From c7e77fcc31878b29a35b01feb82529bd3bd8c457 Mon Sep 17 00:00:00 2001
From: Jordan Justen <jordan.l.justen@intel.com>
Date: Sun, 13 May 2012 00:23:23 -0700
Subject: 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@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_primitive_restart.c | 81 ++++++++++++++++++++++-
 1 file changed, 80 insertions(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_primitive_restart.c b/src/mesa/drivers/dri/i965/brw_primitive_restart.c
index d7136ed6fb9..962ff18fede 100644
--- a/src/mesa/drivers/dri/i965/brw_primitive_restart.c
+++ b/src/mesa/drivers/dri/i965/brw_primitive_restart.c
@@ -31,6 +31,74 @@
 #include "brw_context.h"
 #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.
  *
@@ -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;
 
-- 
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