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SPIR and SPIR-V

'SPIR' is the original 'thing', that was based directly on LLVM bytecode. 'SPIR-V' is the later 'thing', that is orthogonal to llvm bytecode, but based loosely on llvm 3.2.

Version history:

In order of earlier to later:

• SPIR 1.2
• SPIR 2.0
• SPIRV 1.1
• SPIRV 1.2

Repositories

• SPIR:
  • contains the clang compiler, that can take eg OpenCL source-code, and output SPIR-V binary form
  • be careful to choose teh appropriate branch: by default it chagnes to spir_12, which is not SPIR-V, and is pretty old
  • the branch for the latest vailable verison of SPIR-V is spirv-1.1
• SPIRV-LLVM:
  • fork of llvm
  • contain LLVM <-> SPIR-V converter
  • serves as a foundation for LLVM-based front-end compilers targeting SPIR-V
• SPIRV-Tools
  • contains assembler and disassembler, to convert between SPIR-V binary and textual form
  • SPIR-V validator
  • binary parser, usable from C/C++ code, to read SPIR-V binary files
• SPIRV-Headers
  • header files for various languages.
  • JSON files describing the grammar for the SPIR-V core instruction set
  • The XML registry file
• SPIRV-Cross
  • library for performing reflection on SPIR-V and disassembling SPIR-V back to high level languages

Building the various tools etc

• download and build SPIR and LLVM-SPIRV, following this guide
• build SPIRV-Tools, following SPIRV-Tools build guide

I want to ...

Compile OpenCL to SPIR-V

• See creating-spir-v-binaries

Convert between SPIR-V and llvm bytecode, in either direction

• see run instructions for llvm SPIR-V

Read SPIR-V from C++

• you can use the llvm::ReadSPIRV function, in the SPIRV-LLVM repo, in the llvm/Support/SPIRV.h header:

#include "llvm/Support/SPIRV.h"
...
    llvm::LLVMContext Context;
    std::ifstream IFS("somefile.spv", std::ios::binary);
    llvm::Module *M;
    std::string Err;

    if (!llvm::ReadSPIRV(Context, IFS, M, Err)) {
        llvm::errs() << "Fails to load SPIRV as LLVM Module: " << Err << '\n';
        return;
    }

• there is also a binary parser, available in the SPIRV-Tools repo
  • note that you probably need the opcode headers, from SPIRV-Headers
  • very simple example, to get you started
  • better (c++) example

I'm not sure the difference between these, but I assume that:

• the SPIRV-LLVM ReadSPIRV function allows one to bring the full power of llvm to bear on parsing and walking the tree
• the SPIRV-Tools method possibly is lighter-weight, does not need one to link with llvm?