Re: do_div vs sector_t

[Russell King]

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 ([e-mail])                The developer of ARM Linux
             http://www.arm.linux.org.uk/personal/aboutme.html