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Tweak time arithmetic performance

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* 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.
This commit is contained in:
Paul Eggert 2019-08-04 10:04:18 -07:00
parent 5f3f3884a0
commit 7748ef218c
1 changed files with 32 additions and 12 deletions
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44
src/timefns.c
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@ -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
{