
There are two ways we can fix this problem, depending on how the semantics of byval and initializes should interact: * Don't infer initializes on byval arguments. initializes on byval refers to the original caller memory (or having both attributes is made a verifier error). * Infer initializes on byval, but don't use it in DSE. initializes on byval refers to the callee copy. This matches the semantics of readonly on byval. This is slightly more powerful, for example, we could do a backend optimization where byval + initializes will allocate the full size of byval on the stack but not copy over the parts covered by initializes. I went with the second variant here, skipping byval + initializes in DSE (FunctionAttrs already doesn't propagate initializes past byval). I'm open to going in the other direction though. Fixes https://github.com/llvm/llvm-project/issues/126181.
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