SPECULATIVE LOAD OF LOOK UP TABLE ENTRIES BASED UPON COARSE INDEX CALCULATION IN PARALLEL WITH INDEX CALCULATION

摘要

A data processing apparatus execution unit includes a multiplexer having inputs receiving data from sections of a source data register or registers. The multiplexer selects data from one section to store in a destination data register. The execution unit may zero extend or sign extend the remaining most significant bits of the destination data. In an alternative embodiment, the execution unit includes plural multiplexers, one for each section of the destination data. Each multiplexer received data from each section of the source data register or registers. Special codes in the sections of the second source data register may select 0 fill, 1 fill or sign extension from the next most significant section for each multiplexer.