[RFC] Implementation of OpenACC 3.3 for Offload in Clang

[bcardosolopes]

This is cool Erich, makes total sense to have this clang upstream.

@erichkeane

Short term, we are going to start the Clang effort by implementing Parsing and Semantic Analysis of the directives, enabled by the -fopenacc flag, chosen for GCC compatibility. We will also implement a temporary flag to control the __OPENACC macro override (to be removed when we have a complete implementation), which will permit existing programs to be compiled with Clang to leverage our semantic analysis checking.

Sounds like a good incremental approach!

@erichkeane

It is our intent to ‘end up’ there some day (in the OpenACC dialect), with that then lowering to the existing offload mechanisms, yes. We are also investing in the CIR effort with a hope to accelerate that to be ready when we need it.

We’re excited with the ClangIR bits of the collaboration, and happy to help with integration efforts, discussions, PRs, etc.