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

[via llvm-commits]

serge-sans-paille wrote:

The original was actually https://github.com/llvm/llvm-project/pull/114673 which got approved by @hvdijk , maybe he could have a look at this one? I ran the manual testing on ppc and it was fine.

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