From: Ethan Furman <ethan@stoneleaf.us>
Date: Fri, 2 Sep 2016 22:50:21 +0000 (-0700)
Subject: issue23591: optimize _high_bit()
X-Git-Tag: v3.6.0b1~494
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=044395306702fc47e63b43d5ad961a127c19b262;p=thirdparty%2FPython%2Fcpython.git

issue23591: optimize _high_bit()
---

diff --git a/Lib/enum.py b/Lib/enum.py
index 83696313a45e..8d23933d3ed7 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -784,13 +784,8 @@ class IntFlag(int, Flag):
 
 
 def _high_bit(value):
-    """return the highest bit set in value"""
-    bit = 0
-    while 'looking for the highest bit':
-        limit = 2 ** bit
-        if limit > value:
-            return bit - 1
-        bit += 1
+    """returns index of highest bit, or -1 if value is zero or negative"""
+    return value.bit_length() - 1 if value > 0 else -1
 
 def unique(enumeration):
     """Class decorator for enumerations ensuring unique member values."""