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Instruction mmx - PUNPCKHBW/PUNPCKHWD/PUNPCKHDQ—Unpack High Packed Data

Unpacks and interleaves the high-order data elements (bytes, words, or doublewords) of the destination operand (first operand) and source operand (second operand) into the destination operand. The low-order data elements are ignored. The destination operand must be an MMX technology register; the source operand may be either an MMX technology register or a 64-bit memory location. When the source data comes from a memory operand, the full 64-bit operand is accessed from memory, but the instruction uses only the high-order 32 bits. The PUNPCKHBW instruction interleaves the four high-order bytes of the source operand and the four high-order bytes of the destination operand and writes them to the destination operand. The PUNPCKHWD instruction interleaves the two high-order words of the source operand and the two high-order words of the destination operand and writes them to the destination operand. The PUNPCKHDQ instruction interleaves the high-order doubleword of the source operand and the high-order doubleword of the destination operand and writes them to the destination operand. If the source operand is all zeros, the result (stored in the destination operand) contains zero extensions of the high-order data elements from the original value in the destination operand. With the PUNPCKHBW instruction the high-order bytes are zero extended (that is, unpacked into unsigned words), and with the PUNPCKHWD instruction, the high-order words are zero extended (unpacked into unsigned doublewords).