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+/* mpn_powm -- Compute R = U^E mod M.
+
+ Contributed to the GNU project by Torbjorn Granlund.
+
+ THE FUNCTIONS IN THIS FILE ARE INTERNAL WITH MUTABLE INTERFACES. IT IS ONLY
+ SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
+ GUARANTEED THAT THEY WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
+
+Copyright 2007-2012 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of either:
+
+ * the GNU Lesser General Public License as published by the Free
+ Software Foundation; either version 3 of the License, or (at your
+ option) any later version.
+
+or
+
+ * the GNU General Public License as published by the Free Software
+ Foundation; either version 2 of the License, or (at your option) any
+ later version.
+
+or both in parallel, as here.
+
+The GNU MP Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+for more details.
+
+You should have received copies of the GNU General Public License and the
+GNU Lesser General Public License along with the GNU MP Library. If not,
+see https://www.gnu.org/licenses/. */
+
+
+/*
+ BASIC ALGORITHM, Compute U^E mod M, where M < B^n is odd.
+
+ 1. W <- U
+
+ 2. T <- (B^n * U) mod M Convert to REDC form
+
+ 3. Compute table U^1, U^3, U^5... of E-dependent size
+
+ 4. While there are more bits in E
+ W <- power left-to-right base-k
+
+
+ TODO:
+
+ * Make getbits a macro, thereby allowing it to update the index operand.
+ That will simplify the code using getbits. (Perhaps make getbits' sibling
+ getbit then have similar form, for symmetry.)
+
+ * Write an itch function. Or perhaps get rid of tp parameter since the huge
+ pp area is allocated locally anyway?
+
+ * Choose window size without looping. (Superoptimize or think(tm).)
+
+ * Handle small bases with initial, reduction-free exponentiation.
+
+ * Call new division functions, not mpn_tdiv_qr.
+
+ * Consider special code for one-limb M.
+
+ * How should we handle the redc1/redc2/redc_n choice?
+ - redc1: T(binvert_1limb) + e * (n) * (T(mullo-1x1) + n*T(addmul_1))
+ - redc2: T(binvert_2limbs) + e * (n/2) * (T(mullo-2x2) + n*T(addmul_2))
+ - redc_n: T(binvert_nlimbs) + e * (T(mullo-nxn) + T(M(n)))
+ This disregards the addmul_N constant term, but we could think of
+ that as part of the respective mullo.
+
+ * When U (the base) is small, we should start the exponentiation with plain
+ operations, then convert that partial result to REDC form.
+
+ * When U is just one limb, should it be handled without the k-ary tricks?
+ We could keep a factor of B^n in W, but use U' = BU as base. After
+ multiplying by this (pseudo two-limb) number, we need to multiply by 1/B
+ mod M.
+*/
+
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+
+#undef MPN_REDC_1
+#define MPN_REDC_1(rp, up, mp, n, invm) \
+ do { \
+ mp_limb_t cy; \
+ cy = mpn_redc_1 (rp, up, mp, n, invm); \
+ if (cy != 0) \
+ mpn_sub_n (rp, rp, mp, n); \
+ } while (0)
+
+#undef MPN_REDC_2
