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Re: [i386] Scalar DImode instructions on XMM registers


2015-04-24 12:45 GMT+03:00 Uros Bizjak <ubizjak@gmail.com>:
> On Fri, Apr 24, 2015 at 11:22 AM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
>
>> I was looking into PR65105 and tried to generate SSE computation for a
>> simple 64bit  a + b + c sequence. Having no scalar integer instructions in
>> SSE I have to use vector variants.
>
> Is this approach really better that having two add/addc instructions?

We surely shouldn't apply this for each DI instruction and compute
transformation costs. It is profitable if not many conversions
required, it helps to relax GPR pressure, we expect it to be
profitable for mul. Performance tests will show if this is useful. I
want to make a small prototype and try it.

Ilya

>
> Uros.


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