compat: replace int hash

1 files changed, 7 insertions, 6 deletions

diff --git a/compat/int-hash.hpp b/compat/int-hash.hpp
index 43b92605..36f0c8b8 100644
--- a/compat/int-hash.hpp
+++ b/compat/int-hash.hpp
@@ -1,5 +1,6 @@
 #pragma once
 #include <cstddef>
+#include <bit>
 
 namespace floormat {
 
@@ -16,12 +17,12 @@ constexpr inline std::size_t int_hash(std::size_t x) noexcept
     }
     else if constexpr(sizeof(std::size_t) == 8)
     {
-        // splitmix64 by George Marsaglia
-        x ^= x >> 30;
-        x *= 0xbf58476d1ce4e5b9U;
-        x ^= x >> 27;
-        x *= 0x94d049bb133111ebU;
-        x ^= x >> 31;
+        // NASAM by Pelle Evensen <https://mostlymangling.blogspot.com/2020/01/nasam-not-another-strange-acronym-mixer.html>
+        x ^= std::rotr(x, 25) ^ std::rotr(x, 47);
+        x *= 0x9E6C63D0676A9A99UL;
+        x ^= x >> 23 ^ x >> 51;
+        x *= 0x9E6D62D06F6A9A9BUL;
+        x ^= x >> 23 ^ x >> 51;
     }
 
     return x;