What is efficient to check: equal to or not equal to?

Question

I was wondering, if we have if-else condition, then what is computationally more efficient to check: using the equal to operator or the not equal to operator? Is there any difference at all?

E.g., which one of the following is computationally efficient, both cases below will do same thing, but which one is better (if there's any difference)?

Case1:

if (a == x)
{
    // execute Set1 of statements
}
else
{
    // execute Set2 of statements
}

Case 2:

if (a != x)
{
    // execute Set2 of statements
}
else
{
    // execute Set1 of statements
}

Here assumptions are most of the time (say 90% of the cases) a will be equal to x. a and x both are of unsigned integer type.

Answer 1

Generally it shouldn't matter for performance which operator you use. However it is recommended for branching that the most likely outcome of the if-statement comes first.

Answer 2

Usually what you should consider is; what is the simplest and clearest way to write this code? IMHO, the first, positive is the simplest (not requiring a !)

In terms of performance there is no differences as the code is likely to compile to the same thing. (Certainly in the JIT for Java it should)

For Java, the JIT can optimise the code so the most common branch is preferred by the branch prediction.