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[LLVM][ConstantFolding] Extend constantFoldVectorReduce to include scalable vectors. #165437

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Oct 31, 2025
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[LLVM][ConstantFolding] Extend constantFoldVectorReduce to include scalable vectors. #165437

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3538605
[LLVM][ConstantFolding] Extend constantFoldVectorReduce to include sc…
paulwalker-arm Oct 27, 2025
4da9437
Remove unnecessary isa<Posion> check. Add support for vec.reduce.mul.…
paulwalker-arm Oct 29, 2025
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44 changes: 34 additions & 10 deletions llvm/lib/Analysis/ConstantFolding.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2163,18 +2163,42 @@ Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
}

Constant *constantFoldVectorReduce(Intrinsic::ID IID, Constant *Op) {
FixedVectorType *VT = dyn_cast<FixedVectorType>(Op->getType());
if (!VT)
return nullptr;

// This isn't strictly necessary, but handle the special/common case of zero:
// all integer reductions of a zero input produce zero.
if (isa<ConstantAggregateZero>(Op))
return ConstantInt::get(VT->getElementType(), 0);
auto *OpVT = cast<VectorType>(Op->getType());

// This is the same as the underlying binops - poison propagates.
if (isa<PoisonValue>(Op) || Op->containsPoisonElement())
return PoisonValue::get(VT->getElementType());
if (Op->containsPoisonElement())
return PoisonValue::get(OpVT->getElementType());

// Shortcut non-accumulating reductions.
if (Constant *SplatVal = Op->getSplatValue()) {
switch (IID) {
case Intrinsic::vector_reduce_and:
case Intrinsic::vector_reduce_or:
case Intrinsic::vector_reduce_smin:
case Intrinsic::vector_reduce_smax:
case Intrinsic::vector_reduce_umin:
case Intrinsic::vector_reduce_umax:
return SplatVal;
case Intrinsic::vector_reduce_add:
if (SplatVal->isNullValue())
return SplatVal;
break;
case Intrinsic::vector_reduce_mul:
if (SplatVal->isNullValue() || SplatVal->isOneValue())
return SplatVal;
break;
case Intrinsic::vector_reduce_xor:
if (SplatVal->isNullValue())
return SplatVal;
if (OpVT->getElementCount().isKnownMultipleOf(2))
return Constant::getNullValue(OpVT->getElementType());
break;
}
}

FixedVectorType *VT = dyn_cast<FixedVectorType>(OpVT);
if (!VT)
return nullptr;

// TODO: Handle undef.
auto *EltC = dyn_cast_or_null<ConstantInt>(Op->getAggregateElement(0U));
Expand Down
104 changes: 52 additions & 52 deletions llvm/test/Transforms/InstSimplify/ConstProp/vecreduce.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -12,8 +12,7 @@ define i32 @add_0() {

define i32 @add_0_scalable_vector() {
; CHECK-LABEL: @add_0_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.add.nxv8i32(<vscale x 8 x i32> zeroinitializer)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 0
;
%x = call i32 @llvm.vector.reduce.add.nxv8i32(<vscale x 8 x i32> zeroinitializer)
ret i32 %x
Expand Down Expand Up @@ -89,8 +88,7 @@ define i32 @add_poison() {

define i32 @add_poison_scalable_vector() {
; CHECK-LABEL: @add_poison_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.add.nxv8i32(<vscale x 8 x i32> poison)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 poison
;
%x = call i32 @llvm.vector.reduce.add.nxv8i32(<vscale x 8 x i32> poison)
ret i32 %x
Expand Down Expand Up @@ -123,8 +121,7 @@ define i32 @mul_0() {

define i32 @mul_0_scalable_vector() {
; CHECK-LABEL: @mul_0_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.mul.nxv8i32(<vscale x 8 x i32> zeroinitializer)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 0
;
%x = call i32 @llvm.vector.reduce.mul.nxv8i32(<vscale x 8 x i32> zeroinitializer)
ret i32 %x
Expand All @@ -140,13 +137,29 @@ define i32 @mul_1() {

define i32 @mul_1_scalable_vector() {
; CHECK-LABEL: @mul_1_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.mul.nxv8i32(<vscale x 8 x i32> splat (i32 1))
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 1
;
%x = call i32 @llvm.vector.reduce.mul.nxv8i32(<vscale x 8 x i32> splat (i32 1))
ret i32 %x
}

define i32 @mul_2() {
; CHECK-LABEL: @mul_2(
; CHECK-NEXT: ret i32 256
;
%x = call i32 @llvm.vector.reduce.mul.v8i32(<8 x i32> <i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2>)
ret i32 %x
}

define i32 @mul_2_scalable_vector() {
; CHECK-LABEL: @mul_2_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.mul.nxv8i32(<vscale x 8 x i32> splat (i32 2))
; CHECK-NEXT: ret i32 [[X]]
;
%x = call i32 @llvm.vector.reduce.mul.nxv8i32(<vscale x 8 x i32> splat (i32 2))
ret i32 %x
}

