[llvm] [VPlan] Recognize disjoint 'or' in getSCEVExprForVPValue (PR #218405)

[Mel Chen via llvm-commits]

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@@ -164,6 +164,11 @@ const SCEV *vputils::getSCEVExprForVPValue(const VPValue *V,
     return CreateSCEV({LHSVal, RHSVal}, [&](ArrayRef<SCEVUse> Ops) {
       return SE.getAddExpr(Ops[0], Ops[1], SCEV::FlagAnyWrap, 0);
     });
+  if (match(V, m_BinaryOr(m_VPValue(LHSVal), m_VPValue(RHSVal))))
+    if (cast<VPRecipeWithIRFlags>(V->getDefiningRecipe())->isDisjoint())
+      return CreateSCEV({LHSVal, RHSVal}, [&](ArrayRef<SCEVUse> Ops) {
+        return SE.getAddExpr(Ops[0], Ops[1], SCEV::FlagNSW | SCEV::FlagNUW, 0);
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Mel-Chen wrote:

We don't need this flag, and we shouldn't add nsw/nuw without proving UB. Thanks for pointing out this.
fa3c8d0b6f433b0693456798e3c9ef5a94716d06

https://github.com/llvm/llvm-project/pull/218405