Re: openacc reference reductions

[Jakub Jelinek <jakub@redhat.com>]

On Tue, Apr 05, 2016 at 06:53:47PM -0700, Cesar Philippidis wrote:
> --- a/gcc/omp-low.c
> +++ b/gcc/omp-low.c
> @@ -309,6 +309,25 @@ is_oacc_kernels (omp_context *ctx)
>  	      == GF_OMP_TARGET_KIND_OACC_KERNELS));
>  }
>  
> +/* Return true if CTX corresponds to an oacc parallel region and if
> +   VAR is used in a reduction.  */
> +
> +static bool
> +is_oacc_parallel_reduction (tree var, omp_context *ctx)
> +{
> +  if (!is_oacc_parallel (ctx))
> +    return false;
> +
> +  tree clauses = gimple_omp_target_clauses (ctx->stmt);
> +
> +  for (tree c = clauses; c; c = OMP_CLAUSE_CHAIN (c))
> +    if (OMP_CLAUSE_CODE (c) == OMP_CLAUSE_REDUCTION
> +	&& OMP_CLAUSE_DECL (c) == var)
> +      return true;
> +
> +  return false;
> +}
> +
>  /* If DECL is the artificial dummy VAR_DECL created for non-static
>     data member privatization, return the underlying "this" parameter,
>     otherwise return NULL.  */
> @@ -2122,7 +2141,8 @@ scan_sharing_clauses (tree clauses, omp_context *ctx,
>  		  else
>  		    install_var_field (decl, true, 3, ctx,
>  				       base_pointers_restrict);
> -		  if (is_gimple_omp_offloaded (ctx->stmt))
> +		  if (is_gimple_omp_offloaded (ctx->stmt)
> +		      && !is_oacc_parallel_reduction (decl, ctx))
>  		    install_var_local (decl, ctx);
>  		}
>  	    }

The above is O(n^2) in number of clauses on the construct.
Perhaps better define some OMP_CLAUSE_MAP_IN_REDUCTION macro (e.g.
TREE_PRIVATE bit is unused on OMP_CLAUSE_MAP right now), make sure to set it
e.g. during gimplification where you can see all GOVD_* flags for a
particular decl), and then use this flag here?


	Jakub