From: Joe Perches <joe@perches.com>
To: "H. Peter Anvin" <hpa@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
linux-arch <linux-arch@vger.kernel.org>,
mingo@kernel.org, linux-kernel@vger.kernel.org,
tglx@linutronix.de, james.t.kukunas@intel.com,
Linus Torvalds <torvalds@linux-foundation.org>,
David Miller <davem@davemloft.net>
Subject: Re: [tip:x86/asm] x86, bitops: Change bitops to be native operand size
Date: Mon, 11 Nov 2013 18:54:43 -0800 [thread overview]
Message-ID: <1384224883.4771.28.camel@joe-AO722> (raw)
In-Reply-To: <5281698F.9080808@linux.intel.com>
On Mon, 2013-11-11 at 15:34 -0800, H. Peter Anvin wrote:
> On 11/10/2013 06:22 PM, Joe Perches wrote:
> >
> > Perhaps the current x86 bitops asm code is being conflated
> > with the ideal implementation?
> >
> Yes, by you.
Really? I don't think so.
How does the use of signed long for an index where
no negative values are possible or the use of a
negative int for BIT_MASK make sense?
> x86 has instructions that operate on signed bitindicies.
indices.
> It doesn't
> have instructions that operate on unsigned bitindicies. Unless someone
> is willing to do the work to prove that shift and mask is actually
> faster than using the hardware instructions (which I doubt, but it is
> always a possibility), that's what we have.
That doesn't mean x86 is the ideal implementation.
next prev parent reply other threads:[~2013-11-12 2:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-17 1:15 [tip:x86/asm] x86, bitops: Change bitops to be native operand size tip-bot for H. Peter Anvin
2013-11-10 21:09 ` Joe Perches
2013-11-10 22:10 ` H. Peter Anvin
2013-11-10 22:44 ` Joe Perches
2013-11-11 2:06 ` H. Peter Anvin
2013-11-11 2:22 ` Joe Perches
2013-11-11 23:34 ` H. Peter Anvin
2013-11-12 2:54 ` Joe Perches [this message]
2013-11-12 3:15 ` Linus Torvalds
2013-11-12 4:08 ` Joe Perches
2013-11-12 8:52 ` Geert Uytterhoeven
2013-11-30 23:16 ` Rob Landley
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1384224883.4771.28.camel@joe-AO722 \
--to=joe@perches.com \
--cc=davem@davemloft.net \
--cc=hpa@linux.intel.com \
--cc=hpa@zytor.com \
--cc=james.t.kukunas@intel.com \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox