OpenMP 5.0: map this[:1] in C++ non-static member functions (PR 92120)

This is a merge of:
https://gcc.gnu.org/pipermail/gcc-patches/2020-November/558975.html

This patch creates automatic mapping of map(this[:1]) and pointer members
as zero-length array sections, as specified by the OpenMP 5.0 specification.

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

2021-02-02  Chung-Lin Tang  <cltang@codesourcery.com>

PR middle-end/92120

gcc/cp/ChangeLog:

	* cp-tree.h (finish_omp_target): New declaration.
	(set_omp_target_this_expr): Likewise.
	* lambda.c (lambda_expr_this_capture): Add call to
	set_omp_target_this_expr.
	* parser.c (cp_parser_omp_target): Factor out code, change to call
	finish_omp_target, add re-initing call to set_omp_target_this_expr.
	* semantics.c (omp_target_this_expr): New static variable.
	(omp_target_ptr_members_accessed): New static hash_map for tracking
	accessed non-static pointer-type members.
	(finish_non_static_data_member): Add call to set_omp_target_this_expr.
	Add recording of non-static pointer-type members access.
	(finish_this_expr): Add call to set_omp_target_this_expr.
	(set_omp_target_this_expr): New function to set omp_target_this_expr.
	(finish_omp_target): New function with code merged from
	cp_parser_omp_target, plus code to implement this[:1] and __closure map
	clauses	for OpenMP.

	(handle_omp_array_sections_1): Move code to peel of '*' for
	reference-based COMPONENT_REFs before FIELD_DECL transforming.
	(finish_omp_clauses): Handle 'A->member' case in map clauses.

gcc/ChangeLog:

	* omp-low.c (lower_omp_target):
	Handle GOMP_MAP_ATTACH_ZERO_LENGTH_ARRAY_SECTION, and
	GOMP_MAP_POINTER_TO_ZERO_LENGTH_ARRAY_SECTION map kinds.
	* tree-pretty-print.c (dump_omp_clause): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/gomp/target-this-1.C: New testcase.
	* g++.dg/gomp/target-this-2.C: New testcase.
	* g++.dg/gomp/target-this-3.C: New testcase.
	* g++.dg/gomp/target-this-4.C: New testcase.

include/ChangeLog:

	* gomp-constants.h (enum gomp_map_kind):
	Add GOMP_MAP_ATTACH_ZERO_LENGTH_ARRAY_SECTION, and
	GOMP_MAP_POINTER_TO_ZERO_LENGTH_ARRAY_SECTION map kinds.
	(GOMP_MAP_POINTER_P):
	Include GOMP_MAP_POINTER_TO_ZERO_LENGTH_ARRAY_SECTION.

libgomp/ChangeLog:

	* libgomp.h (gomp_attach_pointer): Add bool parameter.
	* oacc-mem.c (acc_attach_async): Update call to gomp_attach_pointer.
	(goacc_enter_data_internal): Likewise.
	* target.c (gomp_map_vars_existing): Update assert condition to
	include GOMP_MAP_ATTACH_ZERO_LENGTH_ARRAY_SECTION.
	(gomp_map_pointer): Add 'bool allow_zero_length_array_sections'
	parameter, add support for mapping a pointer with NULL target.
	(gomp_attach_pointer): Add 'bool allow_zero_length_array_sections'
	parameter, add support for attaching a pointer with NULL target.
	(gomp_map_vars_internal): Update calls to gomp_map_pointer and
	gomp_attach_pointer, add handling for
	GOMP_MAP_ATTACH_ZERO_LENGTH_ARRAY_SECTION, and
	GOMP_MAP_POINTER_TO_ZERO_LENGTH_ARRAY_SECTION cases.
	* testsuite/libgomp.c++/target-this-1.C: New testcase.
	* testsuite/libgomp.c++/target-this-2.C: New testcase.
	* testsuite/libgomp.c++/target-this-3.C: New testcase.
	* testsuite/libgomp.c++/target-this-4.C: New testcase.

1 files changed, 13 insertions, 1 deletions

diff --git a/include/gomp-constants.h b/include/gomp-constants.h
index 45d553c..d3d4514 100644
--- a/include/gomp-constants.h
+++ b/include/gomp-constants.h
@@ -133,6 +133,11 @@ enum gomp_map_kind
        No refcount is bumped by this, and the store is done unconditionally.  */
     GOMP_MAP_ALWAYS_POINTER =		(GOMP_MAP_FLAG_SPECIAL_2
 					 | GOMP_MAP_FLAG_SPECIAL | 1),
+    /* Like GOMP_MAP_POINTER, but allow zero-length array section, i.e. set to
+       NULL if target is not mapped.  */
+    GOMP_MAP_POINTER_TO_ZERO_LENGTH_ARRAY_SECTION
+      =					(GOMP_MAP_FLAG_SPECIAL_2
+					 | GOMP_MAP_FLAG_SPECIAL | 2),
     /* Forced deallocation of zero length array section.  */
     GOMP_MAP_DELETE_ZERO_LEN_ARRAY_SECTION
       =					(GOMP_MAP_FLAG_SPECIAL_2
@@ -178,6 +183,12 @@ enum gomp_map_kind
     GOMP_MAP_NONCONTIG_ARRAY_FORCE_PRESENT =	(GOMP_MAP_NONCONTIG_ARRAY
 						 | GOMP_MAP_FORCE_PRESENT),
 
+    /* Like GOMP_MAP_ATTACH, but allow attaching to zero-length array sections
+       (i.e. set to NULL when array section is not mapped) Currently only used
+       by OpenMP.  */
+    GOMP_MAP_ATTACH_ZERO_LENGTH_ARRAY_SECTION
+      =					(GOMP_MAP_DEEP_COPY | 2),
+
     /* Internal to GCC, not used in libgomp.  */
     /* Do not map, but pointer assign a pointer instead.  */
     GOMP_MAP_FIRSTPRIVATE_POINTER =	(GOMP_MAP_LAST | 1),
@@ -201,7 +212,8 @@ enum gomp_map_kind
   ((X) == GOMP_MAP_ALWAYS_POINTER)
 
 #define GOMP_MAP_POINTER_P(X) \
-  ((X) == GOMP_MAP_POINTER)
+  ((X) == GOMP_MAP_POINTER \
+   || (X) == GOMP_MAP_POINTER_TO_ZERO_LENGTH_ARRAY_SECTION)
 
 #define GOMP_MAP_ALWAYS_TO_P(X) \
   (((X) == GOMP_MAP_ALWAYS_TO) || ((X) == GOMP_MAP_ALWAYS_TOFROM))