Hi,
After the looking at the problem in bug 81150 I was wondering if we
have the same problem when using glClear with integer values. Sure
enough I can trigger a similar bug on 32-bit builds with optimisations
using a piglit test which I've posted here:
http://lists.freedesktop.org/archives/piglit/2014-August/012144.html
- Neil
--- 8 --- (use git am --scissors to automatically chop here)
Similar to the problem described in 2c50212b14da27de4e3, if we copy the clear
value through a regular assignment via a floating point value, then if an
integer clear value is being used that happens to contain a signalling NaN
value then it would get converted to a quiet NaN when stored via the x87
floating-point registers. This would corrupt the integer value. Instead we
should use a memcpy to ensure the exact bit representation is preserved.
This bug can be triggered on 32-bit builds with optimisations by using an
integer clear color with a value like 0x7f817f81.
---
src/mesa/drivers/dri/i965/brw_blorp_clear.cpp | 9 ++---
1 file changed, 2 insertions(+), 7 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
b/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
index ffbcd1a..8db0837 100644
--- a/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
+++ b/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
@@ -202,12 +202,7 @@ brw_blorp_clear_params::brw_blorp_clear_params(struct
brw_context *brw,
y1 = rb-Height - fb-_Ymin;
}
- float *push_consts = (float *)wm_push_consts;
-
- push_consts[0] = ctx-Color.ClearColor.f[0];
- push_consts[1] = ctx-Color.ClearColor.f[1];
- push_consts[2] = ctx-Color.ClearColor.f[2];
- push_consts[3] = ctx-Color.ClearColor.f[3];
+ memcpy(wm_push_consts.dst_x0, ctx-Color.ClearColor.f, sizeof(float) * 4);
use_wm_prog = true;
@@ -250,7 +245,7 @@ brw_blorp_clear_params::brw_blorp_clear_params(struct
brw_context *brw,
if (irb-mt-fast_clear_state != INTEL_FAST_CLEAR_STATE_NO_MCS
!partial_clear wm_prog_key.use_simd16_replicated_data
is_color_fast_clear_compatible(brw, format, ctx-Color.ClearColor)) {
- memset(push_consts, 0xff, 4*sizeof(float));
+ memset(wm_push_consts, 0xff, 4*sizeof(float));
fast_clear_op = GEN7_FAST_CLEAR_OP_FAST_CLEAR;
/* Figure out what the clear rectangle needs to be aligned to, and how
--
1.9.3
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