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

[Luke Lau 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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lukel97 wrote:

Why wouldn't it be valid to add the flags? If the inputs aren't disjoint then it's poison, so we can transform it to whatever. If they are disjoint they won't unsigned or signed wrap, so we can add the flags. https://alive2.llvm.org/ce/z/gB34kE

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