Godson ¢ñ-based Global Register Allocation

Register allocation is an important optimization of compiler back end. Register allo-cator determines which of the values, including variable, temporaries ,and large constants, that might profitably be in a machine's registers should be in registers at each pointin the execution of a program. Physical registers have shorter access time and fewernumbers compared with memory cells. According to the locality of program execution,putting frequently used values into registers can reduce the cost of memory access ,andthus improve the performance of programs. Register allocation can be divided into twocategories: global register allocation and local register allocation. The scope of local regis-ter allocation is in one basic block, but the scopes of global register allocation are programunits and regions. Therefore, global register allocation is more complex and e?ective thanthat of local register allocation. Graph coloring is a highly e?ective approach to globalregister allocation. In this paper, we should study priority-based register allocation, whichis a e?ective method of global register allocation. Our contributions includes followingaspects:1. Design and implement a register allocator which can support register pair and is adi?erent solution compared with that of gcc compiler. The e?ect of live range splittingof is also evaluated in the GODSON I. The result shows that live range splitting canimprove the quality of register allocation e?ectively.2. Evaluate the e?ect of di?erent priority functions in GODSON I. Two potent priorityfunction(improved normalized priority function and calling convention based priorityfunction) are also proposed and the result shows that they can greatly improve thequality of register allocation.