From f797c711cacc2668d0e4e8b51fbb50f4a8c47578 Mon Sep 17 00:00:00 2001
From: WerWolv <werwolv98@gmail.com>
Date: Thu, 4 Jul 2024 17:58:12 +0200
Subject: [PATCH] includes/std: Optimize std::bit::popcount

---
 includes/std/bit.pat | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/includes/std/bit.pat b/includes/std/bit.pat
index 8d21ff3..934e6fc 100644
--- a/includes/std/bit.pat
+++ b/includes/std/bit.pat
@@ -14,9 +14,13 @@ namespace auto std::bit {
         @return The number of bits set to 1 in `x`
     */
     fn popcount(u128 x) {
-        x = (x & (std::limits::u128_max() /  3)) + ((x >> 1) & (std::limits::u128_max() /  3));
-        x = (x & (std::limits::u128_max() /  5)) + ((x >> 2) & (std::limits::u128_max() /  5));
-        x = (x & (std::limits::u128_max() / 17)) + ((x >> 4) & (std::limits::u128_max() / 17));
+        const u128 a = 0x55555555555555555555555555555555;
+        const u128 b = 0x33333333333333333333333333333333;
+        const u128 c = 0x0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F;
+
+        x = (x & a) + ((x >> 1) & a);
+        x = (x & b) + ((x >> 2) & b);
+        x = (x & c) + ((x >> 4) & c);
         
         return x % 0xFF;
     };