Question

How can we do this bit level operation in Matlab:

int instructionWord;
a = (instructionWord >>> 21) & 0x1F;

The code right shifts the instructionWord by 21 and obtains the least 5 bits. How can this be equivalently done in Matlab?

Answer 1

Given that your input value is an integer, you could do the following:

a = mod( floor(instructionWord/2^21), 32)

Another more bit-like solution would be:

a = bitand( bitshift(instructionWord, -21), hex2dec('1F'))

The last method will throw an error if you feed it anything else than intergers.

By the way, your variable instructionWord is declared like a signed integer. But if it is an instruction word or something like that, an unsigned integer would make more sense. The expressions above expect that your input is only positive. If not, it will require a bit more code to model the >>> (logical right-shift) in matlab.