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cmpy x_4_c,c_18_42, t2:t3在上边这行代码中x_4_c是将x4与xc打包，c_18_42是将c18和c42打包 用矩阵形式可表示为：
若x4与xc，c18和c42不再是16位，而是32位的话，那就只可以用32位的乘指令，一下代码是对其进行的替代
mpy32 x4,c42, c42_x4
mpy32 x4,c18, c18_x4
mpy32 xc,c18, c18_xc
mpy32 xc,f42, f42_xc
dadd c42_x4:c18_x4,c18_xc:f42_xc, t3:t2**注意是t2:t3还是t3:t2**