Processor with slave free list that handles overflow of recycled physical registers and method of recycling physical registers in a processor using a slave free list

Abstract

A processor including physical registers, a reorder buffer, a master free list, a slave free list, a master recycle circuit, and a slave recycle circuit. The reorder buffer includes instruction entries in which each entry stores physical register indexes for recycling physical registers. The reorder buffer retires up to N instructions in each processor cycle. Each master and slave free list includes N input ports and stores physical register indexes, in which the master free list stores indexes of physical registers to be allocated to instructions being issued. When an instruction is retired, the master recycle circuit routes a first physical register index stored in an instruction entry of the instruction to an input port of the master free list, and the slave recycle circuit routes a second physical register index stored in the instruction entry of the instruction to an input port of the slave free list.