MULTIPLE INSTRUCTION PREPROCESSING SYSTEM WITH DATA DEPENDENCY RESOLUTION

A method of preprocessing multiple instructions prior to execution in a digital computer, and of avoiding the preprocessing of an instruction to read a register prior to the modification of the contents of that register by a preceding instruction; the method being characterised by: generating a composite write mask having a bit set for each register whose contents are to be modified by at least one decoded but not-yet-executed instruction preceding the said instruction; and stalling the processing of the said instruction when a register to be read by the said instruction is a register corresponding to a bit set in the composite write mask. The method also extends to the avoiding of the preprocessing of an instruction to modify the contents of a register prior to the reading of that register by a preceding instruction.