[gcc/devel/omp/gcc-12] Assumed-size arrays with non-lexical data mappings

[gcc/devel/omp/gcc-12] Assumed-size arrays with non-lexical data mappings

[Kwok Yeung]

https://gcc.gnu.org/g:9f7117014813a510d529583f03c9da48be1a0ae1

commit 9f7117014813a510d529583f03c9da48be1a0ae1
Author: Julian Brown <julian@codesourcery.com>
Date:   Thu Jul 4 18:14:41 2019 -0700

    Assumed-size arrays with non-lexical data mappings
    
            gcc/
            * gimplify.cc (gimplify_adjust_omp_clauses_1): Raise error for
            assumed-size arrays in map clauses for Fortran/OpenMP.
            * omp-low.cc (lower_omp_target): Set the size of assumed-size Fortran
            arrays to one to allow use of data already mapped on the offload device.
    
            gcc/fortran/
            * trans-openmp.cc (gfc_omp_finish_clause): Change clauses mapping
            assumed-size arrays to use the GOMP_MAP_FORCE_PRESENT map type.

Diff:
---
 gcc/ChangeLog.omp           |  8 ++++++++
 gcc/fortran/ChangeLog.omp   |  5 +++++
 gcc/fortran/trans-openmp.cc | 22 +++++++++++++---------
 gcc/gimplify.cc             | 14 ++++++++++++++
 gcc/omp-low.cc              |  5 +++++
 5 files changed, 45 insertions(+), 9 deletions(-)

diff --git a/gcc/ChangeLog.omp b/gcc/ChangeLog.omp
index 40d7e5ad8a5..52d41d4a0c1 100644
--- a/gcc/ChangeLog.omp
+++ b/gcc/ChangeLog.omp
@@ -1,3 +1,11 @@
+2019-07-10  Cesar Philippidis  <cesar@codesourcery.com>
+	    Julian Brown  <julian@codesourcery.com>
+
+	* gimplify.cc (gimplify_adjust_omp_clauses_1): Raise error for
+	assumed-size arrays in map clauses for Fortran/OpenMP.
+	* omp-low.cc (lower_omp_target): Set the size of assumed-size Fortran
+	arrays to one to allow use of data already mapped on the offload device.
+
 2019-05-20  Julian Brown  <julian@codesourcery.com>
 
 	* gimplify.cc (gimplify_adjust_omp_clauses_1): Support implied no_alloc
diff --git a/gcc/fortran/ChangeLog.omp b/gcc/fortran/ChangeLog.omp
index c234fadfe50..176c23274b7 100644
--- a/gcc/fortran/ChangeLog.omp
+++ b/gcc/fortran/ChangeLog.omp
@@ -1,3 +1,8 @@
+2019-07-10  Julian Brown  <julian@codesourcery.com>
+
+	* trans-openmp.cc (gfc_omp_finish_clause): Change clauses mapping
+	assumed-size arrays to use the GOMP_MAP_FORCE_PRESENT map type.
+
 2019-05-19  Julian Brown  <julian@codesourcery.com>
 
 	* trans-openmp.cc (gfc_omp_finish_clause): Guard addition of clauses for
diff --git a/gcc/fortran/trans-openmp.cc b/gcc/fortran/trans-openmp.cc
index 8f4e27cfad1..e0121af1465 100644
--- a/gcc/fortran/trans-openmp.cc
+++ b/gcc/fortran/trans-openmp.cc
@@ -1489,10 +1489,18 @@ gfc_omp_finish_clause (tree c, gimple_seq *pre_p, bool openacc)
   tree decl = OMP_CLAUSE_DECL (c);
 
