src/runtime: switch to stronger hash function

Fixes #2713

src/runtime/memhash_fnv.go

@@ -0,0 +1,32 @@
+//go:build !runtime_memhash_tsip
+// +build !runtime_memhash_tsip
+
+package runtime
+
+import "unsafe"
+
+// Get FNV-1a hash of the given memory buffer.
+//
+// https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function#FNV-1a_hash
+func hash32(ptr unsafe.Pointer, n, seed uintptr) uint32 {
+	var result uint32 = 2166136261 // FNV offset basis
+	result *= uint32(seed)
+	for i := uintptr(0); i < n; i++ {
+		c := *(*uint8)(unsafe.Pointer(uintptr(ptr) + i))
+		result ^= uint32(c) // XOR with byte
+		result *= 16777619  // FNV prime
+	}
+	return result
+}
+
+// Also a FNV-1a hash.
+func hash64(ptr unsafe.Pointer, n, seed uintptr) uint64 {
+	var result uint64 = 14695981039346656037 // FNV offset basis
+	result *= uint64(seed)
+	for i := uintptr(0); i < n; i++ {
+		c := *(*uint8)(unsafe.Pointer(uintptr(ptr) + i))
+		result ^= uint64(c)     // XOR with byte
+		result *= 1099511628211 // FNV prime
+	}
+	return result
+}