[Bug 295089] [libm] implementation of rsqrt, rsqrtf, and rsqrtl.

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=295089

--- Comment #2 from commit-hook@FreeBSD.org ---
A commit in branch main references this bug:

URL:
https://cgit.FreeBSD.org/src/commit/?id=3085fc9d97bd83785ba3ba43e0378d7d67987d1f

commit 3085fc9d97bd83785ba3ba43e0378d7d67987d1f
Author:     Steve Kargl <kargl@FreeBSD.org>
AuthorDate: 2026-05-08 14:06:08 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2026-05-10 16:36:33 +0000

    [libm] implementation of rsqrt, rsqrtf, and rsqrtl

    From the PR:
    The attached diff implements the inverse square root function, i.e,
    rsqrt(x) = 1 / sqrt(x).  Exhaustive testing of the float version
    suggests that it is correctly rounded in round-to-nearest for all
    test values in the range [0x1p-127,0x1p126].
    Exhaustive testing of rsqrt and rsqrtl cannot be done, but 1100M
    values of x for rsqrt and 400M values for rsqrtl were tested.  All
    tested values were correctly rounded.

    I do not have access to LD128 (i.e., IEEE 128-bit floating point)
    hardware, so the implementation of rsqrtl() is untested.

    The following is a summary of changes to source code.

    * lib/msun/Makefile:
      . Add s_rsqrt.c and s_rsqrtf.c to COMMON_SRCS.
      . For non-53-bit long double targets, add s_rsqrtl.c to COMMON_SRCS.
      . Add MLINKS for rsqrt.3, rsqrtf.3, and rsqrtl.3 to sqrt.3.

    * lib/msun/Symbol.map:
      . Add rsqrt, rsqrtf, and rsqrtl to the Symbol map for shared libm.so.

    * lib/msun/man/sqrt.3:
      . Update the sqrt.3 manual page to include information for rsqrt[fl].
      . Note, these function come from ISO C23 (and IEEE-754 2008).

    * lib/msun/src/math.h:
      . Add prototypes for new functions.

    * lib/msun/src/math_private.h:
      . Add _SPLIT, _FAST2SUM, _SLOW2SUM, _XADD, _MUL, and _XMUL
        macros to perform type-type arthimetic (i.e., float-float).

    * src/s_rsqrt.c:
      . New file with the implementation of 'double rsqrt(double)'.
      . For 53-bit long double targets, add a weak reference for rsqrtl.

    * src/s_rsqrtf.c:
      . New file with the implementation of 'float rsqrt(float)'.

    * src/s_rsqrtl.c
      . New file with the implementation of 'long double rsqrt(long double)'.
        Note, the LD80 version uses bit twiddling and LD128 version is a
        straight C language implementation.  The LD128 is untested due to
        lack of hardware.

    PR:     295089
    MFC after:      1 week

 lib/msun/Makefile             |   6 +-
 lib/msun/Symbol.map           |   3 +
 lib/msun/man/sqrt.3           |  53 ++++++++++-
 lib/msun/src/math.h           |   3 +
 lib/msun/src/math_private.h   |  83 +++++++++++++++++
 lib/msun/src/s_rsqrt.c (new)  | 153 +++++++++++++++++++++++++++++++
 lib/msun/src/s_rsqrtf.c (new) | 155 ++++++++++++++++++++++++++++++++
 lib/msun/src/s_rsqrtl.c (new) | 203 ++++++++++++++++++++++++++++++++++++++++++
 8 files changed, 654 insertions(+), 5 deletions(-)

-- 
You are receiving this mail because:
You are the assignee for the bug.