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From: Andrew Thomas Pinski <pinskia@gmail.com> To: "gcc-bugzilla@gcc.gnu.org" <gcc-bugzilla@gcc.gnu.org> Cc: "gcc-bugs@gcc.gnu.org" <gcc-bugs@gcc.gnu.org> Subject: Re: [Bug c/39403] Excessive optimization issue Date: Mon, 09 Mar 2009 15:57:00 -0000 [thread overview] Message-ID: <4D7EC7E4-2908-469D-ABFE-9398E8EB344A@gmail.com> (raw) In-Reply-To: <20090309153629.15991.qmail@sourceware.org> Sent from my iPhone On Mar 9, 2009, at 8:36 AM, "rguenth at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org > wrote: > > > ------- Comment #1 from rguenth at gcc dot gnu dot org 2009-03-09 > 15:36 ------- > You need to specify that the registers are clobbered by the asm. > The only > way to do that is to use output constraints ("+D", "+c", etc.) on > proper > temporaries. > > int lent = len; > char *dstt = dst; > char *srct = src; > __asm__ __volatile__( > "cld\n\t" > "rep movsb" > : "+c" (lent), "+D"(dstt), "+S"(src) > ); > Otherwise GCC thinks the registers still hold the original value. Oh and mark this inline-ask as clobbering memory. > > > > -- > > rguenth at gcc dot gnu dot org changed: > > What |Removed |Added > --- > --- > ---------------------------------------------------------------------- > Status|UNCONFIRMED |RESOLVED > Resolution| |INVALID > > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39403 >
next prev parent reply other threads:[~2009-03-09 15:57 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2009-03-09 4:06 [Bug c/39403] New: " casmyu at gmail dot com 2009-03-09 15:36 ` [Bug c/39403] " rguenth at gcc dot gnu dot org 2009-03-09 15:57 ` Andrew Thomas Pinski [this message] 2009-03-09 15:57 ` pinskia at gmail dot com 2009-03-10 1:23 ` casmyu at gmail dot com 2009-04-16 20:32 ` [Bug target/39403] " pinskia at gcc dot gnu dot org
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