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
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
77 If you wish to assure that SPIR-V generated from HLSL is legal for Vulkan,
78 or wish to invoke -Os to reduce SPIR-V size from HLSL or GLSL, install
79 spirv-tools with this:
82 ./update_glslang_sources.py
87 Assume the source directory is `$SOURCE_DIR` and
88 the build directory is `$BUILD_DIR`:
90 For building on Linux (assuming using the Ninja generator):
95 cmake -GNinja -DCMAKE_BUILD_TYPE={Debug|Release|RelWithDebInfo} \
96 -DCMAKE_INSTALL_PREFIX=`pwd`/install $SOURCE_DIR
99 For building on Windows:
102 cmake $SOURCE_DIR -DCMAKE_INSTALL_PREFIX=`pwd`/install
103 # The CMAKE_INSTALL_PREFIX part is for testing (explained later).
106 The CMake GUI also works for Windows (version 3.4.1 tested).
108 #### 4) Build and Install
115 cmake --build . --config {Release|Debug|MinSizeRel|RelWithDebInfo} \
119 If using MSVC, after running CMake to configure, use the
120 Configuration Manager to check the `INSTALL` project.
122 ### If you need to change the GLSL grammar
124 The grammar in `glslang/MachineIndependent/glslang.y` has to be recompiled with
125 bison if it changes, the output files are committed to the repo to avoid every
126 developer needing to have bison configured to compile the project when grammar
127 changes are quite infrequent. For windows you can get binaries from
128 [GnuWin32][bison-gnu-win32].
130 The command to rebuild is:
133 bison --defines=MachineIndependent/glslang_tab.cpp.h
134 -t MachineIndependent/glslang.y
135 -o MachineIndependent/glslang_tab.cpp
138 The above command is also available in the bash script at
139 `glslang/updateGrammar`.
144 Right now, there are two test harnesses existing in glslang: one is [Google
145 Test](gtests/), one is the [`runtests` script](Test/runtests). The former
146 runs unit tests and single-shader single-threaded integration tests, while
147 the latter runs multiple-shader linking tests and multi-threaded tests.
151 The [`runtests` script](Test/runtests) requires compiled binaries to be
152 installed into `$BUILD_DIR/install`. Please make sure you have supplied the
153 correct configuration to CMake (using `-DCMAKE_INSTALL_PREFIX`) when building;
154 otherwise, you may want to modify the path in the `runtests` script.
156 Running Google Test-backed tests:
165 ctest -C {Debug|Release|RelWithDebInfo|MinSizeRel}
167 # or, run the test binary directly
168 # (which gives more fine-grained control like filtering):
169 <dir-to-glslangtests-in-build-dir>/glslangtests
172 Running `runtests` script-backed tests:
175 cd $SOURCE_DIR/Test && ./runtests
178 ### Contributing tests
180 Test results should always be included with a pull request that modifies
183 If you are writing unit tests, please use the Google Test framework and
184 place the tests under the `gtests/` directory.
186 Integration tests are placed in the `Test/` directory. It contains test input
187 and a subdirectory `baseResults/` that contains the expected results of the
188 tests. Both the tests and `baseResults/` are under source-code control.
190 Google Test runs those integration tests by reading the test input, compiling
191 them, and then compare against the expected results in `baseResults/`. The
192 integration tests to run via Google Test is registered in various
193 `gtests/*.FromFile.cpp` source files. `glslangtests` provides a command-line
194 option `--update-mode`, which, if supplied, will overwrite the golden files
195 under the `baseResults/` directory with real output from that invocation.
196 For more information, please check `gtests/` directory's
197 [README](gtests/README.md).
199 For the `runtests` script, it will generate current results in the
200 `localResults/` directory and `diff` them against the `baseResults/`.
201 When you want to update the tracked test results, they need to be
202 copied from `localResults/` to `baseResults/`. This can be done by
203 the `bump` shell script.
