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[InstSimplify] Add basic simplifications for vp.reverse #144112

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Merged
merged 1 commit into from
Jun 16, 2025
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[InstSimplify] Add basic simplifications for vp.reverse #144112

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17 changes: 17 additions & 0 deletions llvm/lib/Analysis/InstructionSimplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6969,6 +6969,23 @@ static Value *simplifyIntrinsic(CallBase *Call, Value *Callee,
}
return nullptr;
}
case Intrinsic::experimental_vp_reverse: {
Value *Vec = Call->getArgOperand(0);
Value *Mask = Call->getArgOperand(1);
Value *EVL = Call->getArgOperand(2);

Value *X;
// vp.reverse(vp.reverse(X)) == X (with all ones mask and matching EVL)
if (match(Mask, m_AllOnes()) &&
match(Vec, m_Intrinsic<Intrinsic::experimental_vp_reverse>(
m_Value(X), m_AllOnes(), m_Specific(EVL))))
return X;

// vp.reverse(splat(X)) -> splat(X) (regardless of mask and EVL)
if (isSplatValue(Vec))
return Vec;
return nullptr;
}
default:
return nullptr;
}
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19 changes: 6 additions & 13 deletions llvm/test/Transforms/InstSimplify/vp-reverse.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -3,9 +3,7 @@

define <vscale x 4 x i32> @rev_of_rev(<vscale x 4 x i32> %a, i32 %evl) {
; CHECK-LABEL: @rev_of_rev(
; CHECK-NEXT: [[A_REV:%.*]] = tail call <vscale x 4 x i32> @llvm.experimental.vp.reverse.nxv4i32(<vscale x 4 x i32> [[A:%.*]], <vscale x 4 x i1> splat (i1 true), i32 [[EVL:%.*]])
; CHECK-NEXT: [[RES:%.*]] = tail call <vscale x 4 x i32> @llvm.experimental.vp.reverse.nxv4i32(<vscale x 4 x i32> [[A_REV]], <vscale x 4 x i1> splat (i1 true), i32 [[EVL]])
; CHECK-NEXT: ret <vscale x 4 x i32> [[RES]]
; CHECK-NEXT: ret <vscale x 4 x i32> [[A:%.*]]
;
%a.rev = tail call <vscale x 4 x i32> @llvm.experimental.vp.reverse(<vscale x 4 x i32> %a, <vscale x 4 x i1> splat (i1 true), i32 %evl)
%res = tail call <vscale x 4 x i32> @llvm.experimental.vp.reverse(<vscale x 4 x i32> %a.rev, <vscale x 4 x i1> splat (i1 true), i32 %evl)
Expand All @@ -25,26 +23,23 @@ define <vscale x 4 x i32> @rev_of_rev_diffevl(<vscale x 4 x i32> %a, i32 %evl) {

define <vscale x 4 x i32> @rev_of_poison(i32 %evl) {
; CHECK-LABEL: @rev_of_poison(
; CHECK-NEXT: [[REV:%.*]] = tail call <vscale x 4 x i32> @llvm.experimental.vp.reverse.nxv4i32(<vscale x 4 x i32> poison, <vscale x 4 x i1> splat (i1 true), i32 [[EVL:%.*]])
; CHECK-NEXT: ret <vscale x 4 x i32> [[REV]]
; CHECK-NEXT: ret <vscale x 4 x i32> poison
;
%rev = tail call <vscale x 4 x i32> @llvm.experimental.vp.reverse(<vscale x 4 x i32> poison, <vscale x 4 x i1> splat (i1 true), i32 %evl)
ret <vscale x 4 x i32> %rev
}

define <vscale x 4 x i32> @rev_of_undef(i32 %evl) {
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We don't need undef tests. There are many PRs that drop undef tests...

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I want to push back a bit here. There's a big difference between removing undef from tests where the undef is the result of reduction, or doesn't reflect test intention. This case is specifically testing correct behavior of an undef fold. I would hope we are not removing such cases, that would seem actively undesirable.

