[llvm] [SCEV] Discard samesign when analyzing loop invariant exits (PR #181171)

[Nikita Popov via llvm-commits]

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@@ -11496,6 +11496,11 @@ ScalarEvolution::getLoopInvariantExitCondDuringFirstIterationsImpl(
   if (!AR || AR->getLoop() != L)
     return std::nullopt;
 
+  // Even if both are valid, we need to consistently chose the unsigned or the
+  // signed predicate below, not mixtures of both. For now, prefer the unsigned
+  // predicate.
+  Pred = Pred.dropSameSign();
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nikic wrote:

Pred is also used in the return value of the function.

https://github.com/llvm/llvm-project/pull/181171