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Re: [i386] Scalar DImode instructions on XMM registers
- From: Uros Bizjak <ubizjak at gmail dot com>
- To: Ilya Enkovich <enkovich dot gnu at gmail dot com>
- Cc: GCC Development <gcc at gcc dot gnu dot org>
- Date: Fri, 24 Apr 2015 11:49:28 +0200
- 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>
On Fri, Apr 24, 2015 at 11:45 AM, Uros Bizjak <ubizjak@gmail.com> wrote:
> 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?
FYI, V1DI mode was introduced because XMM shift insn were used to
shift DImode values. The cost of moves from/to integer DImode reg pair
was disastrous.
Uros.