Do temp variables slow down my program?

Question

Suppose I have the following C code:

int i = 5;
int j = 10;
int result = i + j;

If I\'m looping over this many times, would it be faster to

Answer 1

The example you gave is easy for a compiler to optimize. Using local variables to cache values pulled out of global structures and arrays can actually speed up execution of your code. If for instance you are fetching something from a complex structure inside a for loop where the compiler can't optimize and you know the value isn't changing, the local variables can save quite a bit of time.

You can use GCC (other compilers too) to generate the intermediate assembly code and see what the compiler is actually doing.

There is discussion of how to turn on the assembly listings here:Using GCC to produce readable assembly?

It can be instructive to examine the generated code and see what a compiler is actually doing.