Blank bit and processor instructions employing the blank bit

摘要

Reading a value into a register, checking to see if the value is a NULL, and then jumping out of a loop if the value is a NULL is a common task that processors perform. To speed performance of such a task, a novel “blank bit” is added to the flag register of a processor. When a first instruction (arithmetic, logic or load) is executed, the instruction operands are checked to see if any is a NULL character value. Information on the result of the check is stored in the blank bit. Execution of a second instruction uses the information stored in the blank bit to determine whether or not a second operation (for example, a jump) will be performed. By using the first and second instructions in a loop, the number of instructions executed to check for NULLs at the end of strings and arrays is reduced.

主权项

1. A non-transitory computer-readable medium encoded with a processor-executable machine code instruction for:
performing an operation if a bit is storing a first value, otherwise not performing the operation if the bit is storing a second value, wherein the bit is a bit in a flag register of a processor that executes the machine code instruction, the first value having been stored in the bit during execution of another machine code instruction by the processor and before an operation of the other machine code instruction was performed, wherein the other machine code instruction used a first operand, and wherein the first value was stored in the bit if the first operand used by the other machine code instruction was equal to zero.