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

[Yingwei Zheng via llvm-commits]

https://github.com/dtcxzyw updated https://github.com/llvm/llvm-project/pull/117443

>From 2183f59c19efd2ecb54627ffe97faed0105f428f Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Mon, 28 Apr 2025 20:22:34 +0800
Subject: [PATCH 1/2] [ValueTracking] Infer `X | Y != 0` from `X != Y`

---
 llvm/lib/Analysis/ValueTracking.cpp          | 4 ++++
 llvm/test/Transforms/InstCombine/icmp-dom.ll | 5 +----
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index d8c1096049dce..7caa0ec57196c 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, 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);
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
 ;

>From da1785059e9c4987b99a72a75419ab65a9a0f3aa Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Sun, 15 Jun 2025 12:43:42 +0800
Subject: [PATCH 2/2] [ValueTracking] Fix compilation error

---
 llvm/lib/Analysis/ValueTracking.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 7caa0ec57196c..99670b92187c5 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -3044,8 +3044,8 @@ static bool isKnownNonZeroFromOperator(const Operator *I,
     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))
+    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) ||