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[InstCombine] Fix missed opportunity to fold 'or' into 'mul' operand. #74225

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Merged
merged 2 commits into from
Dec 3, 2023
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[InstCombine] Fix missed opportunity to fold 'or' into 'mul' operand. #74225

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[InstCombine] Add test for missed opportunity to fold 'or' into 'mul'…
topperc Dec 3, 2023
1810087
[InstCombine] Fix missed opportunity to fold 'or' into 'mul' operand.
topperc Dec 3, 2023
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2 changes: 1 addition & 1 deletion llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3394,7 +3394,7 @@ Instruction *InstCombinerImpl::visitOr(BinaryOperator &I) {
// If the operands have no common bits set:
// or (mul X, Y), X --> add (mul X, Y), X --> mul X, (Y + 1)
if (match(&I,
m_c_Or(m_OneUse(m_Mul(m_Value(X), m_Value(Y))), m_Deferred(X))) &&
m_c_Or(m_Value(X), m_OneUse(m_c_Mul(m_Deferred(X), m_Value(Y))))) &&
haveNoCommonBitsSet(Op0, Op1, DL)) {
Value *IncrementY = Builder.CreateAdd(Y, ConstantInt::get(Ty, 1));
return BinaryOperator::CreateMul(X, IncrementY);
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15 changes: 15 additions & 0 deletions llvm/test/Transforms/InstCombine/or.ll
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Expand Up @@ -1511,6 +1511,21 @@ define <2 x i12> @mul_no_common_bits_commute(<2 x i12> %p) {
ret <2 x i12> %r
}

define i32 @mul_no_common_bits_commute2(i32 %p1, i32 %p2) {
; CHECK-LABEL: @mul_no_common_bits_commute2(
; CHECK-NEXT: [[X:%.*]] = and i32 [[P1:%.*]], 7
; CHECK-NEXT: [[Y:%.*]] = shl i32 [[P2:%.*]], 3
; CHECK-NEXT: [[TMP1:%.*]] = or disjoint i32 [[Y]], 1
; CHECK-NEXT: [[R:%.*]] = mul i32 [[X]], [[TMP1]]
; CHECK-NEXT: ret i32 [[R]]
;
%x = and i32 %p1, 7
%y = shl i32 %p2, 3
%m = mul i32 %y, %x
%r = or i32 %m, %x
ret i32 %r
}

; negative test - extra use requires extra instructions

define i32 @mul_no_common_bits_uses(i32 %p1, i32 %p2) {
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