Date: Tue, 15 Jul 2014 12:52:31 +0700 From: Alexey Dokuchaev <danfe@nsu.ru> To: Justin Hibbits <jrh29@alumni.cwru.edu> Cc: powerpc@freebsd.org Subject: Re: How to convert SSEish _mm_set1_ps() into AltiVec correctly? Message-ID: <20140715055231.GA70698@regency.nsu.ru> In-Reply-To: <CAHSQbTAG8rJbfyYG-FaQjuVm0ZYWAOLN6UcY-ycM%2Byuw0OvESw@mail.gmail.com> References: <20140714154224.GA28612@regency.nsu.ru> <CAHSQbTAG8rJbfyYG-FaQjuVm0ZYWAOLN6UcY-ycM%2Byuw0OvESw@mail.gmail.com>
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On Mon, Jul 14, 2014 at 09:20:55AM -0700, Justin Hibbits wrote:
> On Mon, Jul 14, 2014 at 8:42 AM, Alexey Dokuchaev <danfe@nsu.ru> wrote:
> > I'm a bit confused about how to convert _mm_set1_ps() [1] SSE function into
> > its AltiVec equivalent. To start with, I need to set all four floats of a
> > vector to the same value. So far, I've come up with two versions that work
> > with GCC or Clang, but I want to have a code that works with any compiler,
> > and is technically correct (works not just by accident). [...]
>
> I just tried the following:
>
> vector float a = (vector float){42.0f};
> vector float b = vec_splat(a, 0);
>
> Haven't done anything more than compile test it, but it builds with
> both gcc and clang. GCC uses vspltw, while clang uses vperm.
Awesome, thanks, that works. It did not occur to me that simply casting a
{42.f} and assigning it directly would DTRT on its own.
./danfe
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