C programming tricks

While programming optimization that makes ones' code completely unreadable is often a bad thing, there are places for it, like that one inner loop of your code that takes up 98% of the program's running time.

What are you tricks for improving performance in C, other than the obvious inline assembly or the like?

Of course, as >>12 was hinting at, if you have critical code in a tight loop, it's better to use the inline assembly, which is guaranteed to make your code run faster.

for (int i=0; i<100; ++i)
__asm { mov rax, [i]
        xor rax, rax }