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Speed up % and mod with fixnum denom

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* src/data.c (integer_remainder): New function.  When the
numerator is a bignum and the denominator is small, this function
uses mpz_tdiv_ui, which should be faster than mpz_tdiv_r.
(Frem, Fmod): Use it.
This commit is contained in:
Paul Eggert 2019-08-24 15:46:31 -07:00
parent 2f7ca4020e
commit a050cf80f3
1 changed files with 55 additions and 51 deletions
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106
src/data.c
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@ -3055,6 +3055,59 @@ usage: (/ NUMBER &rest DIVISORS) */)
return arith_driver (Adiv, nargs, args, a);
}
/* Return NUM % DEN (or NUM mod DEN, if MODULO). NUM and DEN must be
integers. */
static Lisp_Object
integer_remainder (Lisp_Object num, Lisp_Object den, bool modulo)
{
if (FIXNUMP (den))
{
EMACS_INT d = XFIXNUM (den);
if (d == 0)
xsignal0 (Qarith_error);
EMACS_INT r;
bool have_r = false;
if (FIXNUMP (num))
{
r = XFIXNUM (num) % d;
have_r = true;
}
else if (eabs (d) <= ULONG_MAX)
{
mpz_t const *n = xbignum_val (num);
bool neg_n = mpz_sgn (*n) < 0;
r = mpz_tdiv_ui (*n, eabs (d));
if (neg_n)
r = -r;
have_r = true;
}
if (have_r)
{
/* If MODULO and the remainder has the wrong sign, fix it. */
if (modulo && (d < 0 ? r > 0 : r < 0))
r += d;
return make_fixnum (r);
}
}
mpz_t const *d = bignum_integer (&mpz[1], den);
mpz_t *r = &mpz[0];
mpz_tdiv_r (*r, *bignum_integer (&mpz[0], num), *d);
if (modulo)
{
/* If the remainder has the wrong sign, fix it. */
int sgn_r = mpz_sgn (*r);
if (mpz_sgn (*d) < 0 ? sgn_r > 0 : sgn_r < 0)
mpz_add (*r, *r, *d);
}
return make_integer_mpz ();
}
DEFUN ("%", Frem, Srem, 2, 2, 0,
doc: /* Return remainder of X divided by Y.
Both must be integers or markers. */)
@ -3062,51 +3115,7 @@ Both must be integers or markers. */)
{
CHECK_INTEGER_COERCE_MARKER (x);
CHECK_INTEGER_COERCE_MARKER (y);
/* A bignum can never be 0, so don't check that case. */
if (EQ (y, make_fixnum (0)))
xsignal0 (Qarith_error);
if (FIXNUMP (x) && FIXNUMP (y))
return make_fixnum (XFIXNUM (x) % XFIXNUM (y));
else
{
mpz_tdiv_r (mpz[0],
*bignum_integer (&mpz[0], x),
*bignum_integer (&mpz[1], y));
return make_integer_mpz ();
}
}
/* Return X mod Y. Both must be integers and Y must be nonzero. */
static Lisp_Object
integer_mod (Lisp_Object x, Lisp_Object y)
{
if (FIXNUMP (x) && FIXNUMP (y))
{
EMACS_INT i1 = XFIXNUM (x), i2 = XFIXNUM (y);
i1 %= i2;
/* If the "remainder" comes out with the wrong sign, fix it. */
if (i2 < 0 ? i1 > 0 : i1 < 0)
i1 += i2;
return make_fixnum (i1);
}
else
{
mpz_t const *ym = bignum_integer (&mpz[1], y);
bool neg_y = mpz_sgn (*ym) < 0;
mpz_tdiv_r (mpz[0], *bignum_integer (&mpz[0], x), *ym);
/* Fix the sign if needed. */
int sgn_r = mpz_sgn (mpz[0]);
if (neg_y ? sgn_r > 0 : sgn_r < 0)
mpz_add (mpz[0], mpz[0], *ym);
return make_integer_mpz ();
}
return integer_remainder (x, y, false);
}
DEFUN ("mod", Fmod, Smod, 2, 2, 0,
@ -3119,12 +3128,7 @@ Both X and Y must be numbers or markers. */)
CHECK_NUMBER_COERCE_MARKER (y);
if (FLOATP (x) || FLOATP (y))
return fmod_float (x, y);
/* A bignum can never be 0, so don't check that case. */
if (EQ (y, make_fixnum (0)))
xsignal0 (Qarith_error);
return integer_mod (x, y);
return integer_remainder (x, y, true);
}
static Lisp_Object