From: Tom Lane <tgl@sss.pgh.pa.us>
To: Michael Paquier <michael.paquier@gmail.com>
cc: Dmitry Dolgov <9erthalion6@gmail.com>, Andres Freund <andres@anarazel.de>,
        Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
        Vincent Lachenal <vincent.lachenal@gmail.com>,
        PostgreSQL mailing lists <pgsql-bugs@postgresql.org>
Subject: Re: [BUGS] BUG #14897: Segfault on statitics SQL request
In-reply-to: 
 <CAB7nPqQ7+rnOsGNDrtVC9uxb6erog2s4faM0FvmY_s-7uUmaNw@mail.gmail.com>
References: <20171110185747.31519.28038@wrigleys.postgresql.org>
 <1415.1510340891@sss.pgh.pa.us>
 <CAA2tJ7o-VK+ghsxifDAszFN5fikmG6U3sWHCEvc9nAVOypfjAw@mail.gmail.com>
 <5652.1510344738@sss.pgh.pa.us>
 <CAA2tJ7qsopt0hHbsm397H62LMsaE4hjRwaUu3FQdNgo5AYAGXA@mail.gmail.com>
 <7710.1510346813@sss.pgh.pa.us>
 <CAA2tJ7odG4KB=wvu_+5FfssxckbLTnEuR9C_TXRyeU_35z+CSA@mail.gmail.com>
 <10197.1510349123@sss.pgh.pa.us>
 <CAA2tJ7p72wbuHEzOA_g2V4YcmeDPHYKggenTR4dXG=kSpCiO8Q@mail.gmail.com>
 <14075.1510352167@sss.pgh.pa.us>
 <CA+q6zcXe9aV5NV88u9Y=vMp+=fP7QOXgTyFQhzuvmCvTBvb_kQ@mail.gmail.com>
 <17617.1510355215@sss.pgh.pa.us>
 <CAB7nPqR7mWvtnALZF93oez_v03NFCJ8dXP9CNicaUDv3KjDbYw@mail.gmail.com>
 <3192.1510508352@sss.pgh.pa.us>
 <CAB7nPqReMmn3Pg942we4aK73SFSVamdM0SAUO0BZHcvzA71h+A@mail.gmail.com>
 <CA+q6zcWnWYX0ArC6QYC3YeRk3WnsyuexV1FzqBuBpGqODEK3fQ@mail.gmail.com>
 <10396.1510621709@sss.pgh.pa.us> <17615.1510630283@sss.pgh.pa.us>
 <CAB7nPqQ7+rnOsGNDrtVC9uxb6erog2s4faM0FvmY_s-7uUmaNw@mail.gmail.com>
Comments: In-reply-to Michael Paquier <michael.paquier@gmail.com>
	message dated "Tue, 14 Nov 2017 14:20:25 +0900"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <23170.1510637495.1@sss.pgh.pa.us>
Date: Tue, 14 Nov 2017 00:31:35 -0500
Message-ID: <23171.1510637495@sss.pgh.pa.us>
Precedence: bulk

Michael Paquier <michael.paquier@gmail.com> writes:
> On Tue, Nov 14, 2017 at 12:31 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Concretely, the attached patch fixes it for me.  I've verified by
>> examining the assembly code that this stops gcc from using movdqa or
>> movaps in numeric.c, except for one place where it apparently can
>> prove that it's dealing with a sufficiently-aligned local variable.

> I am not seeing any difference in the assembly code generated by gcc
> -S with and without your patch. Perhaps I am missing something? What
> are you actually seeing?

Hm, double-check your procedure.  I get this:

$ diff numeric.s.std numeric.s.patch
2746c2746
<       movaps  %xmm0, (%r14)
---
>       movups  %xmm0, (%r14)
13948,13951c13948,13951
<       movdqa  16(%rbp), %xmm0
<       movaps  %xmm0, 16(%rax)
<       movdqa  32(%rbp), %xmm0
<       movaps  %xmm0, 32(%rax)
---
>       movdqu  16(%rbp), %xmm0
>       movups  %xmm0, 16(%rax)
>       movdqu  32(%rbp), %xmm0
>       movups  %xmm0, 32(%rax)
14434,14435c14434,14435
<       movdqa  16(%rbp), %xmm0
<       movaps  %xmm0, 16(%rax)
---
>       movdqu  16(%rbp), %xmm0
>       movups  %xmm0, 16(%rax)

(If using -g, there are a bunch more diffs in the debug tables.)

			regards, tom lane