From: Shawn Landden <shawn@git.icu>
To: "linux-man@vger.kernel.org" <linux-man@vger.kernel.org>
Subject: Re: [PATCH] memcmp.3: note about optimization to bcmp in LLVM 9
Date: Sat, 11 Jan 2020 10:05:36 -0500 [thread overview]
Message-ID: <20698651578755136@sas1-30406100349c.qloud-c.yandex.net> (raw)
In-Reply-To: <20200111150216.5956-1-shawn@git.icu>
11.01.2020, 10:02, "Shawn Landden" <shawn@git.icu>:
> ---
> man3/memcmp.3 | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/man3/memcmp.3 b/man3/memcmp.3
> index 247eed223..6afca5ea4 100644
> --- a/man3/memcmp.3
> +++ b/man3/memcmp.3
> @@ -84,10 +84,17 @@ because the required CPU time depends on the number of equal bytes.
> Instead, a function that performs comparisons in constant time is required.
> Some operating systems provide such a function (e.g., NetBSD's
> .BR consttime_memequal ()),
> but no such function is specified in POSIX.
> On Linux, it may be necessary to implement such a function oneself.
> +.PP
> +LLVM 9, released in 2019, and later will optimize a call
to
> +.BR memcmp ()
> +to a call to
> +.BR bcmp (3)
> +if the return value is only checked for equilivence to zero.
> +.\" http://releases.llvm.org/9.0.0/docs/ReleaseNotes.html#noteworthy-optimizations
> .SH SEE ALSO
> .BR bcmp (3),
> .BR bstring (3),
> .BR strcasecmp (3),
> .BR strcmp (3),
> --
> 2.20.1
--
Shawn Landden
next prev parent reply other threads:[~2020-01-11 15:10 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-11 15:02 [PATCH] memcmp.3: note about optimization to bcmp in LLVM 9 Shawn Landden
2020-01-11 15:05 ` Shawn Landden [this message]
2020-01-21 19:53 ` Michael Kerrisk (man-pages)
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