[varStore.optimize] Use faster intTools.bit_count as popcount

Lib/fontTools/misc/intTools.py

@@ -1,4 +1,4 @@
-__all__ = ["popCount"]
+__all__ = ["popCount", "bit_count", "bit_indices"]
 
 
 try:
@@ -13,7 +13,7 @@ except AttributeError:
 
 See https://docs.python.org/3.10/library/stdtypes.html#int.bit_count
 """
-popCount = bit_count
+popCount = bit_count  # alias
 
 
 def bit_indices(v):

Lib/fontTools/varLib/featureVars.py

@@ -4,7 +4,7 @@ https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#featurevariat
 NOTE: The API is experimental and subject to change.
 """
 from fontTools.misc.dictTools import hashdict
-from fontTools.misc.intTools import popCount
+from fontTools.misc.intTools import bit_count
 from fontTools.ttLib import newTable
 from fontTools.ttLib.tables import otTables as ot
 from fontTools.ttLib.ttVisitor import TTVisitor
@@ -190,7 +190,7 @@ def overlayFeatureVariations(conditionalSubstitutions):
     # Generate output
     items = []
     for box, rank in sorted(
-        boxMap.items(), key=(lambda BoxAndRank: -popCount(BoxAndRank[1]))
+        boxMap.items(), key=(lambda BoxAndRank: -bit_count(BoxAndRank[1]))
     ):
         # Skip any box that doesn't have any substitution.
         if rank == 0:

Lib/fontTools/varLib/varStore.py

@@ -1,4 +1,5 @@
 from fontTools.misc.roundTools import noRound, otRound
+from fontTools.misc.intTools import bit_count
 from fontTools.ttLib.tables import otTables as ot
 from fontTools.varLib.models import supportScalar
 from fontTools.varLib.builder import (
@@ -360,7 +361,7 @@ ot.GPOS.remap_device_varidxes = Object_remap_device_varidxes
 class _Encoding(object):
     def __init__(self, chars):
         self.chars = chars
-        self.width = self._popcount(chars)
+        self.width = bit_count(chars)
         self.columns = self._columns(chars)
         self.overhead = self._characteristic_overhead(self.columns)
         self.items = set()
@@ -400,13 +401,7 @@ class _Encoding(object):
         return not (chars & ~self.chars)
 
     def __sub__(self, other):
-        return self._popcount(self.chars & ~other.chars)
-
-    @staticmethod
-    def _popcount(n):
-        # Apparently this is the fastest native way to do it...
-        # https://stackoverflow.com/a/9831671
-        return bin(n).count("1")
+        return bit_count(self.chars & ~other.chars)
 
     @staticmethod
     def _characteristic_overhead(columns):
@@ -429,7 +424,7 @@ class _Encoding(object):
 
     def gain_from_merging(self, other_encoding):
         combined_chars = other_encoding.chars | self.chars
-        combined_width = _Encoding._popcount(combined_chars)
+        combined_width = bit_count(combined_chars)
         combined_columns = self.columns | other_encoding.columns
         combined_overhead = _Encoding._characteristic_overhead(combined_columns)
         combined_gain = (