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.
jeff
