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Subject: Re: busy loop

Re: busy loop

From: Edgar Toernig <>
Date: Tue, 15 Jun 2010 19:36:45 +0200

pouly amaury wrote:
> for (x = (unsigned)(FREQ>>22); x; x--)
> asm volatile("":::"memory");
> Clobbering memory is likely to prevent gcc from optimizing the loop away.

But it will break with loop-unrolling (i.e. -O3). x times nothing
is nothing ;-) You *have* to use a nop-instruction.

And the cast is bogus - only silences the compiler without fixing
the problem.

Ciao, ET.
Received on 2010-06-15

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