+#define MPN_REDC_2(rp, up, mp, n, mip) \
+ do { \
+ mp_limb_t cy; \
+ cy = mpn_redc_2 (rp, up, mp, n, mip); \
+ if (cy != 0) \
+ mpn_sub_n (rp, rp, mp, n); \
+ } while (0)
+
+#if HAVE_NATIVE_mpn_addmul_2 || HAVE_NATIVE_mpn_redc_2
+#define WANT_REDC_2 1
+#endif
+
+#define getbit(p,bi) \
+ ((p[(bi - 1) / GMP_LIMB_BITS] >> (bi - 1) % GMP_LIMB_BITS) & 1)
+
+static inline mp_limb_t
+getbits (const mp_limb_t *p, mp_bitcnt_t bi, int nbits)
+{
+ int nbits_in_r;
+ mp_limb_t r;
+ mp_size_t i;
+
+ if (bi < nbits)
+ {
+ return p[0] & (((mp_limb_t) 1 << bi) - 1);
+ }
+ else
+ {
+ bi -= nbits; /* bit index of low bit to extract */
+ i = bi / GMP_NUMB_BITS; /* word index of low bit to extract */
+ bi %= GMP_NUMB_BITS; /* bit index in low word */
+ r = p[i] >> bi; /* extract (low) bits */
+ nbits_in_r = GMP_NUMB_BITS - bi; /* number of bits now in r */
+ if (nbits_in_r < nbits) /* did we get enough bits? */
+ r += p[i + 1] << nbits_in_r; /* prepend bits from higher word */
+ return r & (((mp_limb_t ) 1 << nbits) - 1);
+ }
+}
+
+static inline int
+win_size (mp_bitcnt_t eb)
+{
+ int k;
+ static mp_bitcnt_t x[] = {0,7,25,81,241,673,1793,4609,11521,28161,~(mp_bitcnt_t)0};
+ for (k = 1; eb > x[k]; k++)
+ ;
+ return k;
+}
+
+/* Convert U to REDC form, U_r = B^n * U mod M */
+static void
+redcify (mp_ptr rp, mp_srcptr up, mp_size_t un, mp_srcptr mp, mp_size_t n)
+{
+ mp_ptr tp, qp;
+ TMP_DECL;
+ TMP_MARK;
+
+ tp = TMP_ALLOC_LIMBS (un + n);
+ qp = TMP_ALLOC_LIMBS (un + 1); /* FIXME: Put at tp+? */
+
+ MPN_ZERO (tp, n);
+ MPN_COPY (tp + n, up, un);
+ mpn_tdiv_qr (qp, rp, 0L, tp, un + n, mp, n);
+ TMP_FREE;
+}
+
+/* rp[n-1..0] = bp[bn-1..0] ^ ep[en-1..0] mod mp[n-1..0]
+ Requires that mp[n-1..0] is odd.
+ Requires that ep[en-1..0] is > 1.
+ Uses scratch space at tp of MAX(mpn_binvert_itch(n),2n) limbs. */
+void
+mpn_powm (mp_ptr rp, mp_srcptr bp, mp_size_t bn,
+ mp_srcptr ep, mp_size_t en,
+ mp_srcptr mp, mp_size_t n, mp_ptr tp)
+{
+ mp_limb_t ip[2], *mip;
+ int cnt;
+ mp_bitcnt_t ebi;
+ int windowsize, this_windowsize;
+ mp_limb_t expbits;
+ mp_ptr pp, this_pp;
+ long i;
+ TMP_DECL;
+
+ ASSERT (en > 1 || (en == 1 && ep[0] > 1));
+ ASSERT (n >= 1 && ((mp[0] & 1) != 0));
+
+ TMP_MARK;
+
+ MPN_SIZEINBASE_2EXP(ebi, ep, en, 1);
+
+#if 0
+ if (bn < n)
+ {
+ /* Do the first few exponent bits without mod reductions,
+ until the result is greater than the mod argument. */
+ for (;;)
+ {
+ mpn_sqr (tp, this_pp, tn);
+ tn = tn * 2 - 1, tn += tp[tn] != 0;
+ if (getbit (ep, ebi) != 0)
+ mpn_mul (..., tp, tn, bp, bn);
+ ebi--;
+ }
+ }
+#endif
+
+ windowsize = win_size (ebi);
+
+#if WANT_REDC_2
+ if (BELOW_THRESHOLD (n, REDC_1_TO_REDC_2_THRESHOLD))
+ {
+ mip = ip;
+ binvert_limb (mip[0], mp[0]);
+ mip[0] = -mip[0];
+ }
+ else if (BELOW_THRESHOLD (n, REDC_2_TO_REDC_N_THRESHOLD))
+ {
+ mip = ip;
+ mpn_binvert (mip, mp, 2, tp);
+ mip[0] = -mip[0]; mip[1] = ~mip[1];
+ }
+#else
+ if (BELOW_THRESHOLD (n, REDC_1_TO_REDC_N_THRESHOLD))
