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. See [issue 362](https://github.com/KhronosGroup/glslang/issues/362) and [issue 701](https://github.com/KhronosGroup/glslang/issues/701) for current status.
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
52 Instead of building manually, you can also download the binaries for your
53 platform directly from the [master-tot release][master-tot-release] on GitHub.
54 Those binaries are automatically uploaded by the buildbots after successful
55 testing and they always reflect the current top of the tree of the master
61 (For MSVS: 2015 is recommended, 2013 is fully supported/tested, and 2010 support is attempted, but not tested.)
62 * [CMake][cmake]: for generating compilation targets.
63 * make: _Linux_, ninja is an alternative, if configured.
64 * [Python 2.7][python]: for executing SPIRV-Tools scripts. (Optional if not using SPIRV-Tools.)
65 * [bison][bison]: _optional_, but needed when changing the grammar (glslang.y).
66 * [googletest][googletest]: _optional_, but should use if making any changes to glslang.
70 The following steps assume a Bash shell. On Windows, that could be the Git Bash
71 shell or some other shell of your choosing.
73 #### 1) Check-Out this project
76 cd <parent of where you want glslang to be>
77 git clone https://github.com/KhronosGroup/glslang.git
80 #### 2) Check-Out External Projects
83 cd <the directory glslang was cloned to, "External" will be a subdirectory>
84 git clone https://github.com/google/googletest.git External/googletest
87 If you wish to assure that SPIR-V generated from HLSL is legal for Vulkan,
88 or wish to invoke -Os to reduce SPIR-V size from HLSL or GLSL, install
89 spirv-tools with this:
92 ./update_glslang_sources.py
97 Assume the source directory is `$SOURCE_DIR` and the build directory is
98 `$BUILD_DIR`. First ensure the build directory exists, then navigate to it:
105 For building on Linux:
108 cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX="$(pwd)/install" $SOURCE_DIR
109 # "Release" (for CMAKE_BUILD_TYPE) could also be "Debug" or "RelWithDebInfo"
112 For building on Windows:
115 cmake $SOURCE_DIR -DCMAKE_INSTALL_PREFIX="$(pwd)/install"
116 # The CMAKE_INSTALL_PREFIX part is for testing (explained later).
119 The CMake GUI also works for Windows (version 3.4.1 tested).
121 #### 4) Build and Install
128 cmake --build . --config Release --target install
129 # "Release" (for --config) could also be "Debug", "MinSizeRel", or "RelWithDebInfo"
132 If using MSVC, after running CMake to configure, use the
133 Configuration Manager to check the `INSTALL` project.
135 ### If you need to change the GLSL grammar
137 The grammar in `glslang/MachineIndependent/glslang.y` has to be recompiled with
138 bison if it changes, the output files are committed to the repo to avoid every
139 developer needing to have bison configured to compile the project when grammar
140 changes are quite infrequent. For windows you can get binaries from
141 [GnuWin32][bison-gnu-win32].
143 The command to rebuild is:
146 bison --defines=MachineIndependent/glslang_tab.cpp.h
147 -t MachineIndependent/glslang.y
148 -o MachineIndependent/glslang_tab.cpp
151 The above command is also available in the bash script at
152 `glslang/updateGrammar`.
157 Right now, there are two test harnesses existing in glslang: one is [Google
158 Test](gtests/), one is the [`runtests` script](Test/runtests). The former
159 runs unit tests and single-shader single-threaded integration tests, while
160 the latter runs multiple-shader linking tests and multi-threaded tests.
164 The [`runtests` script](Test/runtests) requires compiled binaries to be
165 installed into `$BUILD_DIR/install`. Please make sure you have supplied the
166 correct configuration to CMake (using `-DCMAKE_INSTALL_PREFIX`) when building;
167 otherwise, you may want to modify the path in the `runtests` script.
169 Running Google Test-backed tests:
178 ctest -C {Debug|Release|RelWithDebInfo|MinSizeRel}
180 # or, run the test binary directly
181 # (which gives more fine-grained control like filtering):
182 <dir-to-glslangtests-in-build-dir>/glslangtests
185 Running `runtests` script-backed tests:
188 cd $SOURCE_DIR/Test && ./runtests
191 ### Contributing tests
193 Test results should always be included with a pull request that modifies
196 If you are writing unit tests, please use the Google Test framework and
197 place the tests under the `gtests/` directory.
199 Integration tests are placed in the `Test/` directory. It contains test input
200 and a subdirectory `baseResults/` that contains the expected results of the
201 tests. Both the tests and `baseResults/` are under source-code control.
203 Google Test runs those integration tests by reading the test input, compiling
204 them, and then compare against the expected results in `baseResults/`. The
205 integration tests to run via Google Test is registered in various
206 `gtests/*.FromFile.cpp` source files. `glslangtests` provides a command-line
207 option `--update-mode`, which, if supplied, will overwrite the golden files
208 under the `baseResults/` directory with real output from that invocation.
