bgfx/3rdparty/glsl-optimizer

GLSL optimizer

A C++ library that takes GLSL shaders, does some GPU-independent optimizations on them and outputs GLSL back. Optimizations are function inlining, dead code removal, copy propagation, constant folding, constant propagation, arithmetic optimizations and so on.

Apparently quite a few mobile platforms are pretty bad at optimizing GLSL shaders; and unfortunately they also lack offline shader compilers. So using a GLSL optimizer offline before can make the shader run much faster on a platform like that. See performance numbers in this blog post.

Almost all actual code is Mesa 3D's GLSL compiler; all this library does is spits out optimized GLSL back, and adds GLES type precision handling to the optimizer.

This GLSL optimizer is made for Unity's purposes and is built-in in Unity 3 and later.

GLSL Optimizer is licensed according to the terms of the MIT license.

Usage

Visual Studio 2008 (Windows, x86) and Xcode 4.5+ (Mac, i386) project files for a static library are provided in src/glsl/msvc/mesaglsl2.vcproj and src/glsl/xcode/mesaglsl2 respectively.

For Linux you can use cmake. Just type "cmake . && make" in the root directory. This will build the optimizer library and some executable binaries.

Interface for the library is src/glsl/glsl_optimizer.h. General usage is:

ctx = glslopt_initialize();
for (lots of shaders) {
    shader = glslopt_optimize (ctx, shaderType, shaderSource, options);
    if (glslopt_get_status (shader)) {
        newSource = glslopt_get_output (shader);
    } else {
        errorLog = glslopt_get_log (shader);
    }
    glslopt_shader_delete (shader);
}
glslopt_cleanup (ctx);

Notes

• GLSL versions 1.10 and 1.20 are supported. 1.10 is the default, use #version 120 to specify 1.20.
• GLSL ES version 1.00 is supported.