[Bug middle-end/114552] [13/14 Regression] wrong code at -O1 and above on x86_64-linux-gnu since r13-990

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114552

--- Comment #7 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:03039744f368a24a452e4ea8d946e9c2cedaf1aa

commit r14-9768-g03039744f368a24a452e4ea8d946e9c2cedaf1aa
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Wed Apr 3 09:59:45 2024 +0200

    expr: Fix up emit_push_insn [PR114552]

    r13-990 added optimizations in multiple spots to optimize during
    expansion storing of constant initializers into targets.
    In the load_register_parameters and expand_expr_real_1 cases,
    it checks it has a tree as the source and so knows we are reading
    that whole decl's value, so the code is fine as is, but in the
    emit_push_insn case it checks for a MEM from which something
    is pushed and checks for SYMBOL_REF as the MEM's address, but
    still assumes the whole object is copied, which as the following
    testcase shows might not always be the case.  In the testcase,
    k is 6 bytes, then 2 bytes of padding, then another 4 bytes,
    while the emit_push_insn wants to store just the 6 bytes.

    The following patch simply verifies it is the whole initializer
    that is being stored, I think that is best thing to do so late
    in GCC 14 cycle as well for backporting.

    For GCC 15, perhaps the code could stop requiring it must be at offset
zero,
    nor that the size is equal, but could use
    get_symbol_constant_value/fold_ctor_reference gimple-fold APIs to actually
    extract just part of the initializer if we e.g. push just some subset
    (of course, still verify that it is a subset).  For sizes which are power
    of two bytes and we have some integer modes, we could use as type for
    fold_ctor_reference corresponding integral types, otherwise dunno, punt
    or use some structure (e.g. try to find one in the initializer?), whatever.
    But even in the other spots it could perhaps handle loading of
    COMPONENT_REFs or MEM_REFs from the .rodata vars.

    2024-04-03  Jakub Jelinek  <jakub@redhat.com>

            PR middle-end/114552
            * expr.cc (emit_push_insn): Only use store_constructor for
            immediate_const_ctor_p if int_expr_size matches size.

            * gcc.c-torture/execute/pr114552.c: New test.