draw: fix flatshade stage for constant interpolated values

This stage only worked for traditional old-school flatshading, it did ignore
constant interpolated values and only handled colors, the code probably
predates using of constant interpolated values in gallium. So fix this - the
clip stage apparently did this a long time ago already.
Unfortunately this also means the stage needs to be invoked when flatshading
isn't enabled but some other prim changing stages are - for instance with
fill mode line each of the 3 lines in a tri should get the same attribute
value from the leading vertex in the original tri if interpolation is constant,
which did not happen before
Due to that, the stage is now run in more cases, even unnecessary ones. Could
in theory skip it completely if there aren't any constant interpolated
attributes (and rast->flatshade isn't set), but not sure it's worth bothering,
as it looks kinda complicated getting this information in advance.

No piglit change (doesn't really cover this directly).

Reviewed-by: Jose Fonseca <[email protected]>

3 files changed, 126 insertions, 69 deletions

diff --git a/src/gallium/auxiliary/draw/draw_pipe_clip.c b/src/gallium/auxiliary/draw/draw_pipe_clip.c
index 2fbd655e07f..e1e7dcc6f63 100644
--- a/src/gallium/auxiliary/draw/draw_pipe_clip.c
+++ b/src/gallium/auxiliary/draw/draw_pipe_clip.c
@@ -741,9 +741,10 @@ static void
 clip_init_state( struct draw_stage *stage )
 {
    struct clip_stage *clipper = clip_stage( stage );
-   const struct draw_fragment_shader *fs = stage->draw->fs.fragment_shader;
+   const struct draw_context *draw = stage->draw;
+   const struct draw_fragment_shader *fs = draw->fs.fragment_shader;
+   const struct tgsi_shader_info *info = draw_get_shader_info(draw);
    uint i, j;
-   const struct tgsi_shader_info *info = draw_get_shader_info(stage->draw);
 
    /* We need to know for each attribute what kind of interpolation is
     * done on it (flat, smooth or noperspective).  But the information
@@ -765,7 +766,7 @@ clip_init_state( struct draw_stage *stage )
     * gl_Color/gl_SecondaryColor, with the correct default.
     */
    int indexed_interp[2];
-   indexed_interp[0] = indexed_interp[1] = stage->draw->rasterizer->flatshade ?
+   indexed_interp[0] = indexed_interp[1] = draw->rasterizer->flatshade ?
       TGSI_INTERPOLATE_CONSTANT : TGSI_INTERPOLATE_PERSPECTIVE;
 
    if (fs) {
@@ -802,11 +803,11 @@ clip_init_state( struct draw_stage *stage )
          clipper->noperspective_attribs[i] = interp == TGSI_INTERPOLATE_LINEAR;
    }
    /* Search the extra vertex attributes */
-   for (j = 0; j < stage->draw->extra_shader_outputs.num; j++) {
+   for (j = 0; j < draw->extra_shader_outputs.num; j++) {
       /* Find the interpolation mode for a specific attribute */
       int interp = find_interp(fs, indexed_interp,
-                               stage->draw->extra_shader_outputs.semantic_name[j],
-                               stage->draw->extra_shader_outputs.semantic_index[j]);
+                               draw->extra_shader_outputs.semantic_name[j],
+                               draw->extra_shader_outputs.semantic_index[j]);
       /* If it's flat, add it to the flat vector.  Otherwise update
        * the noperspective mask.
        */
diff --git a/src/gallium/auxiliary/draw/draw_pipe_flatshade.c b/src/gallium/auxiliary/draw/draw_pipe_flatshade.c
index 4d62dbd7f9e..59e33b472f4 100644
--- a/src/gallium/auxiliary/draw/draw_pipe_flatshade.c
+++ b/src/gallium/auxiliary/draw/draw_pipe_flatshade.c
@@ -33,6 +33,7 @@
 
 #include "pipe/p_shader_tokens.h"
 #include "draw_vs.h"
+#include "draw_fs.h"
 #include "draw_pipe.h"
 
 
@@ -41,20 +42,10 @@ struct flat_stage
 {
    struct draw_stage stage;
 
