[clang] [llvm] [BasicAA] Do not decompose past casts with different index width (PR #119365)

[Fraser Cormack via llvm-commits]

frasercrmck wrote:

> @frasercrmck BasicAA returns MayAlias for your example. Presumably AMDGPUAA returns NoAlias because addrspace(3) and addrspace(0) can't alias, or something like that.

Yep, you're right, sorry for the false alarm. Because it's a `amdgpu_kernel` function and `A` (`%incdec.ptr.i`)'s underlying object is a kernel argument - `%arg` - it's returning `NoAlias`. This is despite the fact that `B` is also `%arg`, so is trivially not `NoAlias`. This seems like a bug in AMDGPUAA.

https://github.com/llvm/llvm-project/pull/119365