A Branch Prediction Scheme Designed For MIPS Instruction Set

Through analyzing the methods of branch prediction proposed in recent years, I bring forward a hybrid branch prediction scheme which adapts well to MIPS instruction set.This hybrid branch prediction scheme is made up of two single prediction methods. One is the method which predicts the branch is always true, the other is the method named Improved G-share. To simplify the complexity of the scheme, I classify the MIPS branch instructions into two categories, namely likely instructions and none-likely instructions. I use the first method to predict the likely instructions and the second to predict others.The Improved G-share scheme is proposed by the author from G-share scheme. The new method takes some bits which reflect the information of the Operating System to substitute some part of the branch history records. With these bits and some other parts of global history records, it can predict the behavior of branch instructions like what G-share scheme does. In Linux, I take the highest bit of PC (program counter), PC31, to put it into reality. After simulations on the C simulator, we find the new method has better performance than G-share in the same hardware complexity. Taking use of the effective information provided by the OS, the branch history record of the Improved G-share scheme needs one bit less than that in the original method.