[Bug analyzer/107882] [13 Regression] ICE in get_last_bit_offset, at analyzer/store.h:255 since 13-2582-g0ea5e3f4542832b8

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107882

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by David Malcolm <dmalcolm@gcc.gnu.org>:

https://gcc.gnu.org/g:dfe2ef7f2b6cac7017f32a0a04f74e1b6d9f1311

commit r13-4529-gdfe2ef7f2b6cac7017f32a0a04f74e1b6d9f1311
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Tue Dec 6 18:24:16 2022 -0500

    analyzer: don't create bindings or binding keys for empty regions
[PR107882]

    PR analyzer/107882 reports an ICE, due to trying to get a compound svalue
    for this binding:

      cluster for: a:
        key:   {bytes 0-3}
        value:  {UNKNOWN()}
        key:   {empty}
        value:  {UNKNOWN()}
        key:   {bytes 4-7}
        value:  {UNKNOWN()}

    where there's an binding to the unknown value of zero bits in size
    "somewhere" within "a" (perhaps between bits 3 and 4?)

    This makes no sense, so this patch adds an assertion that we never
    attempt to create a binding key for an empty region, and adds early
    rejection of attempts to get or set the values of such regions, fixing
    the ICE.

    gcc/analyzer/ChangeLog:
            PR analyzer/107882
            * region-model.cc (region_model::get_store_value): Return an
            unknown value for empty regions.
            (region_model::set_value): Bail on empty regions.
            * region.cc (region::empty_p): New.
            * region.h (region::empty_p): New decl.
            * state-purge.cc (same_binding_p): Bail if either region is empty.
            * store.cc (binding_key::make): Assert that a concrete binding's
            bit_size must be > 0.
            (binding_cluster::mark_region_as_unknown): Bail on empty regions.
            (binding_cluster::get_binding): Likewise.
            (binding_cluster::remove_overlapping_bindings): Likewise.
            (binding_cluster::on_unknown_fncall): Don't conjure values for
            empty regions.
            (store::fill_region): Bail on empty regions.
            * store.h (class concrete_binding): Update comment to reflect that
            the range of bits must be non-empty.
            (concrete_binding::concrete_binding): Assert that bit range is
            non-empty.

    gcc/testsuite/ChangeLog:
            PR analyzer/107882
            * gcc.dg/analyzer/memcpy-pr107882.c: New test.

    Signed-off-by: David Malcolm <dmalcolm@redhat.com>