A Superscalar Micro-architecture Supporting Aggressive Instruction Scheduling

[[abstract]]A new micro‐architecture, called IAS‐S, has been found to support boosting efficiently. The new system employs a semantic register and a boosting boundary register to eliminate the dependencies caused by conditional branches. In IAS‐S, there is no dedicated shadow register file. Multilevel boosting is supported without multiple copies of register files. Using a semantic register makes it possible to regard any general‐purpose register in IAS‐S as a sequential register or as a shadow register. Thus, idle registers can be used to help reduce spill code or to relieve storage conflicts. This is a distinct advantage over the dedicated shadow register file scheme, in which idle shadow registers cannot be used for such purposes. Furthermore, the IAS‐S micro‐architecture employs multi‐way jump in conjunction with boosting to reduce the time delays due to frequent control transfers