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
60 * [CMake][cmake]: for generating compilation targets.
61 * [Python 2.7][python]: for executing SPIRV-Tools scripts. (Optional if not using SPIRV-Tools.)
62 * [bison][bison]: _optional_, but needed when changing the grammar (glslang.y).
63 * [googletest][googletest]: _optional_, but should use if making any changes to glslang.
67 #### 1) Check-Out this project
70 cd <parent of where you want glslang to be>
72 git clone git@github.com:KhronosGroup/glslang.git
74 git clone https://github.com/KhronosGroup/glslang.git
77 #### 2) Check-Out External Projects
80 cd <the directory glslang was cloned to, "External" will be a subdirectory>
81 git clone https://github.com/google/googletest.git External/googletest
84 If you wish to assure that SPIR-V generated from HLSL is legal for Vulkan,
85 or wish to invoke -Os to reduce SPIR-V size from HLSL or GLSL, install
86 spirv-tools with this:
89 ./update_glslang_sources.py
92 For running the CMake GUI or Visual Studio with python dependencies, you will,
93 in addition to python within the cygwin environment, need a Windows [python][python]
94 installation, including selecting the `PATH` update.
98 Assume the source directory is `$SOURCE_DIR` and
99 the build directory is `$BUILD_DIR`:
101 For building on Linux (assuming using the Ninja generator):
106 cmake -GNinja -DCMAKE_BUILD_TYPE={Debug|Release|RelWithDebInfo} \
107 -DCMAKE_INSTALL_PREFIX=`pwd`/install $SOURCE_DIR
110 For building on Windows:
113 cmake $SOURCE_DIR -DCMAKE_INSTALL_PREFIX=`pwd`/install
114 # The CMAKE_INSTALL_PREFIX part is for testing (explained later).
117 The CMake GUI also works for Windows (version 3.4.1 tested).
119 #### 4) Build and Install
126 cmake --build . --config {Release|Debug|MinSizeRel|RelWithDebInfo} \
130 If using MSVC, after running CMake to configure, use the
131 Configuration Manager to check the `INSTALL` project.
133 ### If you need to change the GLSL grammar
135 The grammar in `glslang/MachineIndependent/glslang.y` has to be recompiled with
136 bison if it changes, the output files are committed to the repo to avoid every
137 developer needing to have bison configured to compile the project when grammar
138 changes are quite infrequent. For windows you can get binaries from
139 [GnuWin32][bison-gnu-win32].
141 The command to rebuild is:
144 bison --defines=MachineIndependent/glslang_tab.cpp.h
145 -t MachineIndependent/glslang.y
146 -o MachineIndependent/glslang_tab.cpp
149 The above command is also available in the bash script at
150 `glslang/updateGrammar`.
155 Right now, there are two test harnesses existing in glslang: one is [Google
156 Test](gtests/), one is the [`runtests` script](Test/runtests). The former
157 runs unit tests and single-shader single-threaded integration tests, while
158 the latter runs multiple-shader linking tests and multi-threaded tests.
162 The [`runtests` script](Test/runtests) requires compiled binaries to be
163 installed into `$BUILD_DIR/install`. Please make sure you have supplied the
164 correct configuration to CMake (using `-DCMAKE_INSTALL_PREFIX`) when building;
165 otherwise, you may want to modify the path in the `runtests` script.
167 Running Google Test-backed tests:
176 ctest -C {Debug|Release|RelWithDebInfo|MinSizeRel}
178 # or, run the test binary directly
179 # (which gives more fine-grained control like filtering):
180 <dir-to-glslangtests-in-build-dir>/glslangtests
183 Running `runtests` script-backed tests:
186 cd $SOURCE_DIR/Test && ./runtests
189 ### Contributing tests
191 Test results should always be included with a pull request that modifies
194 If you are writing unit tests, please use the Google Test framework and
195 place the tests under the `gtests/` directory.
197 Integration tests are placed in the `Test/` directory. It contains test input
198 and a subdirectory `baseResults/` that contains the expected results of the
199 tests. Both the tests and `baseResults/` are under source-code control.
201 Google Test runs those integration tests by reading the test input, compiling
202 them, and then compare against the expected results in `baseResults/`. The
203 integration tests to run via Google Test is registered in various
204 `gtests/*.FromFile.cpp` source files. `glslangtests` provides a command-line
205 option `--update-mode`, which, if supplied, will overwrite the golden files
206 under the `baseResults/` directory with real output from that invocation.
