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Re: Faster compilation speed
- From: Alan Lehotsky <apl at alum dot mit dot edu>
- To: David Edelsohn <dje at watson dot ibm dot com>
- Cc: Stan Shebs <shebs at apple dot com>, Mike Stump <mrs at apple dot com>,gcc at gcc dot gnu dot org
- Date: Fri, 9 Aug 2002 19:17:20 -0400
- Subject: Re: Faster compilation speed
- References: <200208092203.SAA24908@makai.watson.ibm.com>
At 6:03 PM -0400 8/9/02, David Edelsohn wrote:
>>>>> Stan Shebs writes:
This is DEFINITELY TRUE!
Stan> I think it suffices to have -O0 mean "go as fast as possible".
From time to
Stan> time, I've noticed that there's been a temptation to try to sneak in a
Stan> optimization even at -O0, presumably with the assumption that the time
Stan> penalty was negligible. (There are users who complain that -O0 should
Stan> do some amount of optimization, but IMHO we should ignore them.)
Saying "do not run any optimization at -O0" shows a tremendous
lack of understanding or investigation. One wants minimal optimization
even at -O0 to decrease the size of the IL representation of the function
being compiled. The little bit of computation to perform trivial
optimization more than makes up for itself with the decreased size of the
IL that needs to be processed to generate the output.
For example, the Bliss11 compiler ACTUALLY ran faster with
optimization turned on because assembling the unoptimized code
actually took longer than the time running FULL optimization required
for anything but the most trivial programs.
One needs to be careful about which optimizations are run, but
with the right choices it definitely is a net win.
Carbon Design Systems, Inc.