Messages in this thread | ![/](/images/icornerl.gif) | | Date | Sun, 13 Jul 2003 18:39:37 +0100 | From | Russell King <> | Subject | Re: do_div vs sector_t |
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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
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