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

Author: dtcxzyw

llvm/lib/Analysis/ValueTracking.cpp

@@ -3037,6 +3037,10 @@ 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, Depth,
+                        Q))
+      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);

llvm/test/Transforms/InstCombine/icmp-dom.ll

@@ -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
 ;