https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93246
--- Comment #4 from Martin Liška <marxin at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #3)
> So FRE optimizes
>
> wo.value = &buf;
> _48 = __MEM <struct Optional *> ((struct Optional * *)&wo);
> _20 = __MEM <const bool> ((bool *)_48);
> if (_20 != _Literal (bool) 0)
> goto __BB4;
> else
> goto __BB3;
>
> __BB(3):
> _48->inner.present = _Literal (bool) 1;
> goto __BB4;
>
> __BB(4):
> _49 = __MEM <struct Optional *> ((struct Optional * *)&wo);
> _52 = __MEM <const bool> ((bool *)_49);
>
> in a way disregarding the store via _48->inner.present. Adjusted testcase
> that doesn't need -fsanitize=address. I wonder if that results in the
> same bisection for the "fix"?
>
> #include <iostream>
>
> template <typename = void> struct Optional {
> auto is_present() const { return inner.present; }
>
> auto set_present() {
> if (not is_present())
> inner.present = true;
> }
>
> struct InnerType {
> bool present = false;
> char padding[1] = {0};
> };
>
> using inner_t = InnerType;
> // InnerType inner = {}; // this works as expected!
> inner_t inner = {}; // this doesn't!
> };
>
> template <typename WrappedType> struct Wrapper {
> auto operator-> () { return value; }
>
> WrappedType *value;
> };
>
> void __attribute__((noipa)) foo(Optional<>& x) {}
>
> int main() {
> Optional<> buf{};
> foo(buf);
> Wrapper<Optional<>> wo = {&buf};
>
> wo->set_present();
>
> auto x = wo->is_present();
> auto y = wo->is_present();
> std::cout << "x=" << x << ", y=" << y;
> auto z = wo->is_present();
> std::cout << ", z=" << z << "\n";
> }
This test-case started to be fixed since g:ff6686d2e5f797d6
