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[Bug math/18980] i386 libm functions return with excess range and precision


https://sourceware.org/bugzilla/show_bug.cgi?id=18980

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=6f0f237bf5a3c8d29a6342cbf8b4c17b10aa1d4c

commit 6f0f237bf5a3c8d29a6342cbf8b4c17b10aa1d4c
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Fri Sep 18 21:53:22 2015 +0000

    Avoid excess range in results from i386 exp, hypot, pow functions (bug
18980).

    i386 exp, hypot and pow functions can return overflowing and
    underflowing values with excess range and precision; ; Wilco
    Dijkstra's patches to make isfinite etc. expand inline cause this
    pre-existing issue to result in test failures.

    This patch fixes those functions to avoid excess range and precision
    in their return values.  Appropriate macros are added for the repeated
    code sequences; in future I'll add more such macros and refactor
    existing code forcing underflow (with or without also eliminating
    excess range and precision from the return value) to use such macros.

    Tested for x86.  If, after this patch, you still see x86 libm test
    failures with excess range or precision, please file bugs in Bugzilla.

        [BZ #18980]
        * sysdeps/i386/fpu/i386-math-asm.h (DEFINE_FLT_MIN): New macro.
        (DEFINE_DBL_MIN): Likewise.
        (FLT_NARROW_EVAL_UFLOW_NONNEG_NAN): Likewise.
        (DBL_NARROW_EVAL_UFLOW_NONNEG_NAN): Likewise.
        (FLT_NARROW_EVAL_UFLOW_NONNEG): Likewise.
        (DBL_NARROW_EVAL_UFLOW_NONNEG): Likewise.
        * sysdeps/i386/fpu/e_exp.S: Include <i386-math-asm.h>.
        (dbl_min): Replace with use of DEFINE_DBL_MIN.
        (__ieee754_exp): Use DBL_NARROW_EVAL_UFLOW_NONNEG_NAN.
        (__exp_finite): Use DBL_NARROW_EVAL_UFLOW_NONNEG.
        * sysdeps/i386/fpu/e_exp10.S: Include <i386-math-asm.h>.
        (dbl_min): Replace with use of DEFINE_DBL_MIN.
        (__ieee754_exp10): Use DBL_NARROW_EVAL_UFLOW_NONNEG_NAN.
        * sysdeps/i386/fpu/e_exp10f.S: Include <i386-math-asm.h>.
        (flt_min): Replace with use of DEFINE_FLT_MIN.
        (__ieee754_exp10f): Use FLT_NARROW_EVAL_UFLOW_NONNEG_NAN.
        * sysdeps/i386/fpu/e_exp2.S: Include <i386-math-asm.h>.
        (dbl_min): Replace with use of DEFINE_DBL_MIN.
        (__ieee754_exp2): Use DBL_NARROW_EVAL_UFLOW_NONNEG_NAN.
        * sysdeps/i386/fpu/e_exp2f.S: Include <i386-math-asm.h>.
        (flt_min): Replace with use of DEFINE_FLT_MIN.
        (__ieee754_exp2f): Use FLT_NARROW_EVAL_UFLOW_NONNEG_NAN.
        * sysdeps/i386/fpu/e_expf.S: Include <i386-math-asm.h>.
        (flt_min): Replace with use of DEFINE_FLT_MIN.
        (__ieee754_expf): Use FLT_NARROW_EVAL_UFLOW_NONNEG_NAN.
        (__expf_finite): Use FLT_NARROW_EVAL_UFLOW_NONNEG.
        * sysdeps/i386/fpu/e_hypot.S: Include <i386-math-asm.h>.
        (__ieee754_hypot): Use DBL_NARROW_EVAL.
        * sysdeps/i386/fpu/e_hypotf.S: Include <i386-math-asm.h>.
        (__ieee754_hypotf): Use FLT_NARROW_EVAL.
        * sysdeps/i386/fpu/e_pow.S: Include <i386-math-asm.h>.
        (__ieee754_pow): Use DBL_NARROW_EVAL.
        * sysdeps/i386/fpu/e_powf.S: Include <i386-math-asm.h>.
        (__ieee754_powf): Use FLT_NARROW_EVAL.
        * sysdeps/i386/i686/fpu/multiarch/e_expf-sse2.S
        (__ieee754_expf_sse2): Convert double-precision result to single
        precision.
        * sysdeps/i386/fpu/libm-test-ulps: Update.

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

Summary of changes:
 ChangeLog                                     |   42 +++++
 NEWS                                          |    2 +-
 sysdeps/i386/fpu/e_exp.S                      |   44 +----
 sysdeps/i386/fpu/e_exp10.S                    |   26 +---
 sysdeps/i386/fpu/e_exp10f.S                   |   26 +---
 sysdeps/i386/fpu/e_exp2.S                     |   26 +---
 sysdeps/i386/fpu/e_exp2f.S                    |   26 +---
 sysdeps/i386/fpu/e_expf.S                     |   44 +----
 sysdeps/i386/fpu/e_hypot.S                    |    2 +
 sysdeps/i386/fpu/e_hypotf.S                   |    2 +
 sysdeps/i386/fpu/e_pow.S                      |    3 +
 sysdeps/i386/fpu/e_powf.S                     |    3 +
 sysdeps/i386/fpu/i386-math-asm.h              |   87 +++++++++
 sysdeps/i386/fpu/libm-test-ulps               |  233 +++++++++++++------------
 sysdeps/i386/i686/fpu/multiarch/e_expf-sse2.S |    9 +-
 15 files changed, 292 insertions(+), 283 deletions(-)

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