commit | 65299b9ef0359f486a51b7b3c5c729967f3f2847 | [log] [tgz] |
---|---|---|
author | Lei Zhang <antiagainst@gmail.com> | Sat Jun 27 18:43:26 2015 -0400 |
committer | Lei Zhang <antiagainst@gmail.com> | Sun Jun 28 18:11:13 2015 -0400 |
tree | d4b7bfc569309e5a24a597d249b1fe109e351c42 | |
parent | 140f3df1349bf8bdb29207f4a526c998e2a7f738 [diff] |
Format README using markdown.
An OpenGL and OpenGL ES shader front end and validator.
There are two components:
A front-end library for programmatic parsing of GLSL/ESSL into an AST.
A standalone wrapper, glslangValidator
, that can be used as a shader validation tool.
How to add a feature protected by a version/extension/stage/profile: See the comment in glslang/MachineIndependent/Versions.cpp
.
Things left to do: See Todo.txt
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 shaderThere is also a non-shader extension
.conf
for a configuration file of limits, see usage statement for exampleA 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.
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.
Another piece of software can programmatically translate shaders to an AST using one of two different interfaces:
The main()
in StandAlone/StandAlone.cpp
shows examples using both styles.
This interface is in roughly the last 1/3 of ShaderLang.h
. It is in the glslang namespace and contains the following.
const char* GetEsslVersionString(); const char* GetGlslVersionString(); bool InitializeProcess(); void FinalizeProcess(); class TShader bool parse(...); void setStrings(...); const char* getInfoLog(); class TProgram void addShader(...); bool link(...); const char* getInfoLog(); Reflection queries
See ShaderLang.h
and the usage of it in StandAlone/StandAlone.cpp
for more details.
This interface is in roughly the first 2/3 of ShaderLang.h
, and referred to as the Sh*()
interface, as all the entry points start Sh
.
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.
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.
Initial lexical analysis is done by 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 old-style linker-type code still lying around.
Memory pool: parsing uses types derived from C++ std
types, using a custom allocator that puts them in a memory pool. This makes allocation of individual container/contents just few cycles and deallocation free. This pool is popped after the AST is made and processed.
The use is simple: if you are going to call new
, there are three cases:
the object comes from the pool (its base class has the macro POOL_ALLOCATOR_NEW_DELETE
in it) and you do not have to call delete
it is a TString
, in which case call NewPoolTString()
, which gets it from the pool, and there is no corresponding delete
the object does not come from the pool, and you have to do normal C++ memory management of what you new