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Date: Sun, 02 Dec 2012 10:51:00 -0000
Message-ID: <CAFULd4Z=8xeVScUM7JSqkHHXJrmO7qVa40q-h-mUE+Vehb86vw@mail.gmail.com>
Subject: Re: [i386] scalar ops that preserve the high part of a vector
From: Uros Bizjak <ubizjak@gmail.com>
To: Marc Glisse <marc.glisse@inria.fr>
Cc: gcc-patches@gcc.gnu.org, "H.J. Lu" <hjl.tools@gmail.com>
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On Sat, Dec 1, 2012 at 6:27 PM, Marc Glisse <marc.glisse@inria.fr> wrote:

> here is a patch. If it is accepted, I'll extend it to other vm patterns
> (mul, div, min, max are likely candidates, but I need to check the doc). It
> passed bootstrap+testsuite on x86_64-linux.
>
>
> 2012-12-01  Marc Glisse  <marc.glisse@inria.fr>
>
>         PR target/54855
> gcc/
>         * config/i386/sse.md (<sse>_vm<plusminus_insn><mode>3): Rewrite
>         pattern.
>         * config/i386/i386-builtin-types.def: New function types.
>         * config/i386/i386.c (ix86_expand_args_builtin): Likewise.
>         (bdesc_args) <__builtin_ia32_addss, __builtin_ia32_subss,
>         __builtin_ia32_addsd, __builtin_ia32_subsd>: Change prototype.
>         * config/i386/xmmintrin.h: Adapt to new builtin prototype.
>         * config/i386/emmintrin.h: Likewise.
>         * doc/extend.texi (X86 Built-in Functions): Document changed
> prototype.
>
> testsuite/
>         * gcc.target/i386/pr54855-1.c: New testcase.
>         * gcc.target/i386/pr54855-2.c: New testcase.

Yes, the approach looks correct to me, but I wonder why we have
different representations for v4sf and v2df cases? I'd say that we
should canonicalize patterns somewhere in the middle end (probably to
vec_merge variant, as IMO vec_dup looks like degenerated vec_merge
variant), otherwise we will have pattern explosion.

However, the patch is too late for 4.8, but definitely a wanted
generalization and fix of a (partially) wrong representation.

I have also CCd HJ for his opinion, since the patch touches published headers.

Thanks,
Uros.