vbo: add software primitive restart support

vbo_sw_primitive_restart implements primitive restart in software
by splitting primitive draws apart.

This is based on similar support in mesa/state_tracker/st_draw.c.

Signed-off-by: Jordan Justen <[email protected]>
Reviewed-by: Ian Romanick <[email protected]>
Reviewed-by: Kenneth Graunke <[email protected]>

1 files changed, 233 insertions, 0 deletions

diff --git a/src/mesa/vbo/vbo_primitive_restart.c b/src/mesa/vbo/vbo_primitive_restart.c
new file mode 100644
index 00000000000..18d851c1e1f
--- /dev/null
+++ b/src/mesa/vbo/vbo_primitive_restart.c
@@ -0,0 +1,233 @@
+/*
+ * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
+ * All Rights Reserved.
+ *
+ * Copyright © 2012 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Authors:
+ *    Jordan Justen <[email protected]>
+ *
+ */
+
+#include "main/imports.h"
+#include "main/bufferobj.h"
+#include "main/macros.h"
+
+#include "vbo.h"
+#include "vbo_context.h"
+
+#define UPDATE_MIN2(a, b) (a) = MIN2((a), (b))
+#define UPDATE_MAX2(a, b) (a) = MAX2((a), (b))
+
+/*
+ * Notes on primitive restart:
+ * The code below is used when the driver does not support primitive
+ * restart itself. (ctx->Const.PrimitiveRestartInSoftware == GL_TRUE)
+ *
+ * We map the index buffer, find the restart indexes, unmap
+ * the index buffer then draw the sub-primitives delineated by the restarts.
+ *
+ * A couple possible optimizations:
+ * 1. Save the list of sub-primitive (start, count) values in a list attached
+ *    to the index buffer for re-use in subsequent draws.  The list would be
+ *    invalidated when the contents of the buffer changed.
+ * 2. If drawing triangle strips or quad strips, create a new index buffer
+ *    that uses duplicated vertices to render the disjoint strips as one
+ *    long strip.  We'd have to be careful to avoid using too much memory
+ *    for this.
+ *
+ * Finally, some apps might perform better if they don't use primitive restart
+ * at all rather than this fallback path.  Set MESA_EXTENSION_OVERRIDE to
+ * "-GL_NV_primitive_restart" to test that.
+ */
+
+
+struct sub_primitive
+{
+   GLuint start;
+   GLuint count;
+   GLuint min_index;
+   GLuint max_index;
+};
+
+
+/**
+ * Scan the elements array to find restart indexes.  Return an array
+ * of struct sub_primitive to indicate how to draw the sub-primitives
+ * are delineated by the restart index.
+ */
+static struct sub_primitive *
+find_sub_primitives(const void *elements, unsigned element_size,
+                    unsigned start, unsigned end, unsigned restart_index,
+                    unsigned *num_sub_prims)
+{
+   const unsigned max_prims = end - start;
+   struct sub_primitive *sub_prims;
+   unsigned i, cur_start, cur_count;
+   GLuint scan_index;
+   unsigned scan_num;
+
+   sub_prims = (struct sub_primitive *)
+      malloc(max_prims * sizeof(struct sub_primitive));
+
+   if (!sub_prims) {
+      *num_sub_prims = 0;
+      return NULL;
+   }
+
+   cur_start = start;
+   cur_count = 0;
+   scan_num = 0;
+
+#define IB_INDEX_READ(TYPE, INDEX) (((const GL##TYPE *) elements)[INDEX])
+
+#define SCAN_ELEMENTS(TYPE) \
+   sub_prims[scan_num].min_index = (GL##TYPE) 0xffffffff; \
+   sub_prims[scan_num].max_index = 0; \
+   for (i = start; i < end; i++) { \
+      scan_index = IB_INDEX_READ(TYPE, i); \
+      if (scan_index == restart_index) { \
+         if (cur_count > 0) { \
+            assert(scan_num < max_prims); \
+            sub_prims[scan_num].start = cur_start; \
+            sub_prims[scan_num].count = cur_count; \
+            scan_num++; \
+            sub_prims[scan_num].min_index = (GL##TYPE) 0xffffffff; \
+            sub_prims[scan_num].max_index = 0; \
+         } \