-   uint num_color_attribs;
-   uint color_attribs[2];  /* front/back primary colors */
-
-   uint num_spec_attribs;
-   uint spec_attribs[2];  /* front/back secondary colors */
+   uint num_flat_attribs;
+   uint flat_attribs[PIPE_MAX_SHADER_OUTPUTS];  /* flatshaded attribs */
 };
 
-#define COPY_3FV( DST, SRC )         \
-do {                                \
-   (DST)[0] = (SRC)[0];             \
-   (DST)[1] = (SRC)[1];             \
-   (DST)[2] = (SRC)[2];             \
-} while (0)
-
 
 static INLINE struct flat_stage *
 flat_stage(struct draw_stage *stage)
@@ -63,51 +54,41 @@ flat_stage(struct draw_stage *stage)
 }
 
 
-/** Copy all the color attributes from 'src' vertex to 'dst' vertex */
-static INLINE void copy_colors( struct draw_stage *stage,
-                                struct vertex_header *dst,
-                                const struct vertex_header *src )
+/** Copy all the constant attributes from 'src' vertex to 'dst' vertex */
+static INLINE void copy_flats( struct draw_stage *stage,
+                               struct vertex_header *dst,
+                               const struct vertex_header *src )
 {
    const struct flat_stage *flat = flat_stage(stage);
    uint i;
 
-   for (i = 0; i < flat->num_color_attribs; i++) {
-      const uint attr = flat->color_attribs[i];
+   for (i = 0; i < flat->num_flat_attribs; i++) {
+      const uint attr = flat->flat_attribs[i];
       COPY_4FV(dst->data[attr], src->data[attr]);
    }
-
-   for (i = 0; i < flat->num_spec_attribs; i++) {
-      const uint attr = flat->spec_attribs[i];
-      COPY_3FV(dst->data[attr], src->data[attr]);
-   }
 }
 
 
 /** Copy all the color attributes from src vertex to dst0 & dst1 vertices */
-static INLINE void copy_colors2( struct draw_stage *stage,
-                                 struct vertex_header *dst0,
-                                 struct vertex_header *dst1,
-                                 const struct vertex_header *src )
+static INLINE void copy_flats2( struct draw_stage *stage,
+                                struct vertex_header *dst0,
+                                struct vertex_header *dst1,
+                                const struct vertex_header *src )
 {
    const struct flat_stage *flat = flat_stage(stage);
    uint i;
-   for (i = 0; i < flat->num_color_attribs; i++) {
-      const uint attr = flat->color_attribs[i];
+   for (i = 0; i < flat->num_flat_attribs; i++) {
+      const uint attr = flat->flat_attribs[i];
       COPY_4FV(dst0->data[attr], src->data[attr]);
       COPY_4FV(dst1->data[attr], src->data[attr]);
    }
-
-   for (i = 0; i < flat->num_spec_attribs; i++) {
-      const uint attr = flat->spec_attribs[i];
-      COPY_3FV(dst0->data[attr], src->data[attr]);
-      COPY_3FV(dst1->data[attr], src->data[attr]);
-   }
 }
 
 
 /**
- * Flatshade tri.  Required for clipping and when unfilled tris are
- * active, otherwise handled by hardware.
+ * Flatshade tri. Not required for clipping which handles this on its own,
+ * but required for unfilled tris and other primitive-changing stages
+ * (like widelines). If no such stages are active, handled by hardware.
  */
 static void flatshade_tri_0( struct draw_stage *stage,
                              struct prim_header *header )
@@ -121,8 +102,8 @@ static void flatshade_tri_0( struct draw_stage *stage,
    tmp.v[1] = dup_vert(stage, header->v[1], 0);
    tmp.v[2] = dup_vert(stage, header->v[2], 1);
 
-   copy_colors2(stage, tmp.v[1], tmp.v[2], tmp.v[0]);
-   
+   copy_flats2(stage, tmp.v[1], tmp.v[2], tmp.v[0]);
+
    stage->next->tri( stage->next, &tmp );
 }
 
