[llvm] [LV] Rewrite UDiv A, B -> UDiv A, UMax(B, 1) in trip counts if needed. (PR #92177)

[Eli Friedman via llvm-commits]

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@@ -161,6 +161,11 @@ SCEVExpander::findInsertPointAfter(Instruction *I,
   return IP;
 }
 
+bool SCEVExpander::expansionMayIntroduceUB(const SCEV *Expr) {
+  return SCEVExprContains(Expr,
+                          [](const SCEV *Op) { return isa<SCEVUDivExpr>(Op); });
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efriedma-quic wrote:

There's one more case here I wasn't thinking about: udiv where the RHS is poison.  umax isn't sufficient in that case because umax(1,poison) is still poison,

https://github.com/llvm/llvm-project/pull/92177