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SubjectRe: no-op delay loops
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> On Nov 27, 2015, at 16:53, Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:
>
> Hi,
>
> It seems that gcc happily compiles
>
> for (i = 0; i < 1000000000; ++i) ;
>
> into simply
>
> i = 1000000000;
>
> (which is then usually eliminated as a dead store). At least at -O2, and
> when i is not declared volatile. So it would seem that the loops at
>
> arch/mips/pci/pci-rt2880.c:235
> arch/mips/pmcs-msp71xx/msp_setup.c:80
> arch/mips/sni/reset.c:35
>
> actually don't do anything. (In the middle one, i is 'register', but
> that doesn't change anything.) Is mips compiled with some special flags
> that would make gcc actually emit code for the above?
>
you can try to declare i as volatile int i;
may gcc will not optimize it .

Thanks



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