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 } }; 