Remove memset for the case no any mask

onnxruntime/contrib_ops/cpu/bert/attention_cpu_base.h

@@ -140,17 +140,6 @@ class AttentionCPUBase : public AttentionBase {
       if (mask_data != nullptr) {
         PrepareMask(mask_index, mask_index_dims, mask_data,
                     causal, batch_size, sequence_length, past_sequence_length, mask_filter_value_);
-      } else {  // no any mask
-        const int memset_loop_len = batch_size * num_heads_;
-        const double memset_cost = static_cast<double>(sequence_length) * total_sequence_length;
-
-        ThreadPool::TryParallelFor(tp, memset_loop_len, memset_cost, [&](std::ptrdiff_t begin, std::ptrdiff_t end) {
-          for (std::ptrdiff_t i = begin; i != end; ++i) {
-            const int output_offset = static_cast<int>(i) * sequence_length * total_sequence_length;
-            T* output = attention_probs + output_offset;
-            memset(output, 0, static_cast<size_t>(sequence_length) * total_sequence_length * sizeof(T));
-          }
-        });
       }
 
       const int loop_len = batch_size * num_heads_;
@@ -188,7 +177,7 @@ class AttentionCPUBase : public AttentionBase {
           // B: K'               (B x N x) T x H          (B x N x) H x T        H x T
           // C: attention_probs  (B x N x) S x T          (B x N x) S x T        S x T
           math::Gemm<T, ThreadPool>(CblasNoTrans, CblasTrans, sequence_length, total_sequence_length, head_size, alpha,
-                                    Q + q_input_chunk_length * i, k, 1.0,
+                                    Q + q_input_chunk_length * i, k, mask_data != nullptr ? 1.0 : 0.0,
                                     output, nullptr);
 
           if (relative_position_bias_data != nullptr) {