From: Russell King <rmk@arm.linux.org.uk>
To: Matthew Wilcox <willy@debian.org>,
Bernardo Innocenti <bernie@develer.com>,
Andrew Morton <akpm@zip.com.au>,
linux-kernel@vger.kernel.org
Subject: Re: do_div vs sector_t
Date: Sun, 13 Jul 2003 18:39:37 +0100 [thread overview]
Message-ID: <20030713183937.F2621@flint.arm.linux.org.uk> (raw)
In-Reply-To: <20030713172622.GA13824@twiddle.net>; from rth@twiddle.net on Sun, Jul 13, 2003 at 10:26:23AM -0700
On Sun, Jul 13, 2003 at 10:26:23AM -0700, Richard Henderson wrote:
> On Fri, Jul 11, 2003 at 11:33:59PM +0100, Matthew Wilcox wrote:
> > Better ideas?
>
> if (likely(((n) >> 31 >> 1) == 0)) {
>
Beware - luckily I don't have to worry about that on ARM (we do our own
thing.) However, with this code:
int foo(unsigned long long n)
{
if (((n) >> 31 >> 1) == 0) {
return 1;
} else {
return 0;
}
}
gcc 3.2.2 on ARM (32-bit) produces some not-very-nice code, consisting of
6 shifts and including placing one register on the stack and completely
ignoring a register which it could freely use instead.
--
Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux
http://www.arm.linux.org.uk/personal/aboutme.html
next prev parent reply other threads:[~2003-07-13 17:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-11 22:33 do_div vs sector_t Matthew Wilcox
2003-07-11 22:34 ` Andrew Morton
2003-07-11 22:42 ` Neil Brown
2003-07-12 0:14 ` do_div vs sector_t (patch) Nick Piggin
2003-07-12 6:52 ` do_div vs sector_t Christoph Hellwig
2003-07-12 6:58 ` Andrew Morton
2003-07-13 17:26 ` Richard Henderson
2003-07-13 17:39 ` Russell King [this message]
2003-07-13 19:14 ` Bernardo Innocenti
2003-07-13 20:04 ` Matthew Wilcox
2003-07-14 4:07 ` Peter Chubb
-- strict thread matches above, loose matches on Subject: below --
2003-07-13 18:40 linux
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