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[ValueTracking] Infer X | Y != 0 from X != Y #117443

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Merged
merged 2 commits into from
Jun 15, 2025
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[ValueTracking] Infer X | Y != 0 from X != Y #117443

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2183f59
[ValueTracking] Infer `X | Y != 0` from `X != Y`
dtcxzyw Apr 28, 2025
da17850
[ValueTracking] Fix compilation error
dtcxzyw Jun 15, 2025
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4 changes: 4 additions & 0 deletions llvm/lib/Analysis/ValueTracking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3043,6 +3043,10 @@ static bool isKnownNonZeroFromOperator(const Operator *I,
// (X | (X != 0)) is non zero
if (matchOpWithOpEqZero(I->getOperand(0), I->getOperand(1)))
return true;
// X | Y != 0 if X != Y.
if (isKnownNonEqual(I->getOperand(0), I->getOperand(1), DemandedElts, Q,
Depth))
return true;
// X | Y != 0 if X != 0 or Y != 0.
return isKnownNonZero(I->getOperand(1), DemandedElts, Q, Depth) ||
isKnownNonZero(I->getOperand(0), DemandedElts, Q, Depth);
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5 changes: 1 addition & 4 deletions llvm/test/Transforms/InstCombine/icmp-dom.ll
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Expand Up @@ -535,16 +535,13 @@ else:
ret i1 %cmp1
}

; TODO: X != Y implies X | Y != 0
define i1 @or_nonzero_from_nonequal(i8 %x, i8 %y) {
; CHECK-LABEL: @or_nonzero_from_nonequal(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[COND:%.*]] = icmp eq i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: br i1 [[COND]], label [[IF_ELSE:%.*]], label [[IF_THEN:%.*]]
; CHECK: if.then:
; CHECK-NEXT: [[OR:%.*]] = or i8 [[X]], [[Y]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[OR]], 0
; CHECK-NEXT: ret i1 [[CMP]]
; CHECK-NEXT: ret i1 false
; CHECK: if.else:
; CHECK-NEXT: ret i1 false
;
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