Re: [PATCH] Fix PR80029

[Thomas Schwinge <thomas at codesourcery dot com>]

Hi Cesar!

On Wed, 22 Mar 2017 06:40:03 -0700, Cesar Philippidis <cesar@codesourcery.com> wrote:
> In addition to resolving the memory leak involving OpenACC delare
> clauses, this patch also corrects an ICE involving VLA variables as data
> clause arguments used in acc declare constructs. More details can be
> found here <https://gcc.gnu.org/ml/gcc-patches/2016-09/msg01630.html>.
> 
> Is this OK for trunk?

(Got committed in r246381.)

> 	PR c++/80029
> 
> 	gcc/
> 	* gimplify.c (is_oacc_declared): New function.
> 	(oacc_default_clause): Use it to set default flags for acc declared
> 	variables inside parallel regions.
> 	(gimplify_scan_omp_clauses): Strip firstprivate pointers for acc
> 	declared variables.
> 	(gimplify_oacc_declare): Gimplify the declare clauses.  Add the
> 	declare attribute to any decl as necessary.

> --- a/gcc/gimplify.c
> +++ b/gcc/gimplify.c
> @@ -6787,6 +6787,16 @@ device_resident_p (tree decl)
>    return false;
>  }
>  
> +/* Return true if DECL has an ACC DECLARE attribute.  */
> +
> +static bool
> +is_oacc_declared (tree decl)
> +{

Adding here a "gcc_assert (TREE_CODE (decl) != MEM_REF);", that one never
triggers (at least given the current test coverage), so...

> +  tree t = TREE_CODE (decl) == MEM_REF ? TREE_OPERAND (decl, 0) : decl;

... it would seem that this code can be simplified -- or under which
circumstances should we get a MEM_REF here?  The call from
gimplify_oacc_declare itself does the tree operand 0 indirection, and the
call from oacc_default_clause shouldn't be a MEM_REF, I would think.

> +  tree declared = lookup_attribute ("oacc declare target", DECL_ATTRIBUTES (t));
> +  return declared != NULL_TREE;
> +}

> @@ -6887,6 +6897,7 @@ oacc_default_clause (struct gimplify_omp_ctx *ctx, tree decl, unsigned flags)
>  {
>    const char *rkind;
>    bool on_device = false;
> +  bool declared = is_oacc_declared (decl);
>    tree type = TREE_TYPE (decl);
>  
>    if (lang_hooks.decls.omp_privatize_by_reference (decl))
> @@ -6917,7 +6928,7 @@ oacc_default_clause (struct gimplify_omp_ctx *ctx, tree decl, unsigned flags)
>  
>      case ORT_ACC_PARALLEL:
>        {
> -	if (on_device || AGGREGATE_TYPE_P (type))
> +	if (on_device || AGGREGATE_TYPE_P (type) || declared)
>  	  /* Aggregates default to 'present_or_copy'.  */
>  	  flags |= GOVD_MAP;
>  	else

Isn't this new "declared" logic doing a thing very similar to the
existing "on_device" logic?  Should that be combined/cleaned up?

Why doesn't the same "declared"/"on_device" logic also apply to
ORT_ACC_KERNELS?


Grüße
 Thomas


> @@ -7346,6 +7357,7 @@ gimplify_scan_omp_clauses (tree *list_p, gimple_seq *pre_p,
>        case OMP_TARGET_DATA:
>        case OMP_TARGET_ENTER_DATA:
>        case OMP_TARGET_EXIT_DATA:
> +      case OACC_DECLARE:
>        case OACC_HOST_DATA:
>  	ctx->target_firstprivatize_array_bases = true;
>        default:
> @@ -9231,18 +9243,26 @@ gimplify_oacc_declare (tree *expr_p, gimple_seq *pre_p)
>  {
>    tree expr = *expr_p;
>    gomp_target *stmt;
> -  tree clauses, t;
> +  tree clauses, t, decl;
>  
>    clauses = OACC_DECLARE_CLAUSES (expr);
>  
>    gimplify_scan_omp_clauses (&clauses, pre_p, ORT_TARGET_DATA, OACC_DECLARE);
> +  gimplify_adjust_omp_clauses (pre_p, NULL, &clauses, OACC_DECLARE);
>  
>    for (t = clauses; t; t = OMP_CLAUSE_CHAIN (t))
>      {
> -      tree decl = OMP_CLAUSE_DECL (t);
> +      decl = OMP_CLAUSE_DECL (t);
>  
>        if (TREE_CODE (decl) == MEM_REF)
> -	continue;
> +	decl = TREE_OPERAND (decl, 0);
> +
> +      if (VAR_P (decl) && !is_oacc_declared (decl))
> +	{
> +	  tree attr = get_identifier ("oacc declare target");
> +	  DECL_ATTRIBUTES (decl) = tree_cons (attr, NULL_TREE,
> +					      DECL_ATTRIBUTES (decl));
> +	}
>  
>        if (VAR_P (decl)
>  	  && !is_global_var (decl)
> @@ -9258,7 +9278,8 @@ gimplify_oacc_declare (tree *expr_p, gimple_seq *pre_p)
>  	    }
>  	}
>  
> -      omp_add_variable (gimplify_omp_ctxp, decl, GOVD_SEEN);
> +      if (gimplify_omp_ctxp)
> +	omp_add_variable (gimplify_omp_ctxp, decl, GOVD_SEEN);
>      }
>  
>    stmt = gimple_build_omp_target (NULL, GF_OMP_TARGET_KIND_OACC_DECLARE,
> diff --git a/libgomp/testsuite/libgomp.oacc-c-c++-common/declare-vla.c b/libgomp/testsuite/libgomp.oacc-c-c++-common/declare-vla.c
> new file mode 100644
> index 0000000..3ea148e
> --- /dev/null
> +++ b/libgomp/testsuite/libgomp.oacc-c-c++-common/declare-vla.c
> @@ -0,0 +1,25 @@
> +/* Verify that acc declare accept VLA variables.  */
> +
> +#include <assert.h>
> +
> +int
> +main ()
> +{
> +  int N = 1000;
> +  int i, A[N];
> +#pragma acc declare copy(A)
> +
> +  for (i = 0; i < N; i++)
> +    A[i] = -i;
> +
> +#pragma acc kernels
> +  for (i = 0; i < N; i++)
> +    A[i] = i;
> +
> +#pragma acc update host(A)
> +
> +  for (i = 0; i < N; i++)
> +    assert (A[i] == i);
> +
> +  return 0;
> +}