MICROPROCESSOR INSTRUCTIONS FOR EFFICIENT BIT STREAM EXTRACTIONS

摘要

A method of extracting bits of a bit stream including retrieving bits from the bit stream into an accumulator, specifying a size value specifying a number of bits to extract, storing position value into a control register, and executing a bit extraction instruction. The bit extraction instruction includes copying the size value number of bits from the accumulator beginning at the position value into a target register, setting any remaining bits of the target register to zero, and decrementing the position value by an amount based on the size value. The method may include loading bits from a bit stream into a register and moving the contents of the register into the accumulator to replenish the accumulator. The method may include determining , based on the position value, whether the accumulator needs to be replenished, and if not, branching to bypass replenishing functions.