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[InstCombine] fold shuffles with FP<->Int cast operands

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shuffle (cast X), (cast Y), Mask --> cast (shuffle X, Y, Mask)

This is similar to a recent transform with fneg ( b331a7ebc1 ),
but this is intentionally the most conservative first step to
try to avoid regressions in codegen. There are several
restrictions that could be removed as follow-up enhancements.

Note that a cast with a unary shuffle is currently canonicalized
in the other direction (shuffle after cast - D103038 ). We might
want to invert that to be consistent with this patch.
This commit is contained in:
Sanjay Patel
2022-05-10 14:20:43 -04:00
parent aca33294de
commit 0353c2c996
2 changed files with 75 additions and 12 deletions
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51
llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
View File

@@ -2275,6 +2275,54 @@ static Instruction *foldFNegShuffle(ShuffleVectorInst &Shuf,
return nullptr;
}
/// Canonicalize casts after shuffle.
static Instruction *foldCastShuffle(ShuffleVectorInst &Shuf,
InstCombiner::BuilderTy &Builder) {
// Do we have 2 matching cast operands?
auto *Cast0 = dyn_cast<CastInst>(Shuf.getOperand(0));
auto *Cast1 = dyn_cast<CastInst>(Shuf.getOperand(1));
if (!Cast0 || !Cast1 || Cast0->getOpcode() != Cast1->getOpcode() ||
Cast0->getSrcTy() != Cast1->getSrcTy())
return nullptr;
// TODO: Allow other opcodes? That would require easing the type restrictions
// below here.
CastInst::CastOps CastOpcode = Cast0->getOpcode();
switch (CastOpcode) {
case Instruction::FPToSI:
case Instruction::FPToUI:
case Instruction::SIToFP:
case Instruction::UIToFP:
break;
default:
return nullptr;
}
VectorType *ShufTy = Shuf.getType();
VectorType *ShufOpTy = cast<VectorType>(Shuf.getOperand(0)->getType());
VectorType *CastSrcTy = cast<VectorType>(Cast0->getSrcTy());
// TODO: Allow length-changing shuffles?
if (ShufTy != ShufOpTy)
return nullptr;
// TODO: Allow element-size-changing casts?
assert(isa<FixedVectorType>(CastSrcTy) && isa<FixedVectorType>(ShufOpTy) &&
"Expected fixed vector operands for casts and binary shuffle");
if (CastSrcTy->getPrimitiveSizeInBits() != ShufOpTy->getPrimitiveSizeInBits())
return nullptr;
// At least one of the operands must have only one use (the shuffle).
if (!Cast0->hasOneUse() && !Cast1->hasOneUse())
return nullptr;
// shuffle (cast X), (cast Y), Mask --> cast (shuffle X, Y, Mask)
Value *X = Cast0->getOperand(0);
Value *Y = Cast1->getOperand(0);
Value *NewShuf = Builder.CreateShuffleVector(X, Y, Shuf.getShuffleMask());
return CastInst::Create(CastOpcode, NewShuf, ShufTy);
}
/// Try to fold an extract subvector operation.
static Instruction *foldIdentityExtractShuffle(ShuffleVectorInst &Shuf) {
Value *Op0 = Shuf.getOperand(0), *Op1 = Shuf.getOperand(1);
@@ -2573,6 +2621,9 @@ Instruction *InstCombinerImpl::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
if (Instruction *I = foldFNegShuffle(SVI, Builder))
return I;
if (Instruction *I = foldCastShuffle(SVI, Builder))
return I;
APInt UndefElts(VWidth, 0);
APInt AllOnesEltMask(APInt::getAllOnes(VWidth));
if (Value *V = SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) {