+ {
+ mip = ip;
+ binvert_limb (mip[0], mp[0]);
+ mip[0] = -mip[0];
+ }
+#endif
+ else
+ {
+ mip = TMP_ALLOC_LIMBS (n);
+ mpn_binvert (mip, mp, n, tp);
+ }
+
+ pp = TMP_ALLOC_LIMBS (n << (windowsize - 1));
+
+ this_pp = pp;
+ redcify (this_pp, bp, bn, mp, n);
+
+ /* Store b^2 at rp. */
+ mpn_sqr (tp, this_pp, n);
+#if WANT_REDC_2
+ if (BELOW_THRESHOLD (n, REDC_1_TO_REDC_2_THRESHOLD))
+ MPN_REDC_1 (rp, tp, mp, n, mip[0]);
+ else if (BELOW_THRESHOLD (n, REDC_2_TO_REDC_N_THRESHOLD))
+ MPN_REDC_2 (rp, tp, mp, n, mip);
+#else
+ if (BELOW_THRESHOLD (n, REDC_1_TO_REDC_N_THRESHOLD))
+ MPN_REDC_1 (rp, tp, mp, n, mip[0]);
+#endif
+ else
+ mpn_redc_n (rp, tp, mp, n, mip);
+
+ /* Precompute odd powers of b and put them in the temporary area at pp. */
+ for (i = (1 << (windowsize - 1)) - 1; i > 0; i--)
+ {
+ mpn_mul_n (tp, this_pp, rp, n);
+ this_pp += n;
+#if WANT_REDC_2
+ if (BELOW_THRESHOLD (n, REDC_1_TO_REDC_2_THRESHOLD))
+ MPN_REDC_1 (this_pp, tp, mp, n, mip[0]);
+ else if (BELOW_THRESHOLD (n, REDC_2_TO_REDC_N_THRESHOLD))
+ MPN_REDC_2 (this_pp, tp, mp, n, mip);
+#else
+ if (BELOW_THRESHOLD (n, REDC_1_TO_REDC_N_THRESHOLD))
+ MPN_REDC_1 (this_pp, tp, mp, n, mip[0]);
+#endif
+ else
+ mpn_redc_n (this_pp, tp, mp, n, mip);
+ }
+
+ expbits = getbits (ep, ebi, windowsize);
+ if (ebi < windowsize)
+ ebi = 0;
+ else
+ ebi -= windowsize;
+
+ count_trailing_zeros (cnt, expbits);
+ ebi += cnt;
+ expbits >>= cnt;
+
+ MPN_COPY (rp, pp + n * (expbits >> 1), n);
+
+#define INNERLOOP \
+ while (ebi != 0) \
+ { \
+ while (getbit (ep, ebi) == 0) \
+ { \
+ MPN_SQR (tp, rp, n); \
+ MPN_REDUCE (rp, tp, mp, n, mip); \
+ ebi--; \
+ if (ebi == 0) \
+ goto done; \
+ } \
+ \
+ /* The next bit of the exponent is 1. Now extract the largest \
+ block of bits <= windowsize, and such that the least \
+ significant bit is 1. */ \
+ \
+ expbits = getbits (ep, ebi, windowsize); \
+ this_windowsize = windowsize; \
+ if (ebi < windowsize) \
+ { \
+ this_windowsize -= windowsize - ebi; \
+ ebi = 0; \
+ } \
+ else \
+ ebi -= windowsize; \
+ \
+ count_trailing_zeros (cnt, expbits); \
+ this_windowsize -= cnt; \
+ ebi += cnt; \
+ expbits >>= cnt; \
+ \
+ do \
+ { \
+ MPN_SQR (tp, rp, n); \
+ MPN_REDUCE (rp, tp, mp, n, mip); \
+ this_windowsize--; \
+ } \
+ while (this_windowsize != 0); \
+ \
+ MPN_MUL_N (tp, rp, pp + n * (expbits >> 1), n); \
+ MPN_REDUCE (rp, tp, mp, n, mip); \
+ }
+
+
+#if WANT_REDC_2
+ if (REDC_1_TO_REDC_2_THRESHOLD < MUL_TOOM22_THRESHOLD)
+ {
+ if (BELOW_THRESHOLD (n, REDC_1_TO_REDC_2_THRESHOLD))
+ {
+ if (REDC_1_TO_REDC_2_THRESHOLD < SQR_BASECASE_THRESHOLD
+ || BELOW_THRESHOLD (n, SQR_BASECASE_THRESHOLD))
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_basecase (r,a,n,b,n)
+#define MPN_SQR(r,a,n) mpn_mul_basecase (r,a,n,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) MPN_REDC_1 (rp, tp, mp, n, mip[0])
+ INNERLOOP;
+ }
+ else
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_basecase (r,a,n,b,n)
