From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
To: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org, Waldemar Brodkorb <wbx@openadk.org>
Subject: Re: undefined reference to `__multi3' when building with gcc 7.x
Date: Sat, 5 Aug 2017 13:56:49 +0200 [thread overview]
Message-ID: <20170805135649.152b0739@windsurf> (raw)
In-Reply-To: <20170804222500.GA11675@linux-mips.org>
Hello,
On Sat, 5 Aug 2017 00:25:00 +0200, Ralf Baechle wrote:
> > Great! However, looking at the functions that end up calling __multi3,
> > I'm wondering why suddenly gcc 7.x needs to call such a function, while
> > the same code was compiling without __multi3 in libgcc with gcc 6.x.
>
> Chances are it's something specific to MIPS64 R6. Before trying your
> config file I also tried a number of other defconfigs and all built
> well.
>
> Here's a test case which generates a reference to __multi3:
>
> unsigned long func(unsigned long a, unsigned long b)
> {
> return a > (~0UL) / b;
> }
>
> GCC rearanges above statement to:
>
> return (unsigned __int128)a * (unsigned __int128) b > 0xffffffff;
And this is normal/expected ?
Thomas
--
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
next prev parent reply other threads:[~2017-08-05 11:57 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-03 20:55 undefined reference to `__multi3' when building with gcc 7.x Thomas Petazzoni
2017-08-04 0:05 ` Ralf Baechle
2017-08-04 15:19 ` Ralf Baechle
2017-08-04 15:41 ` Thomas Petazzoni
2017-08-04 22:25 ` Ralf Baechle
2017-08-05 11:56 ` Thomas Petazzoni [this message]
2017-08-07 8:34 ` Ralf Baechle
2017-08-13 20:46 ` Thomas Petazzoni
2017-08-17 7:15 ` Ralf Baechle
2017-08-17 8:49 ` Matthew Fortune
2017-08-17 22:19 ` Ralf Baechle
2017-10-07 19:22 ` Thomas Petazzoni
2017-11-07 17:39 ` Thomas Petazzoni
2017-08-17 1:01 ` Maciej W. Rozycki
2017-08-17 1:01 ` Maciej W. Rozycki
2017-12-03 9:56 ` Thomas Petazzoni
2017-12-05 23:49 ` James Hogan
2017-12-05 23:49 ` James Hogan
2017-12-06 7:50 ` Thomas Petazzoni
2017-12-06 7:50 ` Thomas Petazzoni
2017-12-07 7:20 ` [PATCH] MIPS: Implement __multi3 for GCC7 MIPS64r6 builds James Hogan
2017-12-08 23:52 ` Maciej W. Rozycki
2017-12-08 23:52 ` Maciej W. Rozycki
2017-12-09 7:15 ` James Hogan
2017-12-09 7:15 ` James Hogan
2017-12-27 8:31 ` Waldemar Brodkorb
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170805135649.152b0739@windsurf \
--to=thomas.petazzoni@free-electrons.com \
--cc=linux-mips@linux-mips.org \
--cc=ralf@linux-mips.org \
--cc=wbx@openadk.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox