[Bug middle-end/106831] [13 Regression] mpfr-4.1.0 started failing 2 tests: tget_set_d64 and tget_set_d128

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106831

--- Comment #13 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Aldy Hernandez <aldyh@gcc.gnu.org>:

https://gcc.gnu.org/g:5dba8b2a91376d0518eb21c69a0700f099aa9cc4

commit r13-2714-g5dba8b2a91376d0518eb21c69a0700f099aa9cc4
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Sat Sep 17 08:50:22 2022 +0200

    [PR106831] Avoid propagating long doubles that may have multiple
representations.

    Long doubles are tricky when it comes to considering singletons
    because small numbers and +-INF can have multiple representations for
    the same number.  So we need to be very careful not to treat those as
    singletons, lest they be incorrectly propagated by VRP.  This is
    similar to the -0.0 and +0.0 duality.

    In long doubles +INF can be represented with +INF in the MSB and
    either -0.0 or +0.0 in the LSB.  Similarly for numbers that are exactly
    representable in DF.  For example, 1.0 can be represented as either
    (1.0, +0.0) or (1.0, -0.0).

    This patch avoids treating these numbers as singletons.

    Note that NANs in long double format have a LSB of don't care, but
    this is irrelevant for singleton_p, because NANs are never considered
    singletons.  Also, internally in the frange we store NANs as a pair of
    boolean flags indicating whether they are +NAN or -NAN, so we don't need
    any special treatment here for comparing range equality etc.  We never
    see anything but the boolean flags.

            PR middle-end/106831

    gcc/ChangeLog:

            * value-range.cc (frange::singleton_p): Avoid propagating long
            doubles that may have multiple representations.