[Bug tree-optimization/106904] [12 Regression] Incorrect -Wstringop-overflow with partial memcpy() into a nested structure

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106904

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:97d599e09b0fd389a7cbac8867e56977ec97900f

commit r12-9254-g97d599e09b0fd389a7cbac8867e56977ec97900f
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Dec 7 14:42:24 2022 +0100

    tree-optimization/106904 - bogus -Wstringopt-overflow with vectors

    The following avoids CSE of &ps->wp to &ps->wp.hwnd confusing
    -Wstringopt-overflow by making sure to produce addresses to the
    biggest container from vectorization.  For this I introduce
    strip_zero_offset_components which turns &ps->wp.hwnd into
    &(*ps) and use that to base the vector data references on.
    That will also work for addresses with variable components,
    alternatively emitting pointer arithmetic via calling
    get_inner_reference and gimplifying that would be possible
    but likely more intrusive.

    This is by no means a complete fix for all of those issues
    (avoiding ADDR_EXPRs in favor of pointer arithmetic might be).
    Other passes will have similar issues.

    In theory that might now cause false negatives.

            PR tree-optimization/106904
            * tree.h (strip_zero_offset_components): Declare.
            * tree.cc (strip_zero_offset_components): Define.
            * tree-vect-data-refs.cc (vect_create_addr_base_for_vector_ref):
            Strip zero offset components before building the address.

            * gcc.dg/Wstringop-overflow-pr106904.c: New testcase.

    (cherry picked from commit f8d136e50e6f82cba793483d910a2b2643108508)