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[InstCombine] Guard noundef for transformation from xor to or disjoint #96905

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Merged
merged 2 commits into from
Jul 3, 2024
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[InstCombine] Guard noundef for transformation from xor to or disjoint #96905

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2be397a
[InstCombine] Guard noundef for transformation from xor to or disjoint
vfdff Jun 27, 2024
99be294
It is safe with Poison
vfdff Jun 27, 2024
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8 changes: 6 additions & 2 deletions llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4593,8 +4593,12 @@ Instruction *InstCombinerImpl::visitXor(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
Value *M;
if (match(&I, m_c_Xor(m_c_And(m_Not(m_Value(M)), m_Value()),
m_c_And(m_Deferred(M), m_Value()))))
return BinaryOperator::CreateDisjointOr(Op0, Op1);
m_c_And(m_Deferred(M), m_Value())))) {
if (isGuaranteedNotToBeUndef(M))
return BinaryOperator::CreateDisjointOr(Op0, Op1);
else
return BinaryOperator::CreateOr(Op0, Op1);
}

if (Instruction *Xor = visitMaskedMerge(I, Builder))
return Xor;
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32 changes: 32 additions & 0 deletions llvm/test/Transforms/InstCombine/xor.ll
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Expand Up @@ -1453,3 +1453,35 @@ define i32 @tryFactorization_xor_ashr_ashr(i32 %a) {
%xor = xor i32 %not, %shr1
ret i32 %xor
}

; https://alive2.llvm.org/ce/z/SOxv-e
define i4 @PR96857_xor_with_noundef(i4 %val0, i4 %val1, i4 noundef %val2) {
; CHECK-LABEL: @PR96857_xor_with_noundef(
; CHECK-NEXT: [[VAL4:%.*]] = and i4 [[VAL2:%.*]], [[VAL0:%.*]]
; CHECK-NEXT: [[VAL5:%.*]] = xor i4 [[VAL2]], -1
; CHECK-NEXT: [[VAL6:%.*]] = and i4 [[VAL5]], [[VAL1:%.*]]
; CHECK-NEXT: [[VAL7:%.*]] = or disjoint i4 [[VAL4]], [[VAL6]]
; CHECK-NEXT: ret i4 [[VAL7]]
;
%val4 = and i4 %val2, %val0
%val5 = xor i4 %val2, -1
%val6 = and i4 %val5, %val1
%val7 = xor i4 %val4, %val6
ret i4 %val7
}

; https://alive2.llvm.org/ce/z/whLTaJ
define i4 @PR96857_xor_without_noundef(i4 %val0, i4 %val1, i4 %val2) {
; CHECK-LABEL: @PR96857_xor_without_noundef(
; CHECK-NEXT: [[VAL4:%.*]] = and i4 [[VAL2:%.*]], [[VAL0:%.*]]
; CHECK-NEXT: [[VAL5:%.*]] = xor i4 [[VAL2]], -1
; CHECK-NEXT: [[VAL6:%.*]] = and i4 [[VAL5]], [[VAL1:%.*]]
; CHECK-NEXT: [[VAL7:%.*]] = or i4 [[VAL4]], [[VAL6]]
; CHECK-NEXT: ret i4 [[VAL7]]
;
%val4 = and i4 %val2, %val0
%val5 = xor i4 %val2, -1
%val6 = and i4 %val5, %val1
%val7 = xor i4 %val4, %val6
ret i4 %val7
}