Design tools for application specific instruction set processors (ASIPs) are an important discipline in systemlevel design for wireless communications and other embedded application areas. Some ASIPs are still designed completely from scratch to meet extreme efficiency demands. However, there is also a trend towards use of partially predefined, configurable RISC-like embedded processor cores that can be quickly tuned to given applications by means of instruction set extension (ISE) techniques. While the problem of optimized ISE synthesis has been studied well from a theoretical perspective, there are still few approaches to an overall HW/SW design flow for configurable cores that take all real-life constraints into account. In this paper, we therefore present a novel procedure for automated ISE synthesis that accommodates both user-specified and processor-specific constraints in a flexible way and that produces valid, optimized ISE solutions in short time. Driven by an advanced application C code analysis/profiling frontend, the ISE synthesis core algorithm is embedded into a complete design flow, where the backend is formed by a state-of-the-art industrial tool for processor configuration, ISE HW synthesis, and SW tool retargeting. The proposed design flow, including ISE synthesis, is demonstrated via several benchmarks for the MIPS CorExtend configurable RISC processor platform.

With the growing number of programmable processing elements in today's MultiProcessor System-on-Chip (MPSoC) designs, the synergy required for the development of the hardware architecture and the software running on them is also increasing. In MPSoC development environment, changes in the hardware architecture can bring in extensive re-partitioning or re-parallelization of the software architecture. Fast and accurate functional simulation and performance estimation techniques are needed to cope with this co-design problem at the early phases of MPSoC design space exploration. The current paper addresses this issue by introducing a framework which combines hybrid simulation, cache simulation and online trace-driven replay techniques to accurately predict performance of programmable elements in an MPSoC environment. The resulting simulation technique can easily cope with the continuous re-organizations of software architectures during an Instruction Set Simulator (ISS) based design process. Experimental results show that this framework can improve system simulation speed by 3-5× on average while achieving accuracy closely comparable to traditional ISSes.

Instruction Set Simulators (ISSes) are important tools for cross-platform software development. The simulation speed is a major concern and many approaches have been proposed to improve the performance of ISSes. A prevalent technique is compiled simulation, which translates target programs into host instructions. But orders of magnitude of speed deterioration is inevitable since the difference between target and host Instruction Set Architectures (ISAs) can be large. An alternative is to emulate the program without sticking to binary compatibility. The performance problem is solved by using native execution. However, these emulators either require a special programming language, or a given Application Programming Interface (API). Last but not least, it is not trivial to integrate an emulator into a system simulator (which provides devices, external memory, etc., that the embedded programmers do care). In this paper, we propose a fast and generic hybrid simulation approach using virtualization technique to accelerate simulation and simulator-based debugging of C programs. A novel virtual coprocessor (VCP) is introduced as a processing element which executes C functions at high speed. This approach is C89 compliant and compatible with third party libraries and platform dependent code. It is also retargetable and can be integrated with existing ISSes. Two different ISAs are supported at present: MIPS and mAgic DSP. The average execution speed of the coprocessor is about 100 million simulated instructions per second.

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Current Application Specific Instruction set Processor (ASIP) design methodologies are mostly based on iterative architecture exploration that uses Architecture Description Languages (ADLs) and retargetable software development tools. However, for improved design efficiency, additional pre-architecture exploration tools are required to help narrow-down the huge design space and making coarsegrained Instruction Set Architecture (ISA) decisions before detailed ADL modeling. Extensive application code profiling is the key in such early design stages. Based on a novel code instrumentation technology, we present a microprofiling approach that fills the current gap between sourcelevel and instruction-level profilers and combines their advantages w.r.t. speed and accuracy. We show how the microprofiler is embedded into an advanced ASIP design flow and justify its use in a case study to design an MP3 decoder ASIP.