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/functional b/include/functional
index 243f398..ee0424d 100644
--- a/include/functional
+++ b/include/functional
@@ -1916,123 +1916,91 @@
template <>
struct _LIBCPP_VISIBLE hash<long long>
- : public unary_function<long long, size_t>
+ : public __scalar_hash<long long>
{
- _LIBCPP_INLINE_VISIBILITY
- size_t operator()(long long __v) const _NOEXCEPT
- {
- if (sizeof(long long) == sizeof(size_t))
- return __v;
- union
- {
- long long __l;
- struct
- {
- size_t __a;
- size_t __b;
- } __s;
- } __u;
- __u.__l = __v;
- return __u.__s.__a ^ __u.__s.__b;
- }
};
template <>
struct _LIBCPP_VISIBLE hash<unsigned long long>
- : public unary_function<unsigned long long, size_t>
+ : public __scalar_hash<unsigned long long>
{
- _LIBCPP_INLINE_VISIBILITY
- size_t operator()(unsigned long long __v) const _NOEXCEPT
- {
- if (sizeof(unsigned long long) == sizeof(size_t))
- return __v;
- union
- {
- unsigned long long __l;
- struct
- {
- size_t __a;
- size_t __b;
- } __s;
- } __u;
- __u.__l = __v;
- return __u.__s.__a ^ __u.__s.__b;
- }
};
template <>
struct _LIBCPP_VISIBLE hash<float>
- : public unary_function<float, size_t>
+ : public __scalar_hash<float>
{
_LIBCPP_INLINE_VISIBILITY
size_t operator()(float __v) const _NOEXCEPT
{
+ // -0.0 and 0.0 should return same hash
if (__v == 0)
return 0;
- union
- {
- size_t __d;
- float __f;
- } __u;
- __u.__f = __v;
- return __u.__d;
+ return __scalar_hash<float>::operator()(__v);
}
};
template <>
struct _LIBCPP_VISIBLE hash<double>
- : public unary_function<double, size_t>
+ : public __scalar_hash<double>
{
_LIBCPP_INLINE_VISIBILITY
size_t operator()(double __v) const _NOEXCEPT
{
- if (__v == 0)
- return 0;
- if (sizeof(double) == sizeof(size_t))
- {
- union
- {
- double __f;
- size_t __d;
- } __u;
- __u.__f = __v;
- return __u.__d;
- }
- union
- {
- float __f;
- size_t __d;
- } __u;
- __u.__f = __v;
- return __u.__d;
+ // -0.0 and 0.0 should return same hash
+ if (__v == 0)
+ return 0;
+ return __scalar_hash<double>::operator()(__v);
}
};
template <>
struct _LIBCPP_VISIBLE hash<long double>
- : public unary_function<long double, size_t>
+ : public __scalar_hash<long double>
{
_LIBCPP_INLINE_VISIBILITY
size_t operator()(long double __v) const _NOEXCEPT
{
+ // -0.0 and 0.0 should return same hash
if (__v == 0)
return 0;
- if (sizeof(double) == sizeof(size_t))
+#if defined(__i386__)
+ // Zero out padding bits
+ union
{
- union
+ long double __t;
+ struct
{
- double __f;
+ size_t __a;
+ size_t __b;
+ size_t __c;
size_t __d;
- } __u;
- __u.__f = __v;
- return __u.__d;
- }
- union {
- float __f;
- size_t __d;
+ };
} __u;
- __u.__f = __v;
- return __u.__d;
+ __u.__a = 0;
+ __u.__b = 0;
+ __u.__c = 0;
+ __u.__d = 0;
+ __u.__t = __v;
+ return __u.__a ^ __u.__b ^ __u.__c ^ __u.__d;
+#elif defined(__x86_64__)
+ // Zero out padding bits
+ union
+ {
+ long double __t;
+ struct
+ {
+ size_t __a;
+ size_t __b;
+ };
+ } __u;
+ __u.__a = 0;
+ __u.__b = 0;
+ __u.__t = __v;
+ return __u.__a ^ __u.__b;
+#else
+ return __scalar_hash<long double>::operator()(__v);
+#endif
}
};