Question

Is this:
if(x >= 5)
Slower than
if(x > 4)

Answer 1

I should add that I'm writing in C.
But in general, will the compiler rewrite it to fastest from?

Answer 2

In general, I would expect the compiler to rewrite operations like this to perform as quickly as possible (especially with optimization turned on).

Answer 3

I think assembler will have both operations so it doesn't matter

Answer 4

On the x86 architecture, those should compile down to a subtraction and a JG (jump greater) and JGE (jump greater equal) instruction respectively. On ARM, it would be the subtraction and BGT or BGE. Either of these should have the same cost, and all even remotely recent architectures will have dedicated instructions for both branch types.