--- a/libtommath/bn_mp_reduce.c	Tue May 26 23:27:26 2020 +0800
+++ b/libtommath/bn_mp_reduce.c	Tue May 26 17:36:47 2020 +0200
@@ -1,86 +1,76 @@
 #include "tommath_private.h"
 #ifdef BN_MP_REDUCE_C
-/* LibTomMath, multiple-precision integer library -- Tom St Denis
- *
- * LibTomMath is a library that provides multiple-precision
- * integer arithmetic as well as number theoretic functionality.
- *
- * The library was designed directly after the MPI library by
- * Michael Fromberger but has been written from scratch with
- * additional optimizations in place.
- *
- * SPDX-License-Identifier: Unlicense
- */
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
 
 /* reduces x mod m, assumes 0 < x < m**2, mu is
  * precomputed via mp_reduce_setup.
  * From HAC pp.604 Algorithm 14.42
  */
-int mp_reduce(mp_int *x, const mp_int *m, const mp_int *mu)
+mp_err mp_reduce(mp_int *x, const mp_int *m, const mp_int *mu)
 {
    mp_int  q;
-   int     res, um = m->used;
+   mp_err  err;
+   int     um = m->used;
 
    /* q = x */
-   if ((res = mp_init_copy(&q, x)) != MP_OKAY) {
-      return res;
+   if ((err = mp_init_copy(&q, x)) != MP_OKAY) {
+      return err;
    }
 
    /* q1 = x / b**(k-1)  */
    mp_rshd(&q, um - 1);
 
    /* according to HAC this optimization is ok */
-   if ((mp_digit)um > ((mp_digit)1 << (DIGIT_BIT - 1))) {
-      if ((res = mp_mul(&q, mu, &q)) != MP_OKAY) {
+   if ((mp_digit)um > ((mp_digit)1 << (MP_DIGIT_BIT - 1))) {
+      if ((err = mp_mul(&q, mu, &q)) != MP_OKAY) {
+         goto CLEANUP;
+      }
+   } else if (MP_HAS(S_MP_MUL_HIGH_DIGS)) {
+      if ((err = s_mp_mul_high_digs(&q, mu, &q, um)) != MP_OKAY) {
+         goto CLEANUP;
+      }
+   } else if (MP_HAS(S_MP_MUL_HIGH_DIGS_FAST)) {
+      if ((err = s_mp_mul_high_digs_fast(&q, mu, &q, um)) != MP_OKAY) {
          goto CLEANUP;
       }
    } else {
-#ifdef BN_S_MP_MUL_HIGH_DIGS_C
-      if ((res = s_mp_mul_high_digs(&q, mu, &q, um)) != MP_OKAY) {
-         goto CLEANUP;
-      }
-#elif defined(BN_FAST_S_MP_MUL_HIGH_DIGS_C)
-      if ((res = fast_s_mp_mul_high_digs(&q, mu, &q, um)) != MP_OKAY) {
-         goto CLEANUP;
-      }
-#else
-      {
-         res = MP_VAL;
-         goto CLEANUP;
-      }
-#endif
+      err = MP_VAL;
+      goto CLEANUP;
    }
 
    /* q3 = q2 / b**(k+1) */
    mp_rshd(&q, um + 1);
 
    /* x = x mod b**(k+1), quick (no division) */
-   if ((res = mp_mod_2d(x, DIGIT_BIT * (um + 1), x)) != MP_OKAY) {
+   if ((err = mp_mod_2d(x, MP_DIGIT_BIT * (um + 1), x)) != MP_OKAY) {
       goto CLEANUP;
    }
 
    /* q = q * m mod b**(k+1), quick (no division) */
-   if ((res = s_mp_mul_digs(&q, m, &q, um + 1)) != MP_OKAY) {
+   if ((err = s_mp_mul_digs(&q, m, &q, um + 1)) != MP_OKAY) {
       goto CLEANUP;
    }
 
    /* x = x - q */
-   if ((res = mp_sub(x, &q, x)) != MP_OKAY) {
+   if ((err = mp_sub(x, &q, x)) != MP_OKAY) {
       goto CLEANUP;
    }
 
    /* If x < 0, add b**(k+1) to it */
    if (mp_cmp_d(x, 0uL) == MP_LT) {
       mp_set(&q, 1uL);
-      if ((res = mp_lshd(&q, um + 1)) != MP_OKAY)
+      if ((err = mp_lshd(&q, um + 1)) != MP_OKAY) {
          goto CLEANUP;
-      if ((res = mp_add(x, &q, x)) != MP_OKAY)
+      }
+      if ((err = mp_add(x, &q, x)) != MP_OKAY) {
          goto CLEANUP;
+      }
    }
 
    /* Back off if it's too big */
    while (mp_cmp(x, m) != MP_LT) {
-      if ((res = s_mp_sub(x, m, x)) != MP_OKAY) {
+      if ((err = s_mp_sub(x, m, x)) != MP_OKAY) {
          goto CLEANUP;
       }
    }
@@ -88,10 +78,6 @@
 CLEANUP:
    mp_clear(&q);
 
-   return res;
+   return err;
 }
 #endif
-
-/* ref:         HEAD -> master, tag: v1.1.0 */
-/* git commit:  08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
-/* commit time: 2019-01-28 20:32:32 +0100 */