[clang] [libc] [llvm] [libc] Implement (v|f)printf on the GPU (PR #96369)

[Nick Desaulniers via cfe-commits]

nickdesaulniers wrote:

> Do we want some sort of optimization for constant printf? 99% of the time, we could parse the string at compile-time. (This sort of optimization is common for embedded targets.)

Yes! @michaelrj-google has some ideas. Orthogonal to this PR though.

https://github.com/llvm/llvm-project/pull/96369