state_tracker: Initialize the draw context only when needed.

It's only used for rarely-used deprecated GL features
(feedback/rasterpos), so we can skip the memory allocation and
initialization for it most of the time.

Saves about 659k (out of 1605k) of maximum memory size according to massif
on simulated vc4 glsl-algebraic-add-add-1

Reviewed-by: Brian Paul <[email protected]>

1 files changed, 23 insertions, 8 deletions

diff --git a/src/mesa/state_tracker/st_draw.c b/src/mesa/state_tracker/st_draw.c
index b248dafc9a2..f4af23da97f 100644
--- a/src/mesa/state_tracker/st_draw.c
+++ b/src/mesa/state_tracker/st_draw.c
@@ -346,8 +346,29 @@ st_init_draw(struct st_context *st)
 
    vbo_set_draw_func(ctx, st_draw_vbo);
    vbo_set_indirect_draw_func(ctx, st_indirect_draw_vbo);
+}
+
+
+void
+st_destroy_draw(struct st_context *st)
+{
+   draw_destroy(st->draw);
+}
 
-   st->draw = draw_create(st->pipe); /* for selection/feedback */
+/**
+ * Getter for the draw_context, so that initialization of it can happen only
+ * when needed (the TGSI exec machines take up quite a bit of memory).
+ */
+struct draw_context *
+st_get_draw_context(struct st_context *st)
+{
+   if (!st->draw) {
+      st->draw = draw_create(st->pipe);
+      if (!st->draw) {
+         _mesa_error(st->ctx, GL_OUT_OF_MEMORY, "feedback fallback allocation");
+         return NULL;
+      }
+   }
 
    /* Disable draw options that might convert points/lines to tris, etc.
     * as that would foul-up feedback/selection mode.
@@ -356,16 +377,10 @@ st_init_draw(struct st_context *st)
    draw_wide_point_threshold(st->draw, 1000.0f);
    draw_enable_line_stipple(st->draw, FALSE);
    draw_enable_point_sprites(st->draw, FALSE);
-}
-
 
-void
-st_destroy_draw(struct st_context *st)
-{
-   draw_destroy(st->draw);
+   return st->draw;
 }
 
-
 /**
  * Draw a quad with given position, texcoords and color.
  */