[Mesa-dev] [PATCH 1/9] compiler: Add new system value SYSTEM_VALUE_BASE_VERTEX_ID

[Antia Puentes]

This VS system value will contain the value passed as <basevertex>
for indexed draw calls or the value passed as <first> for non-indexed
draw calls. It will be used to calculate the gl_VertexID as
SYSTEM_VALUE_VERTEX_ID_ZERO_BASE plus SYSTEM_VALUE_BASE_VERTEX_ID.
Note that the current calculation which uses SYSTEM_VALUE_BASE_VERTEX
is not right, as gl_BaseVertex should be zero for non-indexed calls.

Reviewed-by: Neil Roberts <nroberts at igalia.com>
---
 src/compiler/shader_enums.c |  1 +
 src/compiler/shader_enums.h | 15 +++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/src/compiler/shader_enums.c b/src/compiler/shader_enums.c
index b2ca80b49c2..cd8c256f227 100644
--- a/src/compiler/shader_enums.c
+++ b/src/compiler/shader_enums.c
@@ -215,6 +215,7 @@ gl_system_value_name(gl_system_value sysval)
      ENUM(SYSTEM_VALUE_INSTANCE_ID),
      ENUM(SYSTEM_VALUE_INSTANCE_INDEX),
      ENUM(SYSTEM_VALUE_VERTEX_ID_ZERO_BASE),
+     ENUM(SYSTEM_VALUE_BASE_VERTEX_ID),
      ENUM(SYSTEM_VALUE_BASE_VERTEX),
      ENUM(SYSTEM_VALUE_BASE_INSTANCE),
      ENUM(SYSTEM_VALUE_DRAW_ID),
diff --git a/src/compiler/shader_enums.h b/src/compiler/shader_enums.h
index 9d229d4199e..7437cccdd0a 100644
--- a/src/compiler/shader_enums.h
+++ b/src/compiler/shader_enums.h
@@ -474,6 +474,21 @@ typedef enum
     */
    SYSTEM_VALUE_BASE_VERTEX,
 
+
+   /**
+    * Depending on the type of the draw call (indexed or non-indexed),
+    * is the value of \c basevertex passed to \c glDrawElementsBaseVertex and
+    * similar, or is the value of \c first passed to \c glDrawArrays and
+    * similar.
+    *
+    * \note
+    * It can be used to calculate the \c SYSTEM_VALUE_VERTEX_ID as
+    * \c SYSTEM_VALUE_VERTEX_ID_ZERO_BASE plus \c SYSTEM_VALUE_BASE_VERTEX_ID.
+    *
+    * \sa SYSTEM_VALUE_VERTEX_ID_ZERO_BASE, SYSTEM_VALUE_VERTEX_ID
+    */
+   SYSTEM_VALUE_BASE_VERTEX_ID,
+
    /**
     * Value of \c baseinstance passed to instanced draw entry points
     *
-- 
2.14.1