  Deep learning is being used extensively in a variety of software engineering
tasks, e.g., program classification and defect prediction. Although the
technique eliminates the required process of feature engineering, the
construction of source code model significantly affects the performance on
those tasks. Most recent works was mainly focused on complementing AST-based
source code models by introducing contextual dependencies extracted from CFG.
However, all of them pay little attention to the representation of basic
blocks, which are the basis of contextual dependencies.
  In this paper, we integrated AST and CFG and proposed a novel source code
model embedded with hierarchical dependencies. Based on that, we also designed
a neural network that depends on the graph attention mechanism.Specifically, we
introduced the syntactic structural of the basic block, i.e., its corresponding
AST, in source code model to provide sufficient information and fill the gap.
We have evaluated this model on three practical software engineering tasks and
compared it with other state-of-the-art methods. The results show that our
model can significantly improve the performance. For example, compared to the
best performing baseline, our model reduces the scale of parameters by 50\% and
achieves 4\% improvement on accuracy on program classification task.

Software Engineering;Machine Learning