Most optimized way to calculate modulus in C

Question

I have minimize cost of calculating modulus in C. say I have a number x and n is the number which will divide x

when n == 65536 (which happens to be 2^16):

m

Answer 1

idiv — Integer Division

The idiv instruction divides the contents of the 64 bit integer EDX:EAX (constructed by viewing EDX as the most significant four bytes and EAX as the least significant four bytes) by the specified operand value. The quotient result of the division is stored into EAX, while the remainder is placed in EDX.

source: http://www.cs.virginia.edu/~evans/cs216/guides/x86.html