Predictive fetching and decoding for selected instructions

摘要

Predictive fetching and decoding for selected instructions (e.g., operating system instructions, hypervisor instructions or other such instructions). A determination is made that a selected instruction, such as a system call instruction, an asynchronous interrupt, a return from system call instruction or return from asynchronous interrupt, is to be executed. Based on determining that such an instruction is to be executed, a predicted address is determined for the selected instruction, which is the address to which processing transfers in order to provide the requested services. Then, fetching of instructions beginning at the predicted address prior to execution of the selected instruction is commenced. Further, speculative state relating to a selected instruction, including, for instance, an indication of the privilege level of the selected instruction or instructions executed on behalf of the selected instruction, is predicted and maintained.

主权项

1. A computer program product for facilitating processing within a processing environment, the computer program product comprising:
a non-transitory computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method, the method comprising:
predicting that a selected instruction is to execute in a pipelined processor, the pipelined processor having a plurality of stages of processing including an execute stage, and the selected instruction having a first privilege level and one or more other instructions executing in the pipelined processor having a second privilege level different from the first privilege level;based on predicting the selected instruction is to execute, predicting an entry address for the selected instruction and operating state associated therewith, the entry address indicating a location at which an instruction is to be fetched based on the selected instruction, and the operating state comprising a predicted privilege level for the instruction at the entry address;storing the predicted operating state in a data structure coupled to a decode unit of the processing environment;based on predicting the entry address, fetching the instruction at the entry address prior to the selected instruction reaching the execute stage; andinitiating decoding of the fetched instruction based on the predicted operating state, the decode unit to decode the fetched instruction based on the predicted operating state.