From: Paul Eggert <eggert@cs.ucla.edu>
Date: Tue, 4 Sep 2018 17:24:51 +0000 (-0700)
Subject: Tweak nthcdr for bignum efficiency
X-Git-Tag: emacs-27.0.90~4467
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=628f6a2c7a9fe476b7e71efed3a8f8784a00cc54;p=emacs.git

Tweak nthcdr for bignum efficiency

* src/fns.c (Fnthcdr): Use mpz_tdiv_ui and mpz_tdiv_r
instead of mpz_mod_ui and mpz_mod, as they are more efficient.
Suggested by Pip Cet in:
https://lists.gnu.org/r/emacs-devel/2018-09/msg00073.html
---

diff --git a/src/fns.c b/src/fns.c
index 8b25492eaeb..5a98f148818 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -1470,11 +1470,11 @@ DEFUN ("nthcdr", Fnthcdr, Snthcdr, 2, 2, 0,
 	 CYCLE_LENGTH.  */
       /* Add N mod CYCLE_LENGTH to NUM.  */
       if (cycle_length <= ULONG_MAX)
-	num += mpz_mod_ui (mpz[0], XBIGNUM (n)->value, cycle_length);
+	num += mpz_tdiv_ui (XBIGNUM (n)->value, cycle_length);
       else
 	{
 	  mpz_set_intmax (mpz[0], cycle_length);
-	  mpz_mod (mpz[0], XBIGNUM (n)->value, mpz[0]);
+	  mpz_tdiv_r (mpz[0], XBIGNUM (n)->value, mpz[0]);
 	  intptr_t iz;
 	  mpz_export (&iz, NULL, -1, sizeof iz, 0, 0, mpz[0]);
 	  num += iz;