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[InstComb] Handle undef in simplifyMasked(Store|Scatter) #161825

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Merged
merged 2 commits into from
Oct 3, 2025
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[InstComb] Handle undef in simplifyMasked(Store|Scatter) #161825

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ca11ce7
[InstComb] Pre-commit tests for masked_intrinsics
artagnon Oct 3, 2025
da5a889
[InstComb] Handle undef in simplifyMasked(Store|Scatter)
artagnon Oct 3, 2025
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10 changes: 5 additions & 5 deletions llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -318,18 +318,18 @@ Value *InstCombinerImpl::simplifyMaskedLoad(IntrinsicInst &II) {
// * Single constant active lane -> store
// * Narrow width by halfs excluding zero/undef lanes
Instruction *InstCombinerImpl::simplifyMaskedStore(IntrinsicInst &II) {
Value *StorePtr = II.getArgOperand(1);
Align Alignment = cast<ConstantInt>(II.getArgOperand(2))->getAlignValue();
auto *ConstMask = dyn_cast<Constant>(II.getArgOperand(3));
if (!ConstMask)
return nullptr;

// If the mask is all zeros, this instruction does nothing.
if (ConstMask->isNullValue())
if (maskIsAllZeroOrUndef(ConstMask))
return eraseInstFromFunction(II);

// If the mask is all ones, this is a plain vector store of the 1st argument.
if (ConstMask->isAllOnesValue()) {
Value *StorePtr = II.getArgOperand(1);
Align Alignment = cast<ConstantInt>(II.getArgOperand(2))->getAlignValue();
if (maskIsAllOneOrUndef(ConstMask)) {
StoreInst *S =
new StoreInst(II.getArgOperand(0), StorePtr, false, Alignment);
S->copyMetadata(II);
Expand Down Expand Up @@ -389,7 +389,7 @@ Instruction *InstCombinerImpl::simplifyMaskedScatter(IntrinsicInst &II) {
return nullptr;

// If the mask is all zeros, a scatter does nothing.
if (ConstMask->isNullValue())
if (maskIsAllZeroOrUndef(ConstMask))
return eraseInstFromFunction(II);

// Vector splat address -> scalar store
Expand Down
58 changes: 58 additions & 0 deletions llvm/test/Transforms/InstCombine/masked_intrinsics.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,14 @@ define <2 x double> @load_zeromask(ptr %ptr, <2 x double> %passthru) {
ret <2 x double> %res
}

define <2 x double> @load_zero_withpoison_mask(ptr %ptr, <2 x double> %passthru) {
; CHECK-LABEL: @load_zero_withpoison_mask(
; CHECK-NEXT: ret <2 x double> [[PASSTHRU:%.*]]
;
%res = call <2 x double> @llvm.masked.load.v2f64.p0(ptr %ptr, i32 1, <2 x i1> <i1 0, i1 poison>, <2 x double> %passthru)
ret <2 x double> %res
}

define <2 x double> @load_onemask(ptr %ptr, <2 x double> %passthru) {
; CHECK-LABEL: @load_onemask(
; CHECK-NEXT: [[UNMASKEDLOAD:%.*]] = load <2 x double>, ptr [[PTR:%.*]], align 2
Expand Down Expand Up @@ -150,6 +158,14 @@ define void @store_zeromask(ptr %ptr, <2 x double> %val) {
ret void
}

define void @store_poisonmask(ptr %ptr, <2 x double> %val) {
; CHECK-LABEL: @store_poisonmask(
; CHECK-NEXT: ret void
;
call void @llvm.masked.store.v2f64.p0(<2 x double> %val, ptr %ptr, i32 4, <2 x i1> splat(i1 poison))
ret void
}

define void @store_onemask(ptr %ptr, <2 x double> %val) {
; CHECK-LABEL: @store_onemask(
; CHECK-NEXT: store <2 x double> [[VAL:%.*]], ptr [[PTR:%.*]], align 4
Expand All @@ -159,6 +175,15 @@ define void @store_onemask(ptr %ptr, <2 x double> %val) {
ret void
}

define void @store_one_withpoison_mask(ptr %ptr, <2 x double> %val) {
; CHECK-LABEL: @store_one_withpoison_mask(
; CHECK-NEXT: store <2 x double> [[VAL:%.*]], ptr [[PTR:%.*]], align 4
; CHECK-NEXT: ret void
;
call void @llvm.masked.store.v2f64.p0(<2 x double> %val, ptr %ptr, i32 4, <2 x i1> <i1 1, i1 poison>)
ret void
}

define void @store_demandedelts(ptr %ptr, double %val) {
; CHECK-LABEL: @store_demandedelts(
; CHECK-NEXT: [[VALVEC1:%.*]] = insertelement <2 x double> poison, double [[VAL:%.*]], i64 0
Expand Down Expand Up @@ -189,6 +214,13 @@ define <2 x double> @gather_zeromask(<2 x ptr> %ptrs, <2 x double> %passthru) {
ret <2 x double> %res
}

