From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Terry Flannery" To: "Stan Shebs" , "Geoff Keating" Cc: Subject: Re: Faster compilation speed Date: Fri, 09 Aug 2002 16:14:00 -0000 Message-id: <004d01c23ffa$81e752f0$3400a8c0@sknet01> References: <3D54391C.9080307@apple.com> <3D544AAC.2040006@apple.com> X-SW-Source: 2002-08/msg00527.html IMHO, a new flag should be introduced, for example, -Of for maximum compile speed, and no surprises when debugging. -O0 should be minimal optimizations, and -O[s1-3] should remain as they are. I use the preprocessor to generate a preprocessed version of all the system header I use, into one header, and #include that in my program's header (with the flags to dump macros) , saving some time when building. If there was some support for pre-compiled headers, I'm sure that the compiler would be much faster. Terry ----- Original Message ----- From: "Stan Shebs" To: "Geoff Keating" Cc: Sent: Saturday, August 10, 2002 12:05 AM Subject: Re: Faster compilation speed > Geoff Keating wrote: > > >Stan Shebs writes: > > > >>Mike Stump wrote: > >> > >>>The first realization I came to is that the only existing control > >>>for such things is -O[123], and having thought about it, I think it > >>>would be best to retain and use those flags. For minimal user > >>>impact, I think it would be good to not perturb existing users of > >>>-O[0123] too much, or at leaast, not at first. If we wanted to > >>>change them, I think -O0 should be the `fast' version, -O1 should be > >>>what -O0 does now with some additions around the edges, and -O2 and > >>>-O3 also slide over (at least one). What do you think, slide them > >>>all over one or more, or just make -O0 do less, or...? Maybe we > >>>have a -O0.0 to mean compile very quickly? > >>> > >>I think it suffices to have -O0 mean "go as fast as possible". > >> > > > >Note that that's different to what it means now, which is "I want the > >debugger to not surprise me." > > > There's been a little bit of a drift over the years - -O0 used to be > "no opts at all", -O1 was "not too surprising for the debugger", and > -O2 was all-out. I remember some pressure from Cygnus customers to > make -O0 do more optimization, sometimes out of stupidity, but in the > legitimate cases because the -O0 code was too slow and/or large to > fit on the target embedded system, even for debugging. > > So what *should* we do with -O0 optimizations that measurably > slow down the compiler? > > Stan > > >