From: Juri Linkov <juri@jurta.org>
To: 5754@debbugs.gnu.org
Cc: Shigeru Fukaya <shigeru.fukaya@gmail.com>
Subject: bug#5754: Bytecomp Arithmetic test failed
Date: Tue, 30 Mar 2010 19:08:45 +0300 [thread overview]
Message-ID: <871vf2jayi.fsf@mail.jurta.org> (raw)
In-Reply-To: <87k4t027r0.fsf@mail.jurta.org> (Juri Linkov's message of "Thu, 25 Mar 2010 09:19:11 +0200")
I see that this was extensively discussed in bug#1334,
so I Cc:ed Shigeru Fukaya. Shigeru, are you interested in
looking at the test failure reported by bytecomp-testsuite.el?
>> I tried to run some tests in the `test' subdir,
>> and `bytecomp-testsuite-run' in `test/bytecomp-testsuite.el' fails
>> on one test: (let ((a (expt 2 -1074)) (b 0.125)) (* a 8 b))
>> returns 5e-324 when evaluated by interpreter,
>> but after byte-compilation returns 0.0
>>
>> In GNU Emacs 24.0.50 (x86_64-pc-linux-gnu) of 2010-03-23
>
> This bug is caused by optimization in byte-compilation
> that changes the order of function arguments.
>
> It byte-compiles
>
> (let ((a (expt 2 -1074)) (b 0.125)) (* a 8 b))
>
> to
>
> 0 constant expt
> 1 constant 2
> 2 constant -1074
> 3 call 2
> 4 constant 0.125
> 5 varbind b
> 6 varbind a
> 7 constant *
> 8 varref a
> 9 varref b
> 10 constant 8
> 11 call 3
> 12 unbind 2
> 13 return
>
> where the order of arguments 8-10 is changed from (* a 8 b) to (* a b 8)
>
> For this test the different order of arguments changes
> the returned value:
>
> (funcall '* 5e-324 8 0.125)
> => 5e-324
>
> (funcall '* 5e-324 0.125 8)
> => 0.0
--
Juri Linkov
http://www.jurta.org/emacs/
next prev parent reply other threads:[~2010-03-30 16:08 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 [this message]
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
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