Conversion from fixed point to IEEE 754
Basically, you do four things:


convert from 2’s complement to signed magnitude, save the sign
count leading zeroes (find first ‘one’)
add a bias to that to make the exponent
shift the integer to normalize it as the mantissa. 


About four lines of code that synthesizes to some logic, an adder, and a shift mux.

EDIT: As Tim said, before you do all that you also need to convert the 2’s complement integer to signed magnitude. So one more line.