+         cur_start = i + 1; \
+         cur_count = 0; \
+      } \
+      else { \
+         UPDATE_MIN2(sub_prims[scan_num].min_index, scan_index); \
+         UPDATE_MAX2(sub_prims[scan_num].max_index, scan_index); \
+         cur_count++; \
+      } \
+   } \
+   if (cur_count > 0) { \
+      assert(scan_num < max_prims); \
+      sub_prims[scan_num].start = cur_start; \
+      sub_prims[scan_num].count = cur_count; \
+      scan_num++; \
+   }
+
+   switch (element_size) {
+   case 1:
+      SCAN_ELEMENTS(ubyte);
+      break;
+   case 2:
+      SCAN_ELEMENTS(ushort);
+      break;
+   case 4:
+      SCAN_ELEMENTS(uint);
+      break;
+   default:
+      assert(0 && "bad index_size in find_sub_primitives()");
+   }
+
+#undef SCAN_ELEMENTS
+
+   *num_sub_prims = scan_num;
+
+   return sub_prims;
+}
+
+
+/**
+ * Handle primitive restart in software.
+ *
+ * This function breaks up calls into the driver so primitive restart
+ * support is not required in the driver.
+ */
+void
+vbo_sw_primitive_restart(struct gl_context *ctx,
+                         const struct _mesa_prim *prims,
+                         GLuint nr_prims,
+                         const struct _mesa_index_buffer *ib)
+{
+   GLuint prim_num;
+   struct sub_primitive *sub_prims;
+   struct sub_primitive *sub_prim;
+   GLuint num_sub_prims;
+   GLuint sub_prim_num;
+   GLuint end_index;
+   GLuint sub_end_index;
+   GLuint restart_index = ctx->Array.RestartIndex;
+   struct _mesa_prim temp_prim;
+   struct vbo_context *vbo = vbo_context(ctx);
+   vbo_draw_func draw_prims_func = vbo->draw_prims;
+   GLboolean map_ib = ib->obj->Name && !ib->obj->Pointer;
+   void *ptr;
+
+   /* Find the sub-primitives. These are regions in the index buffer which
+    * are split based on the primitive restart index value.
+    */
+   if (map_ib) {
+      ctx->Driver.MapBufferRange(ctx, 0, ib->obj->Size, GL_MAP_READ_BIT,
+                                 ib->obj);
+   }
+
+   ptr = ADD_POINTERS(ib->obj->Pointer, ib->ptr);
+
+   sub_prims = find_sub_primitives(ptr, vbo_sizeof_ib_type(ib->type),
+                                   0, ib->count, restart_index,
+                                   &num_sub_prims);
+
+   if (map_ib) {
+      ctx->Driver.UnmapBuffer(ctx, ib->obj);
+   }
+
+   /* Loop over the primitives, and use the located sub-primitives to draw
+    * each primitive with a break to implement each primitive restart.
+    */
+   for (prim_num = 0; prim_num < nr_prims; prim_num++) {
+      end_index = prims[prim_num].start + prims[prim_num].count;
+      memcpy(&temp_prim, &prims[prim_num], sizeof (temp_prim));
+      /* Loop over the sub-primitives drawing sub-ranges of the primitive. */
+      for (sub_prim_num = 0; sub_prim_num < num_sub_prims; sub_prim_num++) {
+         sub_prim = &sub_prims[sub_prim_num];
+         sub_end_index = sub_prim->start + sub_prim->count;
+         if (prims[prim_num].start <= sub_prim->start) {
+            temp_prim.start = MAX2(prims[prim_num].start, sub_prim->start);
+            temp_prim.count = MIN2(sub_end_index, end_index) - temp_prim.start;
+            if ((temp_prim.start == sub_prim->start) &&
+                (temp_prim.count == sub_prim->count)) {
+               draw_prims_func(ctx, &temp_prim, 1, ib,
+                               GL_TRUE, sub_prim->min_index, sub_prim->max_index,
+                               NULL);
+            } else {
+               draw_prims_func(ctx, &temp_prim, 1, ib,
+                               GL_FALSE, -1, -1,
+                               NULL);
+            }
+         }
+         if (sub_end_index >= end_index) {
+            break;
+         }
+      }
+   }
+
+   if (sub_prims) {
+      free(sub_prims);
+   }
+}
+