[Mesa-dev] [PATCH 03/22] mesa: Keep track of the last looked-up VAO

[Fredrik Höglund]

This saves the cost of repeated hash table lookups when the same
vertex array object is referenced in a sequence of calls such as:

    glVertexArrayAttribFormat(vao, ...);
    glVertexArrayAttribBinding(vao, ...);
    glEnableVertexArrayAttrib(vao, ...);
    ...

Note that VAO's are container objects that are not shared between
contexts.
---
 src/mesa/main/arrayobj.c | 44 ++++++++++++++++++++++++++++----------------
 src/mesa/main/mtypes.h   |  3 +++
 2 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/src/mesa/main/arrayobj.c b/src/mesa/main/arrayobj.c
index ac081b0..862bbb7 100644
--- a/src/mesa/main/arrayobj.c
+++ b/src/mesa/main/arrayobj.c
@@ -100,23 +100,32 @@ _mesa_lookup_vao_err(struct gl_context *ctx, GLuint id, const char *caller)
 
       return ctx->Array.DefaultVAO;
    } else {
-      struct gl_vertex_array_object *vao =
-         (struct gl_vertex_array_object *)
-         _mesa_HashLookup(ctx->Array.Objects, id);
+      struct gl_vertex_array_object *vao;
 
-      /* The ARB_direct_state_access specification says:
-       *
-       *    "An INVALID_OPERATION error is generated if <vaobj> is not
-       *     [compatibility profile: zero or] the name of an existing
-       *     vertex array object."
-       */
-      if (!vao || !vao->EverBound) {
-         const char *format = ctx->API == API_OPENGL_CORE ?
-            "%s(vaobj=%d is not the name of an existing vertex array object)" :
-            "%s(vaobj=%d is not zero or the name of an existing vertex "
-            "array object)";
-         _mesa_error(ctx, GL_INVALID_OPERATION, format, caller, id);
-         return NULL;
+      if (ctx->Array.LastLookedUpVAO &&
+          ctx->Array.LastLookedUpVAO->Name == id) {
+         vao = ctx->Array.LastLookedUpVAO;
+      } else {
+         vao = (struct gl_vertex_array_object *)
+            _mesa_HashLookup(ctx->Array.Objects, id);
+
+         /* The ARB_direct_state_access specification says:
+          *
+          *    "An INVALID_OPERATION error is generated if <vaobj> is not
+          *     [compatibility profile: zero or] the name of an existing
+          *     vertex array object."
+          */
+         if (!vao || !vao->EverBound) {
+            const char *format = ctx->API == API_OPENGL_CORE ?
+               "%s(vaobj=%d is not the name of an existing vertex "
+               "array object)" :
+               "%s(vaobj=%d is not zero or the name of an existing vertex "
+               "array object)";
+            _mesa_error(ctx, GL_INVALID_OPERATION, format, caller, id);
+            return NULL;
+         }
+
+         _mesa_reference_vao(ctx, &ctx->Array.LastLookedUpVAO, vao);
       }
 
       return vao;
@@ -519,6 +528,9 @@ _mesa_DeleteVertexArrays(GLsizei n, const GLuint *ids)
 	 /* The ID is immediately freed for re-use */
 	 remove_array_object(ctx, obj);
 
+         if (ctx->Array.LastLookedUpVAO == obj)
+            _mesa_reference_vao(ctx, &ctx->Array.LastLookedUpVAO, NULL);
+
          /* Unreference the array object. 
           * If refcount hits zero, the object will be deleted.
           */
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index c43c6ac..f46f2b2 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -1687,6 +1687,9 @@ struct gl_array_attrib
    /** The default vertex array object */
    struct gl_vertex_array_object *DefaultVAO;
 
+   /** The last VAO accessed by a DSA function */
+   struct gl_vertex_array_object *LastLookedUpVAO;
+
    /** Array objects (GL_ARB/APPLE_vertex_array_object) */
    struct _mesa_HashTable *Objects;
 
-- 
1.8.5.3