Date: Mon, 04 Dec 2000 16:11:59 -0500 From: "Brian F. Feldman" <green@FreeBSD.org> To: Peter Wemm <peter@netplex.com.au> Cc: John Baldwin <jhb@FreeBSD.org>, Jeroen Ruigrok van der Werven <asmodai@FreeBSD.org>, cvs-all@FreeBSD.org, cvs-committers@FreeBSD.org Subject: Re: cvs commit: src/usr.bin/tail forward.c read.c reverse.c tail Message-ID: <200012042112.eB4LBx736905@green.dyndns.org> In-Reply-To: Message from Peter Wemm <peter@netplex.com.au> of "Mon, 04 Dec 2000 11:55:32 PST." <200012041955.eB4JtWJ11058@mobile.wemm.org>
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Peter Wemm <peter@netplex.com.au> wrote:
> John Baldwin wrote:
> >
> > On 03-Dec-00 Jeroen Ruigrok van der Werven wrote:
> > > asmodai 2000/12/03 09:05:45 PST
> > >
> > > Modified files:
> > > usr.bin/tail forward.c read.c reverse.c tail.c
> > > Log:
> > > Remove register keyword usage with prejudice.
> > > Modern compilers are smarter when it comes to allocating register
> > > usage.
> >
> > They also ignore the register keyword, so this is a rather pointless change,
> > although it does add to repo bloat and in more active code could make diffs
> > harder to read. :-/
>
> It doesn't actually ignore it. Try this:
>
> register int foo;
> printf("%p\n", &foo);
>
> This does get in the way at times, which is why people remove it.
For example, converting macros to side-effect-safe (macros|inline functions).
#define M_PREPEND(m, plen, how) do { \
struct mbuf **_mmp = &(m); \
is my example for why it's useful not to try to force the compiler into
using registers. Besides, I only know of one case when a register keyword
does something: register reg_type variable __asm__("reg"). Even in that
case, it's useless because that declaration will be optimized by the
compiler (volatile doesn't help) and made useless in the process by taking
away the special treatment of it. So I can't see any use of register.
--
Brian Fundakowski Feldman \ FreeBSD: The Power to Serve! /
green@FreeBSD.org `------------------------------'
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