OpenMP 5.0: Allow multiple clauses mapping same variable

This is a merge of:
https://gcc.gnu.org/pipermail/gcc-patches/2020-December/562081.html

This patch now allows multiple clauses on the same construct to map
the same variable, which was not valid in OpenMP 4.5, but now allowed
in 5.0.

This may possibly reverted/updated when a final patch is approved
for mainline.

gcc/c/ChangeLog
	* c-typeck.cc (c_finish_omp_clauses): Adjust to allow duplicate
	mapped variables for OpenMP.

gcc/cp/ChangeLog
	* semantics.cc (finish_omp_clauses): Adjust to allow duplicate
	mapped variables for OpenMP.

gcc/ChangeLog

	* omp-low.cc (install_var_field): Add new 'tree key_expr = NULL_TREE'
	default parameter. Set splay-tree lookup key to key_expr instead of
	var if key_expr is non-NULL. Adjust call to install_parm_decl.
	Update comments.
	(scan_sharing_clauses): Use clause tree expression as splay-tree key
	for map/to/from and OpenACC firstprivate cases when installing the
	variable field into the send/receive record type.
	(maybe_lookup_field_in_outer_ctx): Add code to search through
	construct clauses instead of entirely based on splay-tree lookup.
	(lower_oacc_reductions): Adjust to find map-clause of reduction
	variable, then create receiver-ref.
	(lower_omp_target): Adjust to lookup var field using clause expression.

gcc/testsuite/ChangeLog

	* c-c++-common/gomp/clauses-2.c: Adjust testcase.
	* c-c++-common/gomp/map-6.c: Adjust testcase.

Co-Authored-By: Paul-Antoine Arras <parras@baylibre.com>

5 files changed, 65 insertions, 34 deletions

diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index ad37bae..e390ad7 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -17147,7 +17147,7 @@ c_finish_omp_clauses (tree clauses, enum c_omp_region_type ort)
 	      }
 	    else if (bitmap_bit_p (&map_head, DECL_UID (t))
 		     && !bitmap_bit_p (&map_field_head, DECL_UID (t))
-		     && ort != C_ORT_OMP
+		     && ort != C_ORT_OMP && ort != C_ORT_OMP_TARGET
 		     && ort != C_ORT_OMP_EXIT_DATA)
 	      {
 		if (OMP_CLAUSE_CODE (c) != OMP_CLAUSE_MAP)
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 4f7c314..d37825e 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -9189,7 +9189,7 @@ finish_omp_clauses (tree clauses, enum c_omp_region_type ort)
 	      bitmap_set_bit (&map_firstprivate_head, DECL_UID (t));
 	    else if (bitmap_bit_p (&map_head, DECL_UID (t))
 		     && !bitmap_bit_p (&map_field_head, DECL_UID (t))
-		     && ort != C_ORT_OMP
+		     && ort != C_ORT_OMP && ort != C_ORT_OMP_TARGET
 		     && ort != C_ORT_OMP_EXIT_DATA)
 	      {
 		if (OMP_CLAUSE_CODE (c) != OMP_CLAUSE_MAP)
diff --git a/gcc/omp-low.cc b/gcc/omp-low.cc
index 0d6f947..604b0fe 100644
--- a/gcc/omp-low.cc
+++ b/gcc/omp-low.cc
@@ -780,24 +780,28 @@ build_sender_ref (tree var, omp_context *ctx)
   return build_sender_ref ((splay_tree_key) var, ctx);
 }
 
-/* Add a new field for VAR inside the structure CTX->SENDER_DECL.  If
-   BASE_POINTERS_RESTRICT, declare the field with restrict.  */
-
 static void
-install_var_field (tree var, bool by_ref, int mask, omp_context *ctx)
+install_var_field (tree var, bool by_ref, int mask, omp_context *ctx,
+		   tree key_expr = NULL_TREE)
 {
   tree field, type, sfield = NULL_TREE;
   splay_tree_key key = (splay_tree_key) var;
 
