PR c++/91369 - Implement P0784R7: constexpr new

	PR c++/91369 - Implement P0784R7: constexpr new
c-family/
	* c-cppbuiltin.c (c_cpp_builtins): Predefine
	__cpp_constexpr_dynamic_alloc=201907 for -std=c++2a.
cp/
	* cp-tree.h (enum cp_tree_index): Add CPTI_HEAP_UNINIT_IDENTIFIER,
	CPTI_HEAP_IDENTIFIER and CPTI_HEAP_DELETED_IDENTIFIER.
	(heap_uninit_identifier, heap_identifier, heap_deleted_identifier):
	Define.
	(type_has_constexpr_destructor, build_new_constexpr_heap_type,
	cxx_constant_dtor): Declare.
	* class.c (type_maybe_constexpr_default_constructor): Make static.
	(type_maybe_constexpr_destructor, type_has_constexpr_destructor): New
	functions.
	(finalize_literal_type_property): For c++2a, don't clear
	CLASSTYPE_LITERAL_P for types without trivial destructors unless they
	have non-constexpr destructors.
	(explain_non_literal_class): For c++2a, complain about non-constexpr
	destructors rather than about non-trivial destructors.
	* constexpr.c: Include stor-layout.h.
	(struct constexpr_global_ctx): New type.
	(struct constexpr_ctx): Add global field, remove values and
	constexpr_ops_count.
	(cxx_replaceable_global_alloc_fn): New inline function.
	(cxx_eval_call_expression): For c++2a allow calls to replaceable
	global allocation functions, for new return address of a heap uninit
	var, for delete record its deletion.  Change ctx->values->{get,put} to
	ctx->global->values.{get,put}.
	(non_const_var_error): Add auto_diagnostic_group sentinel.  Emit
	special diagnostics for heap variables.
	(cxx_eval_store_expression): Change ctx->values->{get,put} to
	ctx->global->values.{get,put}.
	(cxx_eval_loop_expr): Initialize jump_target if NULL.  Change
	new_ctx.values->remove to ctx->global->values.remove.
	(cxx_eval_constant_expression): Change *ctx->constexpr_ops_count
	to ctx->global->constexpr_ops_count.  Change ctx->values->{get,put} to
	ctx->global->values.{get,put}.
	<case NOP_EXPR>: Formatting fix.  On cast of replaceable global
	allocation function to some pointer type, adjust the type of
	the heap variable and change name from heap_uninit_identifier
	to heap_identifier.
	(find_heap_var_refs): New function.
	(cxx_eval_outermost_constant_expr): Add constexpr_dtor argument,
	handle evaluation of constexpr dtors and add tracking of heap
	variables.  Use tf_no_cleanup for get_target_expr_with_sfinae.
	(cxx_constant_value): Adjust cxx_eval_outermost_constant_expr caller.
	(cxx_constant_dtor): New function.
	(maybe_constant_value, fold_non_dependent_expr_template,
	maybe_constant_init_1): Adjust cxx_eval_outermost_constant_expr
	callers.
	(potential_constant_expression_1): Ignore clobbers.  Allow
