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Taking another swing at correctly optimizing fill_n.

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git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@187587 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Howard Hinnant 2013-08-01 17:29:28 +00:00
parent eb34122153
commit 56dcf0b809
2 changed files with 52 additions and 9 deletions
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20
include/algorithm
View File

@ -1987,17 +1987,23 @@ replace_copy_if(_InputIterator __first, _InputIterator __last, _OutputIterator _
template <class _OutputIterator, class _Size, class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
_OutputIterator
__fill_n(_OutputIterator __first, _Size __n, const _Tp& __value_, false_type)
__fill_n(_OutputIterator __first, _Size __n, const _Tp& __value_)
{
for (; __n > 0; ++__first, --__n)
*__first = __value_;
return __first;
}
template <class _OutputIterator, class _Size, class _Tp>
template <class _Tp, class _Size, class _Up>
inline _LIBCPP_INLINE_VISIBILITY
_OutputIterator
__fill_n(_OutputIterator __first, _Size __n, const _Tp& __value_, true_type)
typename enable_if
<
is_integral<_Tp>::value && sizeof(_Tp) == 1 &&
!is_same<_Tp, bool>::value &&
is_integral<_Up>::value && sizeof(_Up) == 1,
_Tp*
>::type
__fill_n(_Tp* __first, _Size __n,_Up __value_)
{
if (__n > 0)
_VSTD::memset(__first, (unsigned char)__value_, (size_t)(__n));
@ -2009,11 +2015,7 @@ inline _LIBCPP_INLINE_VISIBILITY
_OutputIterator
fill_n(_OutputIterator __first, _Size __n, const _Tp& __value_)
{
return _VSTD::__fill_n(__first, __n, __value_, integral_constant<bool,
is_pointer<_OutputIterator>::value &&
is_trivially_assignable<typename remove_pointer<_OutputIterator>::type, _Tp>::value &&
is_convertible<_Tp, unsigned char>::value &&
sizeof(typename remove_pointer<_OutputIterator>::type) == 1>());
return _VSTD::__fill_n(__first, __n, __value_);
}
// fill

41
test/algorithms/alg.modifying.operations/alg.fill/fill_n.pass.cpp
View File

@ -94,6 +94,44 @@ test_struct_array()
assert(test1a[3].c == 11);
}
class A
{
char a_;
public:
A() {}
explicit A(char a) : a_(a) {}
operator unsigned char() const {return 'b';}
friend bool operator==(const A& x, const A& y)
{return x.a_ == y.a_;}
};
void
test5()
{
A a[3];
assert(std::fill_n(&a[0], 3, A('a')) == a+3);
assert(a[0] == A('a'));
assert(a[1] == A('a'));
assert(a[2] == A('a'));
}
struct Storage
{
union
{
unsigned char a;
unsigned char b;
};
};
void test6()
{
Storage foo[5];
std::fill_n(&foo[0], 5, Storage());
}
int main()
{
test_char<forward_iterator<char*> >();
@ -109,4 +147,7 @@ int main()
test_int_array();
test_int_array_struct_source();
test_struct_array();
test5();
test6();
}