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From: ron@brl-sem.ARPA (Ron Natalie <ron>)
Newsgroups: net.lang.c
Subject: Re: More extensions to C
Message-ID: <263@brl-sem.ARPA>
Date: Sun, 1-Jun-86 02:50:28 EDT
Article-I.D.: brl-sem.263
Posted: Sun Jun  1 02:50:28 1986
Date-Received: Fri, 20-Jun-86 04:06:47 EDT
References: <1483@mmintl.UUCP> <856@bentley.UUCP>
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 21

In article <856@bentley.UUCP>, kwh@bentley.UUCP (KW Heuer) writes:
> 
> >(BTW, a really good optimizing compiler can optimize out the temporary.  I'm
> >not fully up on what optimizers are doing these days, but I doubt that there
> >are many compilers which do this.  Optimizing it out is easier if it is
> >declared locally ("{int temp = x; x = y; y = temp;}") instead of being
> >declared at the top of the routine.)
> 
> Unfortunately, I think the "clue" gets lost before the optimizing phase.
> 
Eh?  Unless you have a machine that has an exchange operator, the compiler
is going to have to allocate a temporary anyhow.  I can't see yow a compiler
could generate better code for  x,,y than what most compilers (even before
optimization do for {register temp =x; x=y; y=temp}.

-Ron

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