Fix missing exceptions from exp (bugs 13787, 13922, 14036)

[Andreas Jaeger]

On 05/05/2012 07:20 PM, Joseph S. Myers wrote:
> There are various bugs for missing overflow and underflow exceptions
> on exp-family functions, resulting from the wrappers checking for
> overflow and underflow before calling the functions such as
> __ieee754_exp, and in the overflow/underflow cases then calling
> __kernel_standard so setting errno but missing out on the exceptions.
>
> I propose this patch to fix these bugs by using the approach of some
> other wrappers, checking for overflow and underflow based on the
> results after calling __ieee754_exp.  This in turn requires changes to
> the x86/x86_64 code (on top of my previous patch
> <http://sourceware.org/ml/libc-alpha/2012-05/msg00184.html>  to use .S
> files for those) to avoid spurious overflows in internal calculations
> for very large (positive or negative) exponents.  The long double
> wrappers not changed already check for overflow/underflow after
> calling __ieee754_expl, so should not need any changes.
>
> Tested x86_64 and x86.  The underflow part of bug 14036 isn't fixed by
> this patch but hopefully Andreas's patch to use -frounding-math will,
> together with this patch, fix that problem; if not, further
> investigation will be needed.

Looks fine, thanks,

Andreas
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