From: Noah Goldstein <goldstein.w.n@gmail.com>
To: Joseph Myers <joseph@codesourcery.com>
Cc: "H.J. Lu" <hjl.tools@gmail.com>,
GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [PATCH v8 2/3] String: Add hidden defs for __memcmpeq() to enable internal usage
Date: Thu, 21 Oct 2021 18:39:28 -0500 [thread overview]
Message-ID: <CAFUsyfLHVx9MjUzYQeoBMHpTC8McX+_VX1fbhvgZH4YW_DeGQQ@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2110212312210.1372396@digraph.polyomino.org.uk>
On Thu, Oct 21, 2021 at 6:15 PM Joseph Myers <joseph@codesourcery.com> wrote:
>
> On Thu, 21 Oct 2021, H.J. Lu via Libc-alpha wrote:
>
> > On Thu, Oct 21, 2021 at 4:08 PM Joseph Myers <joseph@codesourcery.com> wrote:
> > >
> > > On Thu, 21 Oct 2021, H.J. Lu via Libc-alpha wrote:
> > >
> > > > There are many memcmp calls in ld.so. I think most, if not all, of them
> > > > can be changed to __memcmpeq. Can you make another patch to do
> > > > that?
> > >
> > > Rather than doing that micro-optimization in the glibc sources, I think
> > > it's better to add the relevant feature to GCC and let glibc get optimized
> > > when built with a new-enough compiler.
> >
> > Why not? We don't know when __memcmpeq will be supported by GCC
> > used by glibc developers. If we don't even use it in glibc, why bother?
>
> The point of this function is entirely for compilers to generate for calls
> from memcmp, not for humans to write direct calls to.
>
> The compiler knows other semantics of memcmp (it might sometimes expand a
> memcmp with a small fixed size inline, for example). So changing to a
> direct call to __memcmpeq by hand isn't even always an optimization; it
> seems better to leave the semantics visible to the compiler. Note that in
> other cases we've generally moved *towards* relying on built-in functions
> rather than having our own local inline expansions of those or calls to
> internal names for those functions (we've done that for calls to various
> functions in libm, for example).
I have gone through all non-test .c files in GLIBC and replaced memcmp
with __memcmpeq where it makes sense. I can post that as a separate
patchset and we can decide whether it's a good idea there.
>
> --
> Joseph S. Myers
> joseph@codesourcery.com
next prev parent reply other threads:[~2021-10-21 23:39 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-27 20:38 [PATCH v1] String: Add support for __memcmpeq() ABI on all targets Noah Goldstein
2021-09-27 20:43 ` Joseph Myers
2021-09-27 21:06 ` Noah Goldstein
2021-09-27 21:06 ` [PATCH v2] " Noah Goldstein
2021-09-27 21:52 ` Joseph Myers
2021-09-28 1:24 ` Noah Goldstein
2021-09-28 1:24 ` [PATCH v3] " Noah Goldstein
2021-09-28 8:15 ` Andreas Schwab
2021-09-28 16:47 ` Noah Goldstein
2021-09-28 8:40 ` Florian Weimer
2021-09-28 16:47 ` Noah Goldstein
2021-09-28 16:51 ` Florian Weimer
2021-09-28 16:46 ` [PATCH v4] " Noah Goldstein
2021-09-28 16:50 ` [PATCH v5] " Noah Goldstein
2021-09-28 16:53 ` [PATCH v6] " Noah Goldstein
2021-09-29 8:36 ` Florian Weimer
2021-09-29 15:17 ` Noah Goldstein
2021-09-29 8:52 ` Andreas Schwab
2021-09-29 9:18 ` Florian Weimer
2021-09-29 9:31 ` Andreas Schwab
2021-09-29 9:44 ` Florian Weimer
2021-09-28 16:57 ` [PATCH v1] " Noah Goldstein
2021-09-29 15:17 ` [PATCH v7] " Noah Goldstein
2021-09-30 19:31 ` Noah Goldstein
2021-10-11 2:33 ` Noah Goldstein
2021-10-18 14:47 ` Noah Goldstein
2021-10-21 19:28 ` H.J. Lu
2021-10-21 19:58 ` Noah Goldstein
2021-10-21 20:00 ` H.J. Lu
2021-10-21 21:04 ` Noah Goldstein
2021-10-21 20:02 ` Adhemerval Zanella
2021-10-21 20:23 ` Noah Goldstein
2021-10-21 20:26 ` Adhemerval Zanella
2021-10-21 19:33 ` Adhemerval Zanella
2021-10-21 20:01 ` Noah Goldstein
2021-10-21 20:06 ` Adhemerval Zanella
2021-10-21 21:18 ` Florian Weimer
2021-10-21 20:07 ` H.J. Lu
2021-10-21 20:11 ` Noah Goldstein
2021-10-21 22:38 ` [PATCH v8 1/3] " Noah Goldstein
2021-10-21 22:38 ` [PATCH v8 2/3] String: Add hidden defs for __memcmpeq() to enable internal usage Noah Goldstein
