From: Jeff King <peff@peff.net>
To: "René Scharfe" <l.s.r@web.de>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 1/4] strbuf: add strbuf_add_uint()
Date: Thu, 14 May 2026 23:53:39 -0400 [thread overview]
Message-ID: <20260515035339.GA75627@coredump.intra.peff.net> (raw)
In-Reply-To: <f51cdd89-dab1-44f3-8f63-7d34f6fbbba5@web.de>
On Thu, May 14, 2026 at 01:09:24PM +0200, René Scharfe wrote:
> > And btw, one final thing to look at if you are interested in
> > micro-optimizing strbufs: using intrinsics for overflow detection.
> >
> > Right now we use unsigned_add_overflows(), and then do the actual add.
> > Using __builtin_add_overflow() might be faster.
> Curious. Clang and GCC emit the same instructions for our
> unsigned_add_overflows() vs. __builtin_add_overflow() on x64, but clang
> on ARM64 fails to elide the comparison: https://godbolt.org/z/91d35KofM
Ah, neat. I always assumed there was low-hanging fruit to pick here, but
it sounds like the compiler is (usually) more clever than I expected.
-Peff
next prev parent reply other threads:[~2026-05-15 3:53 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-12 11:55 [PATCH 0/4] strbuf: add and use strbuf_add_uint() René Scharfe
2026-05-12 11:56 ` [PATCH 1/4] strbuf: add strbuf_add_uint() René Scharfe
2026-05-12 18:42 ` Jeff King
2026-05-12 19:32 ` René Scharfe
2026-05-13 16:22 ` Jeff King
2026-05-13 16:47 ` Jeff King
2026-05-13 16:49 ` Jeff King
2026-05-14 11:09 ` René Scharfe
2026-05-14 11:53 ` Junio C Hamano
2026-05-15 3:53 ` Jeff King [this message]
2026-05-13 17:46 ` René Scharfe
2026-05-12 11:56 ` [PATCH 2/4] cat-file: use strbuf_add_uint() René Scharfe
2026-05-12 18:46 ` Jeff King
2026-05-12 11:56 ` [PATCH 3/4] ls-files: " René Scharfe
2026-05-12 19:01 ` Jeff King
2026-05-12 20:44 ` René Scharfe
2026-05-13 16:46 ` Jeff King
2026-05-12 11:56 ` [PATCH 4/4] ls-tree: " René Scharfe
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=20260515035339.GA75627@coredump.intra.peff.net \
--to=peff@peff.net \
--cc=git@vger.kernel.org \
--cc=l.s.r@web.de \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.