DirectX shader bytecode cross compiler
C++ C CMake


DirectX shader bytecode cross compiler.

Originally based on

This library takes DirectX bytecode as input, and translates it into the following languages:

  • GLSL (OpenGL 3.2 and later)
  • GLSL ES (OpenGL ES 3.0 and later)
  • GLSL for Vulkan consumption (as input for Glslang to generate SPIR-V)
  • Metal Shading Language

This library is used to generate all shaders in Unity for OpenGL, OpenGL ES 3.0+, Metal and Vulkan.

Changes from original HLSLCrossCompiler:

  • Codebase changed to C++11, with major code reorganizations.
  • Support for multiple language output backends (currently ToGLSL and ToMetal)
  • Metal language output support
  • Temp register type analysis: In DX bytecode the registers are typeless 32-bit 4-vectors. We do code analysis to infer the actual data types (to prevent the need for tons of bitcasts).
  • Loop transformation: Detect constructs that look like for-loops and transform them back to their original form
  • Support for partial precision variables in HLSL (min16float etc). Do extra analysis pass to infer the intended precision of samplers.
  • Reflection interface to retrieve the shader inputs and their types.
  • Lots of workarounds for various driver/shader compiler bugs.
  • Lots of minor fixes and improvements for correctness
  • Lots of Unity-specific tweaks to allow extending HLSL without having to change the D3D compiler itself.


This project is originally integrated into the Unity build systems. However, building this library should be fairly straightforward: just compile src/*.cpp (in C++11 mode!) and src/cbstring/*.c with the following include paths:

  • include
  • src/internal_includes
  • src/cbstrinc
  • src

Alternatively, a CMakeLists.txt is provided to build the project using cmake.

The main entry point is TranslateHLSLFromMem() function in HLSLcc.cpp (taking DX bytecode as input).


  • Mikko Strandborg
  • Juho Oravainen
  • David Rogers
  • Marton Ekler
  • Antti Tapaninen
  • Florian Penzkofer
  • Alexey Orlov
  • Povilas Kanapickas


MIT license for HLSLcc itself, BSD license for the bstring library. See license.txt.