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 2010 (Windows, x86/x64) and Xcode 4.5+ (Mac, i386) project files for a static library are provided in projects/vs2010/glsl_optimizer.sln and projects/xcode4/glsl_optimizer_lib 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);

Tests

There's a testing suite for catching regressions, see tests folder. In VS, build and run glsl_optimizer_tests project; in Xcode use projects/xcode4/glsl_optimizer_tests project. The test executable requires path to the tests folder as an argument.

Each test comes as three text files; input, expected IR dump and expected optimized GLSL dump.

If you're making changes to the project and want pull requests accepted easier, I'd appreciate if there would be no test suite regressions. If you are implementing a feature, it would be cool to add tests to cover it as well!

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.

Dev Notes

Pulling Mesa upstream:

git fetch upstream master
git merge
sh removeDeletedByUs.sh
# inspect files, git rm unneeded ones, fix conflicts etc.
# git commit

Rebuilding flex/bison parsers:

• When .y/.l files are changed, the parsers are not rebuilt automatically,
• Run ./generateParsers.sh to do that. You'll need bison & flex (on Mac, do "Install Command Line Tools" from Xcode)
• I use bison 2.3 and flex 2.5.35 (in OS X 10.8)