From: Eli Zaretskii <eliz@gnu.org>
To: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: brobecker@adacore.com, gdb-patches@sourceware.org
Subject: Re: [patch 3/4] Fix hw watchpoints #2: reordered / simultaneously hit
Date: Tue, 17 Nov 2009 19:18:00 -0000 [thread overview]
Message-ID: <83fx8dm05c.fsf@gnu.org> (raw)
In-Reply-To: <20091117152912.GA29979@host0.dyn.jankratochvil.net>
> Date: Tue, 17 Nov 2009 16:29:12 +0100
> From: Jan Kratochvil <jan.kratochvil@redhat.com>
> Cc: Eli Zaretskii <eliz@gnu.org>, gdb-patches@sourceware.org
>
> 0000000000000000 <get>:
> 0: 0f b6 47 04 movzbl 0x4(%rdi),%eax
> + 4: 83 e0 01 and $0x1,%eax
> c3 retq
>
> 0000000000000010 <set>:
> - 10: c6 47 04 01 movb $0x1,0x4(%rdi)
> + 10: 80 4f 04 01 orb $0x1,0x4(%rdi)
This is what I remembered, at least for x86. A single additional
instruction can hardly cause any visible slowdown, at least not with
access patterns typical for such flags.
Any other reasons not to use bitfields?
next prev parent reply other threads:[~2009-11-17 19:18 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-16 3:42 Jan Kratochvil
2009-11-17 0:12 ` Joel Brobecker
2009-11-17 4:03 ` Eli Zaretskii
2009-11-17 14:13 ` Joel Brobecker
2009-11-17 15:31 ` Jan Kratochvil
2009-11-17 19:18 ` Eli Zaretskii [this message]
2009-11-17 19:42 ` Joel Brobecker
2009-11-17 22:18 ` Eli Zaretskii
2009-11-17 19:20 ` Eli Zaretskii
2009-11-18 10:09 ` Jan Kratochvil
2009-11-18 11:36 ` Pedro Alves
2009-11-20 16:58 ` Pedro Alves
2009-11-20 17:06 ` Pedro Alves
2009-11-20 17:15 ` Jan Kratochvil
2009-11-20 17:10 ` Daniel Jacobowitz
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