mpfr/src/sub1.c

37   mp_size_t cancel2, an, bn, cn, cn0;
48   an = MPFR_LIMB_SIZE(a);
72    *      But if it is an addition, sign(b) and sign(c) are opposed!
92       /* Remember, we can't have an exact result! */
126              correct (We can't have an exact result).
157       bp = MPFR_MANT(b); /* no need of an extra space */
238   /*               ap[an-1]        ap[0]
251   /* first part: put in ap[0..an-1] the value of high(b) - high(c),
252      where high(b) consists of the high an+cancel1 limbs of b,
253      and high(c) consists of the high an+cancel2 limbs of c.
257   if (MPFR_LIKELY(an + (mp_size_t) cancel1 <= bn))
260       MPN_COPY (ap, bp + bn - (an + cancel1), an);
266         MPN_ZERO (ap, an + cancel1 - bn);
267         MPN_COPY (ap + (an + cancel1 - bn), bp, bn - cancel1);
270       MPN_ZERO (ap, an);
277   if (MPFR_LIKELY(an + cancel2 > 0)) /* otherwise c does not overlap with a */
283           if (an + cancel2 <= cn)
286             mpn_sub_n (ap, ap, cp + cn - (an + cancel2), an);
291               ap2 = ap + an + (cancel2 - cn);
300           if (an + cancel2 <= cn)
303             borrow = mpn_sub_n (ap, ap, cp + cn - (an + cancel2),
304                                 an + cancel2);
309               ap2 = ap + an + cancel2 - cn;
312           ap2 = ap + an + cancel2;
324   sh = (mpfr_prec_t) an * GMP_NUMB_BITS - MPFR_PREC(a);
364   /* we have to consider the low (bn - (an+cancel1)) limbs from b,
365      and the (cn - (an+cancel2)) limbs from c. */
366   bn -= an + cancel1;
368   cn -= an + cancel2;
593   mpn_sub_1 (ap, ap, an, MPFR_LIMB_ONE << sh);
598   if (MPFR_UNLIKELY(mpn_add_1 (ap, ap, an, MPFR_LIMB_ONE << sh)))
601       ap[an-1] = MPFR_LIMB_HIGHBIT;
607   if (MPFR_UNLIKELY((ap[an-1] >> (GMP_NUMB_BITS - 1)) == 0))
610       ap[an-1] = MPFR_LIMB_HIGHBIT;
622       cancel -= add_exp; /* OK: add_exp is an int equal to 0 or 1 */
655   MPFR_ASSERTD(ap[an-1] > ~ap[an-1]);