JPS648445A - Data processor equipped with branching predictive function - Google Patents

Abstract

PURPOSE:To immediately replace a branching instruction and instruction length and to execute rapid processing by predicting a branching by means of an address of an instruction executed immediately before the branching instruction. CONSTITUTION:It is supposed that an instruction immediately preceding a conditional branching instruction is read out from an address (a) in an unshown memory. Whether the branching of an instruction in the next address (a+x) is required or not is predicted by a branching forecasting bit corresponding to the address (a) of an instruction stored in a branching forecasting mechanism 4. When the predictive bit does not indicate branching, selectors 12, 15 select registers 11, 14 respectively, a selector 9 selects an inverter 8 and an adder 61 adds branching displacement (b) to a counter 62. In case of a conditional branching instruction to be predicted, the selector 15 selects the instruction length (y) of the register 14, and in case of non-branching, non-conditional branching or an unpredictive conditional branching instruction, selects the register 13 to replace the instruction length of a conditional instruction to be predicted at its branching by branching displacement. When the conditional branching instruction is fetched and decoded in said constitution, data processing can be immediately and rapidly executed and useless time can be omitted.