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Diffstat (limited to 'docs/shading.html')
| -rw-r--r-- | docs/shading.html | 190 |
1 files changed, 44 insertions, 146 deletions
diff --git a/docs/shading.html b/docs/shading.html index 750884cf36c..c41d4a9be2b 100644 --- a/docs/shading.html +++ b/docs/shading.html @@ -39,19 +39,19 @@ list of keywords to control some aspects of the GLSL compiler and shader execution. These are generally used for debugging. </p> <ul> -<li>dump - print GLSL shader code to stdout at link time -<li>log - log all GLSL shaders to files. +<li><b>dump</b> - print GLSL shader code to stdout at link time +<li><b>log</b> - log all GLSL shaders to files. The filenames will be "shader_X.vert" or "shader_X.frag" where X the shader ID. -<li>nopt - disable compiler optimizations -<li>opt - force compiler optimizations -<li>uniform - print message to stdout when glUniform is called -<li>nopvert - force vertex shaders to be a simple shader that just transforms +<li><b>nopt</b> - disable compiler optimizations +<li><b>opt</b> - force compiler optimizations +<li><b>uniform</b> - print message to stdout when glUniform is called +<li><b>nopvert</b> - force vertex shaders to be a simple shader that just transforms the vertex position with ftransform() and passes through the color and texcoord[0] attributes. -<li>nopfrag - force fragment shader to be a simple shader that passes +<li><b>nopfrag</b> - force fragment shader to be a simple shader that passes through the color attribute. -<li>useprog - log glUseProgram calls to stderr +<li><b>useprog</b> - log glUseProgram calls to stderr </ul> <p> Example: export MESA_GLSL=dump,nopt @@ -59,30 +59,28 @@ Example: export MESA_GLSL=dump,nopt <a name="120"> -<h2>GLSL 1.20 support</h2> +<h2>GLSL Version</h2> <p> -GLSL version 1.20 is supported in Mesa 7.3 and later. -Among the features/differences of GLSL 1.20 are: +The GLSL compiler currently supports version 1.20 of the shading language. +</p> + +<p> +Several GLSL extensions are also supported: +</p> <ul> -<li><code>mat2x3, mat2x4</code>, etc. types and functions -<li><code>transpose(), outerProduct(), matrixCompMult()</code> functions -(but untested) -<li>precision qualifiers (lowp, mediump, highp) -<li><code>invariant</code> qualifier -<li><code>array.length()</code> method -<li><code>float[5] a;</code> array syntax -<li><code>centroid</code> qualifier -<li>unsized array constructors -<li>initializers for uniforms -<li>const initializers calling built-in functions +<li>GL_ARB_draw_buffers +<li>GL_ARB_texture_rectangle +<li>GL_ARB_fragment_coord_conventions +<li>GL_EXT_texture_array </ul> - <a name="unsup"> <h2>Unsupported Features</h2> +<p>XXX update this section</p> + <p> The following features of the shading language are not yet fully supported in Mesa: @@ -130,39 +128,6 @@ These issues will be addressed/resolved in the future. <h2>Programming Hints</h2> <ul> -<li>Declare <em>in</em> function parameters as <em>const</em> whenever possible. - This improves the efficiency of function inlining. -</li> -<br> -<li>To reduce register usage, declare variables within smaller scopes. - For example, the following code: -<pre> - void main() - { - vec4 a1, a2, b1, b2; - gl_Position = expression using a1, a2. - gl_Color = expression using b1, b2; - } -</pre> - Can be rewritten as follows to use half as many registers: -<pre> - void main() - { - { - vec4 a1, a2; - gl_Position = expression using a1, a2. - } - { - vec4 b1, b2; - gl_Color = expression using b1, b2; - } - } -</pre> - Alternately, rather than using several float variables, use - a vec4 instead. Use swizzling and writemasks to access the - components of the vec4 as floats. -</li> -<br> <li>Use the built-in library functions whenever possible. For example, instead of writing this: <pre> @@ -172,8 +137,6 @@ These issues will be addressed/resolved in the