[Mesa-dev] [PATCH 02/13] mesa: Add SYSTEM_VALUE_VERTEX_ID_ZERO_BASE

[Kenneth Graunke]

From: Ian Romanick <ian.d.romanick at intel.com>

There exists hardware, such as i965, that does not implement the OpenGL
semantic for gl_VertexID.  Instead, that hardware does not include the
value of basevertex in the gl_VertexID value.
SYSTEM_VALUE_VERTEX_ID_ZERO_BASE is the system value that represents
this semantic.

Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/main/mtypes.h                     | 12 ++++++++++++
 src/mesa/state_tracker/st_glsl_to_tgsi.cpp |  1 +
 2 files changed, 13 insertions(+)

diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index 207be0a..c603007 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -2083,6 +2083,8 @@ typedef enum
     *
     * gl_VertexID gets basevertex added in.  This differs from DirectX where
     * SV_VertexID does \b not get basevertex added in.
+    *
+    * \sa SYSTEM_VALUE_VERTEX_ID_ZERO_BASE
     */
    SYSTEM_VALUE_VERTEX_ID,
 
@@ -2114,6 +2116,16 @@ typedef enum
     * Note that baseinstance is \b not included in the value of instance.
     */
    SYSTEM_VALUE_INSTANCE_ID,
+
+   /**
+    * DirectX-style vertex ID.
+    *
+    * Unlike \c SYSTEM_VALUE_VERTEX_ID, this system value does \b not include
+    * the value of basevertex.
+    *
+    * \sa SYSTEM_VALUE_VERTEX_ID, SYSTEM_VALUE_BASE_VERTEX
+    */
+   SYSTEM_VALUE_VERTEX_ID_ZERO_BASE,
    /*@}*/
 
    /**
diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index 0290553..81f08cd 100644
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -4171,6 +4171,7 @@ const unsigned _mesa_sysval_to_semantic[SYSTEM_VALUE_MAX] = {
     */
    TGSI_SEMANTIC_VERTEXID,
    TGSI_SEMANTIC_INSTANCEID,
+   0,
 
    /* Geometry shader
     */
-- 
2.0.2