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
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