Reducing the cost of branches by using registers

摘要

In an attempt to reduce the number of operand memory references, many RISC machines have thirty-two or more general-purpose registers (e.g., MIPS, ARM, Spectrum, 88K). Without special compiler optimizations, such as inlining or interprocedural register allocation, it is rare that a compiler will use a majority of these registers for a function. This paper explores the possibility of using some of these registers to hold branch target addresses and the corresponding instruction at each branch target. To evaluate the effectiveness of this scheme, two machines were designed and emulated. One machine had thirty-two general-purpose registers used for data references, while the other machine had sixteen data registers and sixteen registers used for branching. The results show that using registers for branching can effectively reduce the cost of transfers of control.