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[DAG] isSplatValue - only treat binop splats shared undef elements as undef #135597

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Merged
merged 5 commits into from
Apr 15, 2025
Merged

[DAG] isSplatValue - only treat binop splats shared undef elements as undef #135597

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ec0a99f
[DAG] isSplatValue - only accept binop splats if they share all the s…
RKSimon Apr 14, 2025
4f5e866
Relax undef handling to just common undef elements
RKSimon Apr 14, 2025
f4c5629
Tweak comment
RKSimon Apr 14, 2025
4bda47b
Merge branch 'upstream' into dag-issplat-binop-undefs
RKSimon Apr 14, 2025
eff2091
Merge branch 'main' into dag-issplat-binop-undefs
RKSimon Apr 14, 2025
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5 changes: 4 additions & 1 deletion llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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Expand Up @@ -3002,9 +3002,12 @@ bool SelectionDAG::isSplatValue(SDValue V, const APInt &DemandedElts,
APInt UndefLHS, UndefRHS;
SDValue LHS = V.getOperand(0);
SDValue RHS = V.getOperand(1);
// Ensure common demanded undef elts for both operands, otherwise we might
// fail to handle binop-specific undef handling.
// e.g. (and undef, 0) -> 0 etc.
if (isSplatValue(LHS, DemandedElts, UndefLHS, Depth + 1) &&
isSplatValue(RHS, DemandedElts, UndefRHS, Depth + 1)) {
UndefElts = UndefLHS | UndefRHS;
UndefElts = UndefLHS & UndefRHS;
return true;
}
return false;
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3 changes: 1 addition & 2 deletions llvm/test/CodeGen/RISCV/rvv/fixed-vectors-buildvec-of-binop.ll
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Expand Up @@ -452,8 +452,7 @@ define void @buggy(i32 %0) #0 {
; RV64-NEXT: vsetivli zero, 4, e32, m1, ta, ma
; RV64-NEXT: vmv.v.x v8, a0
; RV64-NEXT: vor.vi v8, v8, 1
; RV64-NEXT: vrgather.vi v9, v8, 0
; RV64-NEXT: vse32.v v9, (zero)
; RV64-NEXT: vse32.v v8, (zero)
; RV64-NEXT: ret
entry:
%mul.us.us.i.3 = shl i32 %0, 1
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13 changes: 11 additions & 2 deletions llvm/test/CodeGen/X86/pr134602.ll
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Expand Up @@ -2,7 +2,7 @@
; RUN: llc < %s -mtriple=i686-- | FileCheck %s --check-prefix=X86
; RUN: llc < %s -mtriple=x86_64-- | FileCheck %s --check-prefix=X64

; FIXME: incorrect vector codegen due to bad handling of splats of binops containing undefs
; Test for incorrect vector codegen due to bad handling of splats of binops containing undefs
define i32 @PR134602(i16 %a0) {
; X86-LABEL: PR134602:
; X86: # %bb.0:
Expand All @@ -14,7 +14,16 @@ define i32 @PR134602(i16 %a0) {
;
; X64-LABEL: PR134602:
; X64: # %bb.0:
; X64-NEXT: xorl %eax, %eax
; X64-NEXT: movzwl %di, %eax
; X64-NEXT: movd %eax, %xmm0
; X64-NEXT: por {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
; X64-NEXT: pshuflw {{.*#+}} xmm1 = xmm0[2,2,2,2,4,5,6,7]
; X64-NEXT: paddw %xmm0, %xmm1
; X64-NEXT: movdqa %xmm1, %xmm0
; X64-NEXT: psrld $16, %xmm0
; X64-NEXT: paddw %xmm1, %xmm0
; X64-NEXT: movd %xmm0, %eax
; X64-NEXT: cwtl
; X64-NEXT: retq
%splat= insertelement <4 x i16> zeroinitializer, i16 %a0, i64 0
%mul = mul <4 x i16> %splat, <i16 1, i16 1, i16 0, i16 0>
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