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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/112480] optional<T>::reset emits inefficient code
 when T is trivially-destructible
Date: Mon, 13 Nov 2023 10:11:16 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: libstdc++
X-Bugzilla-Version: 13.2.0
X-Bugzilla-Keywords: missed-optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112480

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I think I prefer:

--- a/libstdc++-v3/include/std/optional
+++ b/libstdc++-v3/include/std/optional
@@ -311,6 +311,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       {
        if (this->_M_engaged)
          _M_destroy();
+
+       // The following seems redundant but improves codegen, see PR 11248=
0.
+       if constexpr (is_trivially_destructible_v<_Tp>)
+         this->_M_engaged =3D false;
       }
     };=