gallium/tgsi: add support for stencil writes.

this adds the capability + a stencil semantic id, + tgsi scan support.

Signed-off-by: Dave Airlie <airlied@redhat.com>

src/gallium/auxiliary/tgsi/tgsi_dump.c

@@ -126,7 +126,8 @@ static const char *semantic_names[] =
    "FACE",
    "EDGEFLAG",
    "PRIM_ID",
-   "INSTANCEID"
+   "INSTANCEID",
+   "STENCIL"
 };
 
 static const char *immediate_type_names[] =

src/gallium/auxiliary/tgsi/tgsi_scan.c

@@ -157,9 +157,11 @@ tgsi_scan_shader(const struct tgsi_token *tokens,
 
                   /* extra info for special outputs */
                   if (procType == TGSI_PROCESSOR_FRAGMENT &&
-                      fulldecl->Semantic.Name == TGSI_SEMANTIC_POSITION) {
-                     info->writes_z = TRUE;
-                  }
+                      fulldecl->Semantic.Name == TGSI_SEMANTIC_POSITION)
+                        info->writes_z = TRUE;
+                  if (procType == TGSI_PROCESSOR_FRAGMENT &&
+                      fulldecl->Semantic.Name == TGSI_SEMANTIC_STENCIL)
+                        info->writes_stencil = TRUE;
                   if (procType == TGSI_PROCESSOR_VERTEX &&
                       fulldecl->Semantic.Name == TGSI_SEMANTIC_EDGEFLAG) {
                      info->writes_edgeflag = TRUE;

src/gallium/auxiliary/tgsi/tgsi_scan.h

@@ -60,6 +60,7 @@ struct tgsi_shader_info
    uint opcode_count[TGSI_OPCODE_LAST];  /**< opcode histogram */
 
    boolean writes_z;  /**< does fragment shader write Z value? */
+   boolean writes_stencil; /**< does fragment shader write stencil value? */
    boolean writes_edgeflag; /**< vertex shader outputs edgeflag */
    boolean uses_kill;  /**< KIL or KILP instruction used? */
 

src/gallium/docs/source/tgsi.rst

@@ -1415,6 +1415,12 @@ Edge flags are used to control which lines or points are actually
 drawn when the polygon mode converts triangles/quads/polygons into
 points or lines.
 
+TGSI_SEMANTIC_STENCIL
+""""""""""""""""""""""
+
+For fragment shaders, this semantic label indicates than an output
+is a writable stencil reference value. Only the Y component is writable.
+This allows the fragment shader to change the fragments stencilref value.
 
 
 Properties

src/gallium/drivers/softpipe/sp_fs_exec.c

@@ -158,9 +158,17 @@ exec_run( const struct sp_fragment_shader *base,
          case TGSI_SEMANTIC_POSITION:
             {
                uint j;
-               for (j = 0; j < 4; j++) {
+
+               for (j = 0; j < 4; j++)
                   quad->output.depth[j] = machine->Outputs[i].xyzw[2].f[j];
-               }
+            }
+            break;
+         case TGSI_SEMANTIC_STENCIL:
+            {
+               uint j;
+
+               for (j = 0; j < 4; j++)
+                  quad->output.stencil[j] = (unsigned)machine->Outputs[i].xyzw[1].f[j];
             }
             break;
          }

src/gallium/include/pipe/p_defines.h

@@ -464,7 +464,8 @@ enum pipe_cap {
    PIPE_CAP_TGSI_FS_COORD_ORIGIN_LOWER_LEFT,
    PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_HALF_INTEGER,
    PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_INTEGER,
-   PIPE_CAP_DEPTH_CLAMP
+   PIPE_CAP_DEPTH_CLAMP,
+   PIPE_CAP_SHADER_STENCIL_EXPORT,
 };
 
 /* Shader caps not specific to any single stage */

src/gallium/include/pipe/p_shader_tokens.h

@@ -143,7 +143,8 @@ struct tgsi_declaration_dimension
 #define TGSI_SEMANTIC_EDGEFLAG   8
 #define TGSI_SEMANTIC_PRIMID     9
 #define TGSI_SEMANTIC_INSTANCEID 10
-#define TGSI_SEMANTIC_COUNT      11 /**< number of semantic values */
+#define TGSI_SEMANTIC_STENCIL    11
+#define TGSI_SEMANTIC_COUNT      12 /**< number of semantic values */
 
 struct tgsi_declaration_semantic
 {