[Python-checkins] cpython: issue23591: optimize _high_bit()

[ethan.furman]

https://hg.python.org/cpython/rev/31586a2f01b6
changeset:   103010:31586a2f01b6
user:        Ethan Furman <ethan at stoneleaf.us>
date:        Fri Sep 02 15:50:21 2016 -0700
summary:
  issue23591: optimize _high_bit()

files:
  Lib/enum.py |  9 ++-------
  1 files changed, 2 insertions(+), 7 deletions(-)


diff --git a/Lib/enum.py b/Lib/enum.py
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -784,13 +784,8 @@
 
 
 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."""

-- 
Repository URL: https://hg.python.org/cpython