Optimization of string::operator< by M.E. O'Neill. Discussion in http://llvm.org/bugs/show_bug.cgi?id=10461

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@135893 91177308-0d34-0410-b5e6-96231b3b80d8

include/string

@@ -3392,7 +3392,17 @@ _LIBCPP_INLINE_VISIBILITY inline
 int
 basic_string<_CharT, _Traits, _Allocator>::compare(const basic_string& __str) const _NOEXCEPT
 {
-    return compare(0, npos, __str.data(), __str.size());
+    size_t __lhs_sz = size();
+    size_t __rhs_sz = __str.size();
+    int __result = traits_type::compare(data(), __str.data(),
+                                        _VSTD::min(__lhs_sz, __rhs_sz));
+    if (__result != 0)
+        return __result;
+    if (__lhs_sz < __rhs_sz)
+        return -1;
+    if (__lhs_sz > __rhs_sz)
+        return 1;
+    return 0;
 }
 
 template <class _CharT, class _Traits, class _Allocator>