define i32 @mul_inc() {
; CHECK-LABEL: @mul_inc(
; CHECK-NEXT: ret i32 40320
Expand Down Expand Up @@ -200,8 +213,7 @@ define i32 @mul_poison() {

define i32 @mul_poison_scalable_vector() {
; CHECK-LABEL: @mul_poison_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.mul.nxv8i32(<vscale x 8 x i32> poison)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 poison
;
%x = call i32 @llvm.vector.reduce.mul.nxv8i32(<vscale x 8 x i32> poison)
ret i32 %x
Expand All @@ -225,8 +237,7 @@ define i32 @and_0() {

define i32 @and_0_scalable_vector() {
; CHECK-LABEL: @and_0_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.and.nxv8i32(<vscale x 8 x i32> zeroinitializer)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 0
;
%x = call i32 @llvm.vector.reduce.and.nxv8i32(<vscale x 8 x i32> zeroinitializer)
ret i32 %x
Expand All @@ -242,8 +253,7 @@ define i32 @and_1() {

define i32 @and_1_scalable_vector() {
; CHECK-LABEL: @and_1_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.and.nxv8i32(<vscale x 8 x i32> splat (i32 1))
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 1
;
%x = call i32 @llvm.vector.reduce.and.nxv8i32(<vscale x 8 x i32> splat (i32 1))
ret i32 %x
Expand Down Expand Up @@ -302,8 +312,7 @@ define i32 @and_poison() {

define i32 @and_poison_scalable_vector() {
; CHECK-LABEL: @and_poison_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.and.nxv8i32(<vscale x 8 x i32> poison)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 poison
;
%x = call i32 @llvm.vector.reduce.and.nxv8i32(<vscale x 8 x i32> poison)
ret i32 %x
Expand All @@ -327,8 +336,7 @@ define i32 @or_0() {

define i32 @or_0_scalable_vector() {
; CHECK-LABEL: @or_0_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.or.nxv8i32(<vscale x 8 x i32> zeroinitializer)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 0
;
%x = call i32 @llvm.vector.reduce.or.nxv8i32(<vscale x 8 x i32> zeroinitializer)
ret i32 %x
Expand All @@ -344,8 +352,7 @@ define i32 @or_1() {

define i32 @or_1_scalable_vector() {
; CHECK-LABEL: @or_1_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.or.nxv8i32(<vscale x 8 x i32> splat (i32 1))
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 1
;
%x = call i32 @llvm.vector.reduce.or.nxv8i32(<vscale x 8 x i32> splat (i32 1))
ret i32 %x
Expand Down Expand Up @@ -404,8 +411,7 @@ define i32 @or_poison() {

define i32 @or_poison_scalable_vector() {
; CHECK-LABEL: @or_poison_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.or.nxv8i32(<vscale x 8 x i32> poison)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 poison
;
%x = call i32 @llvm.vector.reduce.or.nxv8i32(<vscale x 8 x i32> poison)
ret i32 %x
Expand All @@ -429,8 +435,7 @@ define i32 @xor_0() {

define i32 @xor_0_scalable_vector() {
; CHECK-LABEL: @xor_0_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.xor.nxv8i32(<vscale x 8 x i32> zeroinitializer)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 0
;
%x = call i32 @llvm.vector.reduce.xor.nxv8i32(<vscale x 8 x i32> zeroinitializer)
ret i32 %x
Expand All @@ -446,13 +451,21 @@ define i32 @xor_1() {

define i32 @xor_1_scalable_vector() {
; CHECK-LABEL: @xor_1_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.xor.nxv8i32(<vscale x 8 x i32> splat (i32 1))
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 0
;
%x = call i32 @llvm.vector.reduce.xor.nxv8i32(<vscale x 8 x i32> splat(i32 1))
ret i32 %x
}

define i32 @xor_1_scalable_vector_lane_count_not_known_even() {
; CHECK-LABEL: @xor_1_scalable_vector_lane_count_not_known_even(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.xor.nxv1i32(<vscale x 1 x i32> splat (i32 1))
; CHECK-NEXT: ret i32 [[X]]
;
%x = call i32 @llvm.vector.reduce.xor.nxv8i32(<vscale x 1 x i32> splat(i32 1))
ret i32 %x
}

define i32 @xor_inc() {
; CHECK-LABEL: @xor_inc(
; CHECK-NEXT: ret i32 10
Expand Down Expand Up @@ -506,8 +519,7 @@ define i32 @xor_poison() {

define i32 @xor_poison_scalable_vector() {
; CHECK-LABEL: @xor_poison_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.xor.nxv8i32(<vscale x 8 x i32> poison)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 poison
;
%x = call i32 @llvm.vector.reduce.xor.nxv8i32(<vscale x 8 x i32> poison)
ret i32 %x
Expand All @@ -531,8 +543,7 @@ define i32 @smin_0() {

