u_vbuf: use single vertex buffer if it's not possible to have multiple

Put CONST, VERTEX and INSTANCE attributes into one vertex buffer if
necessary due to hardware constraints.

1 files changed, 23 insertions, 4 deletions

diff --git a/src/gallium/auxiliary/util/u_vbuf.c b/src/gallium/auxiliary/util/u_vbuf.c
index 49cc6683d7..799ff24d4c 100644
--- a/src/gallium/auxiliary/util/u_vbuf.c
+++ b/src/gallium/auxiliary/util/u_vbuf.c
@@ -177,7 +177,6 @@ struct u_vbuf {
    /* The vertex buffer slot index where translated vertices have been
     * stored in. */
    unsigned fallback_vbs[VB_NUM];
-
    /* Which buffer is a user buffer. */
    uint32_t user_vb_mask; /* each bit describes a corresp. buffer */
    /* Which buffer is incompatible (unaligned). */
@@ -476,24 +475,44 @@ u_vbuf_translate_find_free_vb_slots(struct u_vbuf *mgr,
    uint32_t unused_vb_mask =
       (mgr->ve->incompatible_vb_mask_all | mgr->incompatible_vb_mask |
       ~mgr->enabled_vb_mask | extra_free_vb_mask) & mgr->allowed_vb_mask;
+   uint32_t unused_vb_mask_temp;
+   boolean insufficient_buffers = false;
 
+   /* No vertex buffers available at all */
+   if(!unused_vb_mask)
+      return FALSE;
    memset(fallback_vbs, ~0, sizeof(fallback_vbs));
 
    /* Find free slots for each type if needed. */
+   unused_vb_mask_temp = unused_vb_mask;
    for (type = 0; type < VB_NUM; type++) {
       if (mask[type]) {
          uint32_t index;
 
-         if (!unused_vb_mask) {
-            return FALSE;
+         if (!unused_vb_mask_temp) {
+            insufficient_buffers = true;
+            break;
          }
 
-         index = ffs(unused_vb_mask) - 1;
+         index = ffs(unused_vb_mask_temp) - 1;
          fallback_vbs[type] = index;
          /*printf("found slot=%i for type=%i\n", index, type);*/
+         unused_vb_mask_temp &= ~(1<<index);
       }
    }
 
+   if(insufficient_buffers)
+   {
+      /* not enough vbs for all types supported by the hardware, they will have to share one
+       * buffer */
+      uint32_t index = ffs(unused_vb_mask) - 1;
+      /* When sharing one vertex buffer use per-vertex frequency for everything. */
+      fallback_vbs[VB_VERTEX] = index;
+      mask[VB_VERTEX] = mask[VB_VERTEX] | mask[VB_CONST] | mask[VB_INSTANCE];
+      mask[VB_CONST] = 0;
+      mask[VB_INSTANCE] = 0;
+   }
+
    for (type = 0; type < VB_NUM; type++) {
       if (mask[type]) {
          mgr->dirty_real_vb_mask |= 1 << fallback_vbs[type];