公开(公告)号：US4477872A

公开(公告)日：1984-10-16

申请号：US339561

申请日：1982-01-15

申请人： Jacques J. Losq ,  Gururaj S. Rao ,  Howard E. Sachar

发明人： Jacques J. Losq ,  Gururaj S. Rao ,  Howard E. Sachar

IPC分类号： G06F9/38

CPC分类号： G06F9/3844

摘要： A method and apparatus predicting the outcome of a conditional branch instruction based on the previous performance of the branch, rather than on the instruction fields. The prediction of the outcome of a conditional branch instruction is performed utilizing a table that records the history of the outcome of the branch at a given memory location. A decode-time history table (DHT) is utilized. The DHT attempts to guess only the outcome of a conditional branch instruction, but not its target address. Thus, it can only be used to guess the branch outcomes at decode time when the target address is available. During the decoding of a conditional branch instruction, a table is accessed using the memory address of the branch instruction itself or some portions thereof. The table records the history of the outcomes of the branch at this memory location up to the congruence of the table size. A combinational circuit determines the guess (taken or not taken) from the branch history as provided by the table.

摘要翻译： 一种方法和装置，其基于分支的先前性能而不是指令字段来预测条件分支指令的结果。 使用在给定存储器位置记录分支的结果的历史的表来执行条件分支指令的结果的预测。 使用解码时间历史表（DHT）。 DHT尝试仅猜测条件分支指令的结果，而不是其目标地址。 因此，当目标地址可用时，它只能用于在解码时猜测分支结果。 在条件转移指令的解码期间，使用分支指令本身的存储器地址或其某些部分访问表。 该表记录了该记录位置上分支结果的历史记录，直到表格大小一致。 组合电路确定从表中提供的分支历史中的猜测（取或未采用）。