   /* Assumed-size arrays can't be mapped implicitly, they have to be mapped
-     explicitly using array sections.  An exception is if the array is
-     mapped explicitly in an enclosing data construct for OpenACC, in which
-     case we see GOMP_MAP_FORCE_PRESENT here and do not need to raise an
-     error.  */
+     explicitly using array sections.  For OpenACC this restriction is lifted
+     if the array has already been mapped:
+
+       - Using a lexically-enclosing data region: in that case we see the
+         GOMP_MAP_FORCE_PRESENT mapping kind here.
+
+       - Using a non-lexical data mapping ("acc enter data").
+
+     In the latter case we change the mapping type to GOMP_MAP_FORCE_PRESENT.
+     This raises an error for OpenMP in the caller
+     (gimplify.c:gimplify_adjust_omp_clauses_1).  OpenACC will raise a runtime
+     error if the implicitly-referenced assumed-size array is not mapped.  */
   if (OMP_CLAUSE_MAP_KIND (c) != GOMP_MAP_FORCE_PRESENT
       && TREE_CODE (decl) == PARM_DECL
       && GFC_ARRAY_TYPE_P (TREE_TYPE (decl))
@@ -1500,11 +1508,7 @@ gfc_omp_finish_clause (tree c, gimple_seq *pre_p, bool openacc)
       && GFC_TYPE_ARRAY_UBOUND (TREE_TYPE (decl),
 				GFC_TYPE_ARRAY_RANK (TREE_TYPE (decl)) - 1)
 	 == NULL)
-    {
-      error_at (OMP_CLAUSE_LOCATION (c),
-		"implicit mapping of assumed size array %qD", decl);
-      return;
-    }
+    OMP_CLAUSE_SET_MAP_KIND (c, GOMP_MAP_FORCE_PRESENT);
 
   if (OMP_CLAUSE_MAP_KIND (c) == GOMP_MAP_FORCE_DEVICEPTR)
     return;
diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
index 477576ff0e7..03769d57200 100644
--- a/gcc/gimplify.cc
+++ b/gcc/gimplify.cc
@@ -11535,12 +11535,26 @@ gimplify_adjust_omp_clauses_1 (splay_tree_node n, void *data)
   *list_p = clause;
   struct gimplify_omp_ctx *ctx = gimplify_omp_ctxp;
   gimplify_omp_ctxp = ctx->outer_context;
+  gomp_map_kind kind = (code == OMP_CLAUSE_MAP) ? OMP_CLAUSE_MAP_KIND (clause)
+						: (gomp_map_kind) GOMP_MAP_LAST;
   /* Don't call omp_finish_clause on implicitly added OMP_CLAUSE_PRIVATE
      in simd.  Those are only added for the local vars inside of simd body
      and they don't need to be e.g. default constructible.  */
   if (code != OMP_CLAUSE_PRIVATE || ctx->region_type != ORT_SIMD) 
     lang_hooks.decls.omp_finish_clause (clause, pre_p,
 					(ctx->region_type & ORT_ACC) != 0);
+  /* Allow OpenACC to have implicit assumed-size arrays via FORCE_PRESENT,
+     which should work as long as the array has previously been mapped
+     explicitly on the target (e.g. by "enter data").  Raise an error for
+     OpenMP.  */
+  if (lang_GNU_Fortran ()
+      && code == OMP_CLAUSE_MAP
+      && (ctx->region_type & ORT_ACC) == 0
+      && kind == GOMP_MAP_TOFROM
+      && OMP_CLAUSE_MAP_KIND (clause) == GOMP_MAP_FORCE_PRESENT)
+    error_at (OMP_CLAUSE_LOCATION (clause),
+	      "implicit mapping of assumed size array %qD",
+	      OMP_CLAUSE_DECL (clause));
   if (gimplify_omp_ctxp)
     for (; clause != chain; clause = OMP_CLAUSE_CHAIN (clause))
       if (OMP_CLAUSE_CODE (clause) == OMP_CLAUSE_MAP
diff --git a/gcc/omp-low.cc b/gcc/omp-low.cc
index 5575ae47ef7..1143f5ac2e3 100644
--- a/gcc/omp-low.cc
+++ b/gcc/omp-low.cc
@@ -13657,6 +13657,11 @@ lower_omp_target (gimple_stmt_iterator *gsi_p, omp_context *ctx)
 	      s = OMP_CLAUSE_SIZE (c);
 	    if (s == NULL_TREE)
 	      s = TYPE_SIZE_UNIT (TREE_TYPE (ovar));
+	    /* Fortran assumed-size arrays have zero size because the type is
+	       incomplete.  Set the size to one to allow the runtime to remap
+	       any existing data that is already present on the accelerator.  */
+	    if (s == NULL_TREE && is_gimple_omp_oacc (ctx->stmt))
+	      s = integer_one_node;
 	    s = fold_convert (size_type_node, s);
 	    purpose = size_int (map_idx++);
 	    CONSTRUCTOR_APPEND_ELT (vsize, purpose, s);