On Fri, Jan 31, 2014 at 04:42:57PM +0100, Jakub Jelinek wrote:
> Can you explain why you emit anything in between the parallel and _Cilk_for?
> I don't see why it should be needed.
> Depending on what the Cilk+ standard allows you to do (can array.begin ()
> be evaluated multiple times or not, and if not, can you invoke say a copy
> constructor on it), you should just emit an EXPR_STMT that initializes
> an artificial scalar (say get_temp_regvar created) to
> (array.end () - array.begin ()) before you add the parallel, or,
> if array.begin () can't be evaluated multiple times, then construct some
> temporary before the parallel with array.begin () as initializer
> and then do the subtraction between array.end () and that temporary.
>
> Then the parallel, with _Cilk_for immediately in it and just another
> temporary scalar as loop iterator there, and only inside of _Cilk_for
> declare the iterator var and construct (if it has been declared in _Cilk_for,
> otherwise
> just initialize it) to, depending on what Cilk+ requires, either to
> array.begin () and then operator+ it to the corresponding value, or
> construct already to array.begin () + scalariv.
Actually, small correction, the iterator variable likely should be
constructed before the parallel and just marked as firstprivate on the
parallel, then you even don't need any special temporary.
So for:
_Cilk_for (vector<int>::iterator iter = array.begin(); iter != array.end();
iter++)
{
if (*iter == 6)
*iter = 13;
}
emit basically:
{
Iterator iter;
Iterator::Iterator(&iter, array.begin());
ptrdiff_t tmpcount = Iterator::operator-(array.end(), &iter);
ptrdiff_t tmpiv;
ptrdiff_t tmplast = 0;
#pragma omp parallel firstprivate(iter, tmpcount, tmplast) private(tmpiv)
{
_Cilk_for(tmpiv = 0; tmpiv < tmpcount; tmpiv++)
{
Iterator::operator+(&iter, tmpiv - tmplast);
tmplast = tmpiv;
{
if (*iter == 6)
*iter = 13;
}
}
}
}
Jakub
