[llvm] [ValueTracking] For NUW, X + Y are not 0 if they are nonequal (PR #148101)

[via llvm-commits]

https://github.com/AZero13 updated https://github.com/llvm/llvm-project/pull/148101

>From 6149ad2f8e20e31e789663a422756f2911d7aae7 Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Thu, 10 Jul 2025 22:05:10 -0400
Subject: [PATCH] [ValueTracking] For NUW, X + Y are not 0 if they are nonequal

In NUW, X + Y is not 0 if X and Y are nonequal.
---
 llvm/lib/Analysis/ValueTracking.cpp | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 21f844c4d2f45..154dce6f1dfd5 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -2833,19 +2833,27 @@ static bool isNonZeroAdd(const APInt &DemandedElts, const SimplifyQuery &Q,
   if (matchOpWithOpEqZero(X, Y))
     return true;
 
-  if (NUW)
+  if (NUW) {
+    // X + Y != 0 if X != Y, and X + Y is NUW.
+    if (isKnownNonEqual(X, Y, DemandedElts, Q, Depth))
+      return true;
     return isKnownNonZero(Y, DemandedElts, Q, Depth) ||
            isKnownNonZero(X, DemandedElts, Q, Depth);
+  }
 
   KnownBits XKnown = computeKnownBits(X, DemandedElts, Q, Depth);
   KnownBits YKnown = computeKnownBits(Y, DemandedElts, Q, Depth);
 
   // If X and Y are both non-negative (as signed values) then their sum is not
   // zero unless both X and Y are zero.
-  if (XKnown.isNonNegative() && YKnown.isNonNegative())
+  if (XKnown.isNonNegative() && YKnown.isNonNegative()) {
     if (isKnownNonZero(Y, DemandedElts, Q, Depth) ||
         isKnownNonZero(X, DemandedElts, Q, Depth))
       return true;
+    // X + Y != 0 if X != Y, and X + Y are both nonnegative.
+    if (isKnownNonEqual(X, Y, DemandedElts, Q, Depth))
+      return true;
+  }
 
   // If X and Y are both negative (as signed values) then their sum is not
   // zero unless both X and Y equal INT_MIN.
@@ -2859,6 +2867,9 @@ static bool isNonZeroAdd(const APInt &DemandedElts, const SimplifyQuery &Q,
     // to INT_MIN.
     if (YKnown.One.intersects(Mask))
       return true;
+    // X + Y != 0 because if they are not equal, they cannot both be INT_MIN.
+    if (isKnownNonEqual(X, Y, DemandedElts, Q, Depth))
+      return true;
   }
 
   // The sum of a non-negative number and a power of two is not zero.