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Reapply r229142 with some enable_if magic to avoid memcpying between differing types. 

Original commit message:
SmallVector: Resolve a long-standing fixme by using the existing unitialized_copy dispatch.

This makes append() use memcpy for trivially copyable types.

llvm-svn: 229149
This commit is contained in:
Benjamin Kramer 2015-02-13 20:45:14 +00:00
parent 14a92711ce
commit bad5a46c05
1 changed files with 6 additions and 5 deletions
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11
llvm/include/llvm/ADT/SmallVector.h
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@ -307,8 +307,11 @@ protected:
/// Copy the range [I, E) onto the uninitialized memory
/// starting with "Dest", constructing elements into it as needed.
template<typename T1, typename T2>
static void uninitialized_copy(T1 *I, T1 *E, T2 *Dest) {
template <typename T1, typename T2>
static void uninitialized_copy(
T1 *I, T1 *E, T2 *Dest,
typename std::enable_if<std::is_same<typename std::remove_const<T1>::type,
T2>::value>::type * = nullptr) {
// Use memcpy for PODs iterated by pointers (which includes SmallVector
// iterators): std::uninitialized_copy optimizes to memmove, but we can
// use memcpy here.
@ -414,9 +417,7 @@ public:
this->grow(this->size()+NumInputs);
// Copy the new elements over.
// TODO: NEED To compile time dispatch on whether in_iter is a random access
// iterator to use the fast uninitialized_copy.
std::uninitialized_copy(in_start, in_end, this->end());
this->uninitialized_copy(in_start, in_end, this->end());
this->setEnd(this->end() + NumInputs);
}