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>
64 git clone git@github.com:KhronosGroup/glslang.git
67 #### 2) Check-Out External Projects
70 cd <the directory glslang was cloned to, "External" will be a subdirectory>
71 git clone https://github.com/google/googletest.git External/googletest
76 Assume the source directory is `$SOURCE_DIR` and
77 the build directory is `$BUILD_DIR`:
79 For building on Linux (assuming using the Ninja generator):
84 cmake -GNinja -DCMAKE_BUILD_TYPE={Debug|Release|RelWithDebInfo} \
85 -DCMAKE_INSTALL_PREFIX=`pwd`/install $SOURCE_DIR
88 For building on Windows:
91 cmake $SOURCE_DIR -DCMAKE_INSTALL_PREFIX=`pwd`/install
92 # The CMAKE_INSTALL_PREFIX part is for testing (explained later).
95 The CMake GUI also works for Windows (version 3.4.1 tested).
97 #### 4) Build and Install
104 cmake --build . --config {Release|Debug|MinSizeRel|RelWithDebInfo} \
108 If using MSVC, after running CMake to configure, use the
109 Configuration Manager to check the `INSTALL` project.
111 ### If you need to change the GLSL grammar
113 The grammar in `glslang/MachineIndependent/glslang.y` has to be recompiled with
114 bison if it changes, the output files are committed to the repo to avoid every
115 developer needing to have bison configured to compile the project when grammar
116 changes are quite infrequent. For windows you can get binaries from
117 [GnuWin32][bison-gnu-win32].
119 The command to rebuild is:
122 bison --defines=MachineIndependent/glslang_tab.cpp.h
123 -t MachineIndependent/glslang.y
124 -o MachineIndependent/glslang_tab.cpp
127 The above command is also available in the bash script at
128 `glslang/updateGrammar`.
133 Right now, there are two test harnesses existing in glslang: one is [Google
134 Test](gtests/), one is the [`runtests` script](Test/runtests). The former
135 runs unit tests and single-shader single-threaded integration tests, while
136 the latter runs multiple-shader linking tests and multi-threaded tests.
140 The [`runtests` script](Test/runtests) requires compiled binaries to be
141 installed into `$BUILD_DIR/install`. Please make sure you have supplied the
142 correct configuration to CMake (using `-DCMAKE_INSTALL_PREFIX`) when building;
143 otherwise, you may want to modify the path in the `runtests` script.
145 Running Google Test-backed tests:
154 ctest -C {Debug|Release|RelWithDebInfo|MinSizeRel}
156 # or, run the test binary directly
157 # (which gives more fine-grained control like filtering):
158 <dir-to-glslangtests-in-build-dir>/glslangtests
161 Running `runtests` script-backed tests:
164 cd $SOURCE_DIR/Test && ./runtests
167 ### Contributing tests
169 Test results should always be included with a pull request that modifies
172 If you are writing unit tests, please use the Google Test framework and
173 place the tests under the `gtests/` directory.
175 Integration tests are placed in the `Test/` directory. It contains test input
176 and a subdirectory `baseResults/` that contains the expected results of the
177 tests. Both the tests and `baseResults/` are under source-code control.
179 Google Test runs those integration tests by reading the test input, compiling
180 them, and then compare against the expected results in `baseResults/`. The
181 integration tests to run via Google Test is registered in various
182 `gtests/*.FromFile.cpp` source files. `glslangtests` provides a command-line
183 option `--update-mode`, which, if supplied, will overwrite the golden files
184 under the `baseResults/` directory with real output from that invocation.
185 For more information, please check `gtests/` directory's
186 [README](gtests/README.md).
188 For the `runtests` script, it will generate current results in the
189 `localResults/` directory and `diff` them against the `baseResults/`.
190 When you want to update the tracked test results, they need to be
191 copied from `localResults/` to `baseResults/`. This can be done by
192 the `bump` shell script.
