[clang] [clang] Add GCC-compatible code model names for sparc64 (PR #79485)

[Fangrui Song via cfe-commits]

MaskRay wrote:

Have you checked whether these code models are actually implemented and how complete they are?
For example, if one model is very far from complete, perhaps we should be honest and say it is unsupported.

https://github.com/llvm/llvm-project/pull/79485