Tweak time arithmetic performance

* src/timefns.c (lispint_arith): New function, which
should be a bit faster if B is 0, or if A is a bignum
and B a fixnum with absolute value in unsigned long range.
(time_arith): Use it.

diff --git a/src/timefns.c b/src/timefns.c
index cce9dd51ba92e312a09f0011400ee78cec5c1acb..ee43014979ec82f75e9f1d41ca59d108769fdfc6 100644 (file)
--- a/src/timefns.c
+++ b/src/timefns.c
@@ -965,6 +965,37 @@ lisp_seconds_argument (Lisp_Object specified_time)
   return t.tv_sec;
 }
 
+/* Return the sum of the Lisp integers A and B.
+   Subtract instead of adding if SUBTRACT.
+   This function is tuned for small B.  */
+static Lisp_Object
+lispint_arith (Lisp_Object a, Lisp_Object b, bool subtract)
+{
+  bool mpz_done = false;
+
+  if (FASTER_TIMEFNS && FIXNUMP (b))
+    {
+      if (EQ (b, make_fixnum (0)))
+       return a;
+      if (FIXNUMP (a))
+       return make_int (subtract
+                        ? XFIXNUM (a) - XFIXNUM (b)
+                        : XFIXNUM (a) + XFIXNUM (b));
+      if (eabs (XFIXNUM (b)) <= ULONG_MAX)
+       {
+         ((XFIXNUM (b) < 0) == subtract ? mpz_add_ui : mpz_sub_ui)
+           (mpz[0], XBIGNUM (a)->value, eabs (XFIXNUM (b)));
+         mpz_done = true;
+       }
+    }
+
+  if (!mpz_done)
+    (subtract ? mpz_sub : mpz_add) (mpz[0],
+                                   *bignum_integer (&mpz[0], a),
+                                   *bignum_integer (&mpz[1], b));
+  return make_integer_mpz ();
+}
+
 /* Given Lisp operands A and B, add their values, and return the
    result as a Lisp timestamp that is in (TICKS . HZ) form if either A
    or B are in that form, (HI LO US PS) form otherwise.  Subtract
@@ -989,18 +1020,7 @@ time_arith (Lisp_Object a, Lisp_Object b, bool subtract)
   if (FASTER_TIMEFNS && EQ (ta.hz, tb.hz))
     {
       hz = ta.hz;
-      if (FIXNUMP (ta.ticks) && FIXNUMP (tb.ticks))
-       ticks = make_int (subtract
-                         ? XFIXNUM (ta.ticks) - XFIXNUM (tb.ticks)
-                         : XFIXNUM (ta.ticks) + XFIXNUM (tb.ticks));
-      else
-       {
-         (subtract ? mpz_sub : mpz_add)
-           (mpz[0],
-            *bignum_integer (&mpz[0], ta.ticks),
-            *bignum_integer (&mpz[1], tb.ticks));
-         ticks = make_integer_mpz ();
-       }
+      ticks = lispint_arith (ta.ticks, tb.ticks, subtract);
     }
   else
     {