On Fri, Jun 15, 2001 at 01:56:45PM +0200, Michel D?nzer wrote: > > > My $CFLAGS looks like this: -pipe -O2 -Wall -mcpu=750 -fstrict-aliasing > > It's not entirely clear from the gcc docs if code generated this way runs on > older CPUs than G3s though. Should I rather use -mtune=750? What would be > optimal for -mcpu for all CPUs we support? > > > I wonder if anyone running on something like 604 or 603 has had strange > problems like illegal instructions with packages I built?
gcc for IA32 uses -march=... to control what instructions it is allowed to use, and what arch to tune for. You can override the tuning target with -mcpu=.... Specifying -mcpu=... without -march still generates code that will run on a 386. I don't know how things are for PPC, but unless things are way different, -mcpu=... shouldn't change what instructions gcc restricts itself to. (i.e. -mcpu shouldn't make it run on any less machines than it would before. Things aren't quite as simple as IA32, because I don't remember if the default instruction set is actually the subset that will work on _all_ ppc machines.) -- #define X(x,y) x##y Peter Cordes ; e-mail: X([EMAIL PROTECTED] , ns.ca) "The gods confound the man who first found out how to distinguish the hours! Confound him, too, who in this place set up a sundial, to cut and hack my day so wretchedly into small pieces!" -- Plautus, 200 BCE