mirror of
https://github.com/libretro/glslang.git
synced 2024-12-14 19:49:14 +00:00
298 lines
10 KiB
Markdown
298 lines
10 KiB
Markdown
Also see the Khronos landing page for glslang as a reference front end:
|
|
|
|
https://www.khronos.org/opengles/sdk/tools/Reference-Compiler/
|
|
|
|
The above page includes where to get binaries, and is kept up to date
|
|
regarding the feature level of glslang.
|
|
|
|
glslang
|
|
=======
|
|
|
|
[](https://travis-ci.org/KhronosGroup/glslang)
|
|
[](https://ci.appveyor.com/project/Khronoswebmaster/glslang/branch/master)
|
|
|
|
An OpenGL and OpenGL ES shader front end and validator.
|
|
|
|
There are two components:
|
|
|
|
1. A front-end library for programmatic parsing of GLSL/ESSL into an AST.
|
|
|
|
2. A standalone wrapper, `glslangValidator`, that can be used as a shader
|
|
validation tool.
|
|
|
|
How to add a feature protected by a version/extension/stage/profile: See the
|
|
comment in `glslang/MachineIndependent/Versions.cpp`.
|
|
|
|
Things left to do: See `Todo.txt`
|
|
|
|
Execution of Standalone Wrapper
|
|
-------------------------------
|
|
|
|
To use the standalone binary form, execute `glslangValidator`, and it will print
|
|
a usage statement. Basic operation is to give it a file containing a shader,
|
|
and it will print out warnings/errors and optionally an AST.
|
|
|
|
The applied stage-specific rules are based on the file extension:
|
|
* `.vert` for a vertex shader
|
|
* `.tesc` for a tessellation control shader
|
|
* `.tese` for a tessellation evaluation shader
|
|
* `.geom` for a geometry shader
|
|
* `.frag` for a fragment shader
|
|
* `.comp` for a compute shader
|
|
|
|
There is also a non-shader extension
|
|
* `.conf` for a configuration file of limits, see usage statement for example
|
|
|
|
Building
|
|
--------
|
|
|
|
### Dependencies
|
|
|
|
* [CMake][cmake]: for generating compilation targets.
|
|
* [bison][bison]: _optional_, but needed when changing the grammar (glslang.y).
|
|
* [googletest][googletest]: _optional_, but should use if making any changes to glslang.
|
|
|
|
### Build steps
|
|
|
|
#### 1) Check-Out External Projects
|
|
|
|
```bash
|
|
cd <the directory glslang was cloned to, External will be a subdirectory>
|
|
git clone https://github.com/google/googletest.git External/googletest
|
|
```
|
|
|
|
#### 2) Configure
|
|
|
|
Assume the source directory is `$SOURCE_DIR` and
|
|
the build directory is `$BUILD_DIR`:
|
|
|
|
For building on Linux (assuming using the Ninja generator):
|
|
|
|
```bash
|
|
cd $BUILD_DIR
|
|
|
|
cmake -GNinja -DCMAKE_BUILD_TYPE={Debug|Release|RelWithDebInfo} \
|
|
-DCMAKE_INSTALL_PREFIX=`pwd`/install $SOURCE_DIR
|
|
```
|
|
|
|
For building on Windows:
|
|
|
|
```bash
|
|
cmake $SOURCE_DIR -DCMAKE_INSTALL_PREFIX=`pwd`/install
|
|
# The CMAKE_INSTALL_PREFIX part is for testing (explained later).
|
|
```
|
|
|
|
The CMake GUI also works for Windows (version 3.4.1 tested).
|
|
|
|
#### 3) Build and Install
|
|
|
|
```bash
|
|
# for Linux:
|
|
ninja install
|
|
|
|
# for Windows:
|
|
cmake --build . --config {Release|Debug|MinSizeRel|RelWithDebInfo} \
|
|
--target install
|
|
```
|
|
|
|
If using MSVC, after running CMake to configure, use the
|
|
Configuration Manager to check the `INSTALL` project.
