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From: Segher Boessenkool <segher@kernel.crashing.org>
To: Richard Biener <richard.guenther@gmail.com>
Cc: luoxhu <luoxhu@linux.ibm.com>,
	GCC Patches <gcc-patches@gcc.gnu.org>,
	David Edelsohn <dje.gcc@gmail.com>,
	Bill Schmidt <wschmidt@linux.ibm.com>,
	linkw@gcc.gnu.org
Subject: Re: [PATCH v2] rs6000: Expand vec_insert in expander instead of gimple [PR79251]
Date: Tue, 15 Sep 2020 11:16:26 -0500	[thread overview]
Message-ID: <20200915161626.GN28786@gate.crashing.org> (raw)
In-Reply-To: <CAFiYyc3a7v-3GL0rHijpautPiwq1z2qJuUWN7FDQEMOyp=yvJg@mail.gmail.com>

On Tue, Sep 15, 2020 at 08:51:09AM +0200, Richard Biener wrote:
> On Tue, Sep 15, 2020 at 5:56 AM luoxhu <luoxhu@linux.ibm.com> wrote:
> > >     u[n % 4] = i;
> > >
> > > I guess.  Is the % 4 mandated by the vec_insert semantics btw?

(As an aside -- please use "& 3" instead: that works fine if n is signed
as well, but modulo doesn't.  Maybe that is in the patch already, I
didn't check, sorry.)

> note this is why I asked about the actual CPU instruction - as I read
> Seghers mail
> the instruction modifies a vector register, not memory.

But note that the builtin is not the same as the machine instruction --
here there shouldn't be a difference if compiling for a new enough ISA,
but the builtin is available on anything with at least AltiVec.


Segher

  reply	other threads:[~2020-09-15 16:17 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-31  9:06 [PATCH] " Xiong Hu Luo
2020-08-31 12:43 ` Richard Biener
2020-08-31 16:47 ` will schmidt
2020-09-01 11:43   ` luoxhu
2020-08-31 17:04 ` Segher Boessenkool
2020-09-01  8:09   ` luoxhu
2020-09-01 13:07     ` Richard Biener
2020-09-02  9:26       ` luoxhu
2020-09-02  9:30         ` Richard Biener
2020-09-03  9:20           ` luoxhu
2020-09-03 10:29             ` Richard Biener
2020-09-04  6:16               ` luoxhu
2020-09-04  6:38                 ` luoxhu
2020-09-04  7:19                   ` Richard Biener
2020-09-04  7:23                     ` Richard Biener
2020-09-04  9:18                       ` luoxhu
2020-09-04 10:23                         ` Segher Boessenkool
2020-09-07  5:43                           ` [PATCH v2] " luoxhu
2020-09-07 11:57                             ` Richard Biener
2020-09-08  8:11                               ` luoxhu
2020-09-08  8:26                                 ` Richard Biener
2020-09-09  1:47                                   ` luoxhu
2020-09-09  7:30                                     ` Richard Biener
2020-09-09 13:47                                   ` Segher Boessenkool
2020-09-09 14:28                                     ` Richard Biener
2020-09-09 16:00                                       ` Segher Boessenkool
2020-09-10 10:08                                         ` Richard Biener
2020-09-14  8:05                                           ` luoxhu
2020-09-14  9:47                                             ` Richard Biener
2020-09-14 10:47                                               ` Richard Sandiford
2020-09-14 11:22                                                 ` Richard Biener
2020-09-14 11:49                                                   ` Richard Sandiford
2020-09-14 21:06                                                 ` Segher Boessenkool
2020-09-14 20:59                                               ` Segher Boessenkool
2020-09-15  3:56                                               ` luoxhu
2020-09-15  6:51                                                 ` Richard Biener
2020-09-15 16:16                                                   ` Segher Boessenkool [this message]
2020-09-16  8:31                                                     ` Richard Biener
2020-09-16 11:11                                                       ` Segher Boessenkool
2020-09-16  6:15                                                   ` luoxhu
2020-09-16  8:41                                                     ` Richard Biener
2020-09-14 20:21                                           ` Segher Boessenkool
2020-09-01 14:02     ` [PATCH] " Segher Boessenkool

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