Mesa (master): i965: use cut index to handle primitive restart when possible

[Jordan Justen]

Module: Mesa
Branch: master
Commit: dc501452534e6e004acf3206a581232971c00cd0
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=dc501452534e6e004acf3206a581232971c00cd0

Author: Jordan Justen <jordan.l.justen at intel.com>
Date:   Sun May 13 00:23:23 2012 -0700

i965: use cut index to handle primitive restart when possible

If the primitive restart index and the primitive type can
be handled by the cut index feature, then use the hardware
to handle the primitive restart feature.

The VBO module's software handling of primitive restart is
used as a fall back.

Signed-off-by: Jordan Justen <jordan.l.justen at intel.com>
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>

---

 src/mesa/drivers/dri/i965/brw_primitive_restart.c |   81 ++++++++++++++++++++-
 1 files changed, 80 insertions(+), 1 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_primitive_restart.c b/src/mesa/drivers/dri/i965/brw_primitive_restart.c
index d7136ed..962ff18 100644
--- a/src/mesa/drivers/dri/i965/brw_primitive_restart.c
+++ b/src/mesa/drivers/dri/i965/brw_primitive_restart.c
@@ -32,6 +32,74 @@
 #include "brw_draw.h"
 
 /**
+ * Check if the hardware's cut index support can handle the primitive
+ * restart index value.
+ */
+static bool
+can_cut_index_handle_restart_index(struct gl_context *ctx,
+                                   const struct _mesa_index_buffer *ib)
+{
+   bool cut_index_will_work;
+
+   switch (ib->type) {
+   case GL_UNSIGNED_BYTE:
+      cut_index_will_work = (ctx->Array.RestartIndex & 0xff) == 0xff;
+      break;
+   case GL_UNSIGNED_SHORT:
+      cut_index_will_work = (ctx->Array.RestartIndex & 0xffff) == 0xffff;
+      break;
+   case GL_UNSIGNED_INT:
+      cut_index_will_work = ctx->Array.RestartIndex == 0xffffffff;
+      break;
+   default:
+      cut_index_will_work = false;
+      assert(0);
+   }
+
+   return cut_index_will_work;
+}
+
+/**
+ * Check if the hardware's cut index support can handle the primitive
+ * restart case.
+ */
+static bool
+can_cut_index_handle_prims(struct gl_context *ctx,
+                           const struct _mesa_prim *prim,
+                           GLuint nr_prims,
+                           const struct _mesa_index_buffer *ib)
+{
+   if (!can_cut_index_handle_restart_index(ctx, ib)) {
+      /* The primitive restart index can't be handled, so take
+       * the software path
+       */
+      return false;
+   }
+
+   for ( ; nr_prims > 0; nr_prims--) {
+      switch(prim->mode) {
+      case GL_POINTS:
+      case GL_LINES:
+      case GL_LINE_STRIP:
+      case GL_TRIANGLES:
+      case GL_TRIANGLE_STRIP:
+         /* Cut index supports these primitive types */
+         break;
+      default:
+         /* Cut index does not support these primitive types */
+      //case GL_LINE_LOOP:
+      //case GL_TRIANGLE_FAN:
+      //case GL_QUADS:
+      //case GL_QUAD_STRIP:
+      //case GL_POLYGON:
+         return false;
+      }
+   }
+
+   return true;
+}
+
+/**
  * Check if primitive restart is enabled, and if so, handle it properly.
  *
  * In some cases the support will be handled in software. When available
@@ -77,7 +145,18 @@ brw_handle_primitive_restart(struct gl_context *ctx,
     */
    brw->prim_restart.in_progress = true;
 
-   vbo_sw_primitive_restart(ctx, prim, nr_prims, ib);
+   if (can_cut_index_handle_prims(ctx, prim, nr_prims, ib)) {
+      /* Cut index should work for primitive restart, so use it
+       */
+      brw->prim_restart.enable_cut_index = true;
+      brw_draw_prims(ctx, prim, nr_prims, ib, GL_FALSE, -1, -1, NULL);
+      brw->prim_restart.enable_cut_index = false;
+   } else {
+      /* Not all the primitive draw modes are supported by the cut index,
+       * so take the software path
+       */
+      vbo_sw_primitive_restart(ctx, prim, nr_prims, ib);
+   }
 
    brw->prim_restart.in_progress = false;