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Re: [i386] Scalar DImode instructions on XMM registers
- From: Ilya Enkovich <enkovich dot gnu at gmail dot com>
- To: Uros Bizjak <ubizjak at gmail dot com>
- Cc: GCC Development <gcc at gcc dot gnu dot org>
- Date: Fri, 24 Apr 2015 13:07:56 +0300
- Subject: Re: [i386] Scalar DImode instructions on XMM registers
- Authentication-results: sourceware.org; auth=none
- References: <CAMbmDYYT6zE86-xAYs08VV2nWDK6Np+qEYoj+6oGM276MtBuPQ at mail dot gmail dot com> <CAFULd4YVruAT=RHgENhBcuKZgE6FvRa=8aR6WygKm9F4GjnJyg at mail dot gmail dot com>
2015-04-24 12:45 GMT+03:00 Uros Bizjak <firstname.lastname@example.org>:
> On Fri, Apr 24, 2015 at 11:22 AM, Ilya Enkovich <email@example.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.