gallium: rework provoking vertex code

Builds on commit ddb0e18f6c5582d4d2cc59ffd16ad9c4639ed059 and fixes
regressions in glean clipFlat test.

We assume that Gallium drivers observe flatshade_first for all triangles
and that all the assorted per-triangle calls in the 'draw' module also
follow flatshade_first.  Everything else builds on those rules.

Gallium does not use follow flatshade_first for GL quads, quad strips
and polygons; the "last" vertex is always the provoking vertex for those
prims.  So now there are separate QUAD_FIRST_PV and QUAD_LAST_PV macros
in the draw primitive decomposition code instead of one QUAD macro.

5 files changed, 123 insertions, 49 deletions

diff --git a/src/gallium/auxiliary/draw/draw_pipe.c b/src/gallium/auxiliary/draw/draw_pipe.c
index 64c35025081..7ea04e38193 100644
--- a/src/gallium/auxiliary/draw/draw_pipe.c
+++ b/src/gallium/auxiliary/draw/draw_pipe.c
@@ -170,7 +170,25 @@ static void do_triangle( struct draw_context *draw,
  * Set up macros for draw_pt_decompose.h template code.
  * This code uses vertex indexes / elements.
  */
-#define QUAD(i0,i1,i2,i3)                       \
+
+/* emit first quad vertex as first vertex in triangles */
+#define QUAD_FIRST_PV(i0,i1,i2,i3)              \
+   do_triangle( draw,                           \
+                ( DRAW_PIPE_RESET_STIPPLE |     \
+                  DRAW_PIPE_EDGE_FLAG_0 |       \
+                  DRAW_PIPE_EDGE_FLAG_1 ),      \
+                verts + stride * elts[i0],      \
+                verts + stride * elts[i1],      \
+                verts + stride * elts[i2]);     \
+   do_triangle( draw,                           \
+                ( DRAW_PIPE_EDGE_FLAG_1 |       \
+                  DRAW_PIPE_EDGE_FLAG_2 ),      \
+                verts + stride * elts[i0],      \
+                verts + stride * elts[i2],      \
+                verts + stride * elts[i3])
+
+/* emit last quad vertex as last vertex in triangles */
+#define QUAD_LAST_PV(i0,i1,i2,i3)               \
    do_triangle( draw,                           \
                 ( DRAW_PIPE_RESET_STIPPLE |     \
                   DRAW_PIPE_EDGE_FLAG_0 |       \
@@ -261,9 +279,27 @@ void draw_pipeline_run( struct draw_context *draw,
 
 /*
  * Set up macros for draw_pt_decompose.h template code.
- * This code is for non-indexed rendering (no elts).
+ * This code is for non-indexed (aka linear) rendering (no elts).
  */
-#define QUAD(i0,i1,i2,i3)                                        \
+
+/* emit first quad vertex as first vertex in triangles */
+#define QUAD_FIRST_PV(i0,i1,i2,i3)                               \
+   do_triangle( draw,                                            \
+                ( DRAW_PIPE_RESET_STIPPLE |                      \
+                  DRAW_PIPE_EDGE_FLAG_0 |                        \
+                  DRAW_PIPE_EDGE_FLAG_1 ),                       \
+                verts + stride * ((i0) & ~DRAW_PIPE_FLAG_MASK),  \
+                verts + stride * (i1),                           \
+                verts + stride * (i2));                          \
+   do_triangle( draw,                                            \
+                ( DRAW_PIPE_EDGE_FLAG_1 |                        \
+                  DRAW_PIPE_EDGE_FLAG_2 ),                       \
+                verts + stride * ((i0) & ~DRAW_PIPE_FLAG_MASK),  \
+                verts + stride * (i2),                           \
+                verts + stride * (i3))
+
+/* emit last quad vertex as last vertex in triangles */
+#define QUAD_LAST_PV(i0,i1,i2,i3)                                \
    do_triangle( draw,                                            \
                 ( DRAW_PIPE_RESET_STIPPLE |                      \
                   DRAW_PIPE_EDGE_FLAG_0 |                        \
diff --git a/src/gallium/auxiliary/draw/draw_pipe_clip.c b/src/gallium/auxiliary/draw/draw_pipe_clip.c
index 428ef4ef67a..d0532cb341e 100644
--- a/src/gallium/auxiliary/draw/draw_pipe_clip.c
+++ b/src/gallium/auxiliary/draw/draw_pipe_clip.c
@@ -164,10 +164,18 @@ static void emit_poly( struct draw_stage *stage,
 {
    struct prim_header header;
    unsigned i;
+   ushort edge_first, edge_middle, edge_last;
 