future. <pre> float x = inversesqrt(y); </pre> -<li> - Use ++i when possible as it's more efficient than i++ </li> </ul> @@ -182,13 +145,8 @@ These issues will be addressed/resolved in the future. <h2>Stand-alone GLSL Compiler</h2> <p> -A unique stand-alone GLSL compiler driver has been added to Mesa. -<p> - -<p> -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. </p> <p> @@ -201,59 +159,25 @@ This tool is useful for: </ul> <p> -After building Mesa, the glslcompiler can be built by manually running: +After building Mesa, the compiler can be found at src/glsl/glsl_compiler </p> -<pre> - make realclean - make linux - cd src/mesa/drivers/glslcompiler - make -</pre> - <p> Here's an example of using the compiler to compile a vertex shader and emit GL_ARB_vertex_program-style instructions: </p> <pre> - bin/glslcompiler --debug --numbers --fs progs/glsl/CH06-brick.frag.txt -</pre> -<p> -results in: -</p> -<pre> -# 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/glslcompiler --dump-ast myshader.vert </pre> -<p> -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. -</p> -<p> -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. -</p> +Options include +<ul> +<li><b>--dump-ast</b> - dump GPU code +<li><b>--dump-hir</b> - dump high-level IR code +<li><b>--dump-lir</b> - dump low-level IR code +<li><b>--link</b> - ??? +</ul> + @@ -262,38 +186,12 @@ and NV languagues, should improve. <p> The source code for Mesa's shading language compiler is in the -<code>src/mesa/shader/slang/</code> directory. +<code>src/glsl/</code> directory. </p> <p> -The compiler follows a fairly standard design and basically works as follows: +XXX provide some info about the compiler.... </p> -<ul> -<li>The input string is tokenized (see grammar.c) and parsed -(see slang_compiler_*.c) to produce an Abstract Syntax Tree (AST). -The nodes in this tree are slang_operation structures -(see slang_compile_operation.h). -The nodes are decorated with symbol table, scoping and datatype information. -<li>The AST is converted into an Intermediate representation (IR) tree -(see the slang_codegen.c file). -The IR nodes represent basic GPU instructions, like add, dot product, -move, etc. -The IR tree is mostly a binary tree, but a few nodes have three or four -children. -In principle, the IR tree could be executed by doing an in-order traversal. -<li>The IR tree is traversed in-order to emit code (see slang_emit.c). -This is also when registers are allocated to store variables and temps. -<li>In the future, a pattern-matching code generator-generator may be -used for code generation. -Programs such as L-BURG (Bottom-Up Rewrite Generator) and Twig look for -patterns in IR trees, compute weights for subtrees and use the weights -to select the best instructions to represent the sub-tree. -<li>The emitted GPU instructions (see prog_instruction.h) are stored in a -gl_program object (see mtypes.h). -<li>When a fragment shader and vertex shader are linked (see slang_link.c) -the varying vars are matched up, uniforms are merged, and vertex -attributes are resolved (rewriting instructions as needed). -</ul> <p> The final vertex and fragment programs may be interpreted in software @@ -351,20 +249,20 @@ Extra NOP instructions will also be inserted. <h2>Compiler Validation</h2> <p> -A <a href="http://glean.sf.net" target="_parent">Glean</a> test has -been create to exercise the GLSL compiler. -</p> -<p> -The <em>glsl1</em> 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. </p> + <p> -The test coverage is reasonably broad and complete but additional tests -should be added. +The <a href="http://people.freedesktop.org/~nh/piglit/">Piglit</a> project +has many GLSL tests and the +<a href="http://glean.sf.net" target="_parent">Glean</a> glsl1 test +tests GLSL features. </p> +<p> +The Mesa demos repository also has some good GLSL tests. +</p> </BODY> </HTML> |