; CHECK-LABEL: @rev_of_undef(
; CHECK-NEXT: [[REV:%.*]] = tail call <vscale x 4 x i32> @llvm.experimental.vp.reverse.nxv4i32(<vscale x 4 x i32> undef, <vscale x 4 x i1> splat (i1 true), i32 [[EVL:%.*]])
; CHECK-NEXT: ret <vscale x 4 x i32> [[REV]]
; CHECK-NEXT: ret <vscale x 4 x i32> undef
;
%rev = tail call <vscale x 4 x i32> @llvm.experimental.vp.reverse(<vscale x 4 x i32> undef, <vscale x 4 x i1> splat (i1 true), i32 %evl)
ret <vscale x 4 x i32> %rev
}

define <vscale x 4 x i32> @rev_of_zero(i32 %evl) {
; CHECK-LABEL: @rev_of_zero(
; CHECK-NEXT: [[REV:%.*]] = tail call <vscale x 4 x i32> @llvm.experimental.vp.reverse.nxv4i32(<vscale x 4 x i32> zeroinitializer, <vscale x 4 x i1> splat (i1 true), i32 [[EVL:%.*]])
; CHECK-NEXT: ret <vscale x 4 x i32> [[REV]]
; CHECK-NEXT: ret <vscale x 4 x i32> zeroinitializer
;
%rev = tail call <vscale x 4 x i32> @llvm.experimental.vp.reverse(<vscale x 4 x i32> zeroinitializer, <vscale x 4 x i1> splat (i1 true), i32 %evl)
ret <vscale x 4 x i32> %rev
Expand All @@ -54,8 +49,7 @@ define <vscale x 4 x i32> @rev_of_splat(i32 %a, i32 %evl) {
; CHECK-LABEL: @rev_of_splat(
; CHECK-NEXT: [[A_INS:%.*]] = insertelement <vscale x 4 x i32> poison, i32 [[A:%.*]], i32 0
; CHECK-NEXT: [[A_VEC:%.*]] = shufflevector <vscale x 4 x i32> [[A_INS]], <vscale x 4 x i32> poison, <vscale x 4 x i32> zeroinitializer
; CHECK-NEXT: [[REV:%.*]] = tail call <vscale x 4 x i32> @llvm.experimental.vp.reverse.nxv4i32(<vscale x 4 x i32> [[A_VEC]], <vscale x 4 x i1> splat (i1 true), i32 [[EVL:%.*]])
; CHECK-NEXT: ret <vscale x 4 x i32> [[REV]]
; CHECK-NEXT: ret <vscale x 4 x i32> [[A_VEC]]
;
%a.ins = insertelement <vscale x 4 x i32> poison, i32 %a, i32 0
%a.vec = shufflevector <vscale x 4 x i32> %a.ins, <vscale x 4 x i32> poison, <vscale x 4 x i32> zeroinitializer
Expand All @@ -67,8 +61,7 @@ define <vscale x 4 x i32> @rev_of_splat2(i32 %a, <vscale x 4 x i1> %m, i32 %evl)
; CHECK-LABEL: @rev_of_splat2(
; CHECK-NEXT: [[A_INS:%.*]] = insertelement <vscale x 4 x i32> poison, i32 [[A:%.*]], i32 0
; CHECK-NEXT: [[A_VEC:%.*]] = shufflevector <vscale x 4 x i32> [[A_INS]], <vscale x 4 x i32> poison, <vscale x 4 x i32> zeroinitializer
; CHECK-NEXT: [[REV:%.*]] = tail call <vscale x 4 x i32> @llvm.experimental.vp.reverse.nxv4i32(<vscale x 4 x i32> [[A_VEC]], <vscale x 4 x i1> [[M:%.*]], i32 [[EVL:%.*]])
; CHECK-NEXT: ret <vscale x 4 x i32> [[REV]]
; CHECK-NEXT: ret <vscale x 4 x i32> [[A_VEC]]
;
%a.ins = insertelement <vscale x 4 x i32> poison, i32 %a, i32 0
%a.vec = shufflevector <vscale x 4 x i32> %a.ins, <vscale x 4 x i32> poison, <vscale x 4 x i32> zeroinitializer
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