[Bug ipa/96482] [10 Regression] Combination of -finline-small-functions and ipa-cp optimisations causes incorrect values being passed to a function since r279523

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96482

--- Comment #20 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Martin Liska
<marxin@gcc.gnu.org>:

https://gcc.gnu.org/g:66780083a0e79e5cb7c3acc8665aa47be4084a67

commit r10-8614-g66780083a0e79e5cb7c3acc8665aa47be4084a67
Author: Martin Liska <mliska@suse.cz>
Date:   Wed Aug 12 09:21:51 2020 +0200

    ipa: fix bit CPP when combined with IPA bit CP

    As mentioned in the PR, let's consider the following example:

    int
    __attribute__((noinline))
    foo(int arg)
    {
      if (arg == 3)
        return 1;
      if (arg == 4)
        return 123;

      __builtin_unreachable ();
    }

    during WPA we find all calls of the function
    (yes the call with value 5 is UBSAN):

      Node: foo/0:
        param [0]: 5 [loc_time: 4, loc_size: 2, prop_time: 0, prop_size: 0]
                   3 [loc_time: 3, loc_size: 3, prop_time: 0, prop_size: 0]
             ctxs: VARIABLE
             Bits: value = 0x5, mask = 0x6

    in LTRANS we have the following VRP info:

      # RANGE [3, 3] NONZERO 3

    when we AND masks in get_default_value we end up with 6 & 3 = 2 (0x010).
    That means the only second (least significant bit) is unknown and
    value (5 = 0x101) & ~mask gives us either 7 (0x111) or 5 (0x101).

    That's why if (arg_2(D) == 3) gets optimized to false.

    gcc/ChangeLog:

            PR ipa/96482
            * ipa-cp.c (ipcp_bits_lattice::meet_with_1): Drop value bits
            for bits that are unknown.
            (ipcp_bits_lattice::set_to_constant): Likewise.
            * tree-ssa-ccp.c (get_default_value): Add sanity check that
            IPA CP bit info has all bits set to zero in bits that
            are unknown.

    gcc/testsuite/ChangeLog:

            PR ipa/96482
            * gcc.dg/ipa/pr96482.c: New test.

    (cherry picked from commit d58f078ce2d53e5dab6b3d0d5f960504268e1894)