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 * [CMake][cmake]: for generating compilation targets.
62 * make: _Linux_, ninja is an alternative, if configured.
63 * [Python 2.7][python]: for executing SPIRV-Tools scripts. (Optional if not using SPIRV-Tools.)
64 * [bison][bison]: _optional_, but needed when changing the grammar (glslang.y).
65 * [googletest][googletest]: _optional_, but should use if making any changes to glslang.
69 The following steps assume a Bash shell. On Windows, that could be the Git Bash
70 shell or some other shell of your choosing.
72 #### 1) Check-Out this project
75 cd <parent of where you want glslang to be>
76 git clone https://github.com/KhronosGroup/glslang.git
79 #### 2) Check-Out External Projects
82 cd <the directory glslang was cloned to, "External" will be a subdirectory>
83 git clone https://github.com/google/googletest.git External/googletest
86 If you wish to assure that SPIR-V generated from HLSL is legal for Vulkan,
87 or wish to invoke -Os to reduce SPIR-V size from HLSL or GLSL, install
88 spirv-tools with this:
91 ./update_glslang_sources.py
96 Assume the source directory is `$SOURCE_DIR` and the build directory is
97 `$BUILD_DIR`. First ensure the build directory exists, then navigate to it:
104 For building on Linux:
107 cmake -DCMAKE_BUILD_TYPE={Debug|Release|RelWithDebInfo} \
108 -DCMAKE_INSTALL_PREFIX="$(pwd)/install" $SOURCE_DIR
111 For building on Windows:
114 cmake $SOURCE_DIR -DCMAKE_INSTALL_PREFIX="$(pwd)/install"
115 # The CMAKE_INSTALL_PREFIX part is for testing (explained later).
118 The CMake GUI also works for Windows (version 3.4.1 tested).
120 #### 4) Build and Install
127 cmake --build . --config {Release|Debug|MinSizeRel|RelWithDebInfo} \
131 If using MSVC, after running CMake to configure, use the
132 Configuration Manager to check the `INSTALL` project.
134 ### If you need to change the GLSL grammar
136 The grammar in `glslang/MachineIndependent/glslang.y` has to be recompiled with
137 bison if it changes, the output files are committed to the repo to avoid every
138 developer needing to have bison configured to compile the project when grammar
139 changes are quite infrequent. For windows you can get binaries from
140 [GnuWin32][bison-gnu-win32].
142 The command to rebuild is:
145 bison --defines=MachineIndependent/glslang_tab.cpp.h
146 -t MachineIndependent/glslang.y
147 -o MachineIndependent/glslang_tab.cpp
150 The above command is also available in the bash script at
151 `glslang/updateGrammar`.
156 Right now, there are two test harnesses existing in glslang: one is [Google
157 Test](gtests/), one is the [`runtests` script](Test/runtests). The former
158 runs unit tests and single-shader single-threaded integration tests, while
159 the latter runs multiple-shader linking tests and multi-threaded tests.
163 The [`runtests` script](Test/runtests) requires compiled binaries to be
164 installed into `$BUILD_DIR/install`. Please make sure you have supplied the
165 correct configuration to CMake (using `-DCMAKE_INSTALL_PREFIX`) when building;
166 otherwise, you may want to modify the path in the `runtests` script.
168 Running Google Test-backed tests:
177 ctest -C {Debug|Release|RelWithDebInfo|MinSizeRel}
179 # or, run the test binary directly
180 # (which gives more fine-grained control like filtering):
181 <dir-to-glslangtests-in-build-dir>/glslangtests
184 Running `runtests` script-backed tests:
187 cd $SOURCE_DIR/Test && ./runtests
190 ### Contributing tests
192 Test results should always be included with a pull request that modifies
195 If you are writing unit tests, please use the Google Test framework and
196 place the tests under the `gtests/` directory.
198 Integration tests are placed in the `Test/` directory. It contains test input
199 and a subdirectory `baseResults/` that contains the expected results of the
200 tests. Both the tests and `baseResults/` are under source-code control.
202 Google Test runs those integration tests by reading the test input, compiling
203 them, and then compare against the expected results in `baseResults/`. The
204 integration tests to run via Google Test is registered in various
205 `gtests/*.FromFile.cpp` source files. `glslangtests` provides a command-line
206 option `--update-mode`, which, if supplied, will overwrite the golden files
207 under the `baseResults/` directory with real output from that invocation.
