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[InstCombine] Extend vector.reduce.add and splat transform to scalable vectors #161101

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[InstCombine] Extend vector.reduce.add and splat transform to scalable vectors #161101

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7d90e64
Extend vector.reduce.add and splat transform to scalable vectors
spaits Sep 28, 2025
f5189ce
Throw out redundant baranch and redundant check
spaits Sep 29, 2025
556e004
Add more tests
spaits Sep 29, 2025
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14 changes: 10 additions & 4 deletions llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
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Expand Up @@ -3785,13 +3785,19 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {

// vector.reduce.add.vNiM(splat(%x)) -> mul(%x, N)
if (Value *Splat = getSplatValue(Arg)) {
ElementCount VecToReduceCount =
cast<VectorType>(Arg->getType())->getElementCount();
VectorType *VecToReduceTy = cast<VectorType>(Arg->getType());
ElementCount VecToReduceCount = VecToReduceTy->getElementCount();
Value *RHS;
if (VecToReduceCount.isFixed()) {
unsigned VectorSize = VecToReduceCount.getFixedValue();
return BinaryOperator::CreateMul(
Splat, ConstantInt::get(Splat->getType(), VectorSize));
RHS = ConstantInt::get(Splat->getType(), VectorSize);
}

RHS = Builder.CreateElementCount(Type::getInt64Ty(II->getContext()),
VecToReduceCount);
if (Splat->getType() != RHS->getType())
RHS = Builder.CreateZExtOrTrunc(RHS, Splat->getType());
return BinaryOperator::CreateMul(Splat, RHS);
}
}
[[fallthrough]];
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7 changes: 4 additions & 3 deletions llvm/test/Transforms/InstCombine/vector-reductions.ll
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Expand Up @@ -469,9 +469,10 @@ define i2 @constant_multiplied_7xi2(i2 %0) {

define i32 @negative_scalable_vector(i32 %0) {
; CHECK-LABEL: @negative_scalable_vector(
; CHECK-NEXT: [[TMP2:%.*]] = insertelement <vscale x 4 x i32> poison, i32 [[TMP0:%.*]], i64 0
; CHECK-NEXT: [[TMP3:%.*]] = shufflevector <vscale x 4 x i32> [[TMP2]], <vscale x 4 x i32> poison, <vscale x 4 x i32> zeroinitializer
; CHECK-NEXT: [[TMP4:%.*]] = tail call i32 @llvm.vector.reduce.add.nxv4i32(<vscale x 4 x i32> [[TMP3]])
; CHECK-NEXT: [[TMP2:%.*]] = call i64 @llvm.vscale.i64()
; CHECK-NEXT: [[DOTTR:%.*]] = trunc i64 [[TMP2]] to i32
; CHECK-NEXT: [[TMP3:%.*]] = shl i32 [[DOTTR]], 2
; CHECK-NEXT: [[TMP4:%.*]] = mul i32 [[TMP0:%.*]], [[TMP3]]
; CHECK-NEXT: ret i32 [[TMP4]]
;
%2 = insertelement <vscale x 4 x i32> poison, i32 %0, i64 0
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