[PATCH] _Cilk_for for C and C++

[Jakub Jelinek]

On Tue, Dec 03, 2013 at 01:25:57PM +0000, Iyer, Balaji V wrote:
> > >> As you can tell, this is not how openmp handles a #pragma omp for loop.
> > >
> > > It's different in detail, but #pragma omp parallel for works very
> > > similarly: it creates a separate function for the body of the loop and
> > > then passes that to GOMP_parallel along with any shared data.
> > My thoughts exactly.
> 
> I understand you both now. Let me look into the OMP routines and see what
> it is doing and see how I can port it to _Cilk_for.

Yeah.  The work is actually multi-stage, first during gimplification
the code does determine what variables are used in the #pragma omp parallel
(etc., in your case _Cilk_for) region, and whether they should be shared,
or privatized (and in that case in what way, normal private, firstprivate,
lastprivate, firstprivate+lastprivate, reduction, ...).  Then there is
omplower pass (already enabled for Cilk+ due to #pragma simd) that e.g.
lowers accesses to shared variables, creates new VAR_DECLs for the
privatized vars etc. and then ompexp pass that will create the outlined body
of the function and create call to the runtime library.
I have no idea what privatization behavior _Cilk_for wants, I'd expect that
at least the IV must be privatized, otherwise it would be racy, but about
other vars?

	Jakub