[compiler-rt] [llvm] [libc] [libcxx] [lldb] [clang] [lld] [clang-tools-extra] [flang] [AMDGPU] Use alias info to relax waitcounts for LDS DMA (PR #74537)

[Stanislav Mekhanoshin via cfe-commits]

rampitec wrote:

> > This is still correct, pointer argument cannot alias module global. A pointer argument to a kernel is an LDS external requested by the host side, and host cannot see module LDS.
> 
> I.e. that is really the point of the patch: if we are able to definitively identify an LDS object targeted by both load and store we only wait on that store or stores. And the only way to definitively identify the object at this stage is via alias.scope info which we are generating ourselves during module LDS lowering.

I have added a check for the presence of alias scope info just in case we get a rogue AA. The testcase with a pointer argument still produces correct code with vmcnt(1).

https://github.com/llvm/llvm-project/pull/74537