Improve performance of SP Intel 64-bit asm

RSA: Only constant time copy out when doing private key op
Improve performance of sp_count_bits

wolfcrypt/src/rsa.c

@@ -2951,6 +2951,7 @@ static int RsaPrivateDecryptEx(byte* in, word32 inLen, byte* out,
             /* only copy output if not inline */
             if (outPtr == NULL) {
 #if !defined(WOLFSSL_RSA_VERIFY_ONLY) && !defined(WOLFSSL_RSA_VERIFY_INLINE)
+                if (rsa_type == RSA_PRIVATE_DECRYPT) {
                     word32 i, j;
                     int start = (int)((size_t)pad - (size_t)key->data);
 
@@ -2961,9 +2962,12 @@ static int RsaPrivateDecryptEx(byte* in, word32 inLen, byte* out,
                         /* 0 - no add, -1 add */
                         i += (word32)((byte)(-c));
                     }
-#else
+                }
-                XMEMCPY(out, pad, ret);
+                else
 #endif
+                {
+                    XMEMCPY(out, pad, ret);
+                }
             }
             else
                 *outPtr = pad;

wolfcrypt/src/sp_int.c

@@ -306,12 +306,21 @@ int sp_count_bits(sp_int* a)
         r = 0;
     else {
         d = a->dp[r];
-        r *= DIGIT_BIT;
+        r *= SP_WORD_SIZE;
+        if (d >= (1L << (SP_WORD_SIZE / 2))) {
+            r += SP_WORD_SIZE;
+            while ((d & (1L << (SP_WORD_SIZE - 1))) == 0) {
+                r--;
+                d <<= 1;
+            }
+        }
+        else {
             while (d != 0) {
                 r++;
                 d >>= 1;
             }
         }
+    }
 
     return r;
 }