Simplify crypto_sort_uint32, delete signed variant.

diff --git a/sntrup761.c b/sntrup761.c
index 96d2eb96b81fc8a2182aa3ef52d45065918e2d6f..f2ffca1a1f941ba361ee5f5fd0bebdb979e83da5 100644 (file)
--- a/sntrup761.c
+++ b/sntrup761.c
@@ -55,24 +55,20 @@ crypto_hash_sha512 (unsigned char *out, const unsigned char *in, int inlen)
   sha512_digest (&ctx, out);
 }
 
-/* from supercop-20201130/crypto_sort/int32/portable4/int32_minmax.inc */
-#define int32_MINMAX(a,b) \
+#define uint32_MINMAX(a,b) \
 do { \
-  int64_t ab = (int64_t)b ^ (int64_t)a; \
-  int64_t c = (int64_t)b - (int64_t)a; \
-  c ^= ab & (c ^ b); \
-  c >>= 31; \
-  c &= ab; \
-  a ^= c; \
-  b ^= c; \
+  uint64_t d = (uint64_t)b - (uint64_t)a; \
+  uint32_t masked_d = (d >> 32) & d; \
+  a += masked_d; \
+  b -= masked_d; \
 } while(0)
 
-/* from supercop-20201130/crypto_sort/int32/portable4/sort.c */
+/* Based on supercop-20201130/crypto_sort/int32/portable4/sort.c, but
+   using uint32_t rather than int32_t. */
 static void
-crypto_sort_int32 (void *array, long long n)
+crypto_sort_uint32 (uint32_t *x, long long n)
 {
   long long top, p, q, r, i, j;
-  int32_t *x = array;
 
   if (n < 2)
     return;
@@ -86,11 +82,11 @@ crypto_sort_int32 (void *array, long long n)
       while (i + 2 * p <= n)
        {
          for (j = i; j < i + p; ++j)
-           int32_MINMAX (x[j], x[j + p]);
+           uint32_MINMAX (x[j], x[j + p]);
          i += 2 * p;
        }
       for (j = i; j < n - p; ++j)
-       int32_MINMAX (x[j], x[j + p]);
+       uint32_MINMAX (x[j], x[j + p]);
 
       i = 0;
       j = 0;
@@ -101,9 +97,9 @@ crypto_sort_int32 (void *array, long long n)
              {
                if (j == n - q)
                  goto done;
-               int32_t a = x[j + p];
+               uint32_t a = x[j + p];
                for (r = q; r > p; r >>= 1)
-                 int32_MINMAX (a, x[j + r]);
+                 uint32_MINMAX (a, x[j + r]);
                x[j + p] = a;
                ++j;
                if (j == i + p)
@@ -116,9 +112,9 @@ crypto_sort_int32 (void *array, long long n)
            {
              for (j = i; j < i + p; ++j)
                {
-                 int32_t a = x[j + p];
+                 uint32_t a = x[j + p];
                  for (r = q; r > p; r >>= 1)
-                   int32_MINMAX (a, x[j + r]);
+                   uint32_MINMAX (a, x[j + r]);
                  x[j + p] = a;
                }
              i += 2 * p;
@@ -127,9 +123,9 @@ crypto_sort_int32 (void *array, long long n)
          j = i;
          while (j < n - q)
            {
-             int32_t a = x[j + p];
+             uint32_t a = x[j + p];
              for (r = q; r > p; r >>= 1)
-               int32_MINMAX (a, x[j + r]);
+               uint32_MINMAX (a, x[j + r]);
              x[j + p] = a;
              ++j;
            }
@@ -139,23 +135,6 @@ crypto_sort_int32 (void *array, long long n)
     }
 }
 
-/* from supercop-20201130/crypto_sort/uint32/useint32/sort.c */
-
-/* can save time by vectorizing xor loops */
-/* can save time by integrating xor loops with int32_sort */
-
-static void
-crypto_sort_uint32 (void *array, long long n)
-{
-  uint32_t *x = array;
-  long long j;
-  for (j = 0; j < n; ++j)
-    x[j] ^= 0x80000000;
-  crypto_sort_int32 (array, n);
-  for (j = 0; j < n; ++j)
-    x[j] ^= 0x80000000;
-}
-
 /* from supercop-20201130/crypto_kem/sntrup761/ref/uint32.c */
 
 /*