[Pixman] [PATCH 5/6] mmx: introduce is_equal and is_zero functions

[Matt Turner]

On Tue, Feb 28, 2012 at 9:25 PM, Søren Sandmann <sandmann at cs.au.dk> wrote:
> Matt Turner <mattst88 at gmail.com> writes:
>
>> To be used by the next commit.
>>
>> Signed-off-by: Matt Turner <mattst88 at gmail.com>
>> ---
>>  pixman/pixman-mmx.c |   17 +++++++++++++++++
>>  1 files changed, 17 insertions(+), 0 deletions(-)
>>
>> diff --git a/pixman/pixman-mmx.c b/pixman/pixman-mmx.c
>> index 8b55b32..63edf18 100644
>> --- a/pixman/pixman-mmx.c
>> +++ b/pixman/pixman-mmx.c
>> @@ -416,6 +416,23 @@ store8888 (uint32_t *dest, __m64 v)
>>      store(dest, v);
>>  }
>>
>> +static force_inline pixman_bool_t
>> +is_equal (__m64 a, __m64 b)
>> +{
>> +#ifdef USE_LOONGSON_MMI
>> +    /* __m64 is double, we can compare directly. */
>> +    return a == b;
>> +#else
>> +    return to_uint64 (a) == to_uint64 (b);
>> +#endif
>> +}
>
> This looks like it will be somewhat less efficient on x86 and possibly
> iwmmxt, because it will result in a and b being converted from mmx to 64
> bit integers before comparing.
>
> A better way probably be to do something along the lines of what the SSE
> implementation does and introduce is_opaque() and is_zero() functions
> that use pcmpeqw and pmovmskb.
>
> The pmovmskb instruction is part of the MMX extended instruction set, so
> it can be handled similarly to pshufw and pmulhuw.

Ah, good suggestion. I'll make that change.