[CIR][ThroughMLIR] Lower ContinueOp nested inside IfOp

[terapines-osc-cir]

As the scf dialect does not support early exits, it might be necessary to change the body of WhileOp to implement the semantics of ContinueOp. I choose to add a guard if (!cond) for everything following the continue.

[terapines-osc-cir]

@felixdaas Thanks for your comment! There's still something I didn't understand about your infinite-loop example here.

void while_continue_2() {
  int i = 0, b;
  while (i < 10) {
    if (i == 5) {
      b = 3;
      continue;
    }
    i++;
  }
}

My understanding is that, the continue is supposed to skip everything after it, including i++, so an infinite loop is desired. You might found out the whole loop is skipped when you compile in -O2, but that's because infinite loop without side effect is UB and gets optimized away, which is not of our concern in lowering.
Could you please elaborate on why the i++ needs to be specially treated?

[felixdaas]

@terapines-osc-cir oh yeah my bad youre right, I was somehow confusing the continue and break semantics here, so youre solution seems good