Mesa (master): i965: Use safer pointer arithmetic in gather_oa_results()

[Chad Versace]

Module: Mesa
Branch: master
Commit: 414be86c96836b35571185da776d2bce1b620c6a
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=414be86c96836b35571185da776d2bce1b620c6a

Author: Chad Versace <chad.versace at linux.intel.com>
Date:   Tue Nov 18 21:11:26 2014 -0800

i965: Use safer pointer arithmetic in gather_oa_results()

This patch reduces the likelihood of pointer arithmetic overflow bugs in
gather_oa_results(), like the one fixed by b69c7c5dac.

I haven't yet encountered any overflow bugs in the wild along this
patch's codepath. But I get nervous when I see code patterns like this:

   (void*) + (int) * (int)

I smell 32-bit overflow all over this code.

This patch retypes 'snapshot_size' to 'ptrdiff_t', which should fix any
potential overflow.

Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
Signed-off-by: Chad Versace <chad.versace at linux.intel.com>

---

 src/mesa/drivers/dri/i965/brw_performance_monitor.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_performance_monitor.c b/src/mesa/drivers/dri/i965/brw_performance_monitor.c
index edfa3d2..e683e40 100644
--- a/src/mesa/drivers/dri/i965/brw_performance_monitor.c
+++ b/src/mesa/drivers/dri/i965/brw_performance_monitor.c
@@ -907,7 +907,7 @@ gather_oa_results(struct brw_context *brw,
       return;
    }
 
-   const int snapshot_size = brw->perfmon.entries_per_oa_snapshot;
+   const ptrdiff_t snapshot_size = brw->perfmon.entries_per_oa_snapshot;
 
    /* First, add the contributions from the "head" interval:
     * (snapshot taken at BeginPerfMonitor time,