[Bug math/16315] Bad overflowing pow results for directed rounding

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https://sourceware.org/bugzilla/show_bug.cgi?id=16315

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4da6db51880289f0bf41b39e05cf9bb1c4769c47

commit 4da6db51880289f0bf41b39e05cf9bb1c4769c47
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Mon Jun 23 20:12:33 2014 +0000

    Fix pow overflow in non-default rounding modes (bug 16315).

    This patch fixes bug 16315, bad pow handling of overflow/underflow in
    non-default rounding modes.  Tests of pow are duly converted to
    ALL_RM_TEST to run all tests in all rounding modes.

    There are two main issues here.  First, various implementations
    compute a negative result by negating a positive result, but this
    yields inappropriate overflow / underflow values for directed
    rounding, so either overflow / underflow results need recomputing in
    the correct sign, or the relevant overflowing / underflowing operation
    needs to be made to have a result of the correct sign.  Second, the
    dbl-64 implementation sets FE_TONEAREST internally; in the overflow /
    underflow case, the result needs recomputing in the original rounding
    mode.

    Tested x86_64 and x86 and ulps updated accordingly.

        [BZ #16315]
        * sysdeps/i386/fpu/e_pow.S (__ieee754_pow): Ensure possibly
        overflowing or underflowing operations take place with sign of
        result.
        * sysdeps/i386/fpu/e_powf.S (__ieee754_powf): Likewise.
        * sysdeps/i386/fpu/e_powl.S (__ieee754_powl): Likewise.
        * sysdeps/ieee754/dbl-64/e_pow.c: Include <math.h>.
        (__ieee754_pow): Recompute overflowing and underflowing results in
        original rounding mode.
        * sysdeps/x86/fpu/powl_helper.c: Include <stdbool.h>.
        (__powl_helper): Allow negative argument X and scale negated value
        as needed.  Avoid passing value outside [-1, 1] to f2xm1.
        * sysdeps/x86_64/fpu/e_powl.S (__ieee754_powl): Ensure possibly
        overflowing or underflowing operations take place with sign of
        result.
        * sysdeps/x86_64/fpu/multiarch/e_pow.c [HAVE_FMA4_SUPPORT]:
        Include <math.h>.
        * math/auto-libm-test-in: Add more tests of pow.
        * math/auto-libm-test-out: Regenerated.
        * math/libm-test.inc (pow_test): Use ALL_RM_TEST.
        (pow_tonearest_test_data): Remove.
        (pow_test_tonearest): Likewise.
        (pow_towardzero_test_data): Likewise.
        (pow_test_towardzero): Likewise.
        (pow_downward_test_data): Likewise.
        (pow_test_downward): Likewise.
        (pow_upward_test_data): Likewise.
        (pow_test_upward): Likewise.
        (main): Don't call removed functions.
        * sysdeps/i386/fpu/libm-test-ulps: Update.
        * sysdeps/x86_64/fpu/libm-test-ulps: Likewise.

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                            |   34 +
 NEWS                                 |   22 +-
 math/auto-libm-test-in               |   65 +
 math/auto-libm-test-out              | 2670 ++++++++++++++++++++++++++++++++++
 math/libm-test.inc                   |   68 +-
 sysdeps/i386/fpu/e_pow.S             |   50 +-
 sysdeps/i386/fpu/e_powf.S            |   12 +-
 sysdeps/i386/fpu/e_powl.S            |   78 +-
 sysdeps/i386/fpu/libm-test-ulps      |    8 +-
 sysdeps/ieee754/dbl-64/e_pow.c       |   61 +-
 sysdeps/x86/fpu/powl_helper.c        |   32 +-
 sysdeps/x86_64/fpu/e_powl.S          |   71 +-
 sysdeps/x86_64/fpu/libm-test-ulps    |   14 +-
 sysdeps/x86_64/fpu/multiarch/e_pow.c |    1 +
 14 files changed, 2953 insertions(+), 233 deletions(-)

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