[Mesa-dev] [Mesa-stable] [PATCH 2/3] i965/fs: Consider cmod when propagating to inst with different type.

[Matt Turner]

On Fri, Feb 27, 2015 at 1:24 PM, Ian Romanick <idr at freedesktop.org> wrote:
> On 02/27/2015 11:34 AM, Matt Turner wrote:
>> We can safely propagate the conditional mod to an instruction with a
>> different type if the conditional mod does not involve comparing for
>> equality with zero (or probably NaN, but ignore that for now).
>>
>> This is because -0.0 and +0.0 are both test equal to zero, but their
>> integer representations do not.
>
> That sounds really sketchy.  Did you try to make a stand-alone test to
> reproduce the problem based on your theory?

I just sent a piglit test that confirms that this is a problem (and
that this patch fixes it).