-Last updated on 15 December 2008. -
-Contents
-GLSL version 1.20 is supported in Mesa 7.3. -Among the features/differences of GLSL 1.20 are: +The MESA_GLSL environment variable can be set to a comma-separated +list of keywords to control some aspects of the GLSL compiler and shader +execution. These are generally used for debugging. +
mat2x3, mat2x4, etc. types and functions
-transpose(), outerProduct(), matrixCompMult() functions
-(but untested)
-invariant qualifier
-array.length() method
-float[5] a; array syntax
-centroid qualifier
-+Example: export MESA_GLSL=dump,nopt +
+ ++The GLSL compiler currently supports version 1.20 of the shading language. +
+ ++Several GLSL extensions are also supported: +
+XXX update this section
+-The following features of the shading language are not yet supported +The following features of the shading language are not yet fully supported in Mesa:
- void main()
- {
- vec4 a1, a2, b1, b2;
- gl_Position = expression using a1, a2.
- gl_Color = expression using b1, b2;
- }
-
- Can be rewritten as follows to use half as many registers:
-
- void main()
- {
- {
- vec4 a1, a2;
- gl_Position = expression using a1, a2.
- }
- {
- vec4 b1, b2;
- gl_Color = expression using b1, b2;
- }
- }
-
- Alternately, rather than using several float variables, use
- a vec4 instead. Use swizzling and writemasks to access the
- components of the vec4 as floats.
-
@@ -145,8 +137,6 @@ These issues will be addressed/resolved in the future.
float x = inversesqrt(y);
--A unique stand-alone GLSL compiler driver has been added to Mesa. -
- -
-The stand-alone compiler (like a conventional command-line compiler) -is a tool that accepts Shading Language programs and emits low-level -GPU programs. +The stand-alone GLSL compiler program can be used to compile GLSL shaders +into low-level GPU code.
@@ -174,57 +159,25 @@ This tool is useful for:
-After building Mesa, the glslcompiler can be built by manually running: +After building Mesa, the compiler can be found at src/glsl/glsl_compiler
-- cd src/mesa/drivers/glslcompiler - make --
Here's an example of using the compiler to compile a vertex shader and emit GL_ARB_vertex_program-style instructions:
- bin/glslcompiler --debug --numbers --fs progs/glsl/CH06-brick.frag.txt --
-results in: -
--# Fragment Program/Shader - 0: RCP TEMP[4].x, UNIFORM[2].xxxx; - 1: RCP TEMP[4].y, UNIFORM[2].yyyy; - 2: MUL TEMP[3].xy, VARYING[0], TEMP[4]; - 3: MOV TEMP[1], TEMP[3]; - 4: MUL TEMP[0].w, TEMP[1].yyyy, CONST[4].xxxx; - 5: FRC TEMP[1].z, TEMP[0].wwww; - 6: SGT.C TEMP[0].w, TEMP[1].zzzz, CONST[4].xxxx; - 7: IF (NE.wwww); # (if false, goto 9); - 8: ADD TEMP[1].x, TEMP[1].xxxx, CONST[4].xxxx; - 9: ENDIF; - 10: FRC TEMP[1].xy, TEMP[1]; - 11: SGT TEMP[2].xy, UNIFORM[3], TEMP[1]; - 12: MUL TEMP[1].z, TEMP[2].xxxx, TEMP[2].yyyy; - 13: LRP TEMP[0], TEMP[1].zzzz, UNIFORM[0], UNIFORM[1]; - 14: MUL TEMP[0].xyz, TEMP[0], VARYING[1].xxxx; - 15: MOV OUTPUT[0].xyz, TEMP[0]; - 16: MOV OUTPUT[0].w, CONST[4].yyyy; - 17: END + src/glsl/glsl_compiler --dump-ast myshader.vert-
-Note that some shading language constructs (such as uniform and varying -variables) aren't expressible in ARB or NV-style programs. -Therefore, the resulting output is not always legal by definition of -those program languages. -
--Also note that this compiler driver is still under development. -Over time, the correctness of the GPU programs, with respect to the ARB -and NV languagues, should improve. -
+Options include +
The source code for Mesa's shading language compiler is in the
-src/mesa/shader/slang/ directory.
+src/glsl/ directory.
-The compiler follows a fairly standard design and basically works as follows: +XXX provide some info about the compiler....
-The final vertex and fragment programs may be interpreted in software @@ -322,20 +249,20 @@ Extra NOP instructions will also be inserted.
-A Glean test has -been create to exercise the GLSL compiler. -
--The glsl1 test runs over 170 sub-tests to check that the language -features and built-in functions work properly. -This test should be run frequently while working on the compiler to catch +Developers working on the GLSL compiler should test frequently to avoid regressions.
+-The test coverage is reasonably broad and complete but additional tests -should be added. +The Piglit project +has many GLSL tests and the +Glean glsl1 test +tests GLSL features.
++The Mesa demos repository also has some good GLSL tests. +