Mechanism for software register renaming and load speculation in an optimizer

The inventive mechanism operates to optimize program efficiency in a two phase process. In the first phase, the mechanism conducts a dependency analysis on the instructions to determine dependency relationships between the various instructions in an instruction window. The mechanism thereby identifies candidates for register renaming and instruction speculation, and provisionally performs the renaming and speculation operations, while preserving information which is preferably used to reverse these operations in the second phase if it is determined that the operations may be effectively rescheduled. In the second phase, the mechanism determines whether the optimizing operations, renaming and speculation, were beneficial in each case. Each instruction for which the mechanism finds the optimizing operation to be beneficial will generally remain in optimized form. Optimizing operations found not be beneficial are generally reversed by the mechanism. The mechanism thus selectively uses renaming and speculation operations so as to ensure that the benefits preferably outweigh the costs of the operation in each case.