1. A system for performing register renaming of source registers in a processor having an instruction window for storing a group of instructions to be executed by the processor, wherein new instructions are added to the instruction window when the processor retires preceding instructions, the system comprising: first means for storing source and destination register addresses for the instructions in the instruction window; second means, coupled to said first means, for accessing said stored source and destination register addresses for performing a data dependency check for each new instruction added to the instruction window; and third means, coupled to said second means, for renaming source register addresses for instructions having dependencies as determined by said second means.