Decompression bit processing with a general purpose alignment tool

Abstract

A method and apparatus for performing single-instruction bit field extraction and for counting a number of leading zeros in a sequence of bits on a general purpose processor are provided. The fast bit extraction operations are accomplished by executing a first instruction for extracting an arbitrary number of bits of a sequence of bits stored in two or more source registers of the processor starting at an arbitrary offset and the storing the extracted bits in a destination register. Both the source and the destination registers are specified by the instruction. In addition, a second instruction is provided for counting the number of leading zeros in a sequence of bits stored in two or more source registers of the processor and then storing a binary value representing the number of leading zeros in a destination register. Again the source and the destination registers are specified by the second instruction. Both the first and the second instructions are pipelined to obtain an effective throughput of one instruction every cycle, respectively. As a result, bit extraction operations are performed very efficiently by the processor, thereby reducing the overall processing time required to compress and decompress multimedia data.