Combining Source- Level Transformations and Instruction Set Extension

Industry’s demand for flexible embedded solutions providing high performance and short time-to-market has led to the development of configurable and extensible processors. These pre-verified baseline cores allow for some degree of customisation through user-defined instruction set extensions (ISE). The tra-ditional design flow for ISE is based on plain C sources of the target application and, after some ISE identification and synthesis stages, a modified source file is produced with explicit handles to the new machine instructions. We combined the exploration of source-level transformations and ISE identifica-tion to explore potential benefits. We show that the instruction extensions generated by automated tools are heavily influenced by source code structure. Our results demonstrate that a combination of source-level transformations and instruction set extensions can yield average performance improvements of 47%. This outperforms instruction set extensions when applied in isolation, and in extreme cases yields a speedup of 2.85. This work is also described in more detail in [1]