|
|
|
|
### If you need to change the GLSL grammar
|
|
|
|
The grammar in `glslang/MachineIndependent/glslang.y` has to be recompiled with
|
|
bison if it changes, the output files are committed to the repo to avoid every
|
|
developer needing to have bison configured to compile the project when grammar
|
|
changes are quite infrequent. For windows you can get binaries from
|
|
[GnuWin32][bison-gnu-win32].
|
|
|
|
The command to rebuild is:
|
|
|
|
```bash
|
|
bison --defines=MachineIndependent/glslang_tab.cpp.h
|
|
-t MachineIndependent/glslang.y
|
|
-o MachineIndependent/glslang_tab.cpp
|
|
```
|
|
|
|
The above command is also available in the bash script at
|
|
`glslang/updateGrammar`.
|
|
|
|
Testing
|
|
-------
|
|
|
|
Right now, there are two test harnesses existing in glslang: one is [Google
|
|
Test](gtests/), one is the [`runtests` script](Test/runtests). The former
|
|
runs unit tests and single-shader single-threaded integration tests, while
|
|
the latter runs multiple-shader linking tests and multi-threaded tests.
|
|
|
|
### Running tests
|
|
|
|
The [`runtests` script](Test/runtests) requires compiled binaries to be
|
|
installed into `$BUILD_DIR/install`. Please make sure you have supplied the
|
|
correct configuration to CMake (using `-DCMAKE_INSTALL_PREFIX`) when building;
|
|
otherwise, you may want to modify the path in the `runtests` script.
|
|
|
|
Running Google Test-backed tests:
|
|
|
|
```bash
|
|
cd $BUILD_DIR
|
|
|
|
# for Linux:
|
|
ctest
|
|
|
|
# for Windows:
|
|
ctest -C {Debug|Release|RelWithDebInfo|MinSizeRel}
|
|
|
|
# or, run the test binary directly
|
|
# (which gives more fine-grained control like filtering):
|
|
<dir-to-glslangtests-in-build-dir>/glslangtests
|
|
```
|
|
|
|
Running `runtests` script-backed tests:
|
|
|
|
```bash
|
|
cd $SOURCE_DIR/Test && ./runtests
|
|
```
|
|
|
|
### Contributing tests
|
|
|
|
Test results should always be included with a pull request that modifies
|
|
functionality.
|
|
|
|
If you are writing unit tests, please use the Google Test framework and
|
|
place the tests under the `gtests/` directory.
|
|
|
|
Integration tests are placed in the `Test/` directory. It contains test input
|
|
and a subdirectory `baseResults/` that contains the expected results of the
|
|
tests. Both the tests and `baseResults/` are under source-code control.
|
|
|
|
Google Test runs those integration tests by reading the test input, compiling
|
|
them, and then compare against the expected results in `baseResults/`. The
|
|
integration tests to run via Google Test is registered in various
|
|
`gtests/*.FromFile.cpp` source files. `glslangtests` provides a command-line
|
|
option `--update-mode`, which, if supplied, will overwrite the golden files
|
|
under the `baseResults/` directory with real output from that invocation.
|
|
For more information, please check `gtests/` directory's
|
|
[README](gtests/README.md).
|
|
|
|
For the `runtests` script, it will generate current results in the
|
|
`localResults/` directory and `diff` them against the `baseResults/`.
|
|
The integration tests to run via the `runtests` script is registered
|
|
via various `Test/test-*` text files and `Test/testlist`.
|
|
When you want to update the tracked test results, they need to be
|
|
copied from `localResults/` to `baseResults/`. This can be done by
|
|
the `bump` shell script.
|
|
|
|
The list of files tested comes from `testlist`, and lists input shaders
|
|
in this directory, which must all be public for this to work. However,
|
|
you can add your own private list of tests, not tracked here, by using
|
|
`localtestlist` to list non-tracked tests. This is automatically read
|
|
by `runtests` and included in the `diff` and `bump` process.
|
|
|
|
Programmatic Interfaces
|
|
-----------------------
|
|
|
|
Another piece of software can programmatically translate shaders to an AST
|
|
using one of two different interfaces:
|
|
* A new C++ class-oriented interface, or
|
|
* The original C functional interface
|
|
|
|
The `main()` in `StandAlone/StandAlone.cpp` shows examples using both styles.
