[Bug tree-optimization/127121] [C++][Optimization] Unnecessary zero-initialization of a parameter from a same-type prvalue with a user-provided default constructor

[danny321974345 at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127121

--- Comment #2 from 沈育霖 <danny321974345 at gmail dot com> ---
I think the change in C++26 is due to the newly introduced erroneous value.
The equivalent C++26 code would therefore be:

struct S {
    S() {}
    int a[5];
};

void foo(int*);

int callee([[indeterminate]] S s) {
    foo(s.a);
    return s.a[0];
}

int caller() {
    return callee(S{});
}

int local() {
    [[indeterminate]] S s{};
    foo(s.a);
    return s.a[0];
}

However, the two cases are still treated differently:
callee(S{}) emits zero-initialization of s.a
local() does not