are 2^n exponent calculations really less efficient than bit-shifts?

Question

if I do:

int x = 4;
pow(2, x);

Is that really that much less efficient than just doing:

1 << 4

?

Answer 1

Generally yes, as bit shift is very basic operation for the processor.

On the other hand many compilers optimise code so that raising to power is in fact just a bit shifting.