(BO->getOpcode() == Instruction::Sub &&
!BO->hasNUsesOrMore(UsesLimit) &&
!InstWithUses->hasNUsesOrMore(UsesLimit) &&
all_of(
BO->uses(),
InstWithUses->uses(),
[](const Use &U) {
// Commutative, if icmp eq/ne sub, 0
CmpPredicate Pred;
Expand All @@ -536,14 +536,16 @@ static bool isCommutative(Instruction *I) {
Flag->isOne());
})) ||
(BO->getOpcode() == Instruction::FSub &&
!BO->hasNUsesOrMore(UsesLimit) &&
all_of(BO->uses(), [](const Use &U) {
!InstWithUses->hasNUsesOrMore(UsesLimit) &&
all_of(InstWithUses->uses(), [](const Use &U) {
return match(U.getUser(),
m_Intrinsic<Intrinsic::fabs>(m_Specific(U.get())));
}));
return I->isCommutative();
}

static bool isCommutative(Instruction *I) { return isCommutative(I, I); }
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@alexey-bataev alexey-bataev Jun 7, 2025

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  1. Add a comment for this function too
  2. Do we need it at all?

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@HanKuanChen HanKuanChen Jun 7, 2025

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We need it. isCommutative(Instruction *I) is used widely. Only interchangeable instruction analysis will change the parameter (InstWithUses).


template <typename T>
static std::optional<unsigned> getInsertExtractIndex(const Value *Inst,
unsigned Offset) {
Expand Down Expand Up @@ -2898,7 +2900,11 @@ class BoUpSLP {
continue;
}
auto [SelectedOp, Ops] = convertTo(cast<Instruction>(V), S);
bool IsInverseOperation = !isCommutative(SelectedOp);
// We cannot check commutativity by the converted instruction
// (SelectedOp) because isCommutative also examines def-use
// relationships.
bool IsInverseOperation =
!isCommutative(SelectedOp, cast<Instruction>(V));
for (unsigned OpIdx : seq<unsigned>(ArgSize)) {
bool APO = (OpIdx == 0) ? false : IsInverseOperation;
OpsVec[OpIdx][Lane] = {Operands[OpIdx][Lane], APO, false};
Expand Down
34 changes: 34 additions & 0 deletions llvm/test/Transforms/SLPVectorizer/bbi-107513.ll
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@mikaelholmen mikaelholmen Jun 9, 2025

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I assume you want to give this regression test a more descriptive name than our downstream error report number :)

Original file line number Diff line number Diff line change
@@ -0,0 +1,34 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -passes=slp-vectorizer -S %s | FileCheck %s

define i16 @foo() {
; CHECK-LABEL: @foo(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[COND3:%.*]] = select i1 true, i16 1, i16 0
; CHECK-NEXT: ret i16 [[COND3]]
;
entry:
%sub = sub i16 0, -1
%cmp = icmp eq i16 %sub, 1

%sub1 = sub i16 0, -1
%cmp2 = icmp eq i16 %sub1, 1
%cond3 = select i1 %cmp2, i16 1, i16 0

%sub5 = sub nsw i16 0, 0
%cmp6 = icmp eq i16 %sub5, 0
%cmp9 = icmp eq i16 %sub5, 0

%sub12 = sub nsw i16 0, 0
%cmp13 = icmp eq i16 %sub12, 0

%sub16 = sub nsw i16 0, 0
%cmp17 = icmp eq i16 %sub16, 0

%sub20 = sub nsw i16 0, 0
%cmp21 = icmp eq i16 %sub20, 0
%cmp24 = icmp eq i16 %sub20, 0

ret i16 %cond3
}

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