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Start to optimize scm_integer_sub_iz

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* libguile/integers.c (scm_integer_sub_iz): Avoid cloning bignum.
This commit is contained in:
Andy Wingo 2022-01-09 21:10:14 +01:00
parent 2723513712
commit cae8b30163
1 changed files with 13 additions and 1 deletions
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14
libguile/integers.c
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@ -2869,7 +2869,19 @@ scm_integer_sub_ii (scm_t_inum x, scm_t_inum y)
SCM
scm_integer_sub_iz (scm_t_inum x, struct scm_bignum *y)
{
return scm_integer_add_zi (negate_bignum (clone_bignum (y)), x);
if (x == 0)
return scm_integer_negate_z (y);
mpz_t result, zx, zy;
mpz_init (result);
mpz_init_set_si (zx, x);
alias_bignum_to_mpz (y, zy);
mpz_sub (result, zx, zy);
scm_remember_upto_here_1 (y);
mpz_clear (zx);
// FIXME: We know that if X is negative, no need to check if
// result is fixable.
return take_mpz (result);
}
SCM