gallium/tgsi: add missing string for layer semantic

Also report if a shader writes the layer semantic

Reviewed-by: Brian Paul <brianp@vmware.com>

src/gallium/auxiliary/tgsi/tgsi_scan.c

@@ -217,6 +217,11 @@ tgsi_scan_shader(const struct tgsi_token *tokens,
                       TGSI_SEMANTIC_VIEWPORT_INDEX) {
                      info->writes_viewport_index = TRUE;
                   }
+                  if (procType == TGSI_PROCESSOR_GEOMETRY &&
+                      fulldecl->Semantic.Name ==
+                      TGSI_SEMANTIC_LAYER) {
+                     info->writes_layer = TRUE;
+                  }
                }
 
              }

src/gallium/auxiliary/tgsi/tgsi_scan.h

@@ -76,6 +76,7 @@ struct tgsi_shader_info
    boolean pixel_center_integer;
    boolean color0_writes_all_cbufs;
    boolean writes_viewport_index;
+   boolean writes_layer;
 
    unsigned num_written_clipdistance;
    /**

src/gallium/auxiliary/tgsi/tgsi_strings.c

@@ -79,7 +79,8 @@ const char *tgsi_semantic_names[TGSI_SEMANTIC_COUNT] =
    "THREAD_ID",
    "TEXCOORD",
    "PCOORD",
-   "VIEWPORT_INDEX"
+   "VIEWPORT_INDEX",
+   "LAYER"
 };
 
 const char *tgsi_texture_names[TGSI_TEXTURE_COUNT] =