[llvm] [AMDGPU] Remove TH_BYPASS from CPol (PR #139887)

[Pierre van Houtryve via llvm-commits]

Pierre-vh wrote:

> > > What's the rationale?
> > 
> > 
> > `TH_BYPASS` is not the canonical way to print this temporal hint bit (see 4.1.1. in https://www.amd.com/content/dam/amd/en/documents/radeon-tech-docs/instruction-set-architectures/rdna4-instruction-set-architecture.pdf ); We use LU/WB.
> 
> Sadly I don't think the public ISA doc is too useful as a reference for assembler syntax. We generally try to follow SP3 instead, unless there is a good reason to diverge from it.

Ah, I thought the public docs mattered more. I just looked at SP3's TH field defs, and from what I understand:

- TH_LU/TH_WB are both available <SCOPE_SYS
- TH_BYPASS is a thing, but only available for SCOPE_SYS

TIL then, I was mistaken. I thought BYPASS was an older spelling but it's the spelling of LU/WB for SCOPE_SYS
So I guess it does not need to be removed then. REAL_BYPASS is confusing though, I don't see the point of that if there's a clear way to tell whether we need to print LU/WB/BYPASS


https://github.com/llvm/llvm-project/pull/139887