Apparatus and method for sharing a branch prediction unit in a microprocessor implementing a two instruction set architecture

摘要

A microprocessor that includes first and second Instruction Fetch Units (IFU) coupled therebetween is provided. The first IFU implements a first Instruction Set Architecture (ISA). The second IFU implements a second ISA. The microprocessor further includes a shared branch prediction unit coupled to the first and second IFU. The shared branch prediction unit stores prediction-related information. In the same paragraph, the present invention also provides a method of performing branch prediction. According to this method, an instruction pointer is provided to a branch prediction unit that stores information shared by first and second IFU. The instruction pointer is generated by one of the first and second IFU that is active. Determination is made of whether an instruction corresponding to the instruction pointer, provided to the branch prediction unit, is a branch instruction, and if so, it is determined if a branch is predicted taken. If the branch instruction is predicted taken, target address corresponding to the branch instruction is provided to the first and second IFU.