+#define MPN_SQR(r,a,n) mpn_sqr_basecase (r,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) MPN_REDC_1 (rp, tp, mp, n, mip[0])
+ INNERLOOP;
+ }
+ }
+ else if (BELOW_THRESHOLD (n, MUL_TOOM22_THRESHOLD))
+ {
+ if (MUL_TOOM22_THRESHOLD < SQR_BASECASE_THRESHOLD
+ || BELOW_THRESHOLD (n, SQR_BASECASE_THRESHOLD))
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_basecase (r,a,n,b,n)
+#define MPN_SQR(r,a,n) mpn_mul_basecase (r,a,n,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) MPN_REDC_2 (rp, tp, mp, n, mip)
+ INNERLOOP;
+ }
+ else
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_basecase (r,a,n,b,n)
+#define MPN_SQR(r,a,n) mpn_sqr_basecase (r,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) MPN_REDC_2 (rp, tp, mp, n, mip)
+ INNERLOOP;
+ }
+ }
+ else if (BELOW_THRESHOLD (n, REDC_2_TO_REDC_N_THRESHOLD))
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_n (r,a,b,n)
+#define MPN_SQR(r,a,n) mpn_sqr (r,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) MPN_REDC_2 (rp, tp, mp, n, mip)
+ INNERLOOP;
+ }
+ else
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_n (r,a,b,n)
+#define MPN_SQR(r,a,n) mpn_sqr (r,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) mpn_redc_n (rp, tp, mp, n, mip)
+ INNERLOOP;
+ }
+ }
+ else
+ {
+ if (BELOW_THRESHOLD (n, MUL_TOOM22_THRESHOLD))
+ {
+ if (MUL_TOOM22_THRESHOLD < SQR_BASECASE_THRESHOLD
+ || BELOW_THRESHOLD (n, SQR_BASECASE_THRESHOLD))
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_basecase (r,a,n,b,n)
+#define MPN_SQR(r,a,n) mpn_mul_basecase (r,a,n,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) MPN_REDC_1 (rp, tp, mp, n, mip[0])
+ INNERLOOP;
+ }
+ else
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_basecase (r,a,n,b,n)
+#define MPN_SQR(r,a,n) mpn_sqr_basecase (r,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) MPN_REDC_1 (rp, tp, mp, n, mip[0])
+ INNERLOOP;
+ }
+ }
+ else if (BELOW_THRESHOLD (n, REDC_1_TO_REDC_2_THRESHOLD))
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_n (r,a,b,n)
+#define MPN_SQR(r,a,n) mpn_sqr (r,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) MPN_REDC_1 (rp, tp, mp, n, mip[0])
+ INNERLOOP;
+ }
+ else if (BELOW_THRESHOLD (n, REDC_2_TO_REDC_N_THRESHOLD))
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_n (r,a,b,n)
+#define MPN_SQR(r,a,n) mpn_sqr (r,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) MPN_REDC_2 (rp, tp, mp, n, mip)
+ INNERLOOP;
+ }
+ else
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_n (r,a,b,n)
+#define MPN_SQR(r,a,n) mpn_sqr (r,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) mpn_redc_n (rp, tp, mp, n, mip)
+ INNERLOOP;
+ }
+ }
+
+#else /* WANT_REDC_2 */
+
+ if (REDC_1_TO_REDC_N_THRESHOLD < MUL_TOOM22_THRESHOLD)
+ {
+ if (BELOW_THRESHOLD (n, REDC_1_TO_REDC_N_THRESHOLD))
+ {
+ if (REDC_1_TO_REDC_N_THRESHOLD < SQR_BASECASE_THRESHOLD
+ || BELOW_THRESHOLD (n, SQR_BASECASE_THRESHOLD))
