Version #next on the hash functions for scalars. This builds on Dave's work, extends it to T*, and changes the way double and long double are handled (no longer convert to float on 32 bit). I also picked up a minor bug with uninitialized bits on the upper end of size_t when sizeof(size_t) > sizeof(T), e.g. in hash<float>. Most of the functionality has been put in one place: __scalar_hash in <memory>. Unfortunately I could not reuse __scalar_hash for hash<long double> on x86 because of the padding bits which need to be zeroed. I didn't want to add this zeroing step to the more general __scalar_hash when it isn't needed (in the absence of padding bits). I'm not ignoring the hash<string> issue (possibly changing that to a better hash). I just haven't gotten there yet.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@145778 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/memory b/include/memory
index e8abdbe..bab71b4 100644
--- a/include/memory
+++ b/include/memory
@@ -2719,18 +2719,116 @@
template <class _Tp> struct hash;
-template<class _Tp>
-struct _LIBCPP_VISIBLE hash<_Tp*>
- : public unary_function<_Tp*, size_t>
+template <class _Tp, size_t = sizeof(_Tp) / sizeof(size_t)>
+struct __scalar_hash;
+
+template <class _Tp>
+struct __scalar_hash<_Tp, 0>
+ : public unary_function<_Tp, size_t>
{
_LIBCPP_INLINE_VISIBILITY
- size_t operator()(_Tp* __v) const _NOEXCEPT
+ size_t operator()(_Tp __v) const _NOEXCEPT
{
- const size_t* const __p = reinterpret_cast<const size_t*>(&__v);
- return *__p;
+ union
+ {
+ _Tp __t;
+ size_t __a;
+ } __u;
+ __u.__a = 0;
+ __u.__t = __v;
+ return __u.__a;
}
};
+template <class _Tp>
+struct __scalar_hash<_Tp, 1>
+ : public unary_function<_Tp, size_t>
+{
+ _LIBCPP_INLINE_VISIBILITY
+ size_t operator()(_Tp __v) const _NOEXCEPT
+ {
+ union
+ {
+ _Tp __t;
+ size_t __a;
+ } __u;
+ __u.__t = __v;
+ return __u.__a;
+ }
+};
+
+template <class _Tp>
+struct __scalar_hash<_Tp, 2>
+ : public unary_function<_Tp, size_t>
+{
+ _LIBCPP_INLINE_VISIBILITY
+ size_t operator()(_Tp __v) const _NOEXCEPT
+ {
+ union
+ {
+ _Tp __t;
+ struct
+ {
+ size_t __a;
+ size_t __b;
+ };
+ } __u;
+ __u.__t = __v;
+ return __u.__a ^ __u.__b;
+ }
+};
+
+template <class _Tp>
+struct __scalar_hash<_Tp, 3>
+ : public unary_function<_Tp, size_t>
+{
+ _LIBCPP_INLINE_VISIBILITY
+ size_t operator()(_Tp __v) const _NOEXCEPT
+ {
+ union
+ {
+ _Tp __t;
+ struct
+ {
+ size_t __a;
+ size_t __b;
+ size_t __c;
+ };
+ } __u;
+ __u.__t = __v;
+ return __u.__a ^ __u.__b ^ __u.__c;
+ }
+};
+
+template <class _Tp>
+struct __scalar_hash<_Tp, 4>
+ : public unary_function<_Tp, size_t>
+{
+ _LIBCPP_INLINE_VISIBILITY
+ size_t operator()(_Tp __v) const _NOEXCEPT
+ {
+ union
+ {
+ _Tp __t;
+ struct
+ {
+ size_t __a;
+ size_t __b;
+ size_t __c;
+ size_t __d;
+ };
+ } __u;
+ __u.__t = __v;
+ return __u.__a ^ __u.__b ^ __u.__c ^ __u.__d;
+ }
+};
+
+template<class _Tp>
+struct _LIBCPP_VISIBLE hash<_Tp*>
+ : public __scalar_hash<_Tp*>
+{
+};
+
template <class _Tp, class _Dp>
struct _LIBCPP_VISIBLE hash<unique_ptr<_Tp, _Dp> >
{