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 several components:
18 1. A GLSL/ESSL front-end for reference validation and translation of GLSL/ESSL into an AST.
20 2. An HLSL front-end for translation of a broad generic HLL into the AST.
22 3. A SPIR-V back end for translating the AST to SPIR-V.
24 4. A standalone wrapper, `glslangValidator`, that can be used as a command-line tool for the above.
26 How to add a feature protected by a version/extension/stage/profile: See the
27 comment in `glslang/MachineIndependent/Versions.cpp`.
29 Tasks waiting to be done are documented as GitHub issues.
31 Execution of Standalone Wrapper
32 -------------------------------
34 To use the standalone binary form, execute `glslangValidator`, and it will print
35 a usage statement. Basic operation is to give it a file containing a shader,
36 and it will print out warnings/errors and optionally an AST.
38 The applied stage-specific rules are based on the file extension:
39 * `.vert` for a vertex shader
40 * `.tesc` for a tessellation control shader
41 * `.tese` for a tessellation evaluation shader
42 * `.geom` for a geometry shader
43 * `.frag` for a fragment shader
44 * `.comp` for a compute shader
46 There is also a non-shader extension
47 * `.conf` for a configuration file of limits, see usage statement for example
54 * [CMake][cmake]: for generating compilation targets.
55 * [bison][bison]: _optional_, but needed when changing the grammar (glslang.y).
56 * [googletest][googletest]: _optional_, but should use if making any changes to glslang.
60 #### 1) Check-Out this project
63 cd <parent of where you want glslang to be>
65 git clone git@github.com:KhronosGroup/glslang.git
67 git clone https://github.com/KhronosGroup/glslang.git
70 #### 2) Check-Out External Projects
73 cd <the directory glslang was cloned to, "External" will be a subdirectory>
74 git clone https://github.com/google/googletest.git External/googletest
79 Assume the source directory is `$SOURCE_DIR` and
80 the build directory is `$BUILD_DIR`:
82 For building on Linux (assuming using the Ninja generator):
87 cmake -GNinja -DCMAKE_BUILD_TYPE={Debug|Release|RelWithDebInfo} \
88 -DCMAKE_INSTALL_PREFIX=`pwd`/install $SOURCE_DIR
91 For building on Windows:
94 cmake $SOURCE_DIR -DCMAKE_INSTALL_PREFIX=`pwd`/install
95 # The CMAKE_INSTALL_PREFIX part is for testing (explained later).
98 The CMake GUI also works for Windows (version 3.4.1 tested).
100 #### 4) Build and Install
107 cmake --build . --config {Release|Debug|MinSizeRel|RelWithDebInfo} \
111 If using MSVC, after running CMake to configure, use the
112 Configuration Manager to check the `INSTALL` project.
114 ### If you need to change the GLSL grammar
116 The grammar in `glslang/MachineIndependent/glslang.y` has to be recompiled with
117 bison if it changes, the output files are committed to the repo to avoid every
118 developer needing to have bison configured to compile the project when grammar
119 changes are quite infrequent. For windows you can get binaries from
120 [GnuWin32][bison-gnu-win32].
122 The command to rebuild is:
125 bison --defines=MachineIndependent/glslang_tab.cpp.h
126 -t MachineIndependent/glslang.y
127 -o MachineIndependent/glslang_tab.cpp
130 The above command is also available in the bash script at
131 `glslang/updateGrammar`.
136 Right now, there are two test harnesses existing in glslang: one is [Google
137 Test](gtests/), one is the [`runtests` script](Test/runtests). The former
138 runs unit tests and single-shader single-threaded integration tests, while
139 the latter runs multiple-shader linking tests and multi-threaded tests.
143 The [`runtests` script](Test/runtests) requires compiled binaries to be
144 installed into `$BUILD_DIR/install`. Please make sure you have supplied the
145 correct configuration to CMake (using `-DCMAKE_INSTALL_PREFIX`) when building;
146 otherwise, you may want to modify the path in the `runtests` script.
148 Running Google Test-backed tests:
157 ctest -C {Debug|Release|RelWithDebInfo|MinSizeRel}
159 # or, run the test binary directly
160 # (which gives more fine-grained control like filtering):
161 <dir-to-glslangtests-in-build-dir>/glslangtests
164 Running `runtests` script-backed tests:
167 cd $SOURCE_DIR/Test && ./runtests
170 ### Contributing tests
172 Test results should always be included with a pull request that modifies
175 If you are writing unit tests, please use the Google Test framework and
176 place the tests under the `gtests/` directory.
178 Integration tests are placed in the `Test/` directory. It contains test input
179 and a subdirectory `baseResults/` that contains the expected results of the
180 tests. Both the tests and `baseResults/` are under source-code control.
