diff options
| -rw-r--r-- | docs/shading.html | 53 |
1 files changed, 51 insertions, 2 deletions
diff --git a/docs/shading.html b/docs/shading.html index 412c89389e..48ae15f940 100644 --- a/docs/shading.html +++ b/docs/shading.html @@ -23,9 +23,10 @@ Contents </p> <ul> <li><a href="#unsup">Unsupported Features</a> -<li><a href="#impl">Implementation Notes</a> +<li><a href="#notes">Implementation Notes</a> <li><a href="#hints">Programming Hints</a> <li><a href="#standalone">Stand-alone Compiler</a> +<li><a href="#implementation">Compiler Implementation</a> </ul> @@ -50,7 +51,7 @@ All other major features of the shading language should function. </p> -<a name="impl"> +<a name="notes"> <h2>Implementation Notes</h2> <ul> @@ -188,5 +189,53 @@ Over time, the correctness of the GPU programs, with respect to the ARB and NV languagues, should improve. </p> + + +<a name="implementation"> +<h2>Compiler Implementation</h2> + +<p> +The source code for Mesa's shading language compiler is in the +<code>src/mesa/shader/slang/</code> directory. +</p> + +<p> +The compiler follows a fairly standard design and basically works as follows: +</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 +(see prog_execute.c) or translated into a specific hardware architecture +(see drivers/dri/i915/i915_fragprog.c for example). +</p> + + + </BODY> </HTML> |