[Bug math/16068] [i386/x86_64] x86 and x86_64 fesetenv exclude state they should include

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https://sourceware.org/bugzilla/show_bug.cgi?id=16068

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=2145f97cee01140d5369a8c67dc92eacfe8e4417

commit 2145f97cee01140d5369a8c67dc92eacfe8e4417
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Wed Oct 28 22:58:29 2015 +0000

    Handle more state in i386/x86_64 fesetenv (bug 16068).

    fenv_t should include architecture-specific floating-point modes and
    status flags.  i386 and x86_64 fesetenv limit which bits they use from
    the x87 status and control words, when using saved state, and limit
    which parts of the state they set to fixed values, when using
    FE_DFL_ENV / FE_NOMASK_ENV.  The following should be included but are
    excluded in at least some cases: status and masking for the "denormal
    operand" exception (which isn't part of FE_ALL_EXCEPT); precision
    control (explicitly mentioned in Annex F as something that counts as
    part of the floating-point environment); MXCSR FZ and DAZ bits (for
    FE_DFL_ENV and FE_NOMASK_ENV).  This patch arranges for this extra
    state to be handled by fesetenv (and thereby by feupdateenv, which
    calls fesetenv).

    (Note that glibc functions using floating point are not generally
    expected to work correctly with non-default values of this state,
    especially precision control, but it is still logically part of the
    floating-point environment and should be handled as such by fesetenv.
    Changes to the state relating to subnormals ought generally to work
    with libm functions when the arguments aren't subnormal and neither
    are the expected results; that's a consequence of functions avoiding
    spurious internal underflows.)

    A question arising from this is whether FE_NOMASK_ENV should or should
    not mask the "denormal operand" exception.  I decided it should mask
    that exception.  This is the status quo - previously that exception
    could only be unmasked by direct manipulation of control registers
    (possibly via <fpu_control.h>).  In addition, it means that use of
    FE_NOMASK_ENV leaves a floating-point environment the same as could be
    obtained by fesetenv (FE_DFL_ENV); feenableexcept (FE_ALL_EXCEPT);,
    rather than an environment in which an exception is unmasked that
    could only be masked again by using fesetenv with FE_DFL_ENV (or a
    previously saved environment) - this exception not being usable with
    other <fenv.h> functions because it's outside FE_ALL_EXCEPT.

    Tested for x86_64 and x86.

        [BZ #16068]
        * sysdeps/i386/fpu/fesetenv.c: Include <fpu_control.h>.
        (FE_ALL_EXCEPT_X86): New macro.
        (__fesetenv): Use FE_ALL_EXCEPT_X86 in most places instead of
        FE_ALL_EXCEPT.  Ensure precision control is included in
        floating-point state.  Ensure that FE_DFL_ENV and FE_NOMASK_ENV
        handle "denormal operand exception" and clear FZ and DAZ bits.
        * sysdeps/x86_64/fpu/fesetenv.c: Include <fpu_control.h>.
        (FE_ALL_EXCEPT_X86): New macro.
        (__fesetenv): Use FE_ALL_EXCEPT_X86 in most places instead of
        FE_ALL_EXCEPT.  Ensure precision control is included in
        floating-point state.  Ensure that FE_DFL_ENV and FE_NOMASK_ENV
        handle "denormal operand exception" and clear FZ and DAZ bits.
        * sysdeps/x86/fpu/test-fenv-sse-2.c: New file.
        * sysdeps/x86/fpu/test-fenv-x87.c: Likewise.
        * sysdeps/x86/fpu/Makefile [$(subdir) = math] (tests): Add
        test-fenv-x87 and test-fenv-sse-2.
        [$(subdir) = math] (CFLAGS-test-fenv-sse-2.c): New variable.

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

Summary of changes:
 ChangeLog                         |   19 ++++
 NEWS                              |   24 +++---
 sysdeps/i386/fpu/fesetenv.c       |   40 ++++++--
 sysdeps/x86/fpu/Makefile          |    3 +-
 sysdeps/x86/fpu/test-fenv-sse-2.c |  176 +++++++++++++++++++++++++++++++++++++
 sysdeps/x86/fpu/test-fenv-x87.c   |  169 +++++++++++++++++++++++++++++++++++
 sysdeps/x86_64/fpu/fesetenv.c     |   40 ++++++--
 7 files changed, 438 insertions(+), 33 deletions(-)
 create mode 100644 sysdeps/x86/fpu/test-fenv-sse-2.c
 create mode 100644 sysdeps/x86/fpu/test-fenv-x87.c

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