182 Google Test runs those integration tests by reading the test input, compiling
183 them, and then compare against the expected results in `baseResults/`. The
184 integration tests to run via Google Test is registered in various
185 `gtests/*.FromFile.cpp` source files. `glslangtests` provides a command-line
186 option `--update-mode`, which, if supplied, will overwrite the golden files
187 under the `baseResults/` directory with real output from that invocation.
188 For more information, please check `gtests/` directory's
189 [README](gtests/README.md).
191 For the `runtests` script, it will generate current results in the
192 `localResults/` directory and `diff` them against the `baseResults/`.
193 When you want to update the tracked test results, they need to be
194 copied from `localResults/` to `baseResults/`. This can be done by
195 the `bump` shell script.
197 You can add your own private list of tests, not tracked publicly, by using
198 `localtestlist` to list non-tracked tests. This is automatically read
199 by `runtests` and included in the `diff` and `bump` process.
201 Programmatic Interfaces
202 -----------------------
204 Another piece of software can programmatically translate shaders to an AST
205 using one of two different interfaces:
206 * A new C++ class-oriented interface, or
207 * The original C functional interface
209 The `main()` in `StandAlone/StandAlone.cpp` shows examples using both styles.
211 ### C++ Class Interface (new, preferred)
213 This interface is in roughly the last 1/3 of `ShaderLang.h`. It is in the
214 glslang namespace and contains the following.
217 const char* GetEsslVersionString();
218 const char* GetGlslVersionString();
219 bool InitializeProcess();
220 void FinalizeProcess();
224 void setStrings(...);
225 const char* getInfoLog();
230 const char* getInfoLog();
234 See `ShaderLang.h` and the usage of it in `StandAlone/StandAlone.cpp` for more
237 ### C Functional Interface (orignal)
239 This interface is in roughly the first 2/3 of `ShaderLang.h`, and referred to
240 as the `Sh*()` interface, as all the entry points start `Sh`.
242 The `Sh*()` interface takes a "compiler" call-back object, which it calls after
243 building call back that is passed the AST and can then execute a backend on it.
245 The following is a simplified resulting run-time call stack:
248 ShCompile(shader, compiler) -> compiler(AST) -> <back end>
251 In practice, `ShCompile()` takes shader strings, default version, and
252 warning/error and other options for controlling compilation.
254 Basic Internal Operation
255 ------------------------
257 * Initial lexical analysis is done by the preprocessor in
258 `MachineIndependent/Preprocessor`, and then refined by a GLSL scanner
259 in `MachineIndependent/Scan.cpp`. There is currently no use of flex.
261 * Code is parsed using bison on `MachineIndependent/glslang.y` with the
262 aid of a symbol table and an AST. The symbol table is not passed on to
263 the back-end; the intermediate representation stands on its own.
264 The tree is built by the grammar productions, many of which are
265 offloaded into `ParseHelper.cpp`, and by `Intermediate.cpp`.
267 * The intermediate representation is very high-level, and represented
268 as an in-memory tree. This serves to lose no information from the
269 original program, and to have efficient transfer of the result from
270 parsing to the back-end. In the AST, constants are propogated and
271 folded, and a very small amount of dead code is eliminated.
273 To aid linking and reflection, the last top-level branch in the AST
274 lists all global symbols.
276 * The primary algorithm of the back-end compiler is to traverse the
277 tree (high-level intermediate representation), and create an internal
278 object code representation. There is an example of how to do this
279 in `MachineIndependent/intermOut.cpp`.
281 * Reduction of the tree to a linear byte-code style low-level intermediate
282 representation is likely a good way to generate fully optimized code.
284 * There is currently some dead old-style linker-type code still lying around.
286 * Memory pool: parsing uses types derived from C++ `std` types, using a
287 custom allocator that puts them in a memory pool. This makes allocation
288 of individual container/contents just few cycles and deallocation free.
289 This pool is popped after the AST is made and processed.
291 The use is simple: if you are going to call `new`, there are three cases:
293 - the object comes from the pool (its base class has the macro
294 `POOL_ALLOCATOR_NEW_DELETE` in it) and you do not have to call `delete`
296 - it is a `TString`, in which case call `NewPoolTString()`, which gets
297 it from the pool, and there is no corresponding `delete`
299 - the object does not come from the pool, and you have to do normal
300 C++ memory management of what you `new`
303 [cmake]: https://cmake.org/
304 [bison]: https://www.gnu.org/software/bison/
305 [googletest]: https://github.com/google/googletest
306 [bison-gnu-win32]: http://gnuwin32.sourceforge.net/packages/bison.htm