[Mesa-dev] [PATCH] gallium/u_vbuf: Protect against overflow with large instance divisors.

[Eric Anholt]

GTF-GLES3.gtf.GL3Tests.instanced_arrays.instanced_arrays_divisor uses -1
as a divisor, so we would overflow to count=0 and upload no data,
triggering the assert below.  We want to upload 1 element in this case,
fixing the test on VC5.
---
 src/gallium/auxiliary/util/u_vbuf.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/gallium/auxiliary/util/u_vbuf.c b/src/gallium/auxiliary/util/u_vbuf.c
index 95d7990c6ca4..9073f3feed98 100644
--- a/src/gallium/auxiliary/util/u_vbuf.c
+++ b/src/gallium/auxiliary/util/u_vbuf.c
@@ -936,7 +936,12 @@ u_vbuf_upload_buffers(struct u_vbuf *mgr,
          size = mgr->ve->src_format_size[i];
       } else if (instance_div) {
          /* Per-instance attrib. */
-         unsigned count = (num_instances + instance_div - 1) / instance_div;
+         unsigned count = (num_instances + instance_div - 1);
+
+         if (count < num_instances)
+            count = 0xffffffff;
+         count /= instance_div;
+
          first += vb->stride * start_instance;
          size = vb->stride * (count - 1) + mgr->ve->src_format_size[i];
       } else {
-- 
2.16.2