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An OpenGL and OpenGL ES shader front end and validator. There are two components: 1) A front-end library for programmatic parsing of GLSL/ESSL into an AST. 2) A standalone wrapper, glslangValidator, that can be used as a shader validation tool. Things left to do: See Todo.txt Execution --------- There are binaries in the Install/Windows and Install/Linux directories. To use the standalone binary form, execute glslangValidator, and it will print a usage statement. Basic operation is to give it a file containing a shader, and it will print out warnings/errors and optionally an AST. The applied stage-specific rules are based on the file extension: .vert for a vertex shader .tesc for a tessellation control shader .tese for a tessellation evaluation shader .geom for a geometry shader .frag for a fragment shader .comp for a compute shader Source: Build and run on linux ------------------------------- A simple bash script "BuildLinux.sh" is provided at the root directory to do the build and run a test cases. You will need a recent version of bison installed. Once the executable is generated, it needs to be dynamically linked with the shared object created in lib directory. To achieve that, "cd" to StandAlone directory to update the LD_LIBRARY_PATH as follows export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:./../glslang/MachineIndependent/lib You can also update LD_LIBRARY_PATH in the .cshrc or .bashrc file, depending on the shell you are using. You will need to give the complete path of "lib" directory in .cshrc or .bashrc files. Source: Build and run on Windows -------------------------------- Current development is with Visual Studio verion 11 (2012). The solution file is in the project's root directory Standalone.sln. Building the StandAlone project (the default) will create glslangValidate.exe and copy it into the Test directory and Install directory. This allows local test scripts to use either the debug or release version, whichever was built last. Windows execution and testing is generally done from within a cygwin shell. Note: Despite appearances, the use of a DLL is currently disabled; it simply makes a standalone executable from a statically linked library. Basic external programmatic interface ------------------------------------- Another piece of software can programmatically translate shaders to an AST using the C-style ShInitialize(), ShCompile(), et. al. interface. The main() in StandAlone/StandAlone.cpp shows an example way of using these. The Sh*() interface takes a "compiler" call-back object, which it calls after building call back that is passed the AST and can then execute a backend on it. The following is a simplified resulting run-time call stack: ShCompile(shader, compiler) -> compiler(AST) -> <back end> In practice, ShCompile() takes shader strings, default version, and warning/error and other options for controling compilation. Testing ------- "Test" is an active test directory that contains test input and a subdirectory baseResults that contains the expected results of the tests. Both the tests and baseResults are under source-code control. Executing the script ./runtests will generate current results in the localResults directory and diff them against the baseResults. When you want to update the tracked test results, they need to be copied from localResults to baseResults There are some tests borrowed from LunarGLASS. If LunarGLASS is missing, those tests just won't run. Basic Internal Operation ------------------------ - Initial lexical analysis is done be the preprocessor in MachineIndependent/Preprocessor, and then refined by a GLSL scanner in MachineIndependent/Scan.cpp. There is currently no use of flex. - Code is parsed using bison on MachineIndependent/glslang.y with the aid of a symbol table and an AST. The symbol table is not passed on to the back-end; the intermediate representation stands on its own. The tree is built by the grammar productions, many of which are offloaded into ParseHelper.cpp, and by Intermediate.cpp. - The intermediate representation is very high-level, and represented as an in-memory tree. This serves to lose no information from the original program, and to have efficient transfer of the result from parsing to the back-end. In the AST, constants are propogated and folded, and a very small amount of dead code is eliminated. To aid linking and reflection, the last top-level branch in the AST lists all global symbols. - The primary algorithm of the back-end compiler is to traverse the tree (high-level intermediate representation), and create an internal object code representation. There is an example of how to do this in MachineIndependent/intermOut.cpp. - Reduction of the tree to a linear byte-code style low-level intermediate representation is likely a good way to generate fully optimized code. - There is currently some dead linker-type code still lying around.