Re: Funny?

danwang@atomic.CS.Princeton.EDU (Daniel Wang)
16 Apr 1997 00:26:55 -0400

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From: danwang@atomic.CS.Princeton.EDU (Daniel Wang)
Newsgroups: comp.compilers
Date: 16 Apr 1997 00:26:55 -0400
Organization: Princeton University Department of Computer Science
References: 97-04-067
Keywords: optimize, performance

<jukkaj@ping.at> writes:


> I just created a Visual C++ program under Windows 95 which runs
> slower when it is optimised for speed. And which runs faster when
> it is a debug version without any optimisation and lot of extra
> debug code.


Just a guess, but sounds like the optimizer is unrolling some loop so that
the "optimized" code no longer fits in the instruction cache, so you're
paying a cache hit on every loop. The debug version is probably faster since
it fits in the cache.


--

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