RandomX: returned old soft AES impl and auto-select between the two

src/crypto/randomx/soft_aes.cpp

@@ -28,6 +28,9 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
 #include "crypto/randomx/soft_aes.h"
+#include "crypto/randomx/aes_hash.hpp"
+#include "base/tools/Chrono.h"
+#include <vector>
 
 alignas(64) uint32_t lutEnc0[256];
 alignas(64) uint32_t lutEnc1[256];
@@ -117,3 +120,43 @@ static struct SAESInitializer
 		}
 	}
 } aes_initializer;
+
+static uint32_t softAESImpl = 1;
+
+uint32_t GetSoftAESImpl()
+{
+	return softAESImpl;
+}
+
+void SelectSoftAESImpl()
+{
+	constexpr int test_length_ms = 100;
+	double speed[2];
+
+	for (int i = 0; i < 2; ++i)
+	{
+		std::vector<uint8_t> scratchpad(10 * 1024);
+		uint8_t hash[64] = {};
+		uint8_t state[64] = {};
+
+		uint64_t t1, t2;
+
+		uint32_t count = 0;
+		t1 = xmrig::Chrono::highResolutionMSecs();
+		do {
+			if (i == 0) {
+				hashAndFillAes1Rx4<1>(scratchpad.data(), scratchpad.size(), hash, state);
+			}
+			else {
+				hashAndFillAes1Rx4<2>(scratchpad.data(), scratchpad.size(), hash, state);
+			}
+			++count;
+
+			t2 = xmrig::Chrono::highResolutionMSecs();
+		} while (t2 - t1 < test_length_ms);
+
+		speed[i] = count * 1e3 / (t2 - t1);
+	}
+
+	softAESImpl = (speed[0] > speed[1]) ? 1 : 2;
+}