On Mon, Jul 28, 2014 at 11:21:53AM +0200, Tom de Vries wrote:
> Jakub,
>
> we're using expand_omp_for_static_chunk with a chunk_size of one to expand the
> openacc loop construct.
>
> This results in an inner and outer loop being generated, with the inner loop
> having a trip count of one, which means that the inner loop can be simplified
> to
> just the inner loop body. However, subsequent optimizations do not manage to
> do
> this simplification.
>
> This patch sets the loop exit condition to true if the chunk_size is one, to
> ensure that the compiler will optimize away the inner loop.
>
> OK for gomp4 branch?
>
> Thanks,
> - Tom
> 2014-07-25 Tom de Vries <t...@codesourcery.com>
>
> * omp-low.c (expand_omp_for_static_chunk): Remove inner loop if
> chunk_size is one.
If that is still the case on the trunk, the patch is ok for trunk after
retesting it. Please mention the PR tree-optimization/65468 in the
ChangeLog entry and make sure there is some runtime testcase that tests
that code path (both OpenMP and OpenACC one).
> diff --git a/gcc/omp-low.c b/gcc/omp-low.c
> index b188e2d..5a73986 100644
> --- a/gcc/omp-low.c
> +++ b/gcc/omp-low.c
> @@ -7345,9 +7345,14 @@ expand_omp_for_static_chunk (struct omp_region *region,
> stmt = gimple_build_assign (vback, t);
> gsi_insert_before (&gsi, stmt, GSI_SAME_STMT);
>
> - t = build2 (fd->loop.cond_code, boolean_type_node,
> - DECL_P (vback) && TREE_ADDRESSABLE (vback)
> - ? t : vback, e);
> + if (tree_int_cst_equal (fd->chunk_size, integer_one_node))
> + t = build2 (EQ_EXPR, boolean_type_node,
> + build_int_cst (itype, 0),
> + build_int_cst (itype, 1));
> + else
> + t = build2 (fd->loop.cond_code, boolean_type_node,
> + DECL_P (vback) && TREE_ADDRESSABLE (vback)
> + ? t : vback, e);
> gsi_insert_before (&gsi, gimple_build_cond_empty (t), GSI_SAME_STMT);
> }
>
Jakub
