| 摘要 |
A line predictor is configured to speculatively fetch instructions following a branch instruction. The line predictor stores a plurality of lines that each contain instruction line information. Each line stored by the line predictor includes a fetch address, information regarding one or more instructions, and one or more next fetch addresses. In response to receiving a fetch address, the line predictor is configured to provide instruction line information corresponding to the one or more instructions located at the fetch address to an alignment unit. The line predictor is also configured to provide a next fetch address associated with the fetch address to an instruction cache for speculative fetching and to a branch prediction unit for a branch prediction. The next fetch address is further fed back into the line predictor to generate the instruction line information associated with it and a subsequent next fetch address. A next fetch address may be the sequential address following the last instruction associated with the instruction line information of the fetch address. If an instruction within the instruction line information of the fetch address is a branch instruction, however, the next fetch address may be the target address of the branch instruction. The branch prediction unit is configured to generate a branch prediction in response to receiving a next fetch address if a branch instruction is detected in the instruction line information of the next fetch address. The branch prediction is then compared to a subsequent next fetch address. If the branch prediction differs from a subsequent next fetch address, operations that were initiated using the subsequent next fetch address are canceled, the subsequent next fetch address is updated in the line predictor, and the updated subsequent next fetch address is refetched. |
