Shift prefix instruction decoder for modifying register information necessary for decoding the target instruction

Abstract

The data processing device and electronic equipment of the present invention perform pipeline control and include a fetch circuit which fetches instruction codes of a plurality of instructions in instruction queues. A prefix instruction decoder circuit performs a decode processing only on a prefix instruction. The prefix instruction decoder circuit receives the instruction code before decoding, judges whether or not the instruction is a given prefix instruction, and causes a target instruction to modify an information register to store information necessary for decoding a target instruction when the instruction is the given prefix instruction. A decoder circuit receives each of the instruction codes of the instructions other than the prefix instruction as a decode instruction and decodes the decode instruction. When the decode instruction is a target instruction, the target instruction modified by the prefix instruction is decoded based on the target instruction modifying information.