> -----Original Message----- > From: Jeff Law [mailto:l...@redhat.com] > Sent: Tuesday, December 3, 2013 1:30 AM > To: Jason Merrill; Iyer, Balaji V; Aldy Hernandez > Cc: gcc-patches@gcc.gnu.org; r...@redhat.com; Jakub Jelinek > Subject: Re: [PATCH] _Cilk_for for C and C++ > > On 11/27/13 17:52, Jason Merrill wrote: > > On 11/27/2013 04:14 PM, Iyer, Balaji V wrote: > >> I completely agree with you that there are certain parts of Cilk > >> Plus that is similar to OMP4, namely #pragma simd and SIMD-enabled > >> functions (formerly called elemental functions). But, the Cilk > >> keywords is almost completely orthogonal to OpenMP. They are > >> semantically different and one cannot be transformed to another. > >> Cilk uses automatically load-balanced work-stealing using the Cilk > >> runtime, whereas OMP uses work sharing via OMP runtime. There are a > >> number of other semantic differences but this is the core-issue. > >> #pragma simd and #pragma omp have converged in several places but the > >> Cilk part has always been different from OpenMP. > > > > Yes, Cilk for loops will use the Cilk runtime and OMP for loops will > > use the OMP runtime, but that doesn't mean they can't share a lot of > > the middle end code along the way. > > > > We already have several different varieties of parallel/simd loops all > > represented by GIMPLE_OMP_FOR, and I think this could be another > > GP_OMP_FOR_KIND_. > Right. It's not a question of what runtime they call back into, but that both > share a common overall structure. > > Conceptually I look at a for loop as having 4 main components. > > Initializer, test condition, increment and the body. > > I'd like to hope things like the syntatic & semantic analysis of the first > three > would be largely the same. Most of the Cilk specific bits would be in the > handling of the body -- but there may be some significant code sharing that > can happen there too. > > > > > > ... > >> 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. Thanks, Balaji V. Iyer. > jeff