2021-10-21 22:52 ` H.J. Lu
2021-10-21 23:08 ` Joseph Myers
2021-10-21 23:10 ` H.J. Lu
2021-10-21 23:14 ` Joseph Myers
2021-10-21 23:39 ` Noah Goldstein [this message]
2021-10-21 23:45 ` Noah Goldstein
2021-10-22 0:19 ` Joseph Myers
2021-10-22 0:40 ` H.J. Lu
2021-10-25 16:41 ` Joseph Myers
2021-10-22 0:18 ` Joseph Myers
2021-10-21 22:38 ` [PATCH v8 3/3] String: Add tests for __memcmpeq Noah Goldstein
2021-10-21 22:57 ` H.J. Lu
2021-10-21 23:47 ` Noah Goldstein
2021-10-22 0:41 ` H.J. Lu
2021-10-22 1:01 ` Noah Goldstein
2021-10-21 22:50 ` [PATCH v8 1/3] String: Add support for __memcmpeq() ABI on all targets H.J. Lu
2021-10-21 23:42 ` Noah Goldstein
2021-10-22 2:38 ` H.J. Lu
2021-10-22 4:04 ` Noah Goldstein
2021-10-22 5:49 ` [PATCH v9 " Noah Goldstein
2021-10-22 12:38 ` H.J. Lu
2021-10-22 16:07 ` Noah Goldstein
2021-10-22 17:19 ` Noah Goldstein
2021-10-22 17:40 ` Noah Goldstein
2021-10-22 17:44 ` H.J. Lu
2021-10-22 18:09 ` Noah Goldstein
2021-10-22 18:33 ` H.J. Lu
2021-10-22 5:49 ` [PATCH v9 2/3] String: Add hidden defs for __memcmpeq() to enable internal usage Noah Goldstein
2021-10-22 12:44 ` H.J. Lu
2021-10-22 5:49 ` [PATCH v9 3/3] String: Add tests for __memcmpeq Noah Goldstein
2021-10-22 12:42 ` H.J. Lu
2021-10-22 16:06 ` [PATCH v10 1/4] String: Add support for __memcmpeq() ABI on all targets Noah Goldstein
2021-10-22 16:06 ` [PATCH v10 2/4] String: Add hidden defs for __memcmpeq() to enable internal usage Noah Goldstein
2021-10-22 16:06 ` [PATCH v10 3/4] String: Add tests for __memcmpeq Noah Goldstein
2021-10-22 16:06 ` [PATCH v10 4/4] NEWS: Add item " Noah Goldstein
2021-10-22 16:12 ` H.J. Lu
2021-10-22 16:12 ` [PATCH v10 1/4] String: Add support for __memcmpeq() ABI on all targets H.J. Lu
2021-10-22 16:18 ` Noah Goldstein
2021-10-22 18:37 ` [PATCH v11 " Noah Goldstein
2021-10-22 18:37 ` [PATCH v11 2/4] String: Add hidden defs for __memcmpeq() to enable internal usage Noah Goldstein
2021-10-22 18:37 ` [PATCH v11 3/4] String: Add tests for __memcmpeq Noah Goldstein
2021-10-22 18:37 ` [PATCH v11 4/4] NEWS: Add item " Noah Goldstein
2021-10-22 19:46 ` [PATCH v12 1/4] String: Add support for __memcmpeq() ABI on all targets Noah Goldstein
2021-10-22 19:46 ` [PATCH v12 2/4] String: Add hidden defs for __memcmpeq() to enable internal usage Noah Goldstein
2021-10-22 19:46 ` [PATCH v12 3/4] String: Add tests for __memcmpeq Noah Goldstein
2021-10-22 19:46 ` [PATCH v12 4/4] NEWS: Add item " Noah Goldstein
2021-10-22 20:28 ` [PATCH v12 1/4] String: Add support for __memcmpeq() ABI on all targets H.J. Lu
2021-10-22 20:33 ` Noah Goldstein
2021-10-22 20:45 ` H.J. Lu
2021-10-22 21:24 ` Noah Goldstein
2021-10-22 21:23 ` [PATCH v13 " Noah Goldstein
2021-10-22 21:23 ` [PATCH v13 2/4] String: Add hidden defs for __memcmpeq() to enable internal usage Noah Goldstein
2021-10-22 21:23 ` [PATCH v13 3/4] String: Add tests for __memcmpeq Noah Goldstein
2021-10-22 21:23 ` [PATCH v13 4/4] NEWS: Add item " Noah Goldstein
2021-10-23 23:23 ` [PATCH v13 1/4] String: Add support for __memcmpeq() ABI on all targets Noah Goldstein
2021-10-23 23:24 ` [PATCH v14 " Noah Goldstein
2021-10-23 23:24 ` [PATCH v14 2/4] String: Add hidden defs for __memcmpeq() to enable internal usage Noah Goldstein
2021-10-26 18:56 ` H.J. Lu
2021-10-23 23:24 ` [PATCH v14 3/4] String: Add tests for __memcmpeq Noah Goldstein
2021-10-26 18:57 ` H.J. Lu
2021-10-23 23:24 ` [PATCH v14 4/4] NEWS: Add item " Noah Goldstein
2021-10-26 18:58 ` H.J. Lu
2021-10-25 2:45 ` [PATCH v14 1/4] String: Add support for __memcmpeq() ABI on all targets Noah Goldstein
2021-10-26 18:55 ` H.J. Lu
2021-10-26 22:29 ` Noah Goldstein
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=CAFUsyfLHVx9MjUzYQeoBMHpTC8McX+_VX1fbhvgZH4YW_DeGQQ@mail.gmail.com \
--to=goldstein.w.n@gmail.com \
--cc=hjl.tools@gmail.com \
--cc=joseph@codesourcery.com \
--cc=libc-alpha@sourceware.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;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).