1 Also see the Khronos landing page for glslang as a reference front end:
3 https://www.khronos.org/opengles/sdk/tools/Reference-Compiler/
5 The above page includes where to get binaries, and is kept up to date
6 regarding the feature level of glslang.
11 [![Build Status](https://travis-ci.org/KhronosGroup/glslang.svg?branch=master)](https://travis-ci.org/KhronosGroup/glslang)
12 [![Build status](https://ci.appveyor.com/api/projects/status/q6fi9cb0qnhkla68/branch/master?svg=true)](https://ci.appveyor.com/project/Khronoswebmaster/glslang/branch/master)
14 An OpenGL and OpenGL ES shader front end and validator.
16 There are two components:
18 1. A front-end library for programmatic parsing of GLSL/ESSL into an AST.
20 2. A standalone wrapper, `glslangValidator`, that can be used as a shader
23 How to add a feature protected by a version/extension/stage/profile: See the
24 comment in `glslang/MachineIndependent/Versions.cpp`.
26 Things left to do: See `Todo.txt`
28 Execution of Standalone Wrapper
29 -------------------------------
31 To use the standalone binary form, execute `glslangValidator`, and it will print
32 a usage statement. Basic operation is to give it a file containing a shader,
33 and it will print out warnings/errors and optionally an AST.
35 The applied stage-specific rules are based on the file extension:
36 * `.vert` for a vertex shader
37 * `.tesc` for a tessellation control shader
38 * `.tese` for a tessellation evaluation shader
39 * `.geom` for a geometry shader
40 * `.frag` for a fragment shader
41 * `.comp` for a compute shader
43 There is also a non-shader extension
44 * `.conf` for a configuration file of limits, see usage statement for example
51 * [CMake][cmake]: for generating compilation targets.
52 * [bison][bison]: _optional_, but needed when changing the grammar (glslang.y).
53 * [googletest][googletest]: _optional_, but should use if making any changes to glslang.
57 #### 1) Check-Out External Projects
60 cd <the directory glslang was cloned to, External will be a subdirectory>
61 git clone https://github.com/google/googletest.git External/googletest
66 Assume the source directory is `$SOURCE_DIR` and
67 the build directory is `$BUILD_DIR`:
69 For building on Linux (assuming using the Ninja generator):
74 cmake -GNinja -DCMAKE_BUILD_TYPE={Debug|Release|RelWithDebInfo} \
75 -DCMAKE_INSTALL_PREFIX=`pwd`/install $SOURCE_DIR
78 For building on Windows:
81 cmake $SOURCE_DIR -DCMAKE_INSTALL_PREFIX=`pwd`/install
82 # The CMAKE_INSTALL_PREFIX part is for testing (explained later).
85 The CMake GUI also works for Windows (version 3.4.1 tested).
87 #### 3) Build and Install
94 cmake --build . --config {Release|Debug|MinSizeRel|RelWithDebInfo} \
98 If using MSVC, after running CMake to configure, use the
99 Configuration Manager to check the `INSTALL` project.
101 ### If you need to change the GLSL grammar
103 The grammar in `glslang/MachineIndependent/glslang.y` has to be recompiled with
104 bison if it changes, the output files are committed to the repo to avoid every
105 developer needing to have bison configured to compile the project when grammar
106 changes are quite infrequent. For windows you can get binaries from
107 [GnuWin32][bison-gnu-win32].
109 The command to rebuild is:
112 bison --defines=MachineIndependent/glslang_tab.cpp.h
113 -t MachineIndependent/glslang.y
114 -o MachineIndependent/glslang_tab.cpp
117 The above command is also available in the bash script at
118 `glslang/updateGrammar`.
123 Right now, there are two test harnesses existing in glslang: one is [Google
124 Test](gtests/), one is the [`runtests` script](Test/runtests). The former
125 runs unit tests and single-shader single-threaded integration tests, while
126 the latter runs multiple-shader linking tests and multi-threaded tests.
130 The [`runtests` script](Test/runtests) requires compiled binaries to be
131 installed into `$BUILD_DIR/install`. Please make sure you have supplied the
132 correct configuration to CMake (using `-DCMAKE_INSTALL_PREFIX`) when building;
133 otherwise, you may want to modify the path in the `runtests` script.
135 Running Google Test-backed tests:
144 ctest -C {Debug|Release|RelWithDebInfo|MinSizeRel}
146 # or, run the test binary directly
147 # (which gives more fine-grained control like filtering):
148 <dir-to-glslangtests-in-build-dir>/glslangtests
151 Running `runtests` script-backed tests:
154 cd $SOURCE_DIR/Test && ./runtests
157 ### Contributing tests
159 Test results should always be included with a pull request that modifies
162 If you are writing unit tests, please use the Google Test framework and
163 place the tests under the `gtests/` directory.
165 Integration tests are placed in the `Test/` directory. It contains test input
166 and a subdirectory `baseResults/` that contains the expected results of the
167 tests. Both the tests and `baseResults/` are under source-code control.
169 Google Test runs those integration tests by reading the test input, compiling
170 them, and then compare against the expected results in `baseResults/`. The
171 integration tests to run via Google Test is registered in various
172 `gtests/*.FromFile.cpp` source files. `glslangtests` provides a command-line
173 option `--update-mode`, which, if supplied, will overwrite the golden files
174 under the `baseResults/` directory with real output from that invocation.
175 For more information, please check `gtests/` directory's
176 [README](gtests/README.md).
178 For the `runtests` script, it will generate current results in the
179 `localResults/` directory and `diff` them against the `baseResults/`.
180 The integration tests to run via the `runtests` script is registered
181 via various `Test/test-*` text files and `Test/testlist`.
182 When you want to update the tracked test results, they need to be
183 copied from `localResults/` to `baseResults/`. This can be done by
184 the `bump` shell script.
186 The list of files tested comes from `testlist`, and lists input shaders
187 in this directory, which must all be public for this to work. However,
188 you can add your own private list of tests, not tracked here, by using
189 `localtestlist` to list non-tracked tests. This is automatically read
190 by `runtests` and included in the `diff` and `bump` process.
192 Programmatic Interfaces
193 -----------------------
195 Another piece of software can programmatically translate shaders to an AST
196 using one of two different interfaces:
197 * A new C++ class-oriented interface, or
198 * The original C functional interface
200 The `main()` in `StandAlone/StandAlone.cpp` shows examples using both styles.
202 ### C++ Class Interface (new, preferred)
204 This interface is in roughly the last 1/3 of `ShaderLang.h`. It is in the
205 glslang namespace and contains the following.
208 const char* GetEsslVersionString();
209 const char* GetGlslVersionString();
210 bool InitializeProcess();
211 void FinalizeProcess();
215 void setStrings(...);
216 const char* getInfoLog();
221 const char* getInfoLog();
225 See `ShaderLang.h` and the usage of it in `StandAlone/StandAlone.cpp` for more
228 ### C Functional Interface (orignal)
230 This interface is in roughly the first 2/3 of `ShaderLang.h`, and referred to
231 as the `Sh*()` interface, as all the entry points start `Sh`.
233 The `Sh*()` interface takes a "compiler" call-back object, which it calls after
234 building call back that is passed the AST and can then execute a backend on it.
236 The following is a simplified resulting run-time call stack:
239 ShCompile(shader, compiler) -> compiler(AST) -> <back end>
242 In practice, `ShCompile()` takes shader strings, default version, and
243 warning/error and other options for controlling compilation.
245 Basic Internal Operation
246 ------------------------
248 * Initial lexical analysis is done by the preprocessor in
249 `MachineIndependent/Preprocessor`, and then refined by a GLSL scanner
250 in `MachineIndependent/Scan.cpp`. There is currently no use of flex.
252 * Code is parsed using bison on `MachineIndependent/glslang.y` with the
253 aid of a symbol table and an AST. The symbol table is not passed on to
254 the back-end; the intermediate representation stands on its own.
255 The tree is built by the grammar productions, many of which are
256 offloaded into `ParseHelper.cpp`, and by `Intermediate.cpp`.
258 * The intermediate representation is very high-level, and represented
259 as an in-memory tree. This serves to lose no information from the
260 original program, and to have efficient transfer of the result from
261 parsing to the back-end. In the AST, constants are propogated and
262 folded, and a very small amount of dead code is eliminated.
264 To aid linking and reflection, the last top-level branch in the AST
265 lists all global symbols.
267 * The primary algorithm of the back-end compiler is to traverse the
268 tree (high-level intermediate representation), and create an internal
269 object code representation. There is an example of how to do this
270 in `MachineIndependent/intermOut.cpp`.
272 * Reduction of the tree to a linear byte-code style low-level intermediate
273 representation is likely a good way to generate fully optimized code.
275 * There is currently some dead old-style linker-type code still lying around.
277 * Memory pool: parsing uses types derived from C++ `std` types, using a
278 custom allocator that puts them in a memory pool. This makes allocation
279 of individual container/contents just few cycles and deallocation free.
280 This pool is popped after the AST is made and processed.
282 The use is simple: if you are going to call `new`, there are three cases:
284 - the object comes from the pool (its base class has the macro
285 `POOL_ALLOCATOR_NEW_DELETE` in it) and you do not have to call `delete`
287 - it is a `TString`, in which case call `NewPoolTString()`, which gets
288 it from the pool, and there is no corresponding `delete`
290 - the object does not come from the pool, and you have to do normal
291 C++ memory management of what you `new`
294 [cmake]: https://cmake.org/
295 [bison]: https://www.gnu.org/software/bison/
296 [googletest]: https://github.com/google/googletest
297 [bison-gnu-win32]: http://gnuwin32.sourceforge.net/packages/bison.htm