Instruction and logic for processing text strings

A processor comprising:

• multiple levels of cache, including a Level 1 (L1) cache;
• a plurality of registers to store 128-bit packed data operands;
• a decoder to decode instructions including a packed comparison instruction, wherein the packed comparison instruction is to identify a first 128-bit source packed data operand in the plurality of registers, and a second 128-bit source packed data operand in memory or the plurality of registers, wherein valid data elements in the first and second source packed data operands are to be implicitly indicated by null elements in the first and second source packed data operands, and wherein the packed comparison instruction is to have an immediate that is to include:
• a first two bits, wherein the first two bits being equal to 00B is to indicate that data elements of the first and second 128-bit source packed data operands are unsigned bytes, being equal to 01B is to indicate that the data elements are unsigned words, being equal to 10B is to indicate that the data elements are signed bytes, and being equal to 11B is to indicate that the data elements are signed words;
• a second two bits, wherein the second two bits being equal to 00B is to indicate that comparisons to be performed are to determine whether any of the valid data elements of the first and second 128-bit source packed data operands are equal, being equal to 01B is to indicate that the comparisons are to involve ranges, and being equal to 11B is to indicate that the comparisons are to determine whether the first and second 128-bit source packed data operands have an equal ordered plurality of data elements;
• a third two bits to control a negation operation, wherein the third two bits being equal to 00B is to indicate that all bits of a result of the comparisons are not to be negated, being equal to 01B is to indicate that said all bits of the result of the comparisons are to be negated, and being equal to 11B is to indicate that only bits of the result of the comparisons that correspond to the valid data elements of one of the first and second 128-bit source packed data operands are to be negated;
• and
• a fourth bit, wherein the fourth bit being equal to 0B is to indicate that a result of the negation operation is to be zero extended to a mask, and being equal to 1B is to indicate that the result of the negation operation is to be expanded to one of a byte mask and word mask;
• and
• an execution unit coupled with the decoder to execute the packed comparison instruction.