| 摘要 |
PURPOSE:To prefetch quickly a following correct instruction in case the branch information is wrong by performing a counting action designated by an instruction prior to a counting action carried out by an instruction executing circuit and checking the presence or absence of branch according to the result of said counting action. CONSTITUTION:When a branch instruction is set to an instruction address register 411, it is checked through a branch history table 410 whether or not the information is registered to designate the address of an instruction prefetched by the table 410. If the prefetched instruction is equal to branch instruction, a counting action is carried out previously by an arithmetic circuit 433 prior to the counting action of an instruction executing circuit 407. Then the presence or absence of branch is checked by an operand address conversion stage estimation confirming circuit 425 in response to the result of said counting action. When a wrong instruction prefetching action is carried out, an instruction prefetch control circuit 423 controls to correct the following wrong instruction prefetching action before execution of a prefetched branch instruction. Thus it is possible to perform quickly the following instruction prefetching action.
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