Mesa (master): slang: add some comments related to geometry shaders

[Zack Rusin]

Module: Mesa
Branch: master
Commit: f11e25ee957549ab867fac4f17a5c61fd9172794
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=f11e25ee957549ab867fac4f17a5c61fd9172794

Author: Zack Rusin <zackr at vmware.com>
Date:   Wed Jul  7 16:41:01 2010 -0400

slang: add some comments related to geometry shaders

---

 src/mesa/slang/slang_codegen.c |    3 +++
 src/mesa/slang/slang_link.c    |   12 ++++++++++++
 2 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/src/mesa/slang/slang_codegen.c b/src/mesa/slang/slang_codegen.c
index b2fe5b1..8ebe298 100644
--- a/src/mesa/slang/slang_codegen.c
+++ b/src/mesa/slang/slang_codegen.c
@@ -4191,6 +4191,9 @@ _slang_gen_variable(slang_assemble_ctx * A, slang_operation *oper)
    slang_variable *var = _slang_variable_locate(oper->locals, name, GL_TRUE);
    slang_ir_node *n;
    if (!var || !var->declared) {
+      /* Geometry shader set gl_VerticesIn at link time
+       * so we need to way with resolving this variable
+       * until then */
       if (A->program->Target == MESA_GEOMETRY_PROGRAM &&
           !strcmp((char*)name, "gl_VerticesIn") ){
          A->UnresolvedRefs = GL_TRUE;
diff --git a/src/mesa/slang/slang_link.c b/src/mesa/slang/slang_link.c
index c89ab8b..bc2bd31 100644
--- a/src/mesa/slang/slang_link.c
+++ b/src/mesa/slang/slang_link.c
@@ -810,6 +810,12 @@ remove_extra_version_directives(GLchar *source)
    }
 }
 
+/* Returns the number of vertices per geometry shader
+ * input primitive.
+ * XXX: duplicated in Gallium in u_vertices_per_prim
+ * method. Once Mesa core will start using Gallium
+ * this should be removed
+ */
 static int
 vertices_per_prim(int prim)
 {
@@ -865,6 +871,8 @@ concat_shaders(struct gl_shader_program *shProg, GLenum shaderType)
       return NULL;
    }
 
+   /* Geometry shader will inject definition of
+    * const int gl_VerticesIn */
    if (shaderType == GL_GEOMETRY_SHADER_ARB) {
       totalLen += 32;
    }
@@ -883,6 +891,10 @@ concat_shaders(struct gl_shader_program *shProg, GLenum shaderType)
          len += shaderLengths[i];
       }
    }
+   /* if it's geometry shader we need to inject definition
+    * of "const int gl_VerticesIn = X;" where X is the number
+    * of vertices per input primitive
+    */
    if (shaderType == GL_GEOMETRY_SHADER_ARB) {
       GLchar gs_pre[32];
       GLuint num_verts = vertices_per_prim(shProg->Geom.InputType);