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winternewt • yesterday at 6:38 PM • 1 reply • view on HN

I see stuff along the lines of:

  if (x == 0) {
      return y;
  }
  
  y += 25*x;
  return y;
and skipping the if just makes the function shorter and simpler, while also not involving the CPU branch prediction. Another one that doesn't necessarily skip all branching but at least drops one - and more importantly makes the code simpler and easy to verify, is removing the if statement in code like

  if (count == 0) {
      return;
  }

  for (int i = 0; i != count; i++) {
    puts("hello");
  }

Replies

GuB-42 • yesterday at 11:22 PM

Both of your examples are optimized by the compiler (gcc 16.1 -O3).

In the first case, the compiler removes the first if/return

In the second case, if you don't have the first if/return the compiler will add it. That's because it will actually convert your loop into a do/while, with the test in the end, because it is more efficient. But it has to handle the count == 0 special case first, so it will do that early return even if it is not explicitly there.

That's the kind of optimization modern compilers are good at.