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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/34027] [4.3 regression] -Os code size nearly doubled
Date: Fri, 09 Nov 2007 12:20:00 -0000 [thread overview]
Message-ID: <20071109122021.3397.qmail@sourceware.org> (raw)
In-Reply-To: <bug-34027-9876@http.gcc.gnu.org/bugzilla/>
------- Comment #3 from rguenther at suse dot de 2007-11-09 12:20 -------
Subject: Re: [4.3 regression] -Os code size
nearly doubled
On Fri, 9 Nov 2007, jakub at gcc dot gnu dot org wrote:
> ------- Comment #2 from jakub at gcc dot gnu dot org 2007-11-09 12:15 -------
> I think whether the modulus will be bigger or smaller is terribly hard to
> estimate. Really, if you file -Os regressions, you should at least compile the
> whole kernel and compare whether the resulting sizes, rather than cherry
> picking one example. E.g. on ppc64 computing modulus rather than doing the
> loop
> is definitely much shorter.
> IMHO if the kernel wants to avoid using modulus, it should just say so
> unsigned long long foobar(unsigned long long ns)
> {
> while(ns >= 1000000000L) {
> ns -= 1000000000L;
> asm ("" : "=r" (ns) : "0" (ns));
> }
> return ns;
> }
> will do that just fine.
Yes, just that at the moment we don't procude the modulus but use
a division, a multiplication and a subtraction.
Richard.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34027
next prev parent reply other threads:[~2007-11-09 12:20 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-08 11:39 [Bug c/34027] New: " bunk at stusta dot de
2007-11-08 21:45 ` [Bug tree-optimization/34027] " rguenth at gcc dot gnu dot org
2007-11-09 12:15 ` jakub at gcc dot gnu dot org
2007-11-09 12:20 ` rguenther at suse dot de [this message]
2007-11-09 12:30 ` jakub at gcc dot gnu dot org
2007-11-09 12:37 ` rguenther at suse dot de
2007-11-10 7:58 ` bunk at stusta dot de
2007-11-10 23:54 ` rguenth at gcc dot gnu dot org
2007-11-12 13:24 ` rguenth at gcc dot gnu dot org
2007-11-12 13:28 ` rguenth at gcc dot gnu dot org
2007-11-12 15:01 ` rguenth at gcc dot gnu dot org
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