From 8e13da1ee83028000e5d7f9f9526379e32765a81 Mon Sep 17 00:00:00 2001
From: pavel <pavel.rosicky@easy.cz>
Date: Fri, 19 Jul 2019 16:23:00 +0200
Subject: [PATCH] optimize get_power2 [Feature #15631]

Merged: https://github.com/ruby/ruby/pull/2292
---
 st.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/st.c b/st.c
index 880ab8769b..618143f29d 100644
--- a/st.c
+++ b/st.c
@@ -345,10 +345,7 @@ do_hash(st_data_t key, st_table *tab)
 static int
 get_power2(st_index_t size)
 {
-    unsigned int n;
-
-    for (n = 0; size != 0; n++)
-        size >>= 1;
+    unsigned int n = ST_INDEX_BITS - nlz_intptr(size);
     if (n <= MAX_POWER2)
         return n < MINIMAL_POWER2 ? MINIMAL_POWER2 : n;
 #ifndef NOT_RUBY