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Improve ‘abs’ performance

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* src/floatfns.c (Fabs): Improve performance by not copying
the argument if it would eql the result.  As a minor detail,
don't assume fixnums are two’s complement.
This commit is contained in:
Paul Eggert 2018-08-17 12:37:57 -07:00
parent 9189afc1a8
commit 3300287236
1 changed files with 31 additions and 18 deletions
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49
src/floatfns.c
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@ -266,30 +266,43 @@ DEFUN ("sqrt", Fsqrt, Ssqrt, 1, 1, 0,
DEFUN ("abs", Fabs, Sabs, 1, 1, 0,
doc: /* Return the absolute value of ARG. */)
(register Lisp_Object arg)
(Lisp_Object arg)
{
CHECK_NUMBER (arg);
if (BIGNUMP (arg))
if (FIXNUMP (arg))
{
mpz_t val;
mpz_init (val);
mpz_abs (val, XBIGNUM (arg)->value);
arg = make_number (val);
mpz_clear (val);
}
else if (FIXNUMP (arg) && XFIXNUM (arg) == MOST_NEGATIVE_FIXNUM)
{
mpz_t val;
mpz_init (val);
mpz_set_intmax (val, - MOST_NEGATIVE_FIXNUM);
arg = make_number (val);
mpz_clear (val);
if (XFIXNUM (arg) < 0)
{
EMACS_INT absarg = -XFIXNUM (arg);
if (absarg <= MOST_POSITIVE_FIXNUM)
arg = make_fixnum (absarg);
else
{
mpz_t val;
mpz_init (val);
mpz_set_intmax (val, absarg);
arg = make_number (val);
mpz_clear (val);
}
}
}
else if (FLOATP (arg))
arg = make_float (fabs (XFLOAT_DATA (arg)));
else if (XFIXNUM (arg) < 0)
XSETINT (arg, - XFIXNUM (arg));
{
if (signbit (XFLOAT_DATA (arg)))
arg = make_float (- XFLOAT_DATA (arg));
}
else
{
if (mpz_sgn (XBIGNUM (arg)->value) < 0)
{
mpz_t val;
mpz_init (val);
mpz_neg (val, XBIGNUM (arg)->value);
arg = make_number (val);
mpz_clear (val);
}
}
return arg;
}