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bug#5754: Bytecomp Arithmetic test failed
From: |
Andreas Schwab |
Subject: |
bug#5754: Bytecomp Arithmetic test failed |
Date: |
Sun, 04 Apr 2010 10:05:03 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.1.95 (gnu/linux) |
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
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