-  if ((mask & 16) != 0)
-    {
-      key = (splay_tree_key) &DECL_NAME (var);
-      gcc_checking_assert (key != (splay_tree_key) var);
-    }
-  if ((mask & 8) != 0)
+  if (key_expr)
+    /* Allow user to explicitly set the expression used as the key.  */
+    key = (splay_tree_key) key_expr;
+  else
     {
-      key = (splay_tree_key) &DECL_UID (var);
-      gcc_checking_assert (key != (splay_tree_key) var);
+      if ((mask & 16) != 0)
+	{
+	  key = (splay_tree_key) &DECL_NAME (var);
+	  gcc_checking_assert (key != (splay_tree_key) var);
+	}
+      if ((mask & 8) != 0)
+	{
+	  key = (splay_tree_key) &DECL_UID (var);
+	  gcc_checking_assert (key != (splay_tree_key) var);
+	}
     }
   gcc_assert ((mask & 1) == 0
 	      || !splay_tree_lookup (ctx->field_map, key));
@@ -1502,8 +1506,13 @@ scan_sharing_clauses (tree clauses, omp_context *ctx)
 		  || (OMP_CLAUSE_CODE (c) == OMP_CLAUSE_HAS_DEVICE_ADDR
 		      && lang_hooks.decls.omp_array_data (decl, true)))
 		{
+		  /* OpenACC firstprivate clauses are later processed with same
+		     code path as map clauses in lower_omp_target, so follow
+		     the same convention of using the whole clause expression
+		     as splay-tree key.  */
+		  tree k = (is_oacc_parallel_or_serial (ctx) ? c : NULL_TREE);
 		  by_ref = !omp_privatize_by_reference (decl);
-		  install_var_field (decl, by_ref, 3, ctx);
+		  install_var_field (decl, by_ref, 3, ctx, k);
 		}
 	      else if (OMP_CLAUSE_CODE (c) == OMP_CLAUSE_HAS_DEVICE_ADDR)
 		{
@@ -1815,7 +1824,7 @@ scan_sharing_clauses (tree clauses, omp_context *ctx)
 		  t = TREE_TYPE (t);
 		}
 
-	      install_var_field (array_decl, by_ref, 3, ctx);
+	      install_var_field (array_decl, by_ref, 3, ctx, c);
 	      install_var_local (array_decl, ctx);
 	      break;
 	    }
@@ -1829,7 +1838,7 @@ scan_sharing_clauses (tree clauses, omp_context *ctx)
 		  gcc_assert (INDIRECT_REF_P (decl2));
 		  decl2 = TREE_OPERAND (decl2, 0);
 		  gcc_assert (DECL_P (decl2));
-		  install_var_field (decl2, true, 3, ctx);
+		  install_var_field (decl2, true, 3, ctx, c);
 		  install_var_local (decl2, ctx);
 		  install_var_local (decl, ctx);
 		}
@@ -1839,9 +1848,9 @@ scan_sharing_clauses (tree clauses, omp_context *ctx)
 		      && OMP_CLAUSE_MAP_KIND (c) == GOMP_MAP_POINTER
 		      && !OMP_CLAUSE_MAP_ZERO_BIAS_ARRAY_SECTION (c)
 		      && TREE_CODE (TREE_TYPE (decl)) == ARRAY_TYPE)
-		    install_var_field (decl, true, 7, ctx);
+		    install_var_field (decl, true, 7, ctx, c);
 		  else
-		    install_var_field (decl, true, 3, ctx);
+		    install_var_field (decl, true, 3, ctx, c);
 		  if (is_gimple_omp_offloaded (ctx->stmt)
 		      && !(is_gimple_omp_oacc (ctx->stmt)
 			   && OMP_CLAUSE_MAP_IN_REDUCTION (c)))
@@ -1876,7 +1885,7 @@ scan_sharing_clauses (tree clauses, omp_context *ctx)
 				  FIELD_DECL, NULL_TREE, ptr_type_node);
 		  SET_DECL_ALIGN (field, TYPE_ALIGN (ptr_type_node));
 		  insert_field_into_struct (ctx->record_type, field);
-		  splay_tree_insert (ctx->field_map, (splay_tree_key) decl,
+		  splay_tree_insert (ctx->field_map, (splay_tree_key) c,
 				     (splay_tree_value) field);
 		}
 	    }
@@ -4661,8 +4670,19 @@ maybe_lookup_field_in_outer_ctx (tree decl, omp_context *ctx)
   omp_context *up;
 
