Mail Archives: djgpp/1997/03/01/12:55:54

To: djgpp AT delorie DOT com
Subject: Re: Loop unrolling: Don't bother
Message-ID: <>
References: <5f5knj$cho AT freenet-news DOT carleton DOT ca>
<5f8vsu$g84 AT flex DOT uunet DOT pipex DOT com>
From: chambersb AT juno DOT com (Benjamin D Chambers)
Date: Sat, 01 Mar 1997 12:48:37 EST

On 1 Mar 1997 10:20:14 GMT nikki AT gameboutique DOT co (nikki) writes:
>> Is it possible that with the -O3 option, the compiler sees that 
>these are
>> indeed constant iteration loops, and unrolls them itself?  Try it 
>with -O0
>> option, because this should turn off all optimisation.  -O3 is the 
>> level of optimisation available.
>i'm fairly sure o3 doesn't unroll loops, or at least it's never 
>unrolled any
>of mine ;) you can also use o4 no? at least i thought you could..
AFAIK, O3 is the highest (anything higher simply defaults to O3 {the
Linux kernel is compiled with O6, isn't it?}).
>From the Info pages on gcc:

	Optimize yet more.  '-O3' turns on all optimizations specified by
	'-O2' and also turns on the 'inline-functions' option.

That's all it says.


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