Initial SPIR-V Backend Code Lands In LLVM 15

The long in-development work by Intel, The Khronos Group, and other organizations on a proper SPIR-V back-end for LLVM is finally seeing code in mainline. As of last night the initial pieces have landed for the LLVM SPIR-V back-end for this Khronos open standard IR used most notably by Vulkan but for OpenCL and OpenGL as well...