Out-of-Order Execution of Buffered Function Units in Exposed Data Path Architectures

摘要

Some of the newer processor architectures are no longer based on registers in order to increase their potential of instruction-level parallelism. Instead, they expose their data paths to the compiler so that the program is able to directly move data values between function units using suitable instructions. Some of these architectures require a synchronous transfer of data values while others use asynchronous transfers by buffering values. In this paper, we discuss the out-of-order execution of function units of exposed data path architectures with asynchronous data transfers. The execution of these function units may locally deviate from the program order which is in analogy to dynamic scheduling used by processors with out-of-order execution. Since our out-of-order execution has only effects inside the function units, it requires no modifications of the compiler or instruction set. We have implemented different variants on FPGAs, and evaluated these for a set of application scenarios showing that the out-of-order extension can considerably increase the performance of these architectures.