From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marc Lehmann <pcg@goof.com>
To: egcs@cygnus.com
Subject: Re: min/max macros
Date: Fri, 12 Dec 1997 10:18:00 -0000
Message-id: <19971212170331.06147@cerebro.laendle>
References: <19971212025753.58271@cerebro.laendle> <199712120317.TAA08800@atrus.synopsys.com>
X-SW-Source: 1997-12/msg00753.html

> > so egcs isn't a decent compiler?
> > 
> > for example, the macro-max(2,3) will be evaluated at compile time,
> > while the function-max(2,3) won't...
> 
> The function max(2,3) will indeed be evaluated at compile time, if it is
> inlined.

sorry, I was just too fast here in replyÄing (and I left the [EGCS] in, soory again ;)

> > this get's even worse on things like:
> > 
> > int mult(int a, int b) { return a*b; };
> > 
> > mult(a,3) will result in an "imul 3" on x86... definitely
> > slower than a lea, for example.
> 
> Same for mult: if it is inlined, it will be evaluated at compile time if
> given constant arguments.

no, mult(a,3) results in:

        movl 4(%esp),%eax
        imull $3,%eax,%eax
        ret

which is highly suboptimal.. a mult(4,5), though, will be evaluated at compile
time. But macros *are* faster than inline functions, despite what the
documentation tells us.


  ---------------------------------------------------------------------

      for a pentium-optimizing gcc, look at http://www.gcc.ml.org/

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