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.

1 files changed, 36 insertions, 2 deletions

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;