bcompressw rd rs1 rs2 31..25=4  14..12=6 6..2=0x0E 1..0=3
bdecompressw rd rs1 rs2 31..25=36 14..12=6 6..2=0x0E 1..0=3
packw      rd rs1 rs2 31..25=4  14..12=4 6..2=0x0E 1..0=3