194 You can add your own private list of tests, not tracked publicly, by using
195 `localtestlist` to list non-tracked tests. This is automatically read
196 by `runtests` and included in the `diff` and `bump` process.
198 Programmatic Interfaces
199 -----------------------
201 Another piece of software can programmatically translate shaders to an AST
202 using one of two different interfaces:
203 * A new C++ class-oriented interface, or
204 * The original C functional interface
206 The `main()` in `StandAlone/StandAlone.cpp` shows examples using both styles.
208 ### C++ Class Interface (new, preferred)
210 This interface is in roughly the last 1/3 of `ShaderLang.h`. It is in the
211 glslang namespace and contains the following.
214 const char* GetEsslVersionString();
215 const char* GetGlslVersionString();
216 bool InitializeProcess();
217 void FinalizeProcess();
221 void setStrings(...);
222 const char* getInfoLog();
227 const char* getInfoLog();
231 See `ShaderLang.h` and the usage of it in `StandAlone/StandAlone.cpp` for more
234 ### C Functional Interface (orignal)
236 This interface is in roughly the first 2/3 of `ShaderLang.h`, and referred to
237 as the `Sh*()` interface, as all the entry points start `Sh`.
239 The `Sh*()` interface takes a "compiler" call-back object, which it calls after
240 building call back that is passed the AST and can then execute a backend on it.
242 The following is a simplified resulting run-time call stack:
245 ShCompile(shader, compiler) -> compiler(AST) -> <back end>
248 In practice, `ShCompile()` takes shader strings, default version, and
249 warning/error and other options for controlling compilation.
251 Basic Internal Operation
252 ------------------------
254 * Initial lexical analysis is done by the preprocessor in
255 `MachineIndependent/Preprocessor`, and then refined by a GLSL scanner
256 in `MachineIndependent/Scan.cpp`. There is currently no use of flex.
258 * Code is parsed using bison on `MachineIndependent/glslang.y` with the
259 aid of a symbol table and an AST. The symbol table is not passed on to
260 the back-end; the intermediate representation stands on its own.
261 The tree is built by the grammar productions, many of which are
262 offloaded into `ParseHelper.cpp`, and by `Intermediate.cpp`.
264 * The intermediate representation is very high-level, and represented
265 as an in-memory tree. This serves to lose no information from the
266 original program, and to have efficient transfer of the result from
267 parsing to the back-end. In the AST, constants are propogated and
268 folded, and a very small amount of dead code is eliminated.
270 To aid linking and reflection, the last top-level branch in the AST
271 lists all global symbols.
273 * The primary algorithm of the back-end compiler is to traverse the
274 tree (high-level intermediate representation), and create an internal
275 object code representation. There is an example of how to do this
276 in `MachineIndependent/intermOut.cpp`.
278 * Reduction of the tree to a linear byte-code style low-level intermediate
279 representation is likely a good way to generate fully optimized code.
281 * There is currently some dead old-style linker-type code still lying around.
283 * Memory pool: parsing uses types derived from C++ `std` types, using a
284 custom allocator that puts them in a memory pool. This makes allocation
285 of individual container/contents just few cycles and deallocation free.
286 This pool is popped after the AST is made and processed.
288 The use is simple: if you are going to call `new`, there are three cases:
290 - the object comes from the pool (its base class has the macro
291 `POOL_ALLOCATOR_NEW_DELETE` in it) and you do not have to call `delete`
293 - it is a `TString`, in which case call `NewPoolTString()`, which gets
294 it from the pool, and there is no corresponding `delete`
296 - the object does not come from the pool, and you have to do normal
297 C++ memory management of what you `new`
300 [cmake]: https://cmake.org/
301 [bison]: https://www.gnu.org/software/bison/
302 [googletest]: https://github.com/google/googletest
303 [bison-gnu-win32]: http://gnuwin32.sourceforge.net/packages/bison.htm