| 摘要 |
PURPOSE:To speed up a branch on counting (BCT) by making a branch history table have forecasting information as to whether an updated data is '1' or not. CONSTITUTION:An instruction address and a branch destination address of a BCT instruction from a write register 2 are stored in a branch history table BHT 6, and also forecasting information which has detected whether the contents of a general register 4 are '1' or not, by a decoder is stored. When a prefetch of an instruction is started, whether the BCT instruction is registered in the BHT 6 or not is retrieved by a comparator 7. When the BCT instruction is detected, a controlling circuit 8 effectuates AND gates 11, 12. Subsequently, the forecasting information is read out of the BHT 6, and whether a branching is successful or unsuccessful is decided by the gates 11, 12. When the branching is successful, the controlling circuit 8 sets the branch destination address to a register 9 from the gate 11. When it is unsuccessful, the controlling circuit 8 does not output a set signal to the register 9 from the gate 12.
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