	COND_EXPR_IS_VEC_DELETE for c++2a.
	* decl.c (initialize_predefined_identifiers): Add heap identifiers.
	(decl_maybe_constant_destruction): New function.
	(cp_finish_decl): Don't clear TREE_READONLY for constexpr variables
	with non-trivial, but constexpr destructors.
	(register_dtor_fn): For constexpr variables with constexpr non-trivial
	destructors call cxx_maybe_build_cleanup instead of adding destructor
	calls at runtime.
	(expand_static_init): For constexpr variables with constexpr
	non-trivial destructors call cxx_maybe_build_cleanup.
	(grokdeclarator): Allow constexpr destructors for c++2a.  Formatting
	fix.
	(cxx_maybe_build_cleanup): For constexpr variables with constexpr
	non-trivial destructors call cxx_constant_dtor instead of adding
	destructor calls at runtime.
	* init.c: Include stor-layout.h.
	(build_new_constexpr_heap_type, maybe_wrap_new_for_constexpr): New
	functions.
	(build_new_1): For c++2a and new[], add cast around the alloc call
	to help constexpr evaluation figure out the type of the heap storage.
	(build_vec_delete_1): Set DECL_INITIAL of tbase and emit a DECL_EXPR
	for it instead of initializing an uninitialized variable.
	* method.c: Include intl.h.
	(SFK_CTOR_P, SFK_DTOR_P, SFK_ASSIGN_P, SFK_COPY_P, SFK_MOVE_P): Move
	definitions earlier.
	(process_subob_fn): Add sfk argument, adjust non-constexpr call
	diagnostics based on it.
	(walk_field_subobs): Formatting fixes.  Adjust process_subob_fn caller.
	(synthesized_method_base_walk): Likewise.
	(synthesized_method_walk): Set *constexpr_p to true for dtors in c++2a.
	Fix up DR number in comment.
	(implicitly_declare_fn): Formatting fix.
	* typeck2.c (store_init_value): Don't call cp_fully_fold_init on
	initializers of automatic non-constexpr variables in constexpr
	functions.
testsuite/
	* g++.dg/cpp0x/constexpr-delete2.C: Adjust expected diagnostics for
	c++2a.
	* g++.dg/cpp0x/locations1.C: Only expect constexpr ~S() diagnostics
	in c++17_down, adjust expected wording.
	* g++.dg/cpp1y/constexpr-new.C: Only expect diagnostics in c++17_down.
	* g++.dg/cpp2a/constexpr-dtor1.C: New test.
	* g++.dg/cpp2a/constexpr-dtor2.C: New test.
	* g++.dg/cpp2a/constexpr-dtor3.C: New test.
	* g++.dg/cpp2a/constexpr-new1.C: New test.
	* g++.dg/cpp2a/constexpr-new2.C: New test.
	* g++.dg/cpp2a/constexpr-new3.C: New test.
	* g++.dg/cpp2a/constexpr-new4.C: New test.
	* g++.dg/cpp2a/feat-cxx2a.C: Add __cpp_constinit and
	__cpp_constexpr_dynamic_alloc tests.  Tweak __cpp_* tests for c++2a
	features to use style like older features, including #ifdef test.
	* g++.dg/ext/is_literal_type3.C: New test.

