[Bug tree-optimization/104497] [11/12 Regression] Invalid gimple produced for (A?vect:vect)[i]

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104497

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:3f10e0d50b5e3b3f64bc9a1a29177518d5f4468d

commit r12-7222-g3f10e0d50b5e3b3f64bc9a1a29177518d5f4468d
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Feb 11 11:08:57 2022 +0100

    middle-end/104497 - gimplification of vector indexing

    The following attempts to address gimplification of

       ... = VIEW_CONVERT_EXPR<int[4]>((i & 1) != 0 ? inv : src)[i];

    which is problematic since gimplifying the base object
    ? inv : src produces a register temporary but GIMPLE does not
    really support a register as a base for an ARRAY_REF (even
    though that's not strictly validated it seems as can be seen
    at -O0).  Interestingly the C++ frontend avoids this issue
    by emitting the following GENERIC instead:

       ... = (i & 1) != 0 ? VIEW_CONVERT_EXPR<int[4]>(inv)[i] :
VIEW_CONVERT_EXPR<int[4]>(src)[i];

    The proposed patch below fixes things up when using an rvalue
    as the base is OK by emitting a copy from a register base to a
    non-register one.  The ?: as lvalue extension seems to be gone
    for C, C++ again unwraps the COND_EXPR in that case.

    2022-02-11  Richard Biener  <rguenther@suse.de>

            PR middle-end/104497
            * gimplify.cc (gimplify_compound_lval): Make sure the
            base is a non-register if needed and possible.

            * c-c++-common/torture/pr104497.c: New testcase.