[llvm] [AIX] Support per global code model. (PR #79202)

[Chen Zheng via llvm-commits]

https://github.com/chenzheng1030 commented:

At first glance, the code diff is larger than what I thought. I original thought we just need a small change to fix the code generation for per global code model in ISEL-DAG phase.

But seems to keep the optimization of keeping large code model symbols with `TE` SMC, most of the code changes are for recording code model for a XCOFF symbol because there is no direct mapping between `MCSymbolXCOFF` and `GlobalVariable`.  I cannot find a better way to avoid these codes either...

https://github.com/llvm/llvm-project/pull/79202