openmp: Add support for strict modifier on grainsize/num_tasks clauses

With strict: modifier on these clauses, the standard is explicit about
how many iterations (and which) each generated task of taskloop directive
should contain.  For num_tasks it actually matches what we were already
implementing, but for grainsize it does not (and even violates the old
rule - without strict it requires that the number of iterations (unspecified
which exactly) handled by each generated task is >= grainsize argument and
< 2 * grainsize argument, with strict: it requires that each generated
task handles exactly == grainsize argument iterations, except for the
generated task handling the last iteration which can handles <= grainsize
iterations).

The following patch implements it for C and C++.

2021-08-23  Jakub Jelinek  <jakub@redhat.com>

gcc/
	* tree.h (OMP_CLAUSE_GRAINSIZE_STRICT): Define.
	(OMP_CLAUSE_NUM_TASKS_STRICT): Define.
	* tree-pretty-print.c (dump_omp_clause) <case OMP_CLAUSE_GRAINSIZE,
	case OMP_CLAUSE_NUM_TASKS>: Print strict: modifier.
	* omp-expand.c (expand_task_call): Use GOMP_TASK_FLAG_STRICT in iflags
	if either grainsize or num_tasks clause has the strict modifier.
gcc/c/
	* c-parser.c (c_parser_omp_clause_num_tasks,
	c_parser_omp_clause_grainsize): Parse the optional strict: modifier.
gcc/cp/
	* parser.c (cp_parser_omp_clause_num_tasks,
	cp_parser_omp_clause_grainsize): Parse the optional strict: modifier.
include/
	* gomp-constants.h (GOMP_TASK_FLAG_STRICT): Define.
libgomp/
	* taskloop.c (GOMP_taskloop): Handle GOMP_TASK_FLAG_STRICT.
	* testsuite/libgomp.c-c++-common/taskloop-4.c (main): Fix up comment.
	* testsuite/libgomp.c-c++-common/taskloop-5.c: New test.

5 files changed, 84 insertions, 5 deletions

diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index c578307..356cf25 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -13786,7 +13786,10 @@ c_parser_omp_clause_num_threads (c_parser *parser, tree list)
 }
 
 /* OpenMP 4.5:
-   num_tasks ( expression ) */
+   num_tasks ( expression )
+
+   OpenMP 5.1:
+   num_tasks ( strict : expression ) */
 
 static tree
 c_parser_omp_clause_num_tasks (c_parser *parser, tree list)
@@ -13795,6 +13798,17 @@ c_parser_omp_clause_num_tasks (c_parser *parser, tree list)
   matching_parens parens;
   if (parens.require_open (parser))
     {
+      bool strict = false;
+      if (c_parser_next_token_is (parser, CPP_NAME)
+	  && c_parser_peek_2nd_token (parser)->type == CPP_COLON
+	  && strcmp (IDENTIFIER_POINTER (c_parser_peek_token (parser)->value),
+		     "strict") == 0)
+	{
+	  strict = true;
+	  c_parser_consume_token (parser);
+	  c_parser_consume_token (parser);
+	}
+
       location_t expr_loc = c_parser_peek_token (parser)->location;
       c_expr expr = c_parser_expr_no_commas (parser, NULL);
       expr = convert_lvalue_to_rvalue (expr_loc, expr, false, true);
@@ -13824,6 +13838,7 @@ c_parser_omp_clause_num_tasks (c_parser *parser, tree list)
 
       c = build_omp_clause (num_tasks_loc, OMP_CLAUSE_NUM_TASKS);
       OMP_CLAUSE_NUM_TASKS_EXPR (c) = t;
+      OMP_CLAUSE_NUM_TASKS_STRICT (c) = strict;
       OMP_CLAUSE_CHAIN (c) = list;
       list = c;
     }
@@ -13832,7 +13847,10 @@ c_parser_omp_clause_num_tasks (c_parser *parser, tree list)
 }
 
