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From: Szabolcs Nagy <Szabolcs.Nagy@arm.com>
To: "naohirot@fujitsu.com" <naohirot@fujitsu.com>
Cc: 'Wilco Dijkstra' <Wilco.Dijkstra@arm.com>,
	'GNU C Library' <libc-alpha@sourceware.org>
Subject: Re: [PATCH 0/5] Added optimized memcpy/memmove/memset for A64FX
Date: Thu, 6 May 2021 15:26:59 +0100	[thread overview]
Message-ID: <20210506142658.GA9028@arm.com> (raw)
In-Reply-To: <TYAPR01MB6025DC532F3C09A0E121188CDF589@TYAPR01MB6025.jpnprd01.prod.outlook.com>

The 05/06/2021 10:01, naohirot@fujitsu.com wrote:
> > From: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
> > > [1]
> > > https://github.com/NaohiroTamura/glibc/commit/c582917071e76cfed84fafb0
> > > c82cb70339294386
> > 
> > I meant using an actual NOP in the #else case so that existing string functions
> > won't change. Also note the #defines in the #if and #else need to be indented.
> > 
> 
> I've read the mail thread regarding BTI, but I think I couldn't fully understand the
> problem. BTI seems available from ARMv8.5, and A64FX is ARMv8.2.
> Even though distro distributed BTI enabled binary, BTI doesn't work on A64FX.
> So BTI_J macro can be removed from A64FX IFUNC code at least, because A64FX
> IFUNC code is executed only on A64FX.
> Are we discussing the BTI_C code which is not in IFUNC code?

BTI_C at function entry.

the slowdown you showed with bti c at function entry
should not be present with a plain nop.

this means a64fx implemented hint space instructions
(such as bti c) slower than plain nops, which is not
expected and will cause slowdowns with distros that
try to distribute binaries with bti c, this problem
goes beyond string functions.

  reply	other threads:[~2021-05-06 14:27 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-12 12:52 Wilco Dijkstra
2021-04-12 18:53 ` Florian Weimer
2021-04-13 12:07 ` naohirot
2021-04-14 16:02   ` Wilco Dijkstra
2021-04-15 12:20     ` naohirot
2021-04-20 16:00       ` Wilco Dijkstra
2021-04-27 11:58         ` naohirot
2021-04-29 15:13           ` Wilco Dijkstra
2021-04-30 15:01             ` Szabolcs Nagy
2021-04-30 15:23               ` Wilco Dijkstra
2021-04-30 15:30                 ` Florian Weimer
2021-04-30 15:40                   ` Wilco Dijkstra
2021-05-04  7:56                     ` Szabolcs Nagy
2021-05-04 10:17                       ` Florian Weimer
2021-05-04 10:38                         ` Wilco Dijkstra
2021-05-04 10:42                         ` Szabolcs Nagy
2021-05-04 11:07                           ` Florian Weimer
2021-05-06 10:01             ` naohirot
2021-05-06 14:26               ` Szabolcs Nagy [this message]
2021-05-06 15:09                 ` Florian Weimer
2021-05-06 17:31               ` Wilco Dijkstra
2021-05-07 12:31                 ` naohirot
2021-04-19  2:51     ` naohirot
2021-04-19 14:57       ` Wilco Dijkstra
2021-04-21 10:10         ` naohirot
2021-04-21 15:02           ` Wilco Dijkstra
2021-04-22 13:17             ` naohirot
2021-04-23  0:58               ` naohirot
2021-04-19 12:43     ` naohirot
2021-04-20  3:31     ` naohirot
2021-04-20 14:44       ` Wilco Dijkstra
2021-04-27  9:01         ` naohirot
2021-04-20  5:49     ` naohirot
2021-04-20 11:39       ` Wilco Dijkstra
2021-04-27 11:03         ` naohirot
2021-04-23 13:22     ` naohirot
  -- strict thread matches above, loose matches on Subject: below --
2021-03-17  2:28 Naohiro Tamura
2021-03-29 12:03 ` Szabolcs Nagy
2021-05-10  1:45 ` naohirot
2021-05-14 13:35   ` Szabolcs Nagy
2021-05-19  0:11     ` naohirot

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