5 files changed, 20 insertions, 2 deletions
diff --git a/src/gallium/auxiliary/tgsi/tgsi_scan.c b/src/gallium/auxiliary/tgsi/tgsi_scan.c
index 872e4ff3a4b..2a37b38d3c7 100644
--- a/src/gallium/auxiliary/tgsi/tgsi_scan.c
+++ b/src/gallium/auxiliary/tgsi/tgsi_scan.c
@@ -200,6 +200,10 @@ tgsi_scan_shader(const struct tgsi_token *tokens,
                       fulldecl->Semantic.Name == TGSI_SEMANTIC_CLIPDIST) {
                      info->num_written_clipdistance += util_bitcount(fulldecl->Declaration.UsageMask);
                   }
+                  if ((procType == TGSI_PROCESSOR_VERTEX || procType == TGSI_PROCESSOR_GEOMETRY) &&
+                      fulldecl->Semantic.Name == TGSI_SEMANTIC_CULLDIST) {
+                     info->num_written_culldistance += util_bitcount(fulldecl->Declaration.UsageMask);
+                  }
                   /* extra info for special outputs */
                   if (procType == TGSI_PROCESSOR_FRAGMENT &&
                       fulldecl->Semantic.Name == TGSI_SEMANTIC_POSITION)
diff --git a/src/gallium/auxiliary/tgsi/tgsi_scan.h b/src/gallium/auxiliary/tgsi/tgsi_scan.h
index a5b70244bd7..91eef67ca0b 100644
--- a/src/gallium/auxiliary/tgsi/tgsi_scan.h
+++ b/src/gallium/auxiliary/tgsi/tgsi_scan.h
@@ -78,6 +78,7 @@ struct tgsi_shader_info
    boolean writes_viewport_index;
    boolean writes_layer;
 
+   unsigned num_written_culldistance;
    unsigned num_written_clipdistance;
    /**
     * Bitmask indicating which register files are accessed with
diff --git a/src/gallium/auxiliary/tgsi/tgsi_strings.c b/src/gallium/auxiliary/tgsi/tgsi_strings.c
index 27856767877..6f244e5142f 100644
--- a/src/gallium/auxiliary/tgsi/tgsi_strings.c
+++ b/src/gallium/auxiliary/tgsi/tgsi_strings.c
@@ -80,7 +80,8 @@ const char *tgsi_semantic_names[TGSI_SEMANTIC_COUNT] =
    "TEXCOORD",
    "PCOORD",
    "VIEWPORT_INDEX",
-   "LAYER"
+   "LAYER",
+   "CULLDIST"
 };
 
 const char *tgsi_texture_names[TGSI_TEXTURE_COUNT] =
diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst
index 926527151c4..f3aebb3b317 100644
--- a/src/gallium/docs/source/tgsi.rst
+++ b/src/gallium/docs/source/tgsi.rst
@@ -2425,6 +2425,17 @@ contains the layer value to use for the color and depth/stencil surfaces.
 Only the X value is used. (Also known as rendertarget array index.)
 
 
+TGSI_SEMANTIC_CULLDIST
+""""""""""""""""""""""
+
+Used as distance to plane for performing application-defined culling
+of individual primitives against a plane. When components of vertex
+elements are given this label, these values are assumed to be a
+float32 signed distance to a plane. Primitives will be completely
+discarded if the plane distance for all of the vertices in the
+primitive are < 0. If a vertex has a cull distance of NaN, that
+vertex counts as "out" (as if its < 0);
+
 
 Declaration Interpolate
 ^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/src/gallium/include/pipe/p_shader_tokens.h b/src/gallium/include/pipe/p_shader_tokens.h
index c984d50abe9..4a6a57fef11 100644
--- a/src/gallium/include/pipe/p_shader_tokens.h
+++ b/src/gallium/include/pipe/p_shader_tokens.h
@@ -166,7 +166,8 @@ struct tgsi_declaration_interp
 #define TGSI_SEMANTIC_PCOORD     20 /**< point sprite coordinate */
 #define TGSI_SEMANTIC_VIEWPORT_INDEX 21 /**< viewport index */
 #define TGSI_SEMANTIC_LAYER      22 /**< layer (rendertarget index) */
-#define TGSI_SEMANTIC_COUNT      23 /**< number of semantic values */
+#define TGSI_SEMANTIC_CULLDIST   23
+#define TGSI_SEMANTIC_COUNT      24 /**< number of semantic values */
 
 struct tgsi_declaration_semantic
 {