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From: Eric Backus <eric_backus AT agilent DOT com>
Subject:  Re: gcc -ffast-math defect with tan(x)
Date: Tue, 17 Nov 2009 13:36:36 +0000 (UTC)
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Dave Korn <dave.korn.cygwin <at> googlemail.com> writes:

>   Thanks for the STC.  The difference between -ffast-math and -fno-fast-math
> is that the fast version calls the _f_tan newlib fast math function rather
> than tan.  I think this is likely to be a calling-convention issue but I'm
> still debugging it.
> 
>     cheers,
>       DaveK

One experiment that I did, which confused me more than anything else, is 
replace the calls to tan() with calls to log() (and change all the 0.0 values 
to something OK for log() like 1.0).  The generated assembly code appears to 
be identical except that _f_tan is replaced by _f_log, but the program works 
correctly.  That would mean that the generated assembly code is correct, and 
the defect is in _f_tan?

-- 
Eric


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