Apple Inc.
Hierarchical reservation station

Abstract:

Systems, apparatuses, and methods for efficiently scheduling processor instructions for execution. The reservation station in a processor stores instructions in each of a primary buffer and a secondary buffer. Control logic selects a first number of instructions with ready source operands in the primary buffer and a second number of instructions with ready source operands in the secondary buffer. If a third number of instructions to issue from the reservation station is greater than the first number of instructions, then the reservation station issues one or more instructions of the second number of instructions from the secondary buffer to the one or more execution units. Control logic selects a fourth number of instructions in the secondary buffer to transfer to the primary buffer, and cancels the transfer of a given instruction in response to determining the given instruction has issued to the one or more execution units.