Will adding a sequence of consecutive numbers after a sequence of ordered, but non-consecutive numbe-CodePudding

I have a switch which has some random numbers: 1,5,16...
Imagine there are 10 or 20 of them.
After them, I have some macros where I can assign my own signed int numbers. So they can be 1000, or 32000...
Imagine there are also 10 or 20 of those.

Now, my question is:

will ordering and making my numbers consecutive even help with optimization if the former numbers are ordered but not consecutive?
will using smaller numbers (like 1000, compared to 32000) affect performance in any theoretical way?

Code:

switch (x) {
    case 1:
    // stuff
    break; 

    case 5:
    // stuff
    break;

    case 16:
    // stuff
    break;

    case 32000:
    // stuff
    break;

    case 32001:
    // stuff
    break;

    case 32002:
    // stuff
    break;

    defult:
    break;
}

If you need hardware specifics, imagine we are talking about the most default theoretical scenario: gcc, intel, no optimizations.

Please advise.

CodePudding user response：

That depends on your compiler, usually it should not help. Some compiler may implement a binary search, others may implement a if/else chain. But as long as not all of your numbers are consecutive there won't be a jump table*. The order of your case statements does not make a difference.

switch (x) {
case 1:
     ...
     break;
case 3:
     ...
     break;
case 5:
     ...
     break;
}

and

switch (x) {
case 1:
     ...
     break;
case 5:
     ...
     break;
case 3:
     ...
     break;
}

Will be (usually) compiled to exactly the same code.

EDIT:

If larger numbers than the type of x can handle, the result is undefined. Otherwise it does not make a difference.

*Sometimes it can be worth, for example if there are just gaps between the numbers.