205 You can add your own private list of tests, not tracked publicly, by using
206 `localtestlist` to list non-tracked tests. This is automatically read
207 by `runtests` and included in the `diff` and `bump` process.
209 Programmatic Interfaces
210 -----------------------
212 Another piece of software can programmatically translate shaders to an AST
213 using one of two different interfaces:
214 * A new C++ class-oriented interface, or
215 * The original C functional interface
217 The `main()` in `StandAlone/StandAlone.cpp` shows examples using both styles.
219 ### C++ Class Interface (new, preferred)
221 This interface is in roughly the last 1/3 of `ShaderLang.h`. It is in the
222 glslang namespace and contains the following.
225 const char* GetEsslVersionString();
226 const char* GetGlslVersionString();
227 bool InitializeProcess();
228 void FinalizeProcess();
232 void setStrings(...);
233 const char* getInfoLog();
238 const char* getInfoLog();
242 See `ShaderLang.h` and the usage of it in `StandAlone/StandAlone.cpp` for more
245 ### C Functional Interface (orignal)
247 This interface is in roughly the first 2/3 of `ShaderLang.h`, and referred to
248 as the `Sh*()` interface, as all the entry points start `Sh`.
250 The `Sh*()` interface takes a "compiler" call-back object, which it calls after
251 building call back that is passed the AST and can then execute a backend on it.
253 The following is a simplified resulting run-time call stack:
256 ShCompile(shader, compiler) -> compiler(AST) -> <back end>
259 In practice, `ShCompile()` takes shader strings, default version, and
260 warning/error and other options for controlling compilation.
262 Basic Internal Operation
263 ------------------------
265 * Initial lexical analysis is done by the preprocessor in
266 `MachineIndependent/Preprocessor`, and then refined by a GLSL scanner
267 in `MachineIndependent/Scan.cpp`. There is currently no use of flex.
269 * Code is parsed using bison on `MachineIndependent/glslang.y` with the
270 aid of a symbol table and an AST. The symbol table is not passed on to
271 the back-end; the intermediate representation stands on its own.
272 The tree is built by the grammar productions, many of which are
273 offloaded into `ParseHelper.cpp`, and by `Intermediate.cpp`.
275 * The intermediate representation is very high-level, and represented
276 as an in-memory tree. This serves to lose no information from the
277 original program, and to have efficient transfer of the result from
278 parsing to the back-end. In the AST, constants are propogated and
279 folded, and a very small amount of dead code is eliminated.
281 To aid linking and reflection, the last top-level branch in the AST
282 lists all global symbols.
284 * The primary algorithm of the back-end compiler is to traverse the
285 tree (high-level intermediate representation), and create an internal
286 object code representation. There is an example of how to do this
287 in `MachineIndependent/intermOut.cpp`.
289 * Reduction of the tree to a linear byte-code style low-level intermediate
290 representation is likely a good way to generate fully optimized code.
292 * There is currently some dead old-style linker-type code still lying around.
294 * Memory pool: parsing uses types derived from C++ `std` types, using a
295 custom allocator that puts them in a memory pool. This makes allocation
296 of individual container/contents just few cycles and deallocation free.
297 This pool is popped after the AST is made and processed.
299 The use is simple: if you are going to call `new`, there are three cases:
301 - the object comes from the pool (its base class has the macro
302 `POOL_ALLOCATOR_NEW_DELETE` in it) and you do not have to call `delete`
304 - it is a `TString`, in which case call `NewPoolTString()`, which gets
305 it from the pool, and there is no corresponding `delete`
307 - the object does not come from the pool, and you have to do normal
308 C++ memory management of what you `new`
311 [cmake]: https://cmake.org/
312 [bison]: https://www.gnu.org/software/bison/
313 [googletest]: https://github.com/google/googletest
314 [bison-gnu-win32]: http://gnuwin32.sourceforge.net/packages/bison.htm