[llvm] [CodeExtractor] Add align metadata to extracted pointers (PR #131131)

[Dominik Adamski via llvm-commits]

DominikAdamski wrote:

> I had some questions about alignment:
> 
> * The StructArgTy is allocated at https://github.com/llvm/llvm-project/blob/e3c80d4496d109397e3c6403df434513fcd50bc6/llvm/lib/Transforms/Utils/CodeExtractor.cpp#L1809
>   . Does this guaranteed to have the alignment returned by `getPointerPrefAlignment`? If so, could add a comment?
> * ~Shouldn't there be a pass or similar that propagates alignment information from the alloca to the load? Interprocedurally we have the attributor, so what is doing this within a function?~ It's not the same function, the LoadGEP is in the extracted function.

I added a comment and ensured that we use the same function for alignment calculation. I modified the struct allocation - I explicitly set the alignment for struct allocation. Changes in the struct allocation constructors are non-functional. I explicitly set the alignment parameter in the constructor just to ease code analysis.

Previous constructor:
https://github.com/llvm/llvm-project/blob/0a5847f1c1445bfe55c9f9241c4d6d89609a7dc0/llvm/lib/IR/Instructions.cpp#L1260
calls `DL.getPrefTypeAlign`:
https://github.com/llvm/llvm-project/blob/0a5847f1c1445bfe55c9f9241c4d6d89609a7dc0/llvm/lib/IR/Instructions.cpp#L1246

https://github.com/llvm/llvm-project/pull/131131