By that do you mean exposing a non-uniform memory hierarchy as separate addressable spaces (but with coherent views from each hardware thread) or something like

By that do you mean exposing a non-uniform memory hierarchy as separate addressable spaces (but with coherent views from each hardware thread) or something like thread-local scratch pads? Either way, C is equipped ok for that - at least as well as most systems languages C++, Rust, etc. - simply because dealing with allocation and raw addressing (at least raw within the process memory space) is a fundamental part of the experience. Throw in a few compiler extensions (because you'll need to change the compiler to make use of this anyway) for things like where to locate static allocations and use library functions that add dynamic allocation in specific spaces. It will get hairy, but it's at least possible with some very careful programming.