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Optimize scm_integer_mul_ii

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* libguile/integers.c (make_bignum_2): Always include.
(scm_integer_mul_ii): Avoid making a temporary allocation.
This commit is contained in:
Andy Wingo 2022-01-09 23:10:18 +01:00
parent 210ab8ff76
commit 2cf80ca238
1 changed files with 17 additions and 11 deletions
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28
libguile/integers.c
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@ -211,7 +211,6 @@ make_bignum_1 (int is_negative, mp_limb_t limb)
return is_negative ? negate_bignum(z) : z; return is_negative ? negate_bignum(z) : z;
} }
#if SCM_SIZEOF_LONG == 4
static struct scm_bignum * static struct scm_bignum *
make_bignum_2 (int is_negative, mp_limb_t lo, mp_limb_t hi) make_bignum_2 (int is_negative, mp_limb_t lo, mp_limb_t hi)
{ {
@ -220,7 +219,6 @@ make_bignum_2 (int is_negative, mp_limb_t lo, mp_limb_t hi)
z->limbs[1] = hi; z->limbs[1] = hi;
return is_negative ? negate_bignum(z) : z; return is_negative ? negate_bignum(z) : z;
} }
#endif
static struct scm_bignum * static struct scm_bignum *
make_bignum_from_uint64 (uint64_t val) make_bignum_from_uint64 (uint64_t val)
@ -3024,17 +3022,25 @@ scm_integer_mul_ii (scm_t_inum x, scm_t_inum y)
int64_t k = x * (int64_t) y; int64_t k = x * (int64_t) y;
if (SCM_FIXABLE (k)) if (SCM_FIXABLE (k))
return SCM_I_MAKINUM (k); return SCM_I_MAKINUM (k);
#else
if (x == 0)
return SCM_INUM0;
scm_t_inum ax = (x > 0) ? x : -x;
scm_t_inum ay = (y > 0) ? y : -y;
if (SCM_MOST_POSITIVE_FIXNUM / ax >= ay)
return SCM_I_MAKINUM (x * y);
#endif #endif
// FIXME: Use mpn_mul with two-limb result to avoid allocating. mp_limb_t xd[1] = { long_magnitude (x) };
return scm_integer_mul_zi (long_to_bignum (x), y); mp_limb_t lo;
int negative = (x < 0) != (y < 0);
mp_limb_t hi = mpn_mul_1 (&lo, xd, 1, long_magnitude (y));
if (!hi)
{
if (negative)
{
if (lo <= long_magnitude (SCM_MOST_NEGATIVE_FIXNUM))
return SCM_I_MAKINUM (negative_long (lo));
}
else if (lo <= SCM_MOST_POSITIVE_FIXNUM)
return SCM_I_MAKINUM (lo);
return scm_from_bignum (make_bignum_1 (negative, lo));
}
return scm_from_bignum (make_bignum_2 (negative, lo, hi));
} }
SCM SCM