@@ -139,14 +120,14 @@ static void flatshade_tri_2( struct draw_stage *stage,
    tmp.v[1] = dup_vert(stage, header->v[1], 1);
    tmp.v[2] = header->v[2];
 
-   copy_colors2(stage, tmp.v[0], tmp.v[1], tmp.v[2]);
-   
+   copy_flats2(stage, tmp.v[0], tmp.v[1], tmp.v[2]);
+
    stage->next->tri( stage->next, &tmp );
 }
 
 
 /**
- * Flatshade line.  Required for clipping.
+ * Flatshade line.
  */
 static void flatshade_line_0( struct draw_stage *stage,
                               struct prim_header *header )
@@ -159,11 +140,12 @@ static void flatshade_line_0( struct draw_stage *stage,
    tmp.v[0] = header->v[0];
    tmp.v[1] = dup_vert(stage, header->v[1], 0);
 
-   copy_colors(stage, tmp.v[1], tmp.v[0]);
-   
+   copy_flats(stage, tmp.v[1], tmp.v[0]);
+
    stage->next->line( stage->next, &tmp );
 }
 
+
 static void flatshade_line_1( struct draw_stage *stage,
                               struct prim_header *header )
 {
@@ -175,36 +157,106 @@ static void flatshade_line_1( struct draw_stage *stage,
    tmp.v[0] = dup_vert(stage, header->v[0], 0);
    tmp.v[1] = header->v[1];
 
-   copy_colors(stage, tmp.v[0], tmp.v[1]);
-   
+   copy_flats(stage, tmp.v[0], tmp.v[1]);
+
    stage->next->line( stage->next, &tmp );
 }
 
 
+static int
+find_interp(const struct draw_fragment_shader *fs, int *indexed_interp,
+            uint semantic_name, uint semantic_index)
+{
+   int interp;
+   /* If it's gl_{Front,Back}{,Secondary}Color, pick up the mode
+    * from the array we've filled before. */
+   if (semantic_name == TGSI_SEMANTIC_COLOR ||
+       semantic_name == TGSI_SEMANTIC_BCOLOR) {
+      interp = indexed_interp[semantic_index];
+   } else {
+      /* Otherwise, search in the FS inputs, with a decent default
+       * if we don't find it.
+       */
+      uint j;
+      interp = TGSI_INTERPOLATE_PERSPECTIVE;
+      if (fs) {
+         for (j = 0; j < fs->info.num_inputs; j++) {
+            if (semantic_name == fs->info.input_semantic_name[j] &&
+                semantic_index == fs->info.input_semantic_index[j]) {
+               interp = fs->info.input_interpolate[j];
+               break;
+            }
+         }
+      }
+   }
+   return interp;
+}
 
 
 static void flatshade_init_state( struct draw_stage *stage )
 {
    struct flat_stage *flat = flat_stage(stage);
-   const struct draw_vertex_shader *vs = stage->draw->vs.vertex_shader;
-   uint i;
+   const struct draw_context *draw = stage->draw;
+   const struct draw_fragment_shader *fs = draw->fs.fragment_shader;
+   const struct tgsi_shader_info *info = draw_get_shader_info(draw);
+   uint i, j;
+
+   /* Find which vertex shader outputs need constant interpolation, make a list */
+
+   /* XXX: this code is a near exact copy of the one in clip_init_state.
+    * The latter also cares about perspective though.
+    */
 
