[Mesa-dev] [PATCH 15/14] i965/fs: Don't emit 16-wide BFI1 instructions.

[Matt Turner]

On Fri, May 3, 2013 at 5:02 PM, Eric Anholt <eric at anholt.net> wrote:
> Matt Turner <mattst88 at gmail.com> writes:
>
>> The Haswell Bspec says "A SIMD16 instruction is not allowed." (but
>> 16-wide BFI1 works for me so far). Since GLSL's bitfieldInsert()
>> function takes int parameters BFI1 produces the same results in all
>> channels, so there's never any reason to emit a 16-wide BFI1.
>
> Suppose the first 8 pixels didn't take a branch, while the second 8 did,
> and you're bitfield inserting in this branch.  You'd be using undefined
> values for src[0].

You're right. Thanks. I'll send an updated patch.