A.5.254 PSHUFW: Shuffle Packed Words
PSHUFW mm1,mm2/m64,imm8 ; 0F 70 /r ib [KATMAI,MMX]
PSHUFW shuffles the words in the source (second) operand according to
the encoding specified by imm8, and stores the result in the destination
(first) operand.
Bits 0 and 1 of imm8 encode the source position of the word to be copied
to position 0 in the destination operand. Bits 2 and 3 encode for
position 1, bits 4 and 5 encode for position 2, and bits 6 and 7 encode
for position 3. For example, an encoding of 10 in bits 0 and 1 of imm8
indicates that the word at bits 32-47 of the source operand will be
copied to bits 0-15 of the destination.