207 For more information, please check `gtests/` directory's
208 [README](gtests/README.md).
210 For the `runtests` script, it will generate current results in the
211 `localResults/` directory and `diff` them against the `baseResults/`.
212 When you want to update the tracked test results, they need to be
213 copied from `localResults/` to `baseResults/`. This can be done by
214 the `bump` shell script.
216 You can add your own private list of tests, not tracked publicly, by using
217 `localtestlist` to list non-tracked tests. This is automatically read
218 by `runtests` and included in the `diff` and `bump` process.
220 Programmatic Interfaces
221 -----------------------
223 Another piece of software can programmatically translate shaders to an AST
224 using one of two different interfaces:
225 * A new C++ class-oriented interface, or
226 * The original C functional interface
228 The `main()` in `StandAlone/StandAlone.cpp` shows examples using both styles.
230 ### C++ Class Interface (new, preferred)
232 This interface is in roughly the last 1/3 of `ShaderLang.h`. It is in the
233 glslang namespace and contains the following.
236 const char* GetEsslVersionString();
237 const char* GetGlslVersionString();
238 bool InitializeProcess();
239 void FinalizeProcess();
243 void setStrings(...);
244 const char* getInfoLog();
249 const char* getInfoLog();
253 See `ShaderLang.h` and the usage of it in `StandAlone/StandAlone.cpp` for more
256 ### C Functional Interface (orignal)
258 This interface is in roughly the first 2/3 of `ShaderLang.h`, and referred to
259 as the `Sh*()` interface, as all the entry points start `Sh`.
261 The `Sh*()` interface takes a "compiler" call-back object, which it calls after
262 building call back that is passed the AST and can then execute a backend on it.
264 The following is a simplified resulting run-time call stack:
267 ShCompile(shader, compiler) -> compiler(AST) -> <back end>
270 In practice, `ShCompile()` takes shader strings, default version, and
271 warning/error and other options for controlling compilation.
273 Basic Internal Operation
274 ------------------------
276 * Initial lexical analysis is done by the preprocessor in
277 `MachineIndependent/Preprocessor`, and then refined by a GLSL scanner
278 in `MachineIndependent/Scan.cpp`. There is currently no use of flex.
280 * Code is parsed using bison on `MachineIndependent/glslang.y` with the
281 aid of a symbol table and an AST. The symbol table is not passed on to
282 the back-end; the intermediate representation stands on its own.
283 The tree is built by the grammar productions, many of which are
284 offloaded into `ParseHelper.cpp`, and by `Intermediate.cpp`.
286 * The intermediate representation is very high-level, and represented
287 as an in-memory tree. This serves to lose no information from the
288 original program, and to have efficient transfer of the result from
289 parsing to the back-end. In the AST, constants are propogated and
290 folded, and a very small amount of dead code is eliminated.
292 To aid linking and reflection, the last top-level branch in the AST
293 lists all global symbols.
295 * The primary algorithm of the back-end compiler is to traverse the
296 tree (high-level intermediate representation), and create an internal
297 object code representation. There is an example of how to do this
298 in `MachineIndependent/intermOut.cpp`.
300 * Reduction of the tree to a linear byte-code style low-level intermediate
301 representation is likely a good way to generate fully optimized code.
303 * There is currently some dead old-style linker-type code still lying around.
305 * Memory pool: parsing uses types derived from C++ `std` types, using a
306 custom allocator that puts them in a memory pool. This makes allocation
307 of individual container/contents just few cycles and deallocation free.
308 This pool is popped after the AST is made and processed.
310 The use is simple: if you are going to call `new`, there are three cases:
312 - the object comes from the pool (its base class has the macro
313 `POOL_ALLOCATOR_NEW_DELETE` in it) and you do not have to call `delete`
315 - it is a `TString`, in which case call `NewPoolTString()`, which gets
316 it from the pool, and there is no corresponding `delete`
318 - the object does not come from the pool, and you have to do normal
319 C++ memory management of what you `new`
322 [cmake]: https://cmake.org/
323 [python]: https://www.python.org/
324 [bison]: https://www.gnu.org/software/bison/
325 [googletest]: https://github.com/google/googletest
326 [bison-gnu-win32]: http://gnuwin32.sourceforge.net/packages/bison.htm
327 [master-tot-release]: https://github.com/KhronosGroup/glslang/releases/tag/master-tot