209 For more information, please check `gtests/` directory's
210 [README](gtests/README.md).
212 For the `runtests` script, it will generate current results in the
213 `localResults/` directory and `diff` them against the `baseResults/`.
214 When you want to update the tracked test results, they need to be
215 copied from `localResults/` to `baseResults/`. This can be done by
216 the `bump` shell script.
218 You can add your own private list of tests, not tracked publicly, by using
219 `localtestlist` to list non-tracked tests. This is automatically read
220 by `runtests` and included in the `diff` and `bump` process.
222 Programmatic Interfaces
223 -----------------------
225 Another piece of software can programmatically translate shaders to an AST
226 using one of two different interfaces:
227 * A new C++ class-oriented interface, or
228 * The original C functional interface
230 The `main()` in `StandAlone/StandAlone.cpp` shows examples using both styles.
232 ### C++ Class Interface (new, preferred)
234 This interface is in roughly the last 1/3 of `ShaderLang.h`. It is in the
235 glslang namespace and contains the following.
238 const char* GetEsslVersionString();
239 const char* GetGlslVersionString();
240 bool InitializeProcess();
241 void FinalizeProcess();
245 setEnvInput(EShSourceHlsl or EShSourceGlsl, stage, EShClientVulkan or EShClientOpenGL, 100);
246 setEnvClient(EShClientVulkan or EShClientOpenGL, EShTargetVulkan_1_0 or EShTargetVulkan_1_1 or EShTargetOpenGL_450);
247 setEnvTarget(EShTargetSpv, EShTargetSpv_1_0 or EShTargetSpv_1_3);
249 const char* getInfoLog();
254 const char* getInfoLog();
258 See `ShaderLang.h` and the usage of it in `StandAlone/StandAlone.cpp` for more
261 ### C Functional Interface (orignal)
263 This interface is in roughly the first 2/3 of `ShaderLang.h`, and referred to
264 as the `Sh*()` interface, as all the entry points start `Sh`.
266 The `Sh*()` interface takes a "compiler" call-back object, which it calls after
267 building call back that is passed the AST and can then execute a backend on it.
269 The following is a simplified resulting run-time call stack:
272 ShCompile(shader, compiler) -> compiler(AST) -> <back end>
275 In practice, `ShCompile()` takes shader strings, default version, and
276 warning/error and other options for controlling compilation.
278 Basic Internal Operation
279 ------------------------
281 * Initial lexical analysis is done by the preprocessor in
282 `MachineIndependent/Preprocessor`, and then refined by a GLSL scanner
283 in `MachineIndependent/Scan.cpp`. There is currently no use of flex.
285 * Code is parsed using bison on `MachineIndependent/glslang.y` with the
286 aid of a symbol table and an AST. The symbol table is not passed on to
287 the back-end; the intermediate representation stands on its own.
288 The tree is built by the grammar productions, many of which are
289 offloaded into `ParseHelper.cpp`, and by `Intermediate.cpp`.
291 * The intermediate representation is very high-level, and represented
292 as an in-memory tree. This serves to lose no information from the
293 original program, and to have efficient transfer of the result from
294 parsing to the back-end. In the AST, constants are propogated and
295 folded, and a very small amount of dead code is eliminated.
297 To aid linking and reflection, the last top-level branch in the AST
298 lists all global symbols.
300 * The primary algorithm of the back-end compiler is to traverse the
301 tree (high-level intermediate representation), and create an internal
302 object code representation. There is an example of how to do this
303 in `MachineIndependent/intermOut.cpp`.
305 * Reduction of the tree to a linear byte-code style low-level intermediate
306 representation is likely a good way to generate fully optimized code.
308 * There is currently some dead old-style linker-type code still lying around.
310 * Memory pool: parsing uses types derived from C++ `std` types, using a
311 custom allocator that puts them in a memory pool. This makes allocation
312 of individual container/contents just few cycles and deallocation free.
313 This pool is popped after the AST is made and processed.
315 The use is simple: if you are going to call `new`, there are three cases:
317 - the object comes from the pool (its base class has the macro
318 `POOL_ALLOCATOR_NEW_DELETE` in it) and you do not have to call `delete`
320 - it is a `TString`, in which case call `NewPoolTString()`, which gets
321 it from the pool, and there is no corresponding `delete`
323 - the object does not come from the pool, and you have to do normal
324 C++ memory management of what you `new`
327 [cmake]: https://cmake.org/
328 [python]: https://www.python.org/
329 [bison]: https://www.gnu.org/software/bison/
330 [googletest]: https://github.com/google/googletest
331 [bison-gnu-win32]: http://gnuwin32.sourceforge.net/packages/bison.htm
332 [master-tot-release]: https://github.com/KhronosGroup/glslang/releases/tag/master-tot