Re: C++: EGCS perf. vs GCC

[Jeffrey A Law <law at hurl dot cygnus dot com>]

  In message <Pine.GSO.3.96.981207163606.5165A-100000@caleyipa.spider.com>you w
  > Hmm, I have not used on the Intel architecture other compilers than gcc,
  > but I trust your judgement;
Good :-)  Both the ppro/pII and the old pentium scheduling need major changes;
as does the entire machine description.  It's going to be a long slow process.

  > processor was running at 248 Mhz), the part which I don't understand is
  > why -mcpu=pentiumpro is worse than -mcpu=i386 on a PII,
Could be anything.  There's no way to know without analyzing code.


  > and why gcc2.8.1 generates better code for i386 than egcs1.1.
Similarly.  It's a suprise, but it does happen from time to time.

  > I understand there is a Pentium compiler around (pcc or something); will
  > it do any difference? (or this is the stuff on which the Pentium support
  > in gcc/egcs is based?)
We are slowly, but surely moving the major features from pgcc into egcs.  Will
pgcc help your code?  Maybe, maybe not.


  > And finally, is Pentium II = Pentium Pro+MMX+better L2 cache? this why I
  > hoped -mcpu=pentiumpro will unleash the demons living in my machine :-)
My understanding is that from a scheduling standpoint PII == PPro.  So what
you did makes sense.  The problem is the x86 port is just not designed to
work with an instruction scheduler.  Thus performance when scheduling varies
wildly.

jeff