-   const ushort edge_first  = DRAW_PIPE_EDGE_FLAG_2;
-   const ushort edge_middle = DRAW_PIPE_EDGE_FLAG_0;
-   const ushort edge_last   = DRAW_PIPE_EDGE_FLAG_1;
+   if (stage->draw->rasterizer->flatshade_first) {
+      edge_first  = DRAW_PIPE_EDGE_FLAG_0;
+      edge_middle = DRAW_PIPE_EDGE_FLAG_1;
+      edge_last   = DRAW_PIPE_EDGE_FLAG_2;
+   }
+   else {
+      edge_first  = DRAW_PIPE_EDGE_FLAG_2;
+      edge_middle = DRAW_PIPE_EDGE_FLAG_0;
+      edge_last   = DRAW_PIPE_EDGE_FLAG_1;
+   }
 
    /* later stages may need the determinant, but only the sign matters */
    header.det = origPrim->det;
@@ -301,21 +309,21 @@ do_clip_tri( struct draw_stage *stage,
 
    /* If flat-shading, copy color to new provoking vertex.
     */
-   if (stage->draw->rasterizer->flatshade_first) {
-      if (clipper->flat && inlist[0] != header->v[0]) {
-         inlist[0] = dup_vert(stage, inlist[0], tmpnr++);
-
-         copy_colors(stage, inlist[0], header->v[0]);
+   if (clipper->flat) {
+      if (stage->draw->rasterizer->flatshade_first) {
+         if (inlist[0] != header->v[0]) {
+            inlist[0] = dup_vert(stage, inlist[0], tmpnr++);
+            copy_colors(stage, inlist[0], header->v[0]);
+         }
       }
-   } else {
-      if (clipper->flat && inlist[0] != header->v[2]) {
-         inlist[0] = dup_vert(stage, inlist[0], tmpnr++);
-
-         copy_colors(stage, inlist[0], header->v[2]);
+      else {
+         if (inlist[0] != header->v[2]) {
+            inlist[0] = dup_vert(stage, inlist[0], tmpnr++);
+            copy_colors(stage, inlist[0], header->v[2]);
+         }
       }
    }
 
-
    /* Emit the polygon as triangles to the setup stage:
     */
    if (n >= 3)
diff --git a/src/gallium/auxiliary/draw/draw_pipe_vbuf.c b/src/gallium/auxiliary/draw/draw_pipe_vbuf.c
index abbf6247ab8..1fd083e54d0 100644
--- a/src/gallium/auxiliary/draw/draw_pipe_vbuf.c
+++ b/src/gallium/auxiliary/draw/draw_pipe_vbuf.c
@@ -159,19 +159,8 @@ vbuf_tri( struct draw_stage *stage,
 
    check_space( vbuf, 3 );
 
-   if (vbuf->stage.draw->rasterizer->flatshade_first) {
-      /* Put provoking vertex in position expected by the driver.
-       * Emit last provoking vertex in first pos.
-       * Swap verts 0 & 1 to preserve polygon winding.
-       */
-      vbuf->indices[vbuf->nr_indices++] = emit_vertex( vbuf, prim->v[2] );
-      vbuf->indices[vbuf->nr_indices++] = emit_vertex( vbuf, prim->v[0] );
-      vbuf->indices[vbuf->nr_indices++] = emit_vertex( vbuf, prim->v[1] );
-   }
-   else {
-      for (i = 0; i < 3; i++) {
-         vbuf->indices[vbuf->nr_indices++] = emit_vertex( vbuf, prim->v[i] );
-      }
+   for (i = 0; i < 3; i++) {
+      vbuf->indices[vbuf->nr_indices++] = emit_vertex( vbuf, prim->v[i] );
    }
 }
 
diff --git a/src/gallium/auxiliary/draw/draw_pt_decompose.h b/src/gallium/auxiliary/draw/draw_pt_decompose.h
index 02567d97f26..52f9593d46e 100644
--- a/src/gallium/auxiliary/draw/draw_pt_decompose.h
+++ b/src/gallium/auxiliary/draw/draw_pt_decompose.h
@@ -57,6 +57,7 @@ static void FUNC( ARGS,
    case PIPE_PRIM_TRIANGLE_STRIP:
       if (flatfirst) {
          for (i = 0; i+2 < count; i++) {
+            /* Emit first triangle vertex as first triangle vertex */
             TRIANGLE( DRAW_PIPE_RESET_STIPPLE | DRAW_PIPE_EDGE_FLAG_ALL,
                       (i + 0),
                       (i + 1 + (i&1)),
@@ -65,6 +66,7 @@ static void FUNC( ARGS,
       }
       else {
          for (i = 0; i+2 < count; i++) {
+            /* Emit last triangle vertex as last triangle vertex */
             TRIANGLE( DRAW_PIPE_RESET_STIPPLE | DRAW_PIPE_EDGE_FLAG_ALL,
                       (i + 0 + (i&1)),
                       (i + 1 - (i&1)),
@@ -96,24 +98,52 @@ static void FUNC( ARGS,
 
