On 07/23/2013 03:26 AM, Chris Forbes wrote:
If any component used the ZERO or ONE swizzle, its corresponding member
in the `swizzle` array would never be initialized. We *mostly* got away
with this, except when that memory happened to contain a value that
clobbered another channel when combined using BRW_SWIZZLE4().
NOTE: This is a candidate for stable branches.
Signed-off-by: Chris Forbes <chr...@ijw.co.nz>
---
src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
index 3eb43a8..1d86b33 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
@@ -2506,7 +2506,7 @@ vec4_visitor::swizzle_result(ir_texture *ir, src_reg
orig_val, int sampler)
}
int zero_mask = 0, one_mask = 0, copy_mask = 0;
- int swizzle[4];
+ int swizzle[4] = {0};
for (int i = 0; i < 4; i++) {
switch (GET_SWZ(s, i)) {
Oh, yikes! Good catch...
A bit more verbose explanation:
BRW_SWIZZLE4 is:
(((a)<<0) | ((b)<<2) | ((c)<<4) | ((d)<<6))
with no bitmasking, which means that if swizzle[i]'s value doesn't fit
in 2 bits, it'll clobber the other swizzle channels, breaking things in
bizarre ways. It doesn't actually matter what channel we pick, but
uninitialized values are often more than 2-bits :)
Reviewed-by: Kenneth Graunke <kenn...@whitecape.org>
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