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Re: Optimizations
- To: egcs at cygnus dot com
- Subject: Re: Optimizations
- From: Jeffrey A Law <law at cygnus dot com>
- Date: Sun, 14 Dec 1997 21:17:33 -0700
- cc: kthomas at gwdg dot de
- Reply-To: egcs at cygnus dot com
In message <19971215000809.60319@cerebro.laendle>you write:
> On Sun, Dec 14, 1997 at 02:34:36PM +0100, Philipp Thomas wrote:
> > Marc Lehmann wrote:
> > > -fschedule-insns is a *loss* on x86 cpu's!
> >
> > care to explain why it is a loss (and most probably also -fschedule-insns
> 2)
> > ?
>
> AFAIR -fschedule-insns (as opposed to -fschedule-insns2) is normally a loss
> sicne the first scheduling pass is done before register allocation, so the
> register pressure increases and local/global get's problems. (for fpu code
> it _could_ be beneficial, though).
To be more correct it may be a loss for machines with a limited number of
registers (such as the x86). On machines with a generous number of registers
-fschedule-insns is generally a win.
jeff