-   /* Find which vertex shader outputs are colors, make a list */
-   flat->num_color_attribs = 0;
-   flat->num_spec_attribs = 0;
-   for (i = 0; i < vs->info.num_outputs; i++) {
-      if (vs->info.output_semantic_name[i] == TGSI_SEMANTIC_COLOR ||
-          vs->info.output_semantic_name[i] == TGSI_SEMANTIC_BCOLOR) {
-         if (vs->info.output_semantic_index[i] == 0)
-            flat->color_attribs[flat->num_color_attribs++] = i;
-         else
-            flat->spec_attribs[flat->num_spec_attribs++] = i;
+   /* First pick up the interpolation mode for
+    * gl_Color/gl_SecondaryColor, with the correct default.
+    */
+   int indexed_interp[2];
+   indexed_interp[0] = indexed_interp[1] = draw->rasterizer->flatshade ?
+      TGSI_INTERPOLATE_CONSTANT : TGSI_INTERPOLATE_PERSPECTIVE;
+
+   if (fs) {
+      for (i = 0; i < fs->info.num_inputs; i++) {
+         if (fs->info.input_semantic_name[i] == TGSI_SEMANTIC_COLOR) {
+            if (fs->info.input_interpolate[i] != TGSI_INTERPOLATE_COLOR)
+               indexed_interp[fs->info.input_semantic_index[i]] = fs->info.input_interpolate[i];
+         }
+      }
+   }
+
+   /* Then resolve the interpolation mode for every output attribute.
+    *
+    * Given how the rest of the code, the most efficient way is to
+    * have a vector of flat-mode attributes.
+    */
+   flat->num_flat_attribs = 0;
+   for (i = 0; i < info->num_outputs; i++) {
+      /* Find the interpolation mode for a specific attribute */
+      int interp = find_interp(fs, indexed_interp,
+                               info->output_semantic_name[i],
+                               info->output_semantic_index[i]);
+      /* If it's flat, add it to the flat vector. */
+
+      if (interp == TGSI_INTERPOLATE_CONSTANT) {
+         flat->flat_attribs[flat->num_flat_attribs] = i;
+         flat->num_flat_attribs++;
+      }
+   }
+   /* Search the extra vertex attributes */
+   for (j = 0; j < draw->extra_shader_outputs.num; j++) {
+      /* Find the interpolation mode for a specific attribute */
+      int interp = find_interp(fs, indexed_interp,
+                               draw->extra_shader_outputs.semantic_name[j],
+                               draw->extra_shader_outputs.semantic_index[j]);
+      /* If it's flat, add it to the flat vector. */
+      if (interp == TGSI_INTERPOLATE_CONSTANT) {
+         flat->flat_attribs[flat->num_flat_attribs] = i + j;
+         flat->num_flat_attribs++;
       }
    }
 
    /* Choose flatshade routine according to provoking vertex:
     */
-   if (stage->draw->rasterizer->flatshade_first) {
+   if (draw->rasterizer->flatshade_first) {
       stage->line = flatshade_line_0;
       stage->tri = flatshade_tri_0;
    }
@@ -215,14 +267,14 @@ static void flatshade_init_state( struct draw_stage *stage )
 }
 
 static void flatshade_first_tri( struct draw_stage *stage,
-				 struct prim_header *header )
+                                 struct prim_header *header )
 {
    flatshade_init_state( stage );
    stage->tri( stage, header );
 }
 
 static void flatshade_first_line( struct draw_stage *stage,
-				  struct prim_header *header )
+                                  struct prim_header *header )
 {
    flatshade_init_state( stage );
    stage->line( stage, header );
@@ -230,7 +282,7 @@ static void flatshade_first_line( struct draw_stage *stage,
 
 
 static void flatshade_flush( struct draw_stage *stage, 
-			     unsigned flags )
+                             unsigned flags )
 {
    stage->tri = flatshade_first_tri;
    stage->line = flatshade_first_line;
diff --git a/src/gallium/auxiliary/draw/draw_pipe_validate.c b/src/gallium/auxiliary/draw/draw_pipe_validate.c
index 5c008c855ae..e69d84a37cd 100644
--- a/src/gallium/auxiliary/draw/draw_pipe_validate.c
+++ b/src/gallium/auxiliary/draw/draw_pipe_validate.c
@@ -221,7 +221,11 @@ static struct draw_stage *validate_pipeline( struct draw_stage *stage )
       need_det = TRUE;
    }
 
-   if (rast->flatshade && precalc_flat) {
+   if (precalc_flat) {
+      /*
+       * could only run the stage if either rast->flatshade is true
+       * or there's constant interpolated values.
+       */
       draw->pipeline.flatshade->next = next;
       next = draw->pipeline.flatshade;
    }