[Bug tree-optimization/108068] [10/11 Regression] decimal floating point signed zero is not honored

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108068

--- Comment #15 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:d8f95474581843c605bb97ba83d482d642da3a1b

commit r11-10695-gd8f95474581843c605bb97ba83d482d642da3a1b
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Dec 23 16:12:21 2022 +0100

    tree-ssa-dom: can_infer_simple_equiv fixes [PR108068]

    As reported in the PR, tree-ssa-dom.cc uses real_zerop call to find
    if a floating point constant is zero and it shouldn't try to infer
    equivalences from comparison against it if signed zeros are honored.
    This doesn't work at all for decimal types, because real_zerop always
    returns false for them (one can have different representations of decimal
    zero beyond -0/+0), and it doesn't work for vector compares either,
    as real_zerop checks if all elements are zero, while we need to avoid
    infering equivalences from comparison against vector constants which have
    at least one zero element in it (if signed zeros are honored).
    Furthermore, as mentioned by Joseph, for decimal types many other values
    aren't singleton.

    So, this patch stops infering anything if element mode is decimal, and
    otherwise uses instead of real_zerop a new function, real_maybe_zerop,
    which will work even for decimal types and for complex or vector will
    return true if any element is or might be zero (so it returns true
    for anything but constants for now).

    2022-12-23  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/108068
            * tree.h (real_maybe_zerop): Declare.
            * tree.c (real_maybe_zerop): Define.
            * tree-ssa-dom.c (record_edge_info): Use it instead of
            real_zerop or TREE_CODE (op1) == SSA_NAME || real_zerop.  Always
set
            can_infer_simple_equiv to false for decimal floating point types.

            * gcc.dg/dfp/pr108068.c: New test.

    (cherry picked from commit fd1b0aefda5b65f3f841ca6e61ccea6a72daa060)