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From: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
To: "Alejandro Colomar (man-pages)" <alx.manpages@gmail.com>
Cc: 'GNU C Library' <libc-alpha@sourceware.org>,
	"gcc@gcc.gnu.org" <gcc@gcc.gnu.org>
Subject: Missing optimization: mempcpy(3) vs memcpy(3)
Date: Mon, 12 Dec 2022 14:34:54 +0000	[thread overview]
Message-ID: <PAWPR08MB898243076FBFBF6C7E919E4183E29@PAWPR08MB8982.eurprd08.prod.outlook.com> (raw)

Hi,

I don't believe there is a missing optimization here: compilers expand mempcpy
by default into memcpy since that is the standard library call. That means even
if your source code contains mempcpy, there will never be any calls to mempcpy.

The reason is obvious: most targets support optimized memcpy in the C library
while very few optimize mempcpy. The same is true for bzero, bcmp and bcopy.

Targets can do it differently, IIRC x86 is the only target that emits calls both to
memcpy and mempcpy.

Cheers,
Wilco

             reply	other threads:[~2022-12-12 14:35 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-12 14:34 Wilco Dijkstra [this message]
2022-12-12 14:57 ` Cristian Rodríguez
  -- strict thread matches above, loose matches on Subject: below --
2022-12-09 17:11 Alejandro Colomar
2022-12-12 13:37 ` Martin Liška
2022-12-12 13:44   ` Alejandro Colomar
2022-12-12 13:56     ` Jakub Jelinek
2022-12-12 14:05       ` Alejandro Colomar
2022-12-12 14:48         ` Jonathan Wakely
2022-12-12 14:53           ` Jakub Jelinek
2022-12-12 15:56             ` Alejandro Colomar
2022-12-12 16:09               ` Jakub Jelinek
2022-12-12 17:15                 ` Alejandro Colomar
2022-12-12 17:42                 ` Jonathan Wakely

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