openmp: Implicitly add 'declare target' directives for dynamic initializers in C++

2020-12-18  Kwok Cheung Yeung  <kcy@codesourcery.com>

	gcc/
	* langhooks-def.h (lhd_get_decl_init): New.
	(lhd_finish_decl_inits): New.
	(LANG_HOOKS_GET_DECL_INIT): New.
	(LANG_HOOKS_OMP_FINISH_DECL_INITS): New.
	(LANG_HOOKS_DECLS): Add LANG_HOOKS_GET_DECL_INIT and
	LANG_HOOKS_OMP_FINISH_DECL_INITS.
	* langhooks.c (lhd_omp_get_decl_init): New.
	(lhd_omp_finish_decl_inits): New.
	* langhooks.h (struct lang_hooks_for_decls): Add omp_get_decl_init
	and omp_finish_decl_inits.
	* omp-offload.c (omp_discover_declare_target_var_r): Use
	get_decl_init langhook in place of DECL_INITIAL.  Call
	omp_finish_decl_inits langhook at end of function.

	gcc/cp/
	* cp-lang.c (cxx_get_decl_init): New.
	(cxx_omp_finish_decl_inits): New.
	(LANG_HOOKS_GET_DECL_INIT): New.
	(LANG_HOOKS_OMP_FINISH_DECL_INITS): New.
	* cp-tree.h (dynamic_initializers): New.
	* decl.c (dynamic_initializers): New.
	* decl2.c (c_parse_final_cleanups): Add initializer entries
	from vars to dynamic_initializers.

	gcc/testsuite/
	* g++.dg/gomp/declare-target-3.C: New.

1 files changed, 32 insertions, 0 deletions

diff --git a/gcc/cp/cp-lang.c b/gcc/cp/cp-lang.c
index 5d2aef4..0c3be0f 100644
--- a/gcc/cp/cp-lang.c
+++ b/gcc/cp/cp-lang.c
@@ -34,6 +34,8 @@ static tree cp_eh_personality (void);
 static tree get_template_innermost_arguments_folded (const_tree);
 static tree get_template_argument_pack_elems_folded (const_tree);
 static tree cxx_enum_underlying_base_type (const_tree);
+static tree *cxx_omp_get_decl_init (tree);
+static void cxx_omp_finish_decl_inits (void);
 
 /* Lang hooks common to C++ and ObjC++ are declared in cp/cp-objcp-common.h;
    consequently, there should be very few hooks below.  */
@@ -92,6 +94,12 @@ static tree cxx_enum_underlying_base_type (const_tree);
 #undef LANG_HOOKS_GET_SUBSTRING_LOCATION
 #define LANG_HOOKS_GET_SUBSTRING_LOCATION c_get_substring_location
 
+#undef LANG_HOOKS_OMP_GET_DECL_INIT
+#define LANG_HOOKS_OMP_GET_DECL_INIT cxx_omp_get_decl_init
+
+#undef LANG_HOOKS_OMP_FINISH_DECL_INITS
+#define LANG_HOOKS_OMP_FINISH_DECL_INITS cxx_omp_finish_decl_inits
+
 /* Each front end provides its own lang hook initializer.  */
 struct lang_hooks lang_hooks = LANG_HOOKS_INITIALIZER;
 
@@ -233,6 +241,30 @@ tree cxx_enum_underlying_base_type (const_tree type)
   return underlying_type;
 }
 
+/* The C++ version of the omp_get_decl_init langhook returns the static
+   initializer for a variable declaration if present, otherwise it
+   tries to find and return the dynamic initializer.  If not present,
+   it returns NULL.  */
+
+static tree *
+cxx_omp_get_decl_init (tree decl)
+{
+  if (DECL_INITIAL (decl))
+    return &DECL_INITIAL (decl);
+
+  return hash_map_safe_get (dynamic_initializers, decl);
+}
+
+/* The C++ version of the omp_finish_decl_inits langhook allows GC to
+   reclaim the memory used by the hash-map used to hold dynamic initializer
+   information.  */
+
+static void
+cxx_omp_finish_decl_inits (void)
+{
+  dynamic_initializers = NULL;
+}
+
 #if CHECKING_P
 
 namespace selftest {