From 9766019525696f76178d4e3eaa02ddeb9e934da6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?An=C4=B1lcan=20G=C3=BClkaya?=
 <48527900+benanil@users.noreply.github.com>
Date: Wed, 16 Jul 2025 13:48:47 +0300
Subject: [PATCH] Faster and less line default ilog2

https://graphics.stanford.edu/~seander/bithacks.html#IntegerLog
---
 sdefl.h | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/sdefl.h b/sdefl.h
index 5d5bcd0..5d44ddf 100644
--- a/sdefl.h
+++ b/sdefl.h
@@ -209,17 +209,11 @@ sdefl_ilog2(int n) {
 #elif defined(__GNUC__) || defined(__clang__)
   return (int)sizeof(unsigned long) * CHAR_BIT - 1 - __builtin_clzl((unsigned long)n);
 #else
-  #define lt(n) n, n, n, n, n, n, n, n, n, n, n, n, n, n, n, n
-  static const char tbl[256] = {
-    0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,lt(4), lt(5), lt(5), lt(6), lt(6), lt(6), lt(6),
-    lt(7), lt(7), lt(7), lt(7), lt(7), lt(7), lt(7), lt(7)};
-  int tt, t;
-  if ((tt = (n >> 16))) {
-    return (t = (tt >> 8)) ? 24 + tbl[t] : 16 + tbl[tt];
-  } else {
-    return (t = (n >> 8)) ? 8 + tbl[t] : tbl[n];
-  }
-  #undef lt
+  static const unsigned char multiply_de_bruijn_bit_position[32] = {
+    0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30,
+    8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31};
+  v |= v >> 1; v |= v >> 2; v |= v >> 4; v |= v >> 8; v |= v >> 16;
+  return multiply_de_bruijn_bit_position[(unsigned int)(v * 0x07C4ACDDU) >> 27];
 #endif
 }
 static unsigned