36
llvm/test/Transforms/InstCombine/vec_shuffle.ll
View File

@@ -2038,9 +2038,8 @@ define <2 x half> @uitofp_unary_shuf_narrow_narrow_elts(<4 x i32> %x) {
define <4 x i32> @fptosi_shuf(<4 x float> %x, <4 x float> %y) {
; CHECK-LABEL: @fptosi_shuf(
; CHECK-NEXT: [[NX:%.*]] = fptosi <4 x float> [[X:%.*]] to <4 x i32>
; CHECK-NEXT: [[NY:%.*]] = fptosi <4 x float> [[Y:%.*]] to <4 x i32>
; CHECK-NEXT: [[R:%.*]] = shufflevector <4 x i32> [[NX]], <4 x i32> [[NY]], <4 x i32> <i32 0, i32 1, i32 4, i32 5>
; CHECK-NEXT: [[TMP1:%.*]] = shufflevector <4 x float> [[X:%.*]], <4 x float> [[Y:%.*]], <4 x i32> <i32 0, i32 1, i32 4, i32 5>
; CHECK-NEXT: [[R:%.*]] = fptosi <4 x float> [[TMP1]] to <4 x i32>
; CHECK-NEXT: ret <4 x i32> [[R]]
;
%nx = fptosi <4 x float> %x to <4 x i32>
@@ -2051,9 +2050,8 @@ define <4 x i32> @fptosi_shuf(<4 x float> %x, <4 x float> %y) {
define <3 x i16> @fptoui_shuf(<3 x half> %x, <3 x half> %y) {
; CHECK-LABEL: @fptoui_shuf(
; CHECK-NEXT: [[NX:%.*]] = fptoui <3 x half> [[X:%.*]] to <3 x i16>
; CHECK-NEXT: [[NY:%.*]] = fptoui <3 x half> [[Y:%.*]] to <3 x i16>
; CHECK-NEXT: [[R:%.*]] = shufflevector <3 x i16> [[NX]], <3 x i16> [[NY]], <3 x i32> <i32 0, i32 undef, i32 4>
; CHECK-NEXT: [[TMP1:%.*]] = shufflevector <3 x half> [[X:%.*]], <3 x half> [[Y:%.*]], <3 x i32> <i32 0, i32 undef, i32 4>
; CHECK-NEXT: [[R:%.*]] = fptoui <3 x half> [[TMP1]] to <3 x i16>
; CHECK-NEXT: ret <3 x i16> [[R]]
;
%nx = fptoui <3 x half> %x to <3 x i16>
@@ -2062,6 +2060,8 @@ define <3 x i16> @fptoui_shuf(<3 x half> %x, <3 x half> %y) {
ret <3 x i16> %r
}
; negative test - must have same source types
define <3 x i16> @fptoui_shuf_different_source_types(<3 x float> %x, <3 x half> %y) {
; CHECK-LABEL: @fptoui_shuf_different_source_types(
; CHECK-NEXT: [[NX:%.*]] = fptoui <3 x float> [[X:%.*]] to <3 x i16>
@@ -2075,6 +2075,8 @@ define <3 x i16> @fptoui_shuf_different_source_types(<3 x float> %x, <3 x half>
ret <3 x i16> %r
}
; negative test - must have same size elements
define <4 x i32> @fptoui_shuf_widen_elts(<4 x half> %x, <4 x half> %y) {
; CHECK-LABEL: @fptoui_shuf_widen_elts(
; CHECK-NEXT: [[NX:%.*]] = fptosi <4 x half> [[X:%.*]] to <4 x i32>
@@ -2088,6 +2090,8 @@ define <4 x i32> @fptoui_shuf_widen_elts(<4 x half> %x, <4 x half> %y) {
ret <4 x i32> %r
}
; negative test - must have same size elements
define <4 x float> @sitofp_shuf_narrow_elts(<4 x i64> %x, <4 x i64> %y) {
; CHECK-LABEL: @sitofp_shuf_narrow_elts(
; CHECK-NEXT: [[NX:%.*]] = sitofp <4 x i64> [[X:%.*]] to <4 x float>
@@ -2101,12 +2105,14 @@ define <4 x float> @sitofp_shuf_narrow_elts(<4 x i64> %x, <4 x i64> %y) {
ret <4 x float> %r
}
; one extra use is ok
