From: Linus Torvalds <torvalds@linux-foundation.org>
To: Michael Cree <mcree@orcon.net.nz>
Cc: David Howells <dhowells@redhat.com>,
David Miller <davem@davemloft.net>,
James.Bottomley@hansenpartnership.com, geert@linux-m68k.org,
linux-arch@vger.kernel.org
Subject: Re: Arch maintainers Ahoy!
Date: Wed, 13 Jun 2012 17:51:32 +0300 [thread overview]
Message-ID: <CA+55aFz+n8T_8xhrTvObtBjziAVTT+YRiHyhEmcmMahdHX-XWw@mail.gmail.com> (raw)
In-Reply-To: <4FD874A4.8060606@orcon.net.nz>
On Wed, Jun 13, 2012 at 2:08 PM, Michael Cree <mcree@orcon.net.nz> wrote:
>
> From commit 36126f8f2ed8 prep_zero_mask() must, and I quote, "generate
> an *exact* mask of which byte had the first zero."
No, that wasn't the intent. It must generate something that can be
or'ed together so that the "generate_zero_mask()" can actually then
generate the mask itself.
It has to be exact in the sense that the value must *exactly* imply
the first byte. That's different from the "has_zero()" function that
doesn't need to calculate which is the *first* byte with the zero,
just that there is at least one byte of zero.
In fact, look at the x86 implementation. The prep_zero_mask() function
is a no-op, because it just leaves the high bit set in the appropriate
byte. The actual bytemask is generated by create_zero_mask().
Linus
next prev parent reply other threads:[~2012-06-13 14:51 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-21 16:50 Arch maintainers Ahoy! (was Re: x86: faster strncpy_from_user()) Linus Torvalds
2012-05-23 5:46 ` Arch maintainers Ahoy! David Miller
2012-05-23 8:02 ` Geert Uytterhoeven
2012-05-23 9:40 ` James Bottomley
2012-05-23 15:15 ` Linus Torvalds
2012-05-23 17:21 ` David Miller
2012-05-23 17:32 ` Linus Torvalds
2012-05-23 18:16 ` David Miller
2012-05-23 18:27 ` Linus Torvalds
2012-05-23 18:35 ` David Miller
2012-05-23 18:44 ` Linus Torvalds
2012-05-23 18:46 ` Linus Torvalds
2012-05-23 20:36 ` David Miller
2012-05-23 21:01 ` Linus Torvalds
2012-05-24 2:11 ` David Miller
2012-05-24 5:25 ` Paul Mackerras
2012-05-24 5:56 ` David Miller
2012-05-24 9:40 ` David Howells
2012-05-24 15:53 ` Linus Torvalds
2012-06-13 11:08 ` Michael Cree
2012-06-13 14:51 ` Linus Torvalds [this message]
2012-05-24 16:45 ` David Howells
2012-05-24 16:56 ` Linus Torvalds
2012-05-24 17:16 ` David Howells
2012-05-23 17:19 ` David Miller
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