define i32 @smin_0_scalable_vector() {
; CHECK-LABEL: @smin_0_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.smin.nxv8i32(<vscale x 8 x i32> zeroinitializer)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 0
;
%x = call i32 @llvm.vector.reduce.smin.nxv8i32(<vscale x 8 x i32> zeroinitializer)
ret i32 %x
Expand All @@ -548,8 +559,7 @@ define i32 @smin_1() {

define i32 @smin_1_scalable_vector() {
; CHECK-LABEL: @smin_1_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.smin.nxv8i32(<vscale x 8 x i32> splat (i32 1))
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 1
;
%x = call i32 @llvm.vector.reduce.smin.nxv8i32(<vscale x 8 x i32> splat(i32 1))
ret i32 %x
Expand Down Expand Up @@ -608,8 +618,7 @@ define i32 @smin_poison() {

define i32 @smin_poison_scalable_vector() {
; CHECK-LABEL: @smin_poison_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.smin.nxv8i32(<vscale x 8 x i32> poison)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 poison
;
%x = call i32 @llvm.vector.reduce.smin.nxv8i32(<vscale x 8 x i32> poison)
ret i32 %x
Expand All @@ -633,8 +642,7 @@ define i32 @smax_0() {

define i32 @smax_0_scalable_vector() {
; CHECK-LABEL: @smax_0_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.smax.nxv8i32(<vscale x 8 x i32> zeroinitializer)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 0
;
%x = call i32 @llvm.vector.reduce.smax.nxv8i32(<vscale x 8 x i32> zeroinitializer)
ret i32 %x
Expand All @@ -650,8 +658,7 @@ define i32 @smax_1() {

define i32 @smax_1_scalable_vector() {
; CHECK-LABEL: @smax_1_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.smax.nxv8i32(<vscale x 8 x i32> splat (i32 1))
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 1
;
%x = call i32 @llvm.vector.reduce.smax.nxv8i32(<vscale x 8 x i32> splat(i32 1))
ret i32 %x
Expand Down Expand Up @@ -710,8 +717,7 @@ define i32 @smax_poison() {

define i32 @smax_poison_scalable_vector() {
; CHECK-LABEL: @smax_poison_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.smax.nxv8i32(<vscale x 8 x i32> poison)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 poison
;
%x = call i32 @llvm.vector.reduce.smax.nxv8i32(<vscale x 8 x i32> poison)
ret i32 %x
Expand All @@ -735,8 +741,7 @@ define i32 @umin_0() {

define i32 @umin_0_scalable_vector() {
; CHECK-LABEL: @umin_0_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.umin.nxv8i32(<vscale x 8 x i32> zeroinitializer)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 0
;
%x = call i32 @llvm.vector.reduce.umin.nxv8i32(<vscale x 8 x i32> zeroinitializer)
ret i32 %x
Expand All @@ -752,8 +757,7 @@ define i32 @umin_1() {

define i32 @umin_1_scalable_vector() {
; CHECK-LABEL: @umin_1_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.umin.nxv8i32(<vscale x 8 x i32> splat (i32 1))
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 1
;
%x = call i32 @llvm.vector.reduce.umin.nxv8i32(<vscale x 8 x i32> splat (i32 1))
ret i32 %x
Expand Down Expand Up @@ -812,8 +816,7 @@ define i32 @umin_poison() {

define i32 @umin_poison_scalable_vector() {
; CHECK-LABEL: @umin_poison_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.umin.nxv8i32(<vscale x 8 x i32> poison)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 poison
;
%x = call i32 @llvm.vector.reduce.umin.nxv8i32(<vscale x 8 x i32> poison)
ret i32 %x
Expand All @@ -837,8 +840,7 @@ define i32 @umax_0() {

define i32 @umax_0_scalable_vector() {
; CHECK-LABEL: @umax_0_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.umax.nxv8i32(<vscale x 8 x i32> zeroinitializer)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 0
;
%x = call i32 @llvm.vector.reduce.umax.nxv8i32(<vscale x 8 x i32> zeroinitializer)
ret i32 %x
Expand All @@ -854,8 +856,7 @@ define i32 @umax_1() {

define i32 @umax_1_scalable_vector() {
; CHECK-LABEL: @umax_1_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.umax.nxv8i32(<vscale x 8 x i32> splat (i32 1))
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 1
;
%x = call i32 @llvm.vector.reduce.umax.nxv8i32(<vscale x 8 x i32> splat(i32 1))
ret i32 %x
Expand Down Expand Up @@ -914,8 +915,7 @@ define i32 @umax_poison() {

define i32 @umax_poison_scalable_vector() {
; CHECK-LABEL: @umax_poison_scalable_vector(
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.vector.reduce.umax.nxv8i32(<vscale x 8 x i32> poison)
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 poison
;
%x = call i32 @llvm.vector.reduce.umax.nxv8i32(<vscale x 8 x i32> poison)
ret i32 %x
Expand Down