[PATCH] Fix exponential complexity in operator< for std::tuple
Matthew Dempsky
matthew at dempsky.org
Tue Dec 16 10:42:30 PST 2014
REPOSITORY
rL LLVM
http://reviews.llvm.org/D6683
Files:
include/tuple
Index: include/tuple
===================================================================
--- include/tuple
+++ include/tuple
@@ -927,8 +927,12 @@
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool operator()(const _Tp& __x, const _Up& __y)
{
- return __tuple_less<_Ip-1>()(__x, __y) ||
- (!__tuple_less<_Ip-1>()(__y, __x) && _VSTD::get<_Ip-1>(__x) < _VSTD::get<_Ip-1>(__y));
+ const size_t __idx = tuple_size<_Tp>::value - _Ip;
+ if (_VSTD::get<__idx>(__x) < _VSTD::get<__idx>(__y))
+ return true;
+ if (_VSTD::get<__idx>(__y) < _VSTD::get<__idx>(__x))
+ return false;
+ return __tuple_less<_Ip-1>()(__x, __y);
}
};
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