[PATCH 2 of 2] reachableroots: unroll loop that checks if one of parents is reachable

[Yuya Nishihara]

On Tue, 08 Sep 2015 13:45:19 -0700, Pierre-Yves David wrote:
> > The difference is small, but fewer loops should be better in general:
> >
> >    revset #0: 0::tip
> >    0) 0.001609
> >    1) 0.001510  93%
> 
> I'm kinda surprise the compiler is not doing this for us.

Perhaps it isn't easy to detect that
  revstates[i + 1] is RS_REACHABLE at k == 1
  if revstates[parents[k] + 1] is RS_REACHABLE at k == 0.

gcc 5.2.1 could generate optimized code if we had "break".

> for (k = 0; k < 2; k++) {
> -				if ((revstates[parents[k] + 1] & RS_REACHABLE)
> -				    && !(revstates[i + 1] & RS_REACHABLE)) {
> -					revstates[i + 1] |= RS_REACHABLE;
> -					val = PyInt_FromLong(i);
> -					if (val == NULL)
> -						goto bail;
> -					r = PyList_Append(reachable, val);
> -					Py_DECREF(val);
> -					if (r < 0)
> -						goto bail;
					break;  /* revision i is reachable */
> -				}