This patch adds extra intrinsics for the GPU. Some of these are unused
for now but will be used later. We use these currently to update the
`RPC` handling. Currently, every thread can update the RPC client, which
isn't correct. This patch adds code neccesary to allow a single thread
to perfrom the write while the others wait.
Feedback is welcome for the naming of these functions. I'm copying the
OpenMP nomenclature where we call an AMD `wavefront` or NVIDIA `warp` a
`lane`.
Reviewed By: tra
Differential Revision: https://reviews.llvm.org/D148810
50445dff43