   for (up = ctx->outer; up; up = up->outer)
-    if (maybe_lookup_field (decl, up))
-      return true;
+    {
+      for (tree c = gimple_omp_target_clauses (up->stmt);
+	   c != NULL_TREE; c = OMP_CLAUSE_CHAIN (c))
+	if ((OMP_CLAUSE_CODE (c) == OMP_CLAUSE_MAP
+	     || OMP_CLAUSE_CODE (c) == OMP_CLAUSE_TO
+	     || OMP_CLAUSE_CODE (c) == OMP_CLAUSE_FROM
+	     || (is_oacc_parallel_or_serial (up)
+		 && OMP_CLAUSE_CODE (c) == OMP_CLAUSE_FIRSTPRIVATE))
+	    && OMP_CLAUSE_DECL (c) == decl)
+	  return true;
+      if (maybe_lookup_field (decl, up))
+	return true;
+    }
 
   return false;
 }
@@ -7659,6 +7679,7 @@ lower_oacc_reductions (location_t loc, tree clauses, tree level, bool inner,
 	gcc_checking_assert (!is_oacc_kernels_decomposed_part (ctx));
 
 	tree orig = OMP_CLAUSE_DECL (c);
+	tree orig_clause;
 	tree var;
 	tree ref_to_res = NULL_TREE;
 	tree incoming, outgoing;
@@ -7741,8 +7762,18 @@ lower_oacc_reductions (location_t loc, tree clauses, tree level, bool inner,
 	  do_lookup:
 	    /* This is the outermost construct with this reduction,
 	       see if there's a mapping for it.  */
-	    if (gimple_code (outer->stmt) == GIMPLE_OMP_TARGET
-		&& (maybe_lookup_field (orig, outer) || is_fpp) && !is_private)
+	    orig_clause = NULL_TREE;
+	    if (gimple_code (outer->stmt) == GIMPLE_OMP_TARGET)
+	      for (tree cls = gimple_omp_target_clauses (outer->stmt);
+		   cls; cls = OMP_CLAUSE_CHAIN (cls))
+		if (OMP_CLAUSE_CODE (cls) == OMP_CLAUSE_MAP
+		    && orig == OMP_CLAUSE_DECL (cls)
+		    && maybe_lookup_field (cls, outer))
+		  {
+		    orig_clause = cls;
+		    break;
+		  }
+	    if ((orig_clause != NULL_TREE || is_fpp) && !is_private)
 	      {
 		tree type = TREE_TYPE (var);
 
@@ -7754,7 +7785,7 @@ lower_oacc_reductions (location_t loc, tree clauses, tree level, bool inner,
 		  }
 		else
 		  {
-		    ref_to_res = build_receiver_ref (orig, false, outer);
+		    ref_to_res = build_receiver_ref (orig_clause, false, outer);
 		    if (omp_privatize_by_reference (orig))
 		      ref_to_res = build_simple_mem_ref (ref_to_res);
 		  }
@@ -13183,7 +13214,7 @@ lower_omp_target (gimple_stmt_iterator *gsi_p, omp_context *ctx)
 	    continue;
 	  }
 
-	if (!maybe_lookup_field (var, ctx))
+	if (!maybe_lookup_field (c, ctx))
 	  continue;
 
 	/* Don't remap compute constructs' reduction variables, because the
@@ -13203,7 +13234,7 @@ lower_omp_target (gimple_stmt_iterator *gsi_p, omp_context *ctx)
 	       && TREE_CODE (var_type) != ARRAY_TYPE
 	       ? false : true);
 
-	    x = build_receiver_ref (var, rcv_by_ref, ctx);
+	    x = build_receiver_ref (c, rcv_by_ref, ctx);
 
 	    if (OMP_CLAUSE_CODE (c) == OMP_CLAUSE_FIRSTPRIVATE
 		&& (FLOAT_TYPE_P (inner_type)
@@ -13547,7 +13578,7 @@ lower_omp_target (gimple_stmt_iterator *gsi_p, omp_context *ctx)
 		  }
 		else
 		  {
-		    tree x = build_sender_ref (ovar, ctx);
+		    tree x = build_sender_ref (c, ctx);
 		    tree v = ovar;
 		    if (in_reduction_clauses
 			&& OMP_CLAUSE_CODE (c) == OMP_CLAUSE_MAP
@@ -13595,7 +13626,7 @@ lower_omp_target (gimple_stmt_iterator *gsi_p, omp_context *ctx)
 		    gcc_assert (DECL_P (ovar2));
 		    ovar = ovar2;
 		  }
-		if (!maybe_lookup_field (ovar, ctx)
+		if (!maybe_lookup_field (c, ctx)
 		    && !(OMP_CLAUSE_CODE (c) == OMP_CLAUSE_MAP
 			 && (OMP_CLAUSE_MAP_KIND (c) == GOMP_MAP_ATTACH
 			     || OMP_CLAUSE_MAP_KIND (c) == GOMP_MAP_DETACH)))
@@ -13645,7 +13676,7 @@ lower_omp_target (gimple_stmt_iterator *gsi_p, omp_context *ctx)
 	      }
 	    else if (nc)
 	      {
-		x = build_sender_ref (ovar, ctx);
+		x = build_sender_ref (nc, ctx);
 
 		if (OMP_CLAUSE_CODE (c) == OMP_CLAUSE_MAP
 		    && OMP_CLAUSE_MAP_KIND (c) == GOMP_MAP_POINTER
@@ -14618,7 +14649,7 @@ lower_omp_target (gimple_stmt_iterator *gsi_p, omp_context *ctx)
 		    type = TREE_TYPE (type);
 		    ref_to_ptr = true;
 		  }
-		x = build_receiver_ref (OMP_CLAUSE_DECL (prev), false, ctx);
+		x = build_receiver_ref (prev, false, ctx);
 		x = fold_convert_loc (clause_loc, type, x);
 		if (!integer_zerop (OMP_CLAUSE_SIZE (c)))
 		  {
diff --git a/gcc/testsuite/c-c++-common/gomp/clauses-2.c b/gcc/testsuite/c-c++-common/gomp/clauses-2.c
index 8f98d57..b4b5004 100644
--- a/gcc/testsuite/c-c++-common/gomp/clauses-2.c
+++ b/gcc/testsuite/c-c++-common/gomp/clauses-2.c
@@ -15,7 +15,7 @@ foo (int *p, int q, struct S t, int i, int j, int k, int l)
     bar (p);
   #pragma omp target map (p) , map (p[0])
     bar (p);
-  #pragma omp target map (q) map (q) /* { dg-error "appears more than once in map clauses" } */
+  #pragma omp target map (q) map (q)
     bar (&q);
   #pragma omp target map (p[0]) map (p[0]) /* { dg-error "appears more than once in data clauses" } */
     bar (p);
diff --git a/gcc/testsuite/c-c++-common/gomp/map-6.c b/gcc/testsuite/c-c++-common/gomp/map-6.c
index 014ed35..1172cdb 100644
--- a/gcc/testsuite/c-c++-common/gomp/map-6.c
+++ b/gcc/testsuite/c-c++-common/gomp/map-6.c
@@ -157,10 +157,10 @@ foo (void)
   #pragma omp target map (always, close)
   ;
 
-  #pragma omp target map (always, always)  /* { dg-error "'always' appears more than once in map clauses" } */
+  #pragma omp target map (always, always)
   ;
 
-  #pragma omp target map (always, always, close)  /* { dg-error "'always' appears more than once in map clauses" } */
+  #pragma omp target map (always, always, close)
   ;
 
   #pragma omp target map (always, close, to: always, close, b7)