 
    case PIPE_PRIM_QUADS:
-      for (i = 0; i+3 < count; i += 4) {
-         QUAD( (i + 0),
-               (i + 1),
-               (i + 2),
-               (i + 3));
+      /* GL quads don't follow provoking vertex convention */
+      if (flatfirst) {
+         for (i = 0; i+3 < count; i += 4) {
+            /* emit last quad vertex as first triangle vertex */
+            QUAD_FIRST_PV( (i + 3),
+                           (i + 0),
+                           (i + 1),
+                           (i + 2) );
+         }
+      }
+      else {
+         for (i = 0; i+3 < count; i += 4) {
+            /* emit last quad vertex as last triangle vertex */
+            QUAD_LAST_PV( (i + 0),
+                          (i + 1),
+                          (i + 2),
+                          (i + 3) );
+         }
       }
       break;
 
    case PIPE_PRIM_QUAD_STRIP:
-      for (i = 0; i+3 < count; i += 2) {
-         QUAD( (i + 2),
-               (i + 0),
-               (i + 1),
-               (i + 3));
+      /* GL quad strips don't follow provoking vertex convention */
+      if (flatfirst) {
+         for (i = 0; i+3 < count; i += 2) {
+            /* emit last quad vertex as first triangle vertex */
+            QUAD_FIRST_PV( (i + 3),
+                           (i + 2),
+                           (i + 0),
+                           (i + 1) );
+
+         }
+      }
+      else {
+         for (i = 0; i+3 < count; i += 2) {
+            /* emit last quad vertex as last triangle vertex */
+            QUAD_LAST_PV( (i + 2),
+                          (i + 0),
+                          (i + 1),
+                          (i + 3) );
+         }
       }
       break;
 
    case PIPE_PRIM_POLYGON:
+      /* GL polygons don't follow provoking vertex convention */
       {
          /* These bitflags look a little odd because we submit the
           * vertices as (1,2,0) to satisfy flatshade requirements.
@@ -129,10 +159,20 @@ static void FUNC( ARGS,
             if (i + 3 == count)
                flags |= edge_last;
 
-	    TRIANGLE( flags,
-                      (i + 1),
-                      (i + 2),
-                      (0));
+            if (flatfirst) {
+               /* emit first polygon vertex as first triangle vertex */
+               TRIANGLE( flags,
+                         (0),
+                         (i + 1),
+                         (i + 2) );
+            }
+            else {
+               /* emit first polygon vertex as last triangle vertex */
+               TRIANGLE( flags,
+                         (i + 1),
+                         (i + 2),
+                         (0));
+            }
 	 }
       }
       break;
@@ -147,7 +187,8 @@ static void FUNC( ARGS,
 
 
 #undef TRIANGLE
-#undef QUAD
+#undef QUAD_FIRST_PV
+#undef QUAD_LAST_PV
 #undef POINT
 #undef LINE
 #undef FUNC
diff --git a/src/gallium/auxiliary/draw/draw_pt_vcache.c b/src/gallium/auxiliary/draw/draw_pt_vcache.c
index 37ffbac4f92..bfcd709f25d 100644
--- a/src/gallium/auxiliary/draw/draw_pt_vcache.c
+++ b/src/gallium/auxiliary/draw/draw_pt_vcache.c
@@ -199,12 +199,12 @@ vcache_ef_quad( struct vcache_frontend *vcache,
                              ( DRAW_PIPE_RESET_STIPPLE |
                                DRAW_PIPE_EDGE_FLAG_0 |
                                DRAW_PIPE_EDGE_FLAG_1 ),
-                             i0, i1, i2 );
+                             i3, i0, i1 );
 
       vcache_triangle_flags( vcache,
-                             ( DRAW_PIPE_EDGE_FLAG_2 |
-                               DRAW_PIPE_EDGE_FLAG_1 ),
-                             i0, i2, i3 );
+                             ( DRAW_PIPE_EDGE_FLAG_1 |
+                               DRAW_PIPE_EDGE_FLAG_2 ),
+                             i3, i1, i2 );
    }
    else {
       vcache_triangle_flags( vcache,