[llvm] [DSE] Consider the aliasing through global variable while checking clobber (PR #120044)

[Haopeng Liu via llvm-commits]

haopliu wrote:

> I think it's unfortunate to require onlyAccessesInaccessibleMemOrArgMem() for all of the cases, it'll probably prevent a lot of valid DSE. can we be more precise on when we need onlyAccessesInaccessibleMemOrArgMem()? if the pointer hasn't escaped yet then we don't need this restriction

Updated the check to require either the argument is from Alloca that doesn't escape or `CB->onlyAccessesInaccessibleMemOrArgMem`. Otherwise, discard the "initializes" info. 

PTAL, thanks.

https://github.com/llvm/llvm-project/pull/120044