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Re: How long should -O1 compiles take?
- To: Brad Lucier <lucier at math dot purdue dot edu>
- Subject: Re: How long should -O1 compiles take?
- From: Jeffrey A Law <law at cygnus dot com>
- Date: Mon, 04 Oct 1999 14:38:15 -0600
- cc: gcc at gcc dot gnu dot org, hosking at cs dot purdue dot edu, feeley at iro dot umontreal dot ca
- Reply-To: law at cygnus dot com
In message <199910050218.VAA24343@polya.math.purdue.edu>you write:
> Sorry, I worded that very poorly. What I should have said is: Do the
> gcc developers want a global register allocator that takes 89 seconds
> in gcc -O1, whether or not it is significantly better than the old one
> that took 2.45 seconds?
We certainly want things that run faster. However, the global allocator
in gcc-2.95 and the current sources is *far* better than previous versions.
rth had some changes which sped things up, but those changes were causing
problems and he's (rightly) put them on the back burner to help work on other
more pressing issues.
> And the same question for other passes in
> the compiler. Is there a specific design trade-off in compilation
> speed/generated code speed for -O1 that decides things like this?
No specific design tradeoffs. -O2 simply turns on additional optimizations,
particularly those which can use lots of time or memory.
jeff