gallium: first steps to treat edgeflags as regular vertex element

The idea here is to eliminate the set_edgeflags() call in pipe_context
by treating edgeflags as a regular vertex element.

Edgeflags provoke special treatment in hardware, which means we need to
label them in some way, in this case we'll be passing them through the
vertex shader and labelling the vertex shader output with a new TGSI
semantic (TGSI_SEMANTIC_EDGEFLAG).

1 files changed, 10 insertions, 1 deletions

diff --git a/src/mesa/state_tracker/st_atom_shader.c b/src/mesa/state_tracker/st_atom_shader.c
index 09baff875b..e209634c90 100644
--- a/src/mesa/state_tracker/st_atom_shader.c
+++ b/src/mesa/state_tracker/st_atom_shader.c
@@ -106,7 +106,16 @@ find_translated_vp(struct st_context *st,
    /* Nothing in our key yet.  This will change:
     */
    memset(&key, 0, sizeof key);
-   key.dummy = 0;
+
+   /* When this is true, we will add an extra input to the vertex
+    * shader translation (for edgeflags), an extra output with
+    * edgeflag semantics, and extend the vertex shader to pass through
+    * the input to the output.  We'll need to use similar logic to set
+    * up the extra vertex_element input for edgeflags.
+    */
+   key.passthrough_edgeflags = (ctx->Polygon.FrontMode != GL_FILL ||
+                                ctx->Polygon.BackMode != GL_FILL);
+      
 
    /* Do we need to throw away old translations after a change in the
     * GL program string?