IDISA Expansion Operations
The IDISA expansion operations produce vectors of 2n bit fields
by operations on input vectors of n bit fields.
Binary Expansion Operations
mergeh(a, b)  merge the high N/2 fields of a and b

mergel(a, b)  merge the low N/2 fields of a and b

multh(a, b)  multiply the high N/2 fields of a and b

multll(a, b)  multiply the low N/2 fields of a and b

Unary Expansion Operations
signextendh(a)  signextend the high N/2 fields of a

signextendl(a)  signextend the low N/2 fields of a

zeroextendh(a)  zeroextend the high N/2 fields of a

zeroextendl(a)  zeroextend the low N/2 fields of a