208 For more information, please check `gtests/` directory's
209 [README](gtests/README.md).
211 For the `runtests` script, it will generate current results in the
212 `localResults/` directory and `diff` them against the `baseResults/`.
213 When you want to update the tracked test results, they need to be
214 copied from `localResults/` to `baseResults/`. This can be done by
215 the `bump` shell script.
217 You can add your own private list of tests, not tracked publicly, by using
218 `localtestlist` to list non-tracked tests. This is automatically read
219 by `runtests` and included in the `diff` and `bump` process.
221 Programmatic Interfaces
222 -----------------------
224 Another piece of software can programmatically translate shaders to an AST
225 using one of two different interfaces:
226 * A new C++ class-oriented interface, or
227 * The original C functional interface
229 The `main()` in `StandAlone/StandAlone.cpp` shows examples using both styles.
231 ### C++ Class Interface (new, preferred)
233 This interface is in roughly the last 1/3 of `ShaderLang.h`. It is in the
234 glslang namespace and contains the following.
237 const char* GetEsslVersionString();
238 const char* GetGlslVersionString();
239 bool InitializeProcess();
240 void FinalizeProcess();
244 void setStrings(...);
245 const char* getInfoLog();
250 const char* getInfoLog();
254 See `ShaderLang.h` and the usage of it in `StandAlone/StandAlone.cpp` for more
257 ### C Functional Interface (orignal)
259 This interface is in roughly the first 2/3 of `ShaderLang.h`, and referred to
260 as the `Sh*()` interface, as all the entry points start `Sh`.
262 The `Sh*()` interface takes a "compiler" call-back object, which it calls after
263 building call back that is passed the AST and can then execute a backend on it.
265 The following is a simplified resulting run-time call stack:
268 ShCompile(shader, compiler) -> compiler(AST) -> <back end>
271 In practice, `ShCompile()` takes shader strings, default version, and
272 warning/error and other options for controlling compilation.
274 Basic Internal Operation
275 ------------------------
277 * Initial lexical analysis is done by the preprocessor in
278 `MachineIndependent/Preprocessor`, and then refined by a GLSL scanner
279 in `MachineIndependent/Scan.cpp`. There is currently no use of flex.
281 * Code is parsed using bison on `MachineIndependent/glslang.y` with the
282 aid of a symbol table and an AST. The symbol table is not passed on to
283 the back-end; the intermediate representation stands on its own.
284 The tree is built by the grammar productions, many of which are
285 offloaded into `ParseHelper.cpp`, and by `Intermediate.cpp`.
287 * The intermediate representation is very high-level, and represented
288 as an in-memory tree. This serves to lose no information from the
289 original program, and to have efficient transfer of the result from
290 parsing to the back-end. In the AST, constants are propogated and
291 folded, and a very small amount of dead code is eliminated.
293 To aid linking and reflection, the last top-level branch in the AST
294 lists all global symbols.
296 * The primary algorithm of the back-end compiler is to traverse the
297 tree (high-level intermediate representation), and create an internal
298 object code representation. There is an example of how to do this
299 in `MachineIndependent/intermOut.cpp`.
301 * Reduction of the tree to a linear byte-code style low-level intermediate
302 representation is likely a good way to generate fully optimized code.
304 * There is currently some dead old-style linker-type code still lying around.
306 * Memory pool: parsing uses types derived from C++ `std` types, using a
307 custom allocator that puts them in a memory pool. This makes allocation
308 of individual container/contents just few cycles and deallocation free.
309 This pool is popped after the AST is made and processed.
311 The use is simple: if you are going to call `new`, there are three cases:
313 - the object comes from the pool (its base class has the macro
314 `POOL_ALLOCATOR_NEW_DELETE` in it) and you do not have to call `delete`
316 - it is a `TString`, in which case call `NewPoolTString()`, which gets
317 it from the pool, and there is no corresponding `delete`
319 - the object does not come from the pool, and you have to do normal
320 C++ memory management of what you `new`
323 [cmake]: https://cmake.org/
324 [python]: https://www.python.org/
325 [bison]: https://www.gnu.org/software/bison/
326 [googletest]: https://github.com/google/googletest
327 [bison-gnu-win32]: http://gnuwin32.sourceforge.net/packages/bison.htm
328 [master-tot-release]: https://github.com/KhronosGroup/glslang/releases/tag/master-tot