[llvm] [CodeGen] Don't allow function alignment less than the target's minimum (PR #90415)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic requested changes to this pull request.

Alignment of functions is already confusing enough... this change makes it more confusing.  We should compute the alignment of a function exactly once, not compute it, then override it later.

Ideally, we should just fix clang so it doesn't make this request in the first place.  The relevant code is in https://github.com/llvm/llvm-project/blob/6566ffdf8a543f50b75e9b3c66d771a3a9eb1560/clang/lib/CodeGen/CodeGenModule.cpp#L2492 ... but really, we should just fix the datalayout so getPointerAlignment() works correctly.  (See https://reviews.llvm.org/D57335 )

CC @daltenty @hubert-reinterpretcast 

https://github.com/llvm/llvm-project/pull/90415