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[InstCombine] Optimize 'xor-and/or-select' sequence to 'or' for bool #66394

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[InstCombine] Optimize 'xor-and/or-select' sequence to 'or' for bool #66394

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20 changes: 20 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3112,6 +3112,26 @@ Instruction *InstCombinerImpl::foldSelectOfBools(SelectInst &SI) {
return SelectInst::Create(FalseVal, One, AndV);
}

// select (~b & a), a, b -> or a, b
// only for scalar types
if (match(CondVal, m_c_And(m_Not(m_Specific(FalseVal)), m_Specific(TrueVal))) &&
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This pattern is similar to, but more specific than, the one on line 3109. You should probably move this transform above that one.

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Correction: Both your patterns are more specific than the ones between lines 3089 and 3109. Move your code above those.

TrueVal->getType()->isIntegerTy(1) &&
FalseVal->getType()->isIntegerTy(1) &&
CondVal->getType()->isIntegerTy(1) &&
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These scalar type checks are not necessary. When given vector operands, the select instruction will perform the selection element by element.

CondVal->hasOneUse()) {
return BinaryOperator::CreateOr(TrueVal, FalseVal);
}

// select (~b | a), a, b -> or a, b
// only for scalar types
if (match(CondVal, m_c_Or(m_Not(m_Specific(FalseVal)), m_Specific(TrueVal))) &&
TrueVal->getType()->isIntegerTy(1) &&
FalseVal->getType()->isIntegerTy(1) &&
CondVal->getType()->isIntegerTy(1) &&
CondVal->hasOneUse()) {
return BinaryOperator::CreateOr(TrueVal, FalseVal);
}

if (match(FalseVal, m_Zero()) || match(TrueVal, m_One())) {
Use *Y = nullptr;
bool IsAnd = match(FalseVal, m_Zero()) ? true : false;
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14 changes: 14 additions & 0 deletions llvm/test/Transforms/InstCombine/fold-xor-and-select-i1.ll
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@@ -0,0 +1,14 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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@bryanpkc bryanpkc Sep 15, 2023 •
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Add your tests into llvm/test/Transforms/InstCombine/select-and-or.ll, instead of creating new files.

; RUN: opt < %s -passes=instcombine -S | FileCheck %s

define i1 @max_if(i1 %a, i1 %b) {
; CHECK-LABEL: define i1 @max_if
; CHECK-SAME: (i1 [[A:%.*]], i1 [[B:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = or i1 [[A]], [[B]]
; CHECK-NEXT: ret i1 [[TMP1]]
;
%1 = xor i1 %b, true
%cmp = and i1 %1, %a
%2 = select i1 %cmp, i1 %a, i1 %b
ret i1 %2
}
14 changes: 14 additions & 0 deletions llvm/test/Transforms/InstCombine/fold-xor-or-select-i1.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -passes=instcombine -S | FileCheck %s

define i1 @max_if(i1 %a, i1 %b) {
; CHECK-LABEL: define i1 @max_if
; CHECK-SAME: (i1 [[A:%.*]], i1 [[B:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = or i1 [[A]], [[B]]
; CHECK-NEXT: ret i1 [[TMP1]]
;
%1 = xor i1 %b, true
%cmp = or i1 %1, %a
%2 = select i1 %cmp, i1 %a, i1 %b
ret i1 %2
}