Research On Green Demands Of Embedded System Oriented Compiling Technique

As the widely popularization and application of portable smart embedded devices, the quality of people’s life has been greatly improved. However, it makes the problems of resources and environments get worse. The green demands with the target of low energy and low pollution has become the inevitable choice for sustainable development of modern society.To reduce the energy consumption of embedded systems, improve the utilization of various resources, and reduce unnecessary equipment wear and tear for reducing e-waste and other harmful substances emission rates, on the one hand, we need to improve the materials and manufacturing of hardware devices. On the other hand, suitable software optimizations are also needed to maximize the effectiveness of various low-power hardware devices to meet the growing demand for green. As the software development and language translation tools, compiler can not only apply the suitable optimizations to guide the generated program has a high green indeicators by combining the specific embedded system hardware characteristics, but also help the programmer find the green-related errors such as energy bug as early as possible by using the analysis results form the program translation. It can improve the software quality and reduce resource and energy consumption by testing and debugging. To optimize the software systemically and automatically, compiler is one of best selection.However, tranditional compilers mainly focus on the performance of software and fewer consider the green factors such as energy and utilization of resource. Performance optimization and green optimization are not always the same. Performance optimization often needs to sacrifice the green targets that need more registers and higher processor’s voltage to increase the running speed. We cannot simply apply the traditional optimization methods to get the green factors improved. Secondly, the traditional auxiliary information supplied by compiler mainly concentrated on programming language syntax errors and other security related information such as null pointer, array bounds and other functional errors. The green related errors such as energy bug are often, not functional errors, the information given in the traditional compiler is useless for the detection of such errors, so the new detecting methods needed to further studied. To compensate for the drawback of traditional compiler in green optimization, the paper analyzes the green demands of embedded systems and optimizes the software in compiling processes to meet the growing demand for green such as getting low energy consumption, balancing the utilization of varied resources to increase the resources utilizations. The mainly contents and innovations are as follows.1. Combining with green related conception and the functional of compiler itself, it gives the definition of green compiler and illustrate the mainly objection of optimizations and features. Then, the formal green evaluation model is described according to the definition to effectively guide the green compilation optimization.2. To maximize the energy efficiency of timing speculative processor, reduce the timing errors caused by forwarding, a data dependency based green evaluation factor is constructed and a game model based instruction scheduling method is proposed. It formalizes the instruction scheduling to strategies selection in game model and increases the clock cycle of read-after-write dependency that can reduce the forwarding to improve the power efficiency of timing speculative processor. And for bus system by bus-invert coding, the invert information based green evaluation model is constructed and a feedback guided instruction scheduling method is proposed. It combines the characteristical of bus-invert coding and dynamic feedback profiling information to reduce the frequency of buses and also balance the inverts between buses which can improve the green indicator significantly.3. Different data assignment strategies significantly influence the utilization of storage resourses and also total energy. In order to further improve the green indicator of the system, memory hierarchy characteristics and green related factors of memory are analyzed. Based on the green evaluation model, the exchangeable class instruction reordering optimization method, extended graph coloring register reallocation optimization method and stack data reallocation method are designed to reorder the memory cells and registers in the backend of compiler. It can obtain a more balanced access frequency to registers and stack memory cell, reduce the dynamic power of instruction data bus invert. Meanwhile, to further improve green indicators of the system, the iterative optimization on the first two optimization method is applied which makes the utilization of registers get more balanced and dynamic energy get lower.4. In order to improve the green quality of software, reduce the energy consumption caused energy bug, the paper concludes the characteristics of energy bugs, and designs the energy bug detection and location methods combined with the symbolic execution technology. It firstly analyzes one single function to get its symbolic execution information. And then based on the single function symbol information, the interprocedural analysis is processed to obtain the global accurate execution overhead, lock variable matching and other related information to detect the corresponding energy bugs. Meanwhile, the symbolic execution records corresponding branch path information. It can not only be used to generate the corresponding test cases, and also to locate the position of errors combined with constraint solver which helps to develop the high green indicator software.