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[InstCombine] Pull shuffles out of binops with splatted ops #137948

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Merged
merged 5 commits into from
May 12, 2025
Merged

[InstCombine] Pull shuffles out of binops with splatted ops #137948

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5ebf099
Precommit tests
lukel97 Apr 30, 2025
8522d21
[InstCombine] Pull shuffles out of binops with splatted ops
lukel97 Apr 30, 2025
401ffa6
Reuse createBinOpShuffle
lukel97 Apr 30, 2025
e9d51e7
Update comment, add test for ub
lukel97 Apr 30, 2025
be22d12
Merge branch 'main' into instcombine/foldVectorBinop-shuffle-scalable
lukel97 May 12, 2025
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21 changes: 21 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
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Expand Up @@ -2271,6 +2271,27 @@ Instruction *InstCombinerImpl::foldVectorBinop(BinaryOperator &Inst) {
}
}

// Similar to the combine above, but handles the case for scalable vectors
// where both V1 and C are splats.
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// where both V1 and C are splats.
// where both shuffle(V1, 0) and C are splats.

V1 is not required to be a splat vector.

//
// Op(shuffle(V1, 0), (splat C)) -> shuffle(Op(V1, (splat C)), 0)
if (isa<ScalableVectorType>(Inst.getType()) &&
match(&Inst, m_c_BinOp(m_OneUse(m_Shuffle(m_Value(V1), m_Poison(),
m_ZeroMask())),
m_ImmConstant(C)))) {
if (Constant *Splat = C->getSplatValue()) {
bool ConstOp1 = isa<Constant>(RHS);
VectorType *V1Ty = cast<VectorType>(V1->getType());
Constant *NewC = ConstantVector::getSplat(V1Ty->getElementCount(), Splat);

Value *NewLHS = ConstOp1 ? V1 : NewC;
Value *NewRHS = ConstOp1 ? NewC : V1;
VectorType *VTy = cast<VectorType>(Inst.getType());
SmallVector<int> Mask(VTy->getElementCount().getKnownMinValue(), 0);
return createBinOpShuffle(NewLHS, NewRHS, Mask);
}
}

// Try to reassociate to sink a splat shuffle after a binary operation.
if (Inst.isAssociative() && Inst.isCommutative()) {
// Canonicalize shuffle operand as LHS.
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4 changes: 2 additions & 2 deletions llvm/test/Transforms/InstCombine/getelementptr.ll
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Expand Up @@ -282,8 +282,8 @@ define <2 x i1> @test13_fixed_scalable(i64 %X, ptr %P, <2 x i64> %y) nounwind {
define <vscale x 2 x i1> @test13_scalable_scalable(i64 %X, ptr %P, <vscale x 2 x i64> %y) nounwind {
; CHECK-LABEL: @test13_scalable_scalable(
; CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <vscale x 2 x i64> poison, i64 [[X:%.*]], i64 0
; CHECK-NEXT: [[DOTSPLAT:%.*]] = shufflevector <vscale x 2 x i64> [[DOTSPLATINSERT]], <vscale x 2 x i64> poison, <vscale x 2 x i32> zeroinitializer
; CHECK-NEXT: [[A_IDX:%.*]] = shl nsw <vscale x 2 x i64> [[DOTSPLAT]], splat (i64 3)
; CHECK-NEXT: [[TMP3:%.*]] = shl nsw <vscale x 2 x i64> [[DOTSPLATINSERT]], splat (i64 3)
; CHECK-NEXT: [[A_IDX:%.*]] = shufflevector <vscale x 2 x i64> [[TMP3]], <vscale x 2 x i64> poison, <vscale x 2 x i32> zeroinitializer
; CHECK-NEXT: [[TMP1:%.*]] = call i64 @llvm.vscale.i64()
; CHECK-NEXT: [[TMP2:%.*]] = shl i64 [[TMP1]], 4
; CHECK-NEXT: [[DOTSPLATINSERT1:%.*]] = insertelement <vscale x 2 x i64> poison, i64 [[TMP2]], i64 0
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23 changes: 23 additions & 0 deletions llvm/test/Transforms/InstCombine/vec_shuffle-inseltpoison.ll
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Expand Up @@ -1789,3 +1789,26 @@ define <4 x i32> @PR46872(<4 x i32> %x) {
ret <4 x i32> %a
}

define <vscale x 4 x i32> @scalable_splat_binop_constant_rhs(<vscale x 4 x i32> %x) {
; CHECK-LABEL: @scalable_splat_binop_constant_rhs(
; CHECK-NEXT: [[R1:%.*]] = add <vscale x 4 x i32> [[R:%.*]], splat (i32 42)
; CHECK-NEXT: [[R2:%.*]] = shufflevector <vscale x 4 x i32> [[R1]], <vscale x 4 x i32> poison, <vscale x 4 x i32> zeroinitializer
; CHECK-NEXT: ret <vscale x 4 x i32> [[R2]]
;

%splatx = shufflevector <vscale x 4 x i32> %x, <vscale x 4 x i32> poison, <vscale x 4 x i32> zeroinitializer
%r = add <vscale x 4 x i32> %splatx, splat (i32 42)
ret <vscale x 4 x i32> %r
}

define <vscale x 4 x float> @scalable_splat_binop_constant_lhs(<vscale x 4 x float> %x) {
; CHECK-LABEL: @scalable_splat_binop_constant_lhs(
; CHECK-NEXT: [[R1:%.*]] = fadd <vscale x 4 x float> [[R:%.*]], splat (float 4.200000e+01)
; CHECK-NEXT: [[R2:%.*]] = shufflevector <vscale x 4 x float> [[R1]], <vscale x 4 x float> poison, <vscale x 4 x i32> zeroinitializer
; CHECK-NEXT: ret <vscale x 4 x float> [[R2]]
;

%splatx = shufflevector <vscale x 4 x float> %x, <vscale x 4 x float> poison, <vscale x 4 x i32> zeroinitializer
%r = fadd <vscale x 4 x float> splat (float 42.0), %splatx
ret <vscale x 4 x float> %r
}