1 files changed, 164 insertions, 44 deletions
diff --git a/libcxx/include/memory b/libcxx/include/memory
index e6cfa07debc..c3e3af4a598 100644
--- a/libcxx/include/memory
+++ b/libcxx/include/memory
@@ -2719,18 +2719,22 @@ operator>=(const unique_ptr<_T1, _D1>& __x, const unique_ptr<_T2, _D2>& __y) {re
 
 template <class _Tp> struct hash;
 
+// We use murmur2 when size_t is 32 bits, and cityhash64 when size_t
+// is 64 bits.  This is because cityhash64 uses 64bit x 64bit
+// multiplication, which can be very slow on 32-bit systems.
 template <class _Size, size_t = sizeof(_Size)*__CHAR_BIT__>
-struct __murmur2;
+struct __murmur2_or_cityhash;
 
 template <class _Size>
-struct __murmur2<_Size, 32>
+struct __murmur2_or_cityhash<_Size, 32>
 {
     _Size operator()(const void* __key, _Size __len);
 };
 
+// murmur2
 template <class _Size>
 _Size
-__murmur2<_Size, 32>::operator()(const void* __key, _Size __len)
+__murmur2_or_cityhash<_Size, 32>::operator()(const void* __key, _Size __len)
 {
     const _Size __m = 0x5bd1e995;
     const _Size __r = 24;
@@ -2762,50 +2766,166 @@ __murmur2<_Size, 32>::operator()(const void* __key, _Size __len)
 }
 
 template <class _Size>
-struct __murmur2<_Size, 64>
+struct __murmur2_or_cityhash<_Size, 64>
 {
     _Size operator()(const void* __key, _Size __len);
-};
 
