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From: Toon Moene <toon@moene.indiv.nluug.nl> To: toon@gcc.gnu.org Cc: gcc-prs@gcc.gnu.org, Subject: Re: c/5914: Infinite loop when compiling with optimisation on of z_log.c of libf2c Date: Wed, 13 Mar 2002 14:06:00 -0000 [thread overview] Message-ID: <20020313220602.21886.qmail@sources.redhat.com> (raw) The following reply was made to PR c/5914; it has been noted by GNATS. From: Toon Moene <toon@moene.indiv.nluug.nl> To: Ulrich Jakobus <jakobus@emss.co.za> Cc: "gcc-bugs@gcc.gnu.org" <gcc-bugs@gcc.gnu.org>, "gcc-gnats@gcc.gnu.org" <gcc-gnats@gcc.gnu.org>, "gcc-prs@gcc.gnu.org" <gcc-prs@gcc.gnu.org>, "nobody@gcc.gnu.org" <nobody@gcc.gnu.org>, "toon@gcc.gnu.org" <toon@gcc.gnu.org> Subject: Re: c/5914: Infinite loop when compiling with optimisation on of z_log.c of libf2c Date: Wed, 13 Mar 2002 21:04:38 +0100 Ulrich Jakobus wrote: > I wrote: > >Ah, now I see - you really meant this a *C* bug report :-) > Yes, I meant this to be a *C* bug of the optimiser (and I > submitted it as a C bug). Obviously the created code with > -O2 or -O3 is not correct, resulting in an infinite loop. > Compiling exactly the same code with -O works, and also > using e.g. gcc-2.95.2 with -O2 or -O3 works fine. Oh, perhaps you think that this is a regression w.r.t. 2.95.2 - it isn't. The fact that 2.95.2 happened to compile this "correctly" is purely by chance. In general, if you code a floating point fixed-point-finder by comparing one estimate with the other for equality, you'll lose on such targets as the x86, because it keeps variables in registers with a different precision than the corresponding memory location. -ffloat-store is the flag to use to circumvent this problem. -- Toon Moene - mailto:toon@moene.indiv.nluug.nl - phoneto: +31 346 214290 Saturnushof 14, 3738 XG Maartensdijk, The Netherlands Maintainer, GNU Fortran 77: http://gcc.gnu.org/onlinedocs/g77_news.html Join GNU Fortran 95: http://g95.sourceforge.net/ (under construction)
next reply other threads:[~2002-03-13 22:06 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2002-03-13 14:06 Toon Moene [this message] -- strict thread matches above, loose matches on Subject: below -- 2002-03-16 7:56 toon 2002-03-12 21:06 Ulrich Jakobus 2002-03-12 13:06 Toon Moene 2002-03-11 21:16 Ulrich Jakobus 2002-03-11 13:59 toon 2002-03-11 13:16 Tim Prince 2002-03-11 7:56 jakobus
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