Test cpow in all rounding modes

[Andreas Jaeger]

On 06/11/2014 01:01 AM, Joseph S. Myers wrote:
> This patch enables testing of cpow in all rounding modes using
> ALL_RM_TEST.  There were two reasons this was previously deferred:
> 
> * MPC has complicated rounding-mode-dependent rules for the signs of
>   exact zero real or imaginary parts in the result of mpc_pow.  Annex
>   G does not impose any such requirements and I don't think glibc
>   should try to implement any particular logic here.  This patch adds
>   support for gen-auto-libm-tests passing the IGNORE_ZERO_INF_SIGN
>   flag to libm-test.inc.
> 
> * Error accumulations in some tests in non-default rounding modes
>   exceed the maximum error permitted in libm-test.inc.  This patch
>   marks the problem tests with xfail-rounding.  (It might be possible
>   to reduce the accumulations a bit by using round-to-nearest when
>   cpow calls clog, but I don't think there's much point; the
>   implementation approach for cpow is fundamentally deficient, as
>   discussed in the existing bug for cpow inaccuracy which can
>   reasonably be considered to cover these less-inaccurate cases as
>   well.  It's possible that the test "cpow 2 0 10 0" will also need
>   xfail-rounding on some platforms.)
> 
> Tested x86_64 and x86 and ulps updated accordingly.

Looks fine, thanks,

Andreas
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