[llvm] [LLVM][MemCpyOpt] Unify alias tags if we optimize allocas (PR #129537)

[Dominik Adamski via llvm-commits]

DominikAdamski wrote:

> Maybe https://godbolt.org/z/qv1Mqo7eP is an interesting test. It comes from a real miscompilation in julia and has alias scopes, no alias and tbaa

Hi @gbaraldi 
Could you check the trunk version of LLVM opt: https://godbolt.org/z/W65KnMx1K ? I noticed that there is difference in LLVM IR output between opt 19.1.0 and opt trunk. Unlike opt trunk, which does not remove any alias metadata and instead copies data to `%5 = alloca [4 x i64]`, opt 19.1.0 outputs as `%4 = alloca { double, double, i64, i64 }`.

https://github.com/llvm/llvm-project/pull/129537