[llvm] [llvm] Use computeConstantRange to improve llvm.objectsize computation (PR #114673)

[via llvm-commits]

serge-sans-paille wrote:

> I did write
> 
> > just make sure that when you merge and squash, you do not accidentally overwrite your correct commit message with the older PR description :)
> 
> for a reason, I have been bit by this before. [f30f00a](https://github.com/llvm/llvm-project/commit/f30f00ab43e0c28d79f12170978330ee5d7901b0) had a correct commit message, the squashed [5f34281](https://github.com/llvm/llvm-project/commit/5f342816efe1854333f2be41a03fdd25fa0db433) has an incorrect commit message.
> 
> It is fine, this has happened before and will happen again, but it is good for us to be aware of it.

Yeah, I did thought it was ok :-/

https://github.com/llvm/llvm-project/pull/114673