INSTRUCTION METHOD FOR FACILITATING EFFICIENT CODING AND INSTRUCTION FETCH OF LOOP CONSTRUCT

摘要

Instruction set techniques have been developed to identify explicitly the beginning of a loop body and to code a conditional loop-end in ways that allow a processor implementation to efficiently manage an instruction fetch buffer and/or entries in an instruction cache. In particular, for some computations and processor implementations, a machine instruction is defined that identifies a loop start, stores a corresponding loop start address on a return stack (or in other suitable storage) and directs fetch logic to take advantage of the identification by retaining in a fetch buffer or instruction cache the instruction(s) beginning at the loop start address, thereby avoiding usual branch delays on subsequent iterations of the loop. A conditional loop-end instruction can be used in conjunction with the loop start instruction to discard (or simply mark as no longer needed) the loop start address and the loop body instructions retained in the fetch buffer or instruction cache.