Switch to FxHasher hash function in int64hash and bitmix

Author: Zentrik

src/support/hashing.c

@@ -25,16 +25,10 @@ uint32_t int32hash(uint32_t a)
     return a;
 }
 
+// FxHasher
 uint64_t int64hash(uint64_t key)
 {
-    key = (~key) + (key << 21);            // key = (key << 21) - key - 1;
-    key =   key  ^ (key >> 24);
-    key = (key + (key << 3)) + (key << 8); // key * 265
-    key =  key ^ (key >> 14);
-    key = (key + (key << 2)) + (key << 4); // key * 21
-    key =  key ^ (key >> 28);
-    key =  key + (key << 31);
-    return key;
+    return key * 0x517cc1b727220a95;
 }
 
 uint32_t int64to32hash(uint64_t key)

src/support/hashing.h

@@ -25,18 +25,25 @@ JL_DLLEXPORT uint64_t memhash_seed(const char *buf, size_t n, uint32_t seed) JL_
 JL_DLLEXPORT uint32_t memhash32(const char *buf, size_t n) JL_NOTSAFEPOINT;
 JL_DLLEXPORT uint32_t memhash32_seed(const char *buf, size_t n, uint32_t seed) JL_NOTSAFEPOINT;
 
+// FxHasher
 #ifdef _P64
-STATIC_INLINE uint64_t bitmix(uint64_t a, uint64_t b) JL_NOTSAFEPOINT
+STATIC_INLINE uint64_t bitmix(uint64_t h, uint64_t a) JL_NOTSAFEPOINT
 {
-    return int64hash(a^bswap_64(b));
+    h = (h << 5) | (h >> (sizeof(h) * 8 - 5)); // rotate 5 bits to the left
+    h ^= a;
+    h *= 0x517cc1b727220a95;
+    return h;
 }
 #else
-STATIC_INLINE uint32_t bitmix(uint32_t a, uint32_t b) JL_NOTSAFEPOINT
+STATIC_INLINE uint32_t bitmix(uint32_t h, uint32_t a) JL_NOTSAFEPOINT
 {
-    return int64to32hash((((uint64_t)a) << 32) | (uint64_t)b);
+    h = (h << 5) | (h >> (sizeof(h) * 8 - 5)); // rotate 5 bits to the left
+    h ^= a;
+    h *= 0x9e3779b9;
+    return h;
 }
 #endif
-#define bitmix(a, b) (bitmix)((uintptr_t)(a), (uintptr_t)(b))
+#define bitmix(h, a) (bitmix)((uintptr_t)(h), (uintptr_t)(a))
 
 #ifdef __cplusplus
 }