公开(公告)号：US5333283A

公开(公告)日：1994-07-26

申请号：US784335

申请日：1991-10-29

申请人： Philip G. Emma ,  David R. Kaeli

发明人： Philip G. Emma ,  David R. Kaeli

IPC分类号： G06F9/32 ,  G06F9/38 ,  G06F9/345

CPC分类号： G06F9/30061 ,  G06F9/3844

摘要： A method and apparatus is disclosed for folding the execution of a multi-way branch or switch based upon an operand (e.g.,the block of instructions normally associated with a case statement) into a single instruction. This insulates branch prediction mechanisms from making incorrect predictions that are normally associated with a multi-way branch. A table saves the past history of multi-way branch execution. This table contains three fields: the starting address of a multi-way branch; a value of the operand used to execute that multi-way branch in the past; and the larger target address generated by that multi-way branch in the past when that particular operand value was used. In accordance with one embodiment of this invention, other branch prediction mechanisms (such as a Branch History Table or Decode History Table) are disabled from redirecting instruction fetching during execution of a multi-way branch in an instruction stream.

摘要翻译： 公开了一种用于基于操作数（例如，通常与案例陈述相关联的指令块）将多路分支或交换机的执行折叠成单个指令的方法和装置。 这使得分支预测机制不能做出通常与多路分支相关联的错误预测。 表保存了多路分支执行的过去历史。 该表包含三个字段：多路分支的起始地址; 过去用于执行该多路分支的操作​​数的值; 以及当使用该特定操作数值时，该多路分支在过去生成的较大的目标地址。 根据本发明的一个实施例，在指令流中的多路分支的执行期间禁止其他分支预测机制（诸如分支历史表或解码历史表）重定向指令获取。