公开(公告)号：US20140181478A1

公开(公告)日：2014-06-26

申请号：US13723974

申请日：2012-12-21

Applicant: ARM LIMITED

Inventor： Cédric Denis Robert AIRAUD ,  Luca Scalabrino ,  Frederic Jean Denis Arsanto ,  Guillaume Schon

IPC: G06F9/30

CPC classification number: G06F9/30145 ,  G06F9/30014 ,  G06F9/30141 ,  G06F9/3857

Abstract: Within a processing pipeline 14, issue control circuitry 12 serves to arbitrate write port availability when floating point multiplication instructions are issued into a floating point pipeline 14. If not operating in a flush-to-zero mode, then depending upon the output operands generated denormal handling may or may not be required. A pessimistic assumption is made upon issue that denormal handling will be required and accordingly the write port reserved is a first predetermined number of processing cycles after the start cycle to take account of use of the denormal handling pipeline stage 20. Partway along the processing pipeline 14, state becomes available which indicates whether or not denormal handling is actually required. If denormal handling is not required and a write port is available one processing cycle earlier, then bypass circuitry 22 serves to bypass the denormal handling pipeline stage 20 such that the output operand will be written to the register bank 16 one processing cycle earlier. Write port usage is tracked by a write port usage scoreboard 26 which is both read and updated by the bypass circuitry 22 when re-arbitrating write port availability partway through a floating point multiplication instruction passing along the pipeline 14.

Abstract translation: 在处理流水线14内，发布控制电路12用于在将浮点乘法指令发布到浮点流水线14时仲裁写端口的可用性。如果不是以冲零模式工作，则根据产生的非正规输出操作数 处理可能或可能不需要。 在需要进行异常处理的问题上做出悲观的假设，因此，保留的写入端口是在开始周期之后的第一预定数量的处理周期，以考虑使用异常处理流水线级20。沿着处理流水线14 ，状态变为可用，其指示是否实际需要异常处理。 如果不需要异常处理并且写入端口可用于处理周期之前，则旁路电路22用于绕过异常处理流水线级20，使得输出操作数将被更早地写入一个处理周期的寄存器组16。 写端口使用记录板26由写入端口使用记分板26跟踪，当通过沿管线14传送的浮点乘法指令重新协商写入端口可用性时，旁路电路22读取和更新。