[Bug ipa/103819] [10/11/12 Regression] ICE in redirect_callee, at cgraph.c:1389 with __attribute__((flatten)) and -O2 since r11-7940-ge7fd3b783238d034

[dani at danielbertalan dot dev via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103819

--- Comment #3 from Daniel Bertalan <dani at danielbertalan dot dev> ---
Here's an even smaller test case (https://gcc.godbolt.org/z/ee9GceMx3):

===
template <typename T> struct Optional {
    ~Optional() {
        if (m_has_value)
            value();
    }
    T value();
    bool m_has_value{};
};
__attribute__((flatten)) int main(){
    Optional<Optional<int>> _temporary_result{};
    return 0;
}
===

during IPA pass: inline
<source>:12:1: internal compiler error: in redirect_callee, at cgraph.cc:1389
   12 | }
      | ^
0x215b739 internal_error(char const*, ...)
        ???:0
0x73b7e7 fancy_abort(char const*, int, char const*)
        ???:0
0xbe2bbe cgraph_edge::redirect_callee(cgraph_node*)
        ???:0
0xe6b781 ipa_merge_fn_summary_after_inlining(cgraph_edge*)
        ???:0
0xe85396 inline_call(cgraph_edge*, bool, vec<cgraph_edge*, va_heap, vl_ptr>*,
int*, bool, bool*)
        ???:0