|
|
|
|
### C++ Class Interface (new, preferred)
|
|
|
|
This interface is in roughly the last 1/3 of `ShaderLang.h`. It is in the
|
|
glslang namespace and contains the following.
|
|
|
|
```cxx
|
|
const char* GetEsslVersionString();
|
|
const char* GetGlslVersionString();
|
|
bool InitializeProcess();
|
|
void FinalizeProcess();
|
|
|
|
class TShader
|
|
bool parse(...);
|
|
void setStrings(...);
|
|
const char* getInfoLog();
|
|
|
|
class TProgram
|
|
void addShader(...);
|
|
bool link(...);
|
|
const char* getInfoLog();
|
|
Reflection queries
|
|
```
|
|
|
|
See `ShaderLang.h` and the usage of it in `StandAlone/StandAlone.cpp` for more
|
|
details.
|
|
|
|
### C Functional Interface (orignal)
|
|
|
|
This interface is in roughly the first 2/3 of `ShaderLang.h`, and referred to
|
|
as the `Sh*()` interface, as all the entry points start `Sh`.
|
|
|
|
The `Sh*()` interface takes a "compiler" call-back object, which it calls after
|
|
building call back that is passed the AST and can then execute a backend on it.
|
|
|
|
The following is a simplified resulting run-time call stack:
|
|
|
|
```c
|
|
ShCompile(shader, compiler) -> compiler(AST) -> <back end>
|
|
```
|
|
|
|
In practice, `ShCompile()` takes shader strings, default version, and
|
|
warning/error and other options for controlling compilation.
|
|
|
|
Basic Internal Operation
|
|
------------------------
|
|
|
|
* Initial lexical analysis is done by the preprocessor in
|
|
`MachineIndependent/Preprocessor`, and then refined by a GLSL scanner
|
|
in `MachineIndependent/Scan.cpp`. There is currently no use of flex.
|
|
|
|
* Code is parsed using bison on `MachineIndependent/glslang.y` with the
|
|
aid of a symbol table and an AST. The symbol table is not passed on to
|
|
the back-end; the intermediate representation stands on its own.
|
|
The tree is built by the grammar productions, many of which are
|
|
offloaded into `ParseHelper.cpp`, and by `Intermediate.cpp`.
|
|
|
|
* The intermediate representation is very high-level, and represented
|
|
as an in-memory tree. This serves to lose no information from the
|
|
original program, and to have efficient transfer of the result from
|
|
parsing to the back-end. In the AST, constants are propogated and
|
|
folded, and a very small amount of dead code is eliminated.
|
|
|
|
To aid linking and reflection, the last top-level branch in the AST
|
|
lists all global symbols.
|
|
|
|
* The primary algorithm of the back-end compiler is to traverse the
|
|
tree (high-level intermediate representation), and create an internal
|
|
object code representation. There is an example of how to do this
|
|
in `MachineIndependent/intermOut.cpp`.
|
|
|
|
* Reduction of the tree to a linear byte-code style low-level intermediate
|
|
representation is likely a good way to generate fully optimized code.
|
|
|
|
* There is currently some dead old-style linker-type code still lying around.
|
|
|
|
* Memory pool: parsing uses types derived from C++ `std` types, using a
|
|
custom allocator that puts them in a memory pool. This makes allocation
|
|
of individual container/contents just few cycles and deallocation free.
|
|
This pool is popped after the AST is made and processed.
|
|
|
|
The use is simple: if you are going to call `new`, there are three cases:
|
|
|
|
- the object comes from the pool (its base class has the macro
|
|
`POOL_ALLOCATOR_NEW_DELETE` in it) and you do not have to call `delete`
|
|
|
|
- it is a `TString`, in which case call `NewPoolTString()`, which gets
|
|
it from the pool, and there is no corresponding `delete`
|
|
|
|
- the object does not come from the pool, and you have to do normal
|
|
C++ memory management of what you `new`
|
|
|
|
|
|
[cmake]: https://cmake.org/
|
|
[bison]: https://www.gnu.org/software/bison/
|
|
[googletest]: https://github.com/google/googletest
|
|
[bison-gnu-win32]: http://gnuwin32.sourceforge.net/packages/bison.htm
|