define <4 x float> @uitofp_shuf_extra_use1(<4 x i32> %x, <4 x i32> %y) {
; CHECK-LABEL: @uitofp_shuf_extra_use1(
; CHECK-NEXT: [[NX:%.*]] = uitofp <4 x i32> [[X:%.*]] to <4 x float>
; CHECK-NEXT: call void @use4(<4 x float> [[NX]])
; CHECK-NEXT: [[NY:%.*]] = uitofp <4 x i32> [[Y:%.*]] to <4 x float>
; CHECK-NEXT: [[R:%.*]] = shufflevector <4 x float> [[NX]], <4 x float> [[NY]], <4 x i32> <i32 0, i32 0, i32 4, i32 5>
; CHECK-NEXT: [[TMP1:%.*]] = shufflevector <4 x i32> [[X]], <4 x i32> [[Y:%.*]], <4 x i32> <i32 0, i32 0, i32 4, i32 5>
; CHECK-NEXT: [[R:%.*]] = uitofp <4 x i32> [[TMP1]] to <4 x float>
; CHECK-NEXT: ret <4 x float> [[R]]
;
%nx = uitofp <4 x i32> %x to <4 x float>
@@ -2116,12 +2122,14 @@ define <4 x float> @uitofp_shuf_extra_use1(<4 x i32> %x, <4 x i32> %y) {
ret <4 x float> %r
}
; one extra use is ok
define <4 x float> @sitofp_shuf_extra_use2(<4 x i32> %x, <4 x i32> %y) {
; CHECK-LABEL: @sitofp_shuf_extra_use2(
; CHECK-NEXT: [[NX:%.*]] = sitofp <4 x i32> [[X:%.*]] to <4 x float>
; CHECK-NEXT: [[NY:%.*]] = sitofp <4 x i32> [[Y:%.*]] to <4 x float>
; CHECK-NEXT: call void @use4(<4 x float> [[NY]])
; CHECK-NEXT: [[R:%.*]] = shufflevector <4 x float> [[NX]], <4 x float> [[NY]], <4 x i32> <i32 7, i32 1, i32 4, i32 0>
; CHECK-NEXT: [[TMP1:%.*]] = shufflevector <4 x i32> [[X:%.*]], <4 x i32> [[Y]], <4 x i32> <i32 7, i32 1, i32 4, i32 0>
; CHECK-NEXT: [[R:%.*]] = sitofp <4 x i32> [[TMP1]] to <4 x float>
; CHECK-NEXT: ret <4 x float> [[R]]
;
%nx = sitofp <4 x i32> %x to <4 x float>
@@ -2131,6 +2139,8 @@ define <4 x float> @sitofp_shuf_extra_use2(<4 x i32> %x, <4 x i32> %y) {
ret <4 x float> %r
}
; negative test - both ops have extra uses
define <2 x float> @sitofp_shuf_extra_use3(<2 x i32> %x, <2 x i32> %y) {
; CHECK-LABEL: @sitofp_shuf_extra_use3(
; CHECK-NEXT: [[NX:%.*]] = sitofp <2 x i32> [[X:%.*]] to <2 x float>
@@ -2148,6 +2158,8 @@ define <2 x float> @sitofp_shuf_extra_use3(<2 x i32> %x, <2 x i32> %y) {
ret <2 x float> %r
}
; negative test - mismatched casts
define <4 x i32> @fptoi_shuf(<4 x float> %x, <4 x float> %y) {
; CHECK-LABEL: @fptoi_shuf(
; CHECK-NEXT: [[NX:%.*]] = fptoui <4 x float> [[X:%.*]] to <4 x i32>
@@ -2161,7 +2173,7 @@ define <4 x i32> @fptoi_shuf(<4 x float> %x, <4 x float> %y) {
ret <4 x i32> %r
}
; length-changing shuffle
; negative test - length-changing shuffle
define <4 x float> @sitofp_shuf_widen(<2 x i32> %x, <2 x i32> %y) {
; CHECK-LABEL: @sitofp_shuf_widen(
@@ -2176,7 +2188,7 @@ define <4 x float> @sitofp_shuf_widen(<2 x i32> %x, <2 x i32> %y) {
ret <4 x float> %r
}
; length-changing shuffle
; negative test - length-changing shuffle
define <2 x float> @uitofp_shuf_narrow(<4 x i32> %x, <4 x i32> %y) {
; CHECK-LABEL: @uitofp_shuf_narrow(