mesa/dlist: shortcircuit some redundant statechanges at compile time

Currently, state-changes in mesa display lists are more or less
a verbatim recording of the GL calls made during compilation.

This change introduces a minor optimization to recognize and eliminate
cases where the application emits redundant state changes, eg:

  glShadeModel( GL_FLAT );
  glBegin( prim )
  ...
  glEnd()
  glShadeModel( GL_FLAT );
  glBegin( prim )
  ...
  glEnd()

The big win is when we can eliminate all the statechanges between two
primitive blocks and combine them into a single VBO node.

This commit implements state-change elimination for Material and ShadeModel
only.  This is enough to make a start on debugging, etc.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index 84a082b253e..bdaa4977b72 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -2806,6 +2806,13 @@ struct gl_dlist_state
    
    GLubyte ActiveEdgeFlag;
    GLboolean CurrentEdgeFlag;
+
+   struct {
+      /* State known to have been set by the currently-compiling display
+       * list.  Used to eliminate some redundant state changes.
+       */
+      GLenum ShadeModel;
+   } Current;
 };