+ private:
+  // Some primes between 2^63 and 2^64.
+  static const _Size __k0 = 0xc3a5c85c97cb3127ULL;
+  static const _Size __k1 = 0xb492b66fbe98f273ULL;
+  static const _Size __k2 = 0x9ae16a3b2f90404fULL;
+  static const _Size __k3 = 0xc949d7c7509e6557ULL;
+
+  static _Size __rotate(_Size __val, int __shift) {
+    return __shift == 0 ? __val : ((__val >> __shift) | (__val << (64 - __shift)));
+  }
+
+  static _Size __rotate_by_at_least_1(_Size __val, int __shift) {
+    return (__val >> __shift) | (__val << (64 - __shift));
+  }
+
+  static _Size __shift_mix(_Size __val) {
+    return __val ^ (__val >> 47);
+  }
+
+  static _Size __hash_len_16(_Size __u, _Size __v) {
+    const _Size __mul = 0x9ddfea08eb382d69ULL;
+    _Size __a = (__u ^ __v) * __mul;
+    __a ^= (__a >> 47);
+    _Size __b = (__v ^ __a) * __mul;
+    __b ^= (__b >> 47);
+    __b *= __mul;
+    return __b;
+  }
+
+  static _Size __hash_len_0_to_16(const char* __s, _Size __len) {
+    if (__len > 8) {
+      const _Size __a = *(const _Size*)__s;
+      const _Size __b = *(const _Size*)(__s + __len - 8);
+      return __hash_len_16(__a, __rotate_by_at_least_1(__b + __len, __len)) ^ __b;
+    }
+    if (__len >= 4) {
+      const uint32_t __a = *(const uint32_t*)(__s);
+      const uint32_t __b = *(const uint32_t*)(__s + __len - 4);
+      return __hash_len_16(__len + (__a << 3), __b);
+    }
+    if (__len > 0) {
+      const unsigned char __a = __s[0];
+      const unsigned char __b = __s[__len >> 1];
+      const unsigned char __c = __s[__len - 1];
+      const uint32_t __y = static_cast<uint32_t>(__a) +
+                           (static_cast<uint32_t>(__b) << 8);
+      const uint32_t __z = __len + (static_cast<uint32_t>(__c) << 2);
+      return __shift_mix(__y * __k2 ^ __z * __k3) * __k2;
+    }
+    return __k2;
+  }
+
+  static _Size __hash_len_17_to_32(const char *__s, _Size __len) {
+    const _Size __a = *(const _Size*)(__s) * __k1;
+    const _Size __b = *(const _Size*)(__s + 8);
+    const _Size __c = *(const _Size*)(__s + __len - 8) * __k2;
+    const _Size __d = *(const _Size*)(__s + __len - 16) * __k0;
+    return __hash_len_16(__rotate(__a - __b, 43) + __rotate(__c, 30) + __d,
+                         __a + __rotate(__b ^ __k3, 20) - __c + __len);
+  }
+
+  // Return a 16-byte hash for 48 bytes.  Quick and dirty.
+  // Callers do best to use "random-looking" values for a and b.
+  static pair<_Size, _Size> __weak_hash_len_32_with_seeds(
+      _Size __w, _Size __x, _Size __y, _Size __z, _Size __a, _Size __b) {
+    __a += __w;
+    __b = __rotate(__b + __a + __z, 21);
+    const _Size __c = __a;
+    __a += __x;
+    __a += __y;
+    __b += __rotate(__a, 44);
+    return pair<_Size, _Size>(__a + __z, __b + __c);
+  }
+
+  // Return a 16-byte hash for s[0] ... s[31], a, and b.  Quick and dirty.
+  static pair<_Size, _Size> __weak_hash_len_32_with_seeds(
+      const char* __s, _Size __a, _Size __b) {
+    return __weak_hash_len_32_with_seeds(*(const _Size*)(__s),
+                                         *(const _Size*)(__s + 8),
+                                         *(const _Size*)(__s + 16),
+                                         *(const _Size*)(__s + 24),
+                                         __a,
+                                         __b);
+  }
+
+  // Return an 8-byte hash for 33 to 64 bytes.
+  static _Size __hash_len_33_to_64(const char *__s, size_t __len) {
+    _Size __z = *(const _Size*)(__s + 24);
+    _Size __a = *(const _Size*)(__s) +
+                (__len + *(const _Size*)(__s + __len - 16)) * __k0;
+    _Size __b = __rotate(__a + __z, 52);
+    _Size __c = __rotate(__a, 37);
+    __a += *(const _Size*)(__s + 8);
+    __c += __rotate(__a, 7);
+    __a += *(const _Size*)(__s + 16);
+    _Size __vf = __a + __z;
+    _Size __vs = __b + __rotate(__a, 31) + __c;
+    __a = *(const _Size*)(__s + 16) + *(const _Size*)(__s + __len - 32);
+    __z += *(const _Size*)(__s + __len - 8);
+    __b = __rotate(__a + __z, 52);
+    __c = __rotate(__a, 37);
+    __a += *(const _Size*)(__s + __len - 24);
+    __c += __rotate(__a, 7);
+    __a += *(const _Size*)(__s + __len - 16);
+    _Size __wf = __a + __z;
+    _Size __ws = __b + __rotate(__a, 31) + __c;
+    _Size __r = __shift_mix((__vf + __ws) * __k2 + (__wf + __vs) * __k0);
+    return __shift_mix(__r * __k0 + __vs) * __k2;
+  }
+};
+
+// cityhash64
 template <class _Size>
 _Size
-__murmur2<_Size, 64>::operator()(const void* __key, _Size __len)
-{
-    const _Size __m = 0xc6a4a7935bd1e995ull;
-    const _Size __r = 47;
-    _Size __h = __len * __m;
-    const unsigned char* __data = static_cast<const unsigned char*>(__key);
-    for (; __len >= 8; __data += 8, __len -= 8)
-    {
-        _Size __k = *(const _Size*)__data;
-        __k *= __m;
-        __k ^= __k >> __r;
-        __k *= __m;
-        __h ^= __k;
-        __h *= __m;
+__murmur2_or_cityhash<_Size, 64>::operator()(const void* __key, _Size __len)
+{
+  const char* __s = static_cast<const char*>(__key);
+  if (__len <= 32) {
+    if (__len <= 16) {
+      return __hash_len_0_to_16(__s, __len);
+    } else {
+      return __hash_len_17_to_32(__s, __len);
     }
-    switch (__len)
-    {
-    case 7:
-        __h ^= __data[6] << 48;
-    case 6:
-        __h ^= __data[5] << 40;
-    case 5:
-        __h ^= __data[4] << 32;
-    case 4:
-        __h ^= __data[3] << 24;
-    case 3:
-        __h ^= __data[2] << 16;
-    case 2:
-        __h ^= __data[1] << 8;
-    case 1:
-        __h ^= __data[0];
-        __h *= __m;
-    }
-    __h ^= __h >> __r;
-    __h *= __m;
-    __h ^= __h >> __r;
-    return __h;
+  } else if (__len <= 64) {
+    return __hash_len_33_to_64(__s, __len);
+  }
+
+  // For strings over 64 bytes we hash the end first, and then as we
+  // loop we keep 56 bytes of state: v, w, x, y, and z.
+  _Size __x = *(const _Size*)(__s + __len - 40);
+  _Size __y = *(const _Size*)(__s + __len - 16) +
+              *(const _Size*)(__s + __len - 56);
+  _Size __z = __hash_len_16(*(const _Size*)(__s + __len - 48) + __len,
+                          *(const _Size*)(__s + __len - 24));
+  pair<_Size, _Size> __v = __weak_hash_len_32_with_seeds(__s + __len - 64, __len, __z);
+  pair<_Size, _Size> __w = __weak_hash_len_32_with_seeds(__s + __len - 32, __y + __k1, __x);
+  __x = __x * __k1 + *(const _Size*)(__s);
+
+  // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.
+  __len = (__len - 1) & ~static_cast<_Size>(63);
+  do {
+    __x = __rotate(__x + __y + __v.first + *(const _Size*)(__s + 8), 37) * __k1;
+    __y = __rotate(__y + __v.second + *(const _Size*)(__s + 48), 42) * __k1;
+    __x ^= __w.second;
+    __y += __v.first + *(const _Size*)(__s + 40);
+    __z = __rotate(__z + __w.first, 33) * __k1;
+    __v = __weak_hash_len_32_with_seeds(__s, __v.second * __k1, __x + __w.first);
+    __w = __weak_hash_len_32_with_seeds(__s + 32, __z + __w.second,
+                                        __y + *(const _Size*)(__s + 16));
+    std::swap(__z, __x);
+    __s += 64;
+    __len -= 64;
+  } while (__len != 0);
+  return __hash_len_16(
+      __hash_len_16(__v.first, __w.first) + __shift_mix(__y) * __k1 + __z,
+      __hash_len_16(__v.second, __w.second) + __x);
 }
 
 template <class _Tp, size_t = sizeof(_Tp) / sizeof(size_t)>
@@ -2863,7 +2983,7 @@ struct __scalar_hash<_Tp, 2>
             };
         } __u;
         __u.__t = __v;
-        return __murmur2<size_t>()(&__u, sizeof(__u));
+        return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
     }
 };
 
@@ -2885,7 +3005,7 @@ struct __scalar_hash<_Tp, 3>
             };
         } __u;
         __u.__t = __v;
-        return __murmur2<size_t>()(&__u, sizeof(__u));
+        return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
     }
 };
 
@@ -2908,7 +3028,7 @@ struct __scalar_hash<_Tp, 4>
             };
         } __u;
         __u.__t = __v;
-        return __murmur2<size_t>()(&__u, sizeof(__u));
+        return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
     }
 };