 /* OpenMP 4.5:
-   grainsize ( expression ) */
+   grainsize ( expression )
+
+   OpenMP 5.1:
+   grainsize ( strict : expression ) */
 
 static tree
 c_parser_omp_clause_grainsize (c_parser *parser, tree list)
@@ -13841,6 +13859,17 @@ c_parser_omp_clause_grainsize (c_parser *parser, tree list)
   matching_parens parens;
   if (parens.require_open (parser))
     {
+      bool strict = false;
+      if (c_parser_next_token_is (parser, CPP_NAME)
+	  && c_parser_peek_2nd_token (parser)->type == CPP_COLON
+	  && strcmp (IDENTIFIER_POINTER (c_parser_peek_token (parser)->value),
+		     "strict") == 0)
+	{
+	  strict = true;
+	  c_parser_consume_token (parser);
+	  c_parser_consume_token (parser);
+	}
+
       location_t expr_loc = c_parser_peek_token (parser)->location;
       c_expr expr = c_parser_expr_no_commas (parser, NULL);
       expr = convert_lvalue_to_rvalue (expr_loc, expr, false, true);
@@ -13870,6 +13899,7 @@ c_parser_omp_clause_grainsize (c_parser *parser, tree list)
 
       c = build_omp_clause (grainsize_loc, OMP_CLAUSE_GRAINSIZE);
       OMP_CLAUSE_GRAINSIZE_EXPR (c) = t;
+      OMP_CLAUSE_GRAINSIZE_STRICT (c) = strict;
       OMP_CLAUSE_CHAIN (c) = list;
       list = c;
     }
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 63c9503..a959c71 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -37237,7 +37237,10 @@ cp_parser_omp_clause_num_threads (cp_parser *parser, tree list,
 }
 
 /* OpenMP 4.5:
-   num_tasks ( expression ) */
+   num_tasks ( expression )
+
+   OpenMP 5.1:
+   num_tasks ( strict : expression ) */
 
 static tree
 cp_parser_omp_clause_num_tasks (cp_parser *parser, tree list,
@@ -37249,6 +37252,19 @@ cp_parser_omp_clause_num_tasks (cp_parser *parser, tree list,
   if (!parens.require_open (parser))
     return list;
 
+  bool strict = false;
+  if (cp_lexer_next_token_is (parser->lexer, CPP_NAME)
+      && cp_lexer_nth_token_is (parser->lexer, 2, CPP_COLON))
+    {
+      tree id = cp_lexer_peek_token (parser->lexer)->u.value;
+      if (!strcmp (IDENTIFIER_POINTER (id), "strict"))
+	{
+	  strict = true;
+	  cp_lexer_consume_token (parser->lexer);
+	  cp_lexer_consume_token (parser->lexer);
+	}
+    }
+
   t = cp_parser_assignment_expression (parser);
 
   if (t == error_mark_node
@@ -37262,13 +37278,17 @@ cp_parser_omp_clause_num_tasks (cp_parser *parser, tree list,
 
   c = build_omp_clause (location, OMP_CLAUSE_NUM_TASKS);
   OMP_CLAUSE_NUM_TASKS_EXPR (c) = t;
+  OMP_CLAUSE_NUM_TASKS_STRICT (c) = strict;
   OMP_CLAUSE_CHAIN (c) = list;
 
   return c;
 }
 
 /* OpenMP 4.5:
-   grainsize ( expression ) */
+   grainsize ( expression )
+
+   OpenMP 5.1:
+   grainsize ( strict : expression ) */
 
 static tree
 cp_parser_omp_clause_grainsize (cp_parser *parser, tree list,
@@ -37280,6 +37300,19 @@ cp_parser_omp_clause_grainsize (cp_parser *parser, tree list,
   if (!parens.require_open (parser))
     return list;
 
+  bool strict = false;
+  if (cp_lexer_next_token_is (parser->lexer, CPP_NAME)
+      && cp_lexer_nth_token_is (parser->lexer, 2, CPP_COLON))
+    {
+      tree id = cp_lexer_peek_token (parser->lexer)->u.value;
+      if (!strcmp (IDENTIFIER_POINTER (id), "strict"))
+	{
+	  strict = true;
+	  cp_lexer_consume_token (parser->lexer);
+	  cp_lexer_consume_token (parser->lexer);
+	}
+    }
+
   t = cp_parser_assignment_expression (parser);
 
   if (t == error_mark_node
@@ -37293,6 +37326,7 @@ cp_parser_omp_clause_grainsize (cp_parser *parser, tree list,
 
