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Re: 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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Thread

no-op delay loops Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-11-27 10:00 +0100
  Re: no-op delay loops yalin wang <yalin.wang2010@gmail.com> - 2015-11-27 10:10 +0100
    Re: no-op delay loops Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-27 10:30 +0100
  Re: no-op delay loops Arnd Bergmann <arnd@arndb.de> - 2015-11-27 12:20 +0100
  Re: no-op delay loops Ralf Baechle <ralf@linux-mips.org> - 2015-11-27 12:50 +0100

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