INSTRUCTION PRE-DECODING OF MULTIPLE INSTRUCTION SETS

PROBLEM TO BE SOLVED: To provide instruction pre-decoding of multiple instruction sets. SOLUTION: A data processing apparatus comprises a pre-decoding circuit 10 having a function of generating pre-decoded instructions which are stored within instruction cache 20. The pre-decoded instructions from the instruction cache 20 are read by decoding circuits 45, 50, 46 and used to form control signals that control corresponding processing operations. The originally fetched program instructions may belong to respective ones of a plurality of instruction sets. Instructions from one instruction set are pre-decoded by the pre-decoding circuit 10 into pre-decoded instructions having a shared format to represent shared functionality with corresponding instructions taken from other instruction sets. This allows a shared portion of the decoding circuit to generate control signals with respect to the shared functionality of instructions from the different instruction sets. COPYRIGHT: (C)2009,JPO&INPIT