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Remove the unnecessary `is_nothrow_swappable` condition in `swap`. 

Thanks to @lewissbaker who pointed out the unnecessary condition in
https://reviews.llvm.org/D81954#inline-756872. Since this codepath does not
make use of `swap` anyway (that codepath is a different branch), we can safely
remove this condition and produce better codegen when all types are nothrow
movable but are potentially-throwing swappable.

See codegen in https://gcc.godbolt.org/z/uDFZjz

Reviewed By: ldionne, #libc

Differential Revision: https://reviews.llvm.org/D83274
This commit is contained in:
Michael Park 2020-07-08 10:46:02 -07:00
parent 82206e7fb4
commit 6ab3208d77
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1 changed files with 1 additions and 2 deletions
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3
libcxx/include/variant
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@ -1063,8 +1063,7 @@ public:
}
__impl __tmp(_VSTD::move(*__rhs));
#ifndef _LIBCPP_NO_EXCEPTIONS
if constexpr (__all<(is_nothrow_move_constructible_v<_Types> &&
is_nothrow_swappable_v<_Types>)...>::value) {
if constexpr (__all<is_nothrow_move_constructible_v<_Types>...>::value) {
this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
} else {
// EXTENSION: When the move construction of `__lhs` into `__rhs` throws