From: Jason Ekstrand <jason.ekstrand@intel.com>
Date: Wed, 18 May 2016 20:05:48 +0000 (-0700)
Subject: i965/draw: Properly handle rounding when dividing by InstanceDivisor
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=d5b4ab2c5f700087ac09238e3cf8252aa3d31d54;p=mesa.git

i965/draw: Properly handle rounding when dividing by InstanceDivisor

The old code always divided rounded down and then subtracted 1.  What we
wanted was to divide rounded up and then subtract 1 which is equivalent to
subtracting 1 and then dividing rounded down.

Cc: "11.1 11.2" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
---

diff --git a/src/mesa/drivers/dri/i965/brw_draw_upload.c b/src/mesa/drivers/dri/i965/brw_draw_upload.c
index 6d9e65e9cfa..b651fd202cd 100644
--- a/src/mesa/drivers/dri/i965/brw_draw_upload.c
+++ b/src/mesa/drivers/dri/i965/brw_draw_upload.c
@@ -474,8 +474,8 @@ brw_prepare_vertices(struct brw_context *brw)
          if (glarray->InstanceDivisor) {
             if (brw->num_instances) {
                start = offset + glarray->StrideB * brw->baseinstance;
-               range = (glarray->StrideB * ((brw->num_instances /
-                                             glarray->InstanceDivisor) - 1) +
+               range = (glarray->StrideB * ((brw->num_instances - 1) /
+                                            glarray->InstanceDivisor) +
                         glarray->_ElementSize);
             }
          } else {