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Re: egcs 1.0 *faster* than Sun's C compiler!!!!
Marcus Thiessel <thiessel@itwm.uni-kl.de> writes:
>
> >>>>> "Harvey" == Harvey J Stein <hjstein@bfr.co.il> writes:
>
> Harvey> Is it typical that gcc optimizes *better* than Sun's C
> Harvey> compiler?
>
> Well, SUNPro should be faster since you've pay for it.
I didn't notice any smiley there. If that's your belief, why are you
even reading the egcs mailing list? Although in my lifetime I've
often noticed a loose correlation between price and value, I've also
noticed that it's only a correlation - not a physical law.
> A major point
> to argue about are the options to use. For example I don't what
> -ffast-math does but what about enabling a simliar feature when
> running SUNPro!? And why limit the instruction set to -xarch=v8plusa!?
Then maybe you'd like to look at the man pages in question. I'm not
"limiting the instruction set". I'm telling the compiler to use all
features available on the v8plusa, and not to try to produce a binary
that'll run a larger family of CPUs. Since the machine in question is
a v8plusa, this produces better code. RTFM. In any case, these are
the options that *Sun* told me to use. Good enough for you?
> My choice when running those tests is to iterate on set of options for
> a certain compiler (and machine) in order to get the fastest run. This
> is rather time consuming and the results merly depend on the fact how
> much you know aboutn the compiler.
Time consuming isn't the word for it. With 20 switches that can
be set independently, you'd be talking about 1,048,576 tests. At 40
seconds a run (and 10 minutes to build the application), that'd take
about 13 years, at which point faster hardware and better compilers
would be available. Hopeless is more the word for it.
So yes, we come to a point where we agree. The more you know about
your compiler, the better the chances of you using it effectively to
produce fast code.
--
Harvey J. Stein
Berger Financial Research
hjstein@bfr.co.il