In recent years

extensible processors have been increasingly applied in various embedded systems. The use of custom instructions around the extensible processors can guarantee flexibility while still meeting the high performance and low power requirements of embedded applications. Automatic custom instruction identification is one of the key issues involved in the design of extensible processors. In view of the application fields and development trends of extensible processors

this survey introduces the research progress of automatic identification of custom instructions in recent years. On this basis

there are four key issues involved in the automatic identification of custom instructions: intermediate representation generation

custom instructions enumeration

custom instructions selection and code transformation. This survey analyzes the advantages and difficulties of previous methods

and presents the summary of the applications of extensible processor in terms of different application fields. Finally

the trends and possible research directions of automatic identification of custom instructions is presented.