Software pipelining

Software pipelining is a technique used to optimize loops, in a manner that parallels hardware pipelining. It is a type of out-of-order execution, except that the reordering is done by a compiler, or by the programmer in the case of hand-written assembly code, instead of by the processor. Some computer architectures have explicit support for it, notably Intel's IA-64 architecture. Software pipelining is a target code technique for overlapping loop iterations and should be distinguished from modulo scheduling, the currently most effective known compiler technique for generating software pipelined loops. Effective compiler generation of such code dates to the invention of modulo scheduling by Rau and Glaeser.