Sun Performance and Tuning: Java™ and the Internet, Second Edition

Register Windows and Different SPARC CPUs

SPARC defines an instruction set that uses 32 integer registers in a conventional way but has many sets of these registers arranged in overlapping register windows. A single instruction is used to switch in a new set of registers very quickly. The overlap means that 8 of the registers from the previous window are part of the new window, and these are used for fast parameter passing between subroutines. A further 8 global registers are always the same; of the 24 that make up a register window, 8 are passed in from the previous window, 8 are local, and 8 will be passed out to the next window. This usage is described further in The SPARC Architecture Manual Version 8 and Version 9 both published as books ...