define <2 x double> @gather_zero_withpoison_mask(<2 x ptr> %ptrs, <2 x double> %passthru) {
; CHECK-LABEL: @gather_zero_withpoison_mask(
; CHECK-NEXT: ret <2 x double> [[PASSTHRU:%.*]]
;
%res = call <2 x double> @llvm.masked.gather.v2f64.v2p0(<2 x ptr> %ptrs, i32 4, <2 x i1> <i1 0, i1 poison>, <2 x double> %passthru)
ret <2 x double> %res
}

define <2 x double> @gather_onemask(<2 x ptr> %ptrs, <2 x double> %passthru) {
; CHECK-LABEL: @gather_onemask(
Expand All @@ -199,6 +231,15 @@ define <2 x double> @gather_onemask(<2 x ptr> %ptrs, <2 x double> %passthru) {
ret <2 x double> %res
}

define <2 x double> @gather_one_withpoisonmask(<2 x ptr> %ptrs, <2 x double> %passthru) {
; CHECK-LABEL: @gather_one_withpoisonmask(
; CHECK-NEXT: [[RES:%.*]] = call <2 x double> @llvm.masked.gather.v2f64.v2p0(<2 x ptr> [[PTRS:%.*]], i32 4, <2 x i1> <i1 true, i1 poison>, <2 x double> [[PASSTHRU:%.*]])
; CHECK-NEXT: ret <2 x double> [[RES]]
;
%res = call <2 x double> @llvm.masked.gather.v2f64.v2p0(<2 x ptr> %ptrs, i32 4, <2 x i1> <i1 true, i1 poison>, <2 x double> %passthru)
ret <2 x double> %res
}

define <4 x double> @gather_lane2(ptr %base, double %pt) {
; CHECK-LABEL: @gather_lane2(
; CHECK-NEXT: [[PTRS:%.*]] = getelementptr double, ptr [[BASE:%.*]], <4 x i64> <i64 poison, i64 poison, i64 2, i64 poison>
Expand Down Expand Up @@ -257,6 +298,23 @@ define void @scatter_zeromask(<2 x ptr> %ptrs, <2 x double> %val) {
ret void
}

define void @scatter_zero_withpoison_mask(<2 x ptr> %ptrs, <2 x double> %val) {
; CHECK-LABEL: @scatter_zero_withpoison_mask(
; CHECK-NEXT: ret void
;
call void @llvm.masked.scatter.v2f64.v2p0(<2 x double> %val, <2 x ptr> %ptrs, i32 8, <2 x i1> <i1 0, i1 poison>)
ret void
}

define void @scatter_one_withpoison_mask(<2 x ptr> %ptrs, <2 x double> %val) {
; CHECK-LABEL: @scatter_one_withpoison_mask(
; CHECK-NEXT: call void @llvm.masked.scatter.v2f64.v2p0(<2 x double> [[VAL:%.*]], <2 x ptr> [[PTRS:%.*]], i32 8, <2 x i1> <i1 true, i1 poison>)
; CHECK-NEXT: ret void
;
call void @llvm.masked.scatter.v2f64.v2p0(<2 x double> %val, <2 x ptr> %ptrs, i32 8, <2 x i1> <i1 1, i1 poison>)
ret void
}

define void @scatter_demandedelts(ptr %ptr, double %val) {
; CHECK-LABEL: @scatter_demandedelts(
; CHECK-NEXT: [[PTRS:%.*]] = getelementptr double, ptr [[PTR:%.*]], <2 x i64> <i64 0, i64 poison>
Expand Down
2 changes: 0 additions & 2 deletions llvm/test/Transforms/InstCombine/pr83947.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,6 @@ define void @masked_scatter2() {

define void @masked_scatter3() {
; CHECK-LABEL: define void @masked_scatter3() {
; CHECK-NEXT: store i32 0, ptr @c, align 4
; CHECK-NEXT: ret void
;
call void @llvm.masked.scatter.v2i32.v2p0(<2 x i32> zeroinitializer, <2 x ptr> splat (ptr @c), i32 4, <2 x i1> undef)
Expand All @@ -50,7 +49,6 @@ define void @masked_scatter5() {

define void @masked_scatter6() {
; CHECK-LABEL: define void @masked_scatter6() {
; CHECK-NEXT: store i32 0, ptr @c, align 4
; CHECK-NEXT: ret void
;
call void @llvm.masked.scatter.v2i32.v2p0(<2 x i32> zeroinitializer, <2 x ptr> splat (ptr @c), i32 4, <2 x i1> <i1 undef, i1 false>)
Expand Down