From: Paul Eggert <eggert@cs.ucla.edu>
Date: Fri, 17 Aug 2018 02:53:21 +0000 (-0700)
Subject: Speed up logcount on bignums
X-Git-Tag: emacs-27.0.90~4555
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=bb7e0338919d1c7068a64b3855e50fac345e4e05;p=emacs.git

Speed up logcount on bignums

* src/data.c (Flogcount): Speed up by using the mpz equivalent
of ~X instead of -X-1.
---

diff --git a/src/data.c b/src/data.c
index a1215b9d6bf..66f508c8f43 100644
--- a/src/data.c
+++ b/src/data.c
@@ -3350,8 +3350,7 @@ representation.  */)
 	return make_fixnum (mpz_popcount (XBIGNUM (value)->value));
       mpz_t tem;
       mpz_init (tem);
-      mpz_neg (tem, XBIGNUM (value)->value);
-      mpz_sub_ui (tem, tem, 1);
+      mpz_com (tem, XBIGNUM (value)->value);
       Lisp_Object result = make_fixnum (mpz_popcount (tem));
       mpz_clear (tem);
       return result;