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| author | Jonathan Wakely <jwakely@redhat.com> | 2018-09-25 15:59:16 +0100 |
|---|---|---|
| committer | Jonathan Wakely <redi@gcc.gnu.org> | 2018-09-25 15:59:16 +0100 |
| commit | 16d30bbd4dae88ceb08bf8b965c8fd61b25b558c (patch) | |
| tree | 8e0042be0f57004e04a37b31814ddd8dedeea26d | |
| parent | 4fb792e189c183aa499e834d9cdc4b3ee3bd064a (diff) | |
| download | gcc-16d30bbd4dae88ceb08bf8b965c8fd61b25b558c.zip gcc-16d30bbd4dae88ceb08bf8b965c8fd61b25b558c.tar.gz gcc-16d30bbd4dae88ceb08bf8b965c8fd61b25b558c.tar.bz2 | |
PR libstdc++/87431 optimise valueless_by_exception()
If a std::variant can never get into valueless state then we don't need
to do a runtime check for a valid alternative.
PR libstdc++/87431
* include/std/variant (_Variant_storage<true, _Types...>::_M_valid):
Avoid runtime test when all alternatives are scalars and so cannot
throw during initialization.
From-SVN: r264574
| -rw-r--r-- | libstdc++-v3/ChangeLog | 7 | ||||
| -rw-r--r-- | libstdc++-v3/include/std/variant | 2 |
2 files changed, 9 insertions, 0 deletions
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog index ff53017..67b3eb4 100644 --- a/libstdc++-v3/ChangeLog +++ b/libstdc++-v3/ChangeLog @@ -1,3 +1,10 @@ +2018-09-25 Jonathan Wakely <jwakely@redhat.com> + + PR libstdc++/87431 + * include/std/variant (_Variant_storage<true, _Types...>::_M_valid): + Avoid runtime test when all alternatives are scalars and so cannot + throw during initialization. + 2018-09-25 Gerald Pfeifer <gerald@pfeifer.com> * doc/xml/manual/codecvt.xml: Move link to "UTF-8 and Unicode FAQ" diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant index 5a77e9e..9289eef 100644 --- a/libstdc++-v3/include/std/variant +++ b/libstdc++-v3/include/std/variant @@ -439,6 +439,8 @@ namespace __variant constexpr bool _M_valid() const noexcept { + if constexpr ((is_scalar_v<_Types> && ...)) + return true; return this->_M_index != __index_type(variant_npos); } |