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_basecase (r,a,n,b,n)
+#define MPN_SQR(r,a,n) mpn_mul_basecase (r,a,n,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) MPN_REDC_1 (rp, tp, mp, n, mip[0])
+ INNERLOOP;
+ }
+ else
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_basecase (r,a,n,b,n)
+#define MPN_SQR(r,a,n) mpn_sqr_basecase (r,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) MPN_REDC_1 (rp, tp, mp, n, mip[0])
+ INNERLOOP;
+ }
+ }
+ else if (BELOW_THRESHOLD (n, MUL_TOOM22_THRESHOLD))
+ {
+ if (MUL_TOOM22_THRESHOLD < SQR_BASECASE_THRESHOLD
+ || BELOW_THRESHOLD (n, SQR_BASECASE_THRESHOLD))
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_basecase (r,a,n,b,n)
+#define MPN_SQR(r,a,n) mpn_mul_basecase (r,a,n,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) mpn_redc_n (rp, tp, mp, n, mip)
+ INNERLOOP;
+ }
+ else
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_basecase (r,a,n,b,n)
+#define MPN_SQR(r,a,n) mpn_sqr_basecase (r,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) mpn_redc_n (rp, tp, mp, n, mip)
+ INNERLOOP;
+ }
+ }
+ else
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_n (r,a,b,n)
+#define MPN_SQR(r,a,n) mpn_sqr (r,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) mpn_redc_n (rp, tp, mp, n, mip)
+ INNERLOOP;
+ }
+ }
+ else
+ {
+ if (BELOW_THRESHOLD (n, MUL_TOOM22_THRESHOLD))
+ {
+ if (MUL_TOOM22_THRESHOLD < SQR_BASECASE_THRESHOLD
+ || BELOW_THRESHOLD (n, SQR_BASECASE_THRESHOLD))
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_basecase (r,a,n,b,n)
+#define MPN_SQR(r,a,n) mpn_mul_basecase (r,a,n,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) MPN_REDC_1 (rp, tp, mp, n, mip[0])
+ INNERLOOP;
+ }
+ else
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_basecase (r,a,n,b,n)
+#define MPN_SQR(r,a,n) mpn_sqr_basecase (r,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) MPN_REDC_1 (rp, tp, mp, n, mip[0])
+ INNERLOOP;
+ }
+ }
+ else if (BELOW_THRESHOLD (n, REDC_1_TO_REDC_N_THRESHOLD))
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_n (r,a,b,n)
+#define MPN_SQR(r,a,n) mpn_sqr (r,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) MPN_REDC_1 (rp, tp, mp, n, mip[0])
+ INNERLOOP;
+ }
+ else
+ {
+#undef MPN_MUL_N
+#undef MPN_SQR
+#undef MPN_REDUCE
+#define MPN_MUL_N(r,a,b,n) mpn_mul_n (r,a,b,n)
+#define MPN_SQR(r,a,n) mpn_sqr (r,a,n)
+#define MPN_REDUCE(rp,tp,mp,n,mip) mpn_redc_n (rp, tp, mp, n, mip)
+ INNERLOOP;
+ }
+ }
+#endif /* WANT_REDC_2 */
+
+ done:
+
+ MPN_COPY (tp, rp, n);
+ MPN_ZERO (tp + n, n);
+
+#if WANT_REDC_2
+ if (BELOW_THRESHOLD (n, REDC_1_TO_REDC_2_THRESHOLD))
+ MPN_REDC_1 (rp, tp, mp, n, mip[0]);
+ else if (BELOW_THRESHOLD (n, REDC_2_TO_REDC_N_THRESHOLD))
+ MPN_REDC_2 (rp, tp, mp, n, mip);
+#else
+ if (BELOW_THRESHOLD (n, REDC_1_TO_REDC_N_THRESHOLD))
+ MPN_REDC_1 (rp, tp, mp, n, mip[0]);
+#endif
+ else
+ mpn_redc_n (rp, tp, mp, n, mip);
+
+ if (mpn_cmp (rp, mp, n) >= 0)
+ mpn_sub_n (rp, rp, mp, n);
+
+ TMP_FREE;
+}