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Re: Arithmetic overflow checking

Cross-posted to 2 groups.

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Am Thu, 8 Sep 2011 19:15:13 +0000 (UTC)
schrieb Willem <willem@toad.stack.nl>:

> So if an overflow condition typically occurs less than 1 in 10000
> times, the interrupt solution is better.

Theoretically yes, practically no!

It depends on the architecture. On ARM it doesn't matter at all, since
ALL instructions are conditional.

On x86 architecture due to pipelining and OOE the differences are not
measureable as well (the overflow case code executes in parallel and
may have been finished, before the code, creating the overflow executed
at all). Also the overflow condition will probably not do any
arithmetic, in contrast to the arithmetic that does overflow. So these
are separate functional units at work, so pipelining will execute them
in parallel.

Really, there no cost to speak of in doing overflow checks.


Wolfgang

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Re: Arithmetic overflow checking Wolfgang Draxinger <wdraxinger@darkstargames.de> - 2011-09-08 21:02 +0200
  Re: Arithmetic overflow checking Wolfgang Draxinger <wdraxinger@darkstargames.de> - 2011-09-08 21:12 +0200
    Re: Arithmetic overflow checking Willem <willem@toad.stack.nl> - 2011-09-08 19:15 +0000
      Re: Arithmetic overflow checking Wolfgang Draxinger <wdraxinger@darkstargames.de> - 2011-09-08 22:24 +0200

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