[llvm] [SeparateConstOffsetFromGEP] Preserve inbounds flag based on ValueTracking and NUW (PR #130617)

[Fabian Ritter via llvm-commits]

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@@ -811,6 +780,30 @@ Value *ConstantOffsetExtractor::removeConstOffset(unsigned ChainIndex) {
   return NewBO;
 }
 
+/// A helper function to check if reassociating through an entry in the user
+/// chain would invalidate the GEP's nuw flag.
+static bool allowsPreservingNUW(User *U) {
+  assert(isa<BinaryOperator>(U) || isa<CastInst>(U) || isa<ConstantInt>(U));
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ritter-x2a wrote:

> A ConstantInt can't be a user.

This statement sounds reasonable, but the inheritance diagram disagrees: https://llvm.org/doxygen/classllvm_1_1ConstantInt.html
The assertion does fail if the last disjunct is removed.
Anyway, I'll look into turning it into a conservative return instead.

https://github.com/llvm/llvm-project/pull/130617