[clang] [llvm] [SPIRV] Add more id and range builtIns (PR #143909)

[Nathan Gauër via cfe-commits]

Keenuts wrote:

> For the HLSL FE, there are already a few ids represented using intrinsics (unfortunately they use the DXIL naming rather than the SPIR-V but that's another point). I extended on that, were there reasons to not pursue this ?

The main reason was simplicity: we had many things to work on (structurizer, basic entrypoint handling), and we needed at least 1/2 builtins to get started.
Following what OpenCL has been doing for other built-ins was the path with the less friction.

Once we have a few implemented to start building the rest (structurizer, etc), we started to look into a more generic approach to handle input/output builtins in HLSL->SPV.
The proposal I wrote at the time is here:
https://github.com/llvm/wg-hlsl/pull/97

In short: for input builtins, I don't see issues with using pure intrinsics.
For output builtins, there is an issue in doing so.
To avoid having different handling for inputs & outputs, we settled on handling both using globals (which is compatible with the output side-effect).

That said, I'm not completely against having 2 ways to do the same thing in the backend if that's really a requirement on your end. Some FE could use intrinsics, other the global approach.

@s-perron FYI 



https://github.com/llvm/llvm-project/pull/143909