gallium: add TGSI_SEMANTIC_TEXCOORD,PCOORD v3

This makes it possible to identify gl_TexCoord and gl_PointCoord
for drivers where sprite coordinate replacement is restricted.

The new PIPE_CAP_TGSI_TEXCOORD decides whether these varyings
should be hidden behind the GENERIC semantic or not.

With this patch only nvc0 and nv30 will request that they be used.

v2: introduce a CAP so other drivers don't have to bother with
the new semantic

v3: adapt to introduction gl_varying_slot enum

3 files changed, 32 insertions, 19 deletions

diff --git a/src/gallium/auxiliary/draw/draw_pipe_wide_point.c b/src/gallium/auxiliary/draw/draw_pipe_wide_point.c
index 8e0a117843e..0d3fee4bb0d 100644
--- a/src/gallium/auxiliary/draw/draw_pipe_wide_point.c
+++ b/src/gallium/auxiliary/draw/draw_pipe_wide_point.c
@@ -52,6 +52,7 @@
  */
 
 
+#include "pipe/p_screen.h"
 #include "pipe/p_context.h"
 #include "util/u_math.h"
 #include "util/u_memory.h"
@@ -74,6 +75,9 @@ struct widepoint_stage {
    uint num_texcoord_gen;
    uint texcoord_gen_slot[PIPE_MAX_SHADER_OUTPUTS];
 
+   /* TGSI_SEMANTIC to which sprite_coord_enable applies */
+   unsigned sprite_coord_semantic;
+
    int psize_slot;
 };
 
@@ -233,28 +237,29 @@ widepoint_first_point(struct draw_stage *stage,
 
       wide->num_texcoord_gen = 0;
 
-      /* Loop over fragment shader inputs looking for generic inputs
+      /* Loop over fragment shader inputs looking for the PCOORD input or inputs
        * for which bit 'k' in sprite_coord_enable is set.
        */
       for (i = 0; i < fs->info.num_inputs; i++) {
-         if (fs->info.input_semantic_name[i] == TGSI_SEMANTIC_GENERIC) {
-            const int generic_index = fs->info.input_semantic_index[i];
-            /* Note that sprite_coord enable is a bitfield of
-             * PIPE_MAX_SHADER_OUTPUTS bits.
-             */
-            if (generic_index < PIPE_MAX_SHADER_OUTPUTS &&
-                (rast->sprite_coord_enable & (1 << generic_index))) {
-               /* OK, this generic attribute needs to be replaced with a
-                * texcoord (see above).
-                */
-               int slot = draw_alloc_extra_vertex_attrib(draw,
-                                                         TGSI_SEMANTIC_GENERIC,
-                                                         generic_index);
-
-               /* add this slot to the texcoord-gen list */
-               wide->texcoord_gen_slot[wide->num_texcoord_gen++] = slot;
-            }
+         int slot;
+         const unsigned sn = fs->info.input_semantic_name[i];
+         const unsigned si = fs->info.input_semantic_index[i];
+
+         if (sn == wide->sprite_coord_semantic) {
+            /* Note that sprite_coord_enable is a bitfield of 32 bits. */
+            if (si >= 32 || !(rast->sprite_coord_enable & (1 << si)))
+               continue;
+         } else if (sn != TGSI_SEMANTIC_PCOORD) {
+            continue;
          }
+
+         /* OK, this generic attribute needs to be replaced with a
+          * sprite coord (see above).
+          */
+         slot = draw_alloc_extra_vertex_attrib(draw, sn, si);
+
+         /* add this slot to the texcoord-gen list */
+         wide->texcoord_gen_slot[wide->num_texcoord_gen++] = slot;
       }
    }
 
@@ -326,6 +331,11 @@ struct draw_stage *draw_wide_point_stage( struct draw_context *draw )
    if (!draw_alloc_temp_verts( &wide->stage, 4 ))
       goto fail;
 
+   wide->sprite_coord_semantic =
+      draw->pipe->screen->get_param(draw->pipe->screen, PIPE_CAP_TGSI_TEXCOORD)
+      ?
+      TGSI_SEMANTIC_TEXCOORD : TGSI_SEMANTIC_GENERIC;
+
    return &wide->stage;
 
  fail:
diff --git a/src/gallium/auxiliary/tgsi/tgsi_dump.c b/src/gallium/auxiliary/tgsi/tgsi_dump.c
index d98f6c49366..365665fa6f7 100644
--- a/src/gallium/auxiliary/tgsi/tgsi_dump.c
+++ b/src/gallium/auxiliary/tgsi/tgsi_dump.c
@@ -305,6 +305,7 @@ iter_declaration(
       TXT( ", " );
       ENM( decl->Semantic.Name, tgsi_semantic_names );
       if (decl->Semantic.Index != 0 ||
+          decl->Semantic.Name == TGSI_SEMANTIC_TEXCOORD ||
           decl->Semantic.Name == TGSI_SEMANTIC_GENERIC) {
          CHR( '[' );
          UID( decl->Semantic.Index );
diff --git a/src/gallium/auxiliary/tgsi/tgsi_strings.c b/src/gallium/auxiliary/tgsi/tgsi_strings.c
index 5c92e9a1001..95a5aded819 100644
--- a/src/gallium/auxiliary/tgsi/tgsi_strings.c
+++ b/src/gallium/auxiliary/tgsi/tgsi_strings.c
@@ -76,7 +76,9 @@ const char *tgsi_semantic_names[TGSI_SEMANTIC_COUNT] =
    "GRID_SIZE",
    "BLOCK_ID",
    "BLOCK_SIZE",
-   "THREAD_ID"
+   "THREAD_ID",
+   "TEXCOORD",
+   "PCOORD"
 };
 
 const char *tgsi_texture_names[TGSI_TEXTURE_COUNT] =