[llvm] 149cb5c - [ValueTracking] Infer `X | Y != 0` from `X != Y` (#117443)

[via llvm-commits]

Author: Yingwei Zheng
Date: 2025-06-15T15:17:53+08:00
New Revision: 149cb5c43c3a75ecb827b8b7ae853250c3c09449

URL: https://github.com/llvm/llvm-project/commit/149cb5c43c3a75ecb827b8b7ae853250c3c09449
DIFF: https://github.com/llvm/llvm-project/commit/149cb5c43c3a75ecb827b8b7ae853250c3c09449.diff

LOG: [ValueTracking] Infer `X | Y != 0` from `X != Y` (#117443)

Alive2: https://alive2.llvm.org/ce/z/cJ75Ya

Closes https://github.com/llvm/llvm-project/issues/117436.

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp
    llvm/test/Transforms/InstCombine/icmp-dom.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index d8c1096049dce..99670b92187c5 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -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);

diff  --git a/llvm/test/Transforms/InstCombine/icmp-dom.ll b/llvm/test/Transforms/InstCombine/icmp-dom.ll
index 6613bbeb8d6ae..a72b5e0bbfa03 100644
--- a/llvm/test/Transforms/InstCombine/icmp-dom.ll
+++ b/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
 ;