From: Andreas Schwab <schwab@linux-m68k.org>
To: Chong Yidong <cyd@stupidchicken.com>
Cc: 5754@debbugs.gnu.org
Subject: bug#5754: Bytecomp Arithmetic test failed
Date: Sun, 04 Apr 2010 10:05:03 +0200 [thread overview]
Message-ID: <m2vdc7iqxc.fsf@whitebox.home> (raw)
In-Reply-To: <87iq88ma6c.fsf@stupidchicken.com> (Chong Yidong's message of "Sat, 03 Apr 2010 18:40:59 -0400")
Chong Yidong <cyd@stupidchicken.com> writes:
> The key is that if I compile Emacs with CFLAGS="-g", then
>
> (funcall
> (byte-compile
> (list 'lambda nil
> (quote (let ((a (expt 2 -1074)) (b 0.125)) (* a 8 b))))))
>
> returns 0.0. If I compile Emacs with CFLAGS="-g -O2", then it returns
> 5e-324.
>
> It looks like this may be a compiler bug.
It's most likely the effect of excess precision, due to floating point
values being held in registers instead of reloaded from memory. Try
-ffloat-store.
Andreas.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
prev parent reply other threads:[~2010-04-04 8:05 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-23 7:47 bug#5754: Bytecomp Arithmetic test failed Juri Linkov
2010-03-23 8:38 ` Lennart Borgman
2010-03-23 9:03 ` Juri Linkov
2010-03-23 13:31 ` Lennart Borgman
2010-03-24 22:15 ` Chong Yidong
2010-03-24 22:52 ` Lennart Borgman
2010-03-25 1:15 ` Stefan Monnier
2010-03-25 1:19 ` Lennart Borgman
2010-03-25 7:19 ` Juri Linkov
2010-03-30 16:08 ` Juri Linkov
2010-04-03 22:18 ` Juri Linkov
2010-04-03 22:40 ` Chong Yidong
2010-04-03 22:54 ` Juri Linkov
2010-04-03 23:31 ` Chong Yidong
2010-04-04 6:25 ` Eli Zaretskii
2010-04-04 8:05 ` Andreas Schwab [this message]
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