[llvm] [llvm] Improve llvm.objectsize computation by computing GEP, alloca a… (PR #117849)

[Mikael Holmén via llvm-commits]

mikaelholmen wrote:

We also start seeing problems with this patch.
E.g. we hit an UBSan error like
```load of address 0x811 with insufficient space for an object of type 'int'```
on a variable access that looks perfectly fine.
Unfortunately I don't have a reproducer I can share at the moment.

https://github.com/llvm/llvm-project/pull/117849