SPIR-V is a binary intermediate representation interchange format used to interface with a heterogeneous machine. SPIR-V expresses the operations that can be broken down to match an ISA found on a GPU, FPGA, DSP, CPU, etc. The most common use cases of SPIR-V is to be used for graphical-shader stages and compute kernels in other APIs such as Vulkan, OpenGL and OpenCL.
The Khronos SPIR-V Registry is the home for:
- The SPIR-V specification,
- Specifications for supported extended instruction sets, and
- Specifications for Khronos and vendor extensions to SPIR-V.
LunarG has written a very nice white paper about SPIR-V and its advantages, and a high-level description of the binary representation. There are also two great Khronos presentations from Vulkan DevDay 2016 here and here (video of both).
Compiler technology and languages evolve quickly. SPIR-V provides a common interchange format to transition, not just into Vulkan, OpenGL, and OpenCL drivers, but between different tool chains. With a well defined format, validation rules, and rich tools SPIR-V enables custom shader compiler flows, choice of language, and debuggability not available with graphical shaders and compute kernels before.
Likely people are used to the idea of how LLVM is used as a IR for the CPU world to get any front end langage to various ISA
We can take that same idea and replace LLVM IR here with SPIR-V
SPIR-V design has many aspects taken from how LLVM IR is structured