From-SVN: r276622

1 files changed, 86 insertions, 11 deletions

diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index 857f360..1c51e26 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -33,6 +33,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "stringpool.h"
 #include "attribs.h"
 #include "asan.h"
+#include "stor-layout.h"
 
 static bool begin_init_stmts (tree *, tree *);
 static tree finish_init_stmts (bool, tree, tree);
@@ -2860,6 +2861,82 @@ std_placement_new_fn_p (tree alloc_fn)
   return false;
 }
 
+/* For element type ELT_TYPE, return the appropriate type of the heap object
+   containing such element(s).  COOKIE_SIZE is NULL or the size of cookie
+   in bytes.  FULL_SIZE is NULL if it is unknown how big the heap allocation
+   will be, otherwise size of the heap object.  If COOKIE_SIZE is NULL,
+   return array type ELT_TYPE[FULL_SIZE / sizeof(ELT_TYPE)], otherwise return
+   struct { size_t[COOKIE_SIZE/sizeof(size_t)]; ELT_TYPE[N]; }
+   where N is nothing (flexible array member) if FULL_SIZE is NULL, otherwise
+   it is computed such that the size of the struct fits into FULL_SIZE.  */
+
+tree
+build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree full_size)
+{
+  gcc_assert (cookie_size == NULL_TREE || tree_fits_uhwi_p (cookie_size));
+  gcc_assert (full_size == NULL_TREE || tree_fits_uhwi_p (full_size));
+  unsigned HOST_WIDE_INT csz = cookie_size ? tree_to_uhwi (cookie_size) : 0;
+  tree itype2 = NULL_TREE;
+  if (full_size)
+    {
+      unsigned HOST_WIDE_INT fsz = tree_to_uhwi (full_size);
+      gcc_assert (fsz >= csz);
+      fsz -= csz;
+      fsz /= int_size_in_bytes (elt_type);
+      itype2 = build_index_type (size_int (fsz - 1));
+      if (!cookie_size)
+	return build_cplus_array_type (elt_type, itype2);
+    }
+  else
+    gcc_assert (cookie_size);
+  csz /= int_size_in_bytes (sizetype);
+  tree itype1 = build_index_type (size_int (csz - 1));
+  tree atype1 = build_cplus_array_type (sizetype, itype1);
+  tree atype2 = build_cplus_array_type (elt_type, itype2);
+  tree rtype = cxx_make_type (RECORD_TYPE);
+  TYPE_NAME (rtype) = heap_identifier;
+  tree fld1 = build_decl (UNKNOWN_LOCATION, FIELD_DECL, NULL_TREE, atype1);
+  tree fld2 = build_decl (UNKNOWN_LOCATION, FIELD_DECL, NULL_TREE, atype2);
+  DECL_FIELD_CONTEXT (fld1) = rtype;
+  DECL_FIELD_CONTEXT (fld2) = rtype;
+  DECL_ARTIFICIAL (fld1) = true;
+  DECL_ARTIFICIAL (fld2) = true;
+  TYPE_FIELDS (rtype) = fld1;
+  DECL_CHAIN (fld1) = fld2;
+  layout_type (rtype);
+  return rtype;
+}
+
+/* Help the constexpr code to find the right type for the heap variable
+   by adding a NOP_EXPR around ALLOC_CALL if needed for cookie_size.
+   Return ALLOC_CALL or ALLOC_CALL cast to a pointer to
+   struct { size_t[cookie_size/sizeof(size_t)]; elt_type[]; }.  */
+
+static tree
+maybe_wrap_new_for_constexpr (tree alloc_call, tree elt_type, tree cookie_size)
+{
+  if (cxx_dialect < cxx2a)
+    return alloc_call;
+
+  if (current_function_decl != NULL_TREE
+      && !DECL_DECLARED_CONSTEXPR_P (current_function_decl))
+    return alloc_call;
+  
+  tree call_expr = extract_call_expr (alloc_call);
+  if (call_expr == error_mark_node)
+    return alloc_call;
+
+  tree alloc_call_fndecl = cp_get_callee_fndecl_nofold (call_expr);
+  if (alloc_call_fndecl == NULL_TREE
+      || !IDENTIFIER_NEW_OP_P (DECL_NAME (alloc_call_fndecl))
+      || CP_DECL_CONTEXT (alloc_call_fndecl) != global_namespace)
+    return alloc_call;
+
+  tree rtype = build_new_constexpr_heap_type (elt_type, cookie_size,
+					      NULL_TREE);
+  return build_nop (build_pointer_type (rtype), alloc_call);
+}
+
 /* Generate code for a new-expression, including calling the "operator
    new" function, initializing the object, and, if an exception occurs
    during construction, cleaning up.  The arguments are as for
@@ -3327,6 +3404,10 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
 	}
     }
 
+  if (cookie_size)
+    alloc_call = maybe_wrap_new_for_constexpr (alloc_call, elt_type,
+					       cookie_size);
+
   /* In the simple case, we can stop now.  */
   pointer_type = build_pointer_type (type);
   if (!cookie_size && !is_initialized)
@@ -3902,17 +3983,11 @@ build_vec_delete_1 (tree base, tree maxindex, tree type,
 			     fold_convert (sizetype, maxindex));
 
   tbase = create_temporary_var (ptype);
-  tbase_init
-    = cp_build_modify_expr (input_location, tbase, NOP_EXPR,
-			    fold_build_pointer_plus_loc (input_location,
-							 fold_convert (ptype,
-								       base),
-							 virtual_size),
-			    complain);
-  if (tbase_init == error_mark_node)
-    return error_mark_node;
-  controller = build3 (BIND_EXPR, void_type_node, tbase,
-		       NULL_TREE, NULL_TREE);
+  DECL_INITIAL (tbase)
+    = fold_build_pointer_plus_loc (input_location, fold_convert (ptype, base),
+				   virtual_size);
+  tbase_init = build_stmt (input_location, DECL_EXPR, tbase);
+  controller = build3 (BIND_EXPR, void_type_node, tbase, NULL_TREE, NULL_TREE);
   TREE_SIDE_EFFECTS (controller) = 1;
 
   body = build1 (EXIT_EXPR, void_type_node,