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glslang
=======
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
-------------------------------
There are binaries in the `Install/Windows` and `Install/Linux` directories.
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
Source: Build and run on Linux
-------------------------------
A simple bash script `BuildLinux.sh` is provided at the root directory
to do the build and run a test cases. You will need a recent version of
bison installed.
Once the executable is generated, it needs to be dynamically linked with the
shared object created in `lib` directory. To achieve that, `cd` to
`StandAlone` directory to update the `LD_LIBRARY_PATH` as follows
```bash
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:./../glslang/MachineIndependent/lib
```
You can also update `LD_LIBRARY_PATH` in the `.cshrc` or `.bashrc` file,
depending on the shell you are using. You will need to give the complete path
of `lib` directory in `.cshrc` or `.bashrc` files.
Source: Build and run on Windows
--------------------------------
Current development is with Visual Studio verion 11 (2012). The solution
file is in the project's root directory `Standalone.sln`.
Building the StandAlone project (the default) will create `glslangValidate.exe`
and copy it into the `Test` directory and `Install` directory. This allows
local test scripts to use either the debug or release version, whichever was
built last.
Windows execution and testing is generally done from within a cygwin
shell.
Note: Despite appearances, the use of a DLL is currently disabled; it
simply makes a standalone executable from a statically linked library.
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 (orginal)
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 controling compilation.
Testing
-------
`Test` is an active test directory that 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.
Executing the script `./runtests` will generate current results in
the `localResults` directory and `diff` them against the `baseResults`.
When you want to update the tracked test results, they need to be
copied from `localResults` to `baseResults`.
There are some tests borrowed from LunarGLASS. If LunarGLASS is
missing, those tests just won't run.
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`
README.txt deleted 100644 → 0
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
-------------------------------
There are binaries in the Install/Windows and Install/Linux directories.
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
Source: Build and run on Linux
-------------------------------
A simple bash script "BuildLinux.sh" is provided at the root directory
to do the build and run a test cases. You will need a recent version of
bison installed.
Once the executable is generated, it needs to be dynamically linked with the
shared object created in lib directory. To achieve that, "cd" to
StandAlone directory to update the LD_LIBRARY_PATH as follows
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:./../glslang/MachineIndependent/lib
You can also update LD_LIBRARY_PATH in the .cshrc or .bashrc file, depending on
the shell you are using. You will need to give the complete path of "lib" directory
in .cshrc or .bashrc files.
Source: Build and run on Windows
--------------------------------
Current development is with Visual Studio verion 11 (2012). The solution
file is in the project's root directory Standalone.sln.
Building the StandAlone project (the default) will create glslangValidate.exe and
copy it into the Test directory and Install directory. This allows local
test scripts to use either the debug or release version, whichever was
built last.
Windows execution and testing is generally done from within a cygwin
shell.
Note: Despite appearances, the use of a DLL is currently disabled; it
simply makes a standalone executable from a statically linked library.
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.
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 (orginal):
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:
ShCompile(shader, compiler) -> compiler(AST) -> <back end>
In practice, ShCompile() takes shader strings, default version, and
warning/error and other options for controling compilation.
Testing
-------
"Test" is an active test directory that 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.
Executing the script ./runtests will generate current results in
the localResults directory and diff them against the baseResults.
When you want to update the tracked test results, they need to be
copied from localResults to baseResults
There are some tests borrowed from LunarGLASS. If LunarGLASS is
missing, those tests just won't run.
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'
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