Date: Mon, 9 Feb 1998 20:41:46 -0800 (PST)
Message-Id: <199802100441.UAA02942@adit.ap.net>
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To: DJ Delorie <dj AT delorie DOT com>, eliz AT is DOT elta DOT co DOT il
From: Nate Eldredge <eldredge AT ap DOT net>
Subject: Re: src/gcc.opt in alpha 980101
Cc: djgpp-workers AT delorie DOT com
Precedence: bulk

At 08:41  2/8/1998 -0500, DJ Delorie wrote:
>
>My best recollection is that the Linux FAQ recommended these options
>for best overall library performance there.  They were unrelated to
>the gcc optimization bug.
>
>> Why do the switches used to compile the library still include 
>> -fno-strength-reduce?  Doesn't this belong to pre-2.7.2.1 gcc and is 
>> solved in later versions?
>> 
>> Also, is there any particular reason that -O3 was replaced by -O2?  
>> AFAIK, in short functions this *does* generate faster code, no?
FYI, it's in the GCC-HOWTO (at least, was last I checked and I doubt it's
gone away). Look on:

ftp://sunsite.unc.edu/pub/linux/docs/HOWTO/GCC-HOWTO

and see section 4.22. Basically, the theory is that strength reduction tends
to replace multiplication with shifts and adds, costing more registers which
the x86 can ill afford.

They do give the caveat, however, that one should try different flags and
see. Has anyone done this with the libc, or do they plan to?

Nate Eldredge
eldredge AT ap DOT net