From: Matthew Wilcox <matthew@wil.cx>
To: David Howells <dhowells@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
mingo@elte.hu, tglx@linutronix.de, linux-arch@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64()
Date: Fri, 26 Mar 2010 11:52:26 -0600 [thread overview]
Message-ID: <20100326175226.GO3875@parisc-linux.org> (raw)
In-Reply-To: <28287.1269625325@redhat.com>
On Fri, Mar 26, 2010 at 05:42:05PM +0000, David Howells wrote:
> Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
> > Where did you find that "doesn't modify its output" thing? It's not true.
> > The truth is that the destination is undefined. Just read the dang Intel
> > documentation, it's very clearly stated right there.
>
> Hmmm... My ancient Borland Assembler dead-tree manual doesn't mention that.
The only x86 manuals I have are encased in the Itanium SDM from 2002,
and they agree with Linus that BSF and BSR undefine the contents of the
destination operand if the source operand contains zero.
--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
next prev parent reply other threads:[~2010-03-26 17:52 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4BACCB4E.7010108@draigBrady.com>
2010-03-26 14:42 ` [PATCH 1/3] X86: Optimise fls(), ffs() and fls64() David Howells
2010-03-26 14:42 ` [PATCH 2/3] Adjust the comment on get_order() to describe the size==0 case David Howells
2010-03-26 14:42 ` [PATCH 3/3] Optimise get_order() David Howells
2010-03-26 14:42 ` David Howells
2010-03-26 17:23 ` [PATCH 1/3] X86: Optimise fls(), ffs() and fls64() Linus Torvalds
2010-03-26 17:37 ` Scott Lurndal
2010-03-26 17:42 ` Linus Torvalds
2010-04-06 13:57 ` Jamie Lokier
2010-04-06 14:40 ` Linus Torvalds
2010-03-26 17:42 ` David Howells
2010-03-26 17:45 ` Linus Torvalds
2010-03-26 17:58 ` Ralf Baechle
2010-03-26 18:03 ` Linus Torvalds
2010-03-26 18:16 ` Matthew Wilcox
2010-04-06 13:30 ` Matthew Wilcox
2010-04-14 11:49 ` David Howells
2010-04-14 14:30 ` Avi Kivity
2010-04-15 8:48 ` David Howells
2010-04-15 8:49 ` Avi Kivity
2010-04-15 11:41 ` Jamie Lokier
2010-03-26 17:52 ` Matthew Wilcox [this message]
2010-04-14 13:13 ` David Howells
2010-01-13 19:39 David Howells
2010-01-13 20:15 ` Geert Uytterhoeven
2010-01-13 21:59 ` David Howells
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=20100326175226.GO3875@parisc-linux.org \
--to=matthew@wil.cx \
--cc=dhowells@redhat.com \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--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;
as well as URLs for NNTP newsgroup(s).