   c = build_omp_clause (location, OMP_CLAUSE_GRAINSIZE);
   OMP_CLAUSE_GRAINSIZE_EXPR (c) = t;
+  OMP_CLAUSE_GRAINSIZE_STRICT (c) = strict;
   OMP_CLAUSE_CHAIN (c) = list;
 
   return c;
diff --git a/gcc/omp-expand.c b/gcc/omp-expand.c
index c868b8c..66c64f5 100644
--- a/gcc/omp-expand.c
+++ b/gcc/omp-expand.c
@@ -791,13 +791,19 @@ expand_task_call (struct omp_region *region, basic_block bb,
       tree tclauses = gimple_omp_for_clauses (g);
       num_tasks = omp_find_clause (tclauses, OMP_CLAUSE_NUM_TASKS);
       if (num_tasks)
-	num_tasks = OMP_CLAUSE_NUM_TASKS_EXPR (num_tasks);
+	{
+	  if (OMP_CLAUSE_NUM_TASKS_STRICT (num_tasks))
+	    iflags |= GOMP_TASK_FLAG_STRICT;
+	  num_tasks = OMP_CLAUSE_NUM_TASKS_EXPR (num_tasks);
+	}
       else
 	{
 	  num_tasks = omp_find_clause (tclauses, OMP_CLAUSE_GRAINSIZE);
 	  if (num_tasks)
 	    {
 	      iflags |= GOMP_TASK_FLAG_GRAINSIZE;
+	      if (OMP_CLAUSE_GRAINSIZE_STRICT (num_tasks))
+		iflags |= GOMP_TASK_FLAG_STRICT;
 	      num_tasks = OMP_CLAUSE_GRAINSIZE_EXPR (num_tasks);
 	    }
 	  else
diff --git a/gcc/tree-pretty-print.c b/gcc/tree-pretty-print.c
index 0570fdc..e103d2c 100644
--- a/gcc/tree-pretty-print.c
+++ b/gcc/tree-pretty-print.c
@@ -1066,6 +1066,8 @@ dump_omp_clause (pretty_printer *pp, tree clause, int spc, dump_flags_t flags)
 
     case OMP_CLAUSE_GRAINSIZE:
       pp_string (pp, "grainsize(");
+      if (OMP_CLAUSE_GRAINSIZE_STRICT (clause))
+	pp_string (pp, "strict:");
       dump_generic_node (pp, OMP_CLAUSE_GRAINSIZE_EXPR (clause),
 			 spc, flags, false);
       pp_right_paren (pp);
@@ -1073,6 +1075,8 @@ dump_omp_clause (pretty_printer *pp, tree clause, int spc, dump_flags_t flags)
 
     case OMP_CLAUSE_NUM_TASKS:
       pp_string (pp, "num_tasks(");
+      if (OMP_CLAUSE_NUM_TASKS_STRICT (clause))
+	pp_string (pp, "strict:");
       dump_generic_node (pp, OMP_CLAUSE_NUM_TASKS_EXPR (clause),
 			 spc, flags, false);
       pp_right_paren (pp);
diff --git a/gcc/tree.h b/gcc/tree.h
index 905417f..060a41f 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -1612,6 +1612,11 @@ class auto_suppress_location_wrappers
 #define OMP_CLAUSE_PRIORITY_EXPR(NODE) \
   OMP_CLAUSE_OPERAND (OMP_CLAUSE_SUBCODE_CHECK (NODE, OMP_CLAUSE_PRIORITY),0)
 
+#define OMP_CLAUSE_GRAINSIZE_STRICT(NODE) \
+  TREE_PRIVATE (OMP_CLAUSE_SUBCODE_CHECK (NODE, OMP_CLAUSE_GRAINSIZE))
+#define OMP_CLAUSE_NUM_TASKS_STRICT(NODE) \
+  TREE_PRIVATE (OMP_CLAUSE_SUBCODE_CHECK (NODE, OMP_CLAUSE_NUM_TASKS))
+
 /* OpenACC clause expressions  */
 #define OMP_CLAUSE_EXPR(NODE, CLAUSE) \
   OMP_CLAUSE_OPERAND (OMP_CLAUSE_SUBCODE_CHECK (NODE, CLAUSE), 0)