[llvm] [ValueTracking] Infer NonEqual from dominating conditions/assumptions (PR #117442)

[Yingwei Zheng via llvm-commits]

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@@ -3748,6 +3745,50 @@ static bool isKnownNonEqual(const Value *V1, const Value *V2,
       match(V2, m_PtrToIntSameSize(Q.DL, m_Value(B))))
     return isKnownNonEqual(A, B, DemandedElts, Depth + 1, Q);
 
+  if (!Q.CxtI)
+    return false;
+
+  // Try to infer NonEqual based on information from dominating conditions.
+  if (Q.DC && Q.DT) {
+    for (BranchInst *BI : Q.DC->conditionsFor(V1)) {
+      Value *Cond = BI->getCondition();
+      BasicBlockEdge Edge0(BI->getParent(), BI->getSuccessor(0));
+      if (Q.DT->dominates(Edge0, Q.CxtI->getParent()) &&
+          isImpliedCondition(Cond, ICmpInst::ICMP_NE, V1, V2, Q.DL,
+                             /*LHSIsTrue=*/true, Depth)
+              .value_or(false))
+        return true;
+
+      BasicBlockEdge Edge1(BI->getParent(), BI->getSuccessor(1));
+      if (Q.DT->dominates(Edge1, Q.CxtI->getParent()) &&
+          isImpliedCondition(Cond, ICmpInst::ICMP_NE, V1, V2, Q.DL,
+                             /*LHSIsTrue=*/false, Depth)
+              .value_or(false))
+        return true;
+    }
+  }
+
+  if (!Q.AC)
+    return false;
+
+  // Try to infer NonEqual based on information from assumptions.
+  for (auto &AssumeVH : Q.AC->assumptionsFor(V1)) {
----------------
dtcxzyw wrote:

We add both `V1` and `V2` in `findValuesAffectedByCondition`. So it is ok to iterate on conditions related to `V1`.

https://github.com/llvm/llvm-project/pull/117442