From 227ffed7dbbdffeeb5bc013852d61a97aa468c62 Mon Sep 17 00:00:00 2001
From: Nathan Sidwell <nathan@acm.org>
Date: Wed, 8 Jun 2022 11:25:14 -0700
Subject: [PATCH] c++: Better module initializer code
Every module interface needs to emit a global initializer, but it
might have nothing to init. In those cases, there's no need for any
idempotency boolean to be emitted.
gcc/cp
* cp-tree.h (module_initializer_kind): Replace with ...
(module_global_init_needed, module_has_import_inits): ...
these.
* decl2.cc (start_objects): Add has_body parm. Reorganize
module initializer creation.
(generate_ctor_or_dtor_function): Adjust.
(c_parse_final_cleanups): Adjust.
(vtv_start_verification_constructor_init_function): Adjust.
* module.cc (module_initializer_kind): Replace with ...
(module_global_init_needed, module_has_import_inits): ...
these.
gcc/testsuite/
* g++.dg/modules/init-2_a.C: Check no idempotency.
* g++.dg/modules/init-2_b.C: Check idempotency.
---
gcc/cp/cp-tree.h | 3 ++-
gcc/cp/decl2.cc | 32 +++++++++++++------------
gcc/cp/module.cc | 23 +++++++++---------
gcc/testsuite/g++.dg/modules/init-2_a.C | 2 ++
gcc/testsuite/g++.dg/modules/init-2_b.C | 2 ++
5 files changed, 34 insertions(+), 28 deletions(-)
@@ -7179,7 +7179,8 @@ extern module_state *get_module (tree name, module_state *parent = NULL,
bool partition = false);
extern bool module_may_redeclare (tree decl);
-extern int module_initializer_kind ();
+extern bool module_global_init_needed ();
+extern bool module_has_import_inits ();
extern void module_add_import_initializers ();
/* Where the namespace-scope decl was originally declared. */
@@ -55,7 +55,7 @@ int raw_dump_id;
extern cpp_reader *parse_in;
-static tree start_objects (bool, unsigned);
+static tree start_objects (bool, unsigned, bool);
static tree finish_objects (bool, unsigned, tree);
static tree start_partial_init_fini_fn (bool, unsigned, unsigned);
static void finish_partial_init_fini_fn (tree);
@@ -3848,15 +3848,13 @@ generate_tls_wrapper (tree fn)
/* Start a global constructor or destructor function. */
static tree
-start_objects (bool initp, unsigned priority)
+start_objects (bool initp, unsigned priority, bool has_body)
{
- int module_init = 0;
-
- if (priority == DEFAULT_INIT_PRIORITY && initp)
- module_init = module_initializer_kind ();
-
+ bool default_init = initp && priority == DEFAULT_INIT_PRIORITY;
+ bool is_module_init = default_init && module_global_init_needed ();
tree name = NULL_TREE;
- if (module_init > 0)
+
+ if (is_module_init)
name = mangle_module_global_init (0);
else
{
@@ -3880,7 +3878,7 @@ start_objects (bool initp, unsigned priority)
tree fntype = build_function_type (void_type_node, void_list_node);
tree fndecl = build_lang_decl (FUNCTION_DECL, name, fntype);
DECL_CONTEXT (fndecl) = FROB_CONTEXT (global_namespace);
- if (module_init > 0)
+ if (is_module_init)
{
SET_DECL_ASSEMBLER_NAME (fndecl, name);
TREE_PUBLIC (fndecl) = true;
@@ -3905,8 +3903,10 @@ start_objects (bool initp, unsigned priority)
tree body = begin_compound_stmt (BCS_FN_BODY);
- if (module_init > 0)
+ bool has_import_inits = default_init && module_has_import_inits ();
+ if (is_module_init && (has_import_inits || has_body))
{
+ // If the function is going to be empty, don't emit idempotency.
// 'static bool __in_chrg = false;
// if (__inchrg) return;
// __inchrg = true
@@ -3930,7 +3930,7 @@ start_objects (bool initp, unsigned priority)
finish_expr_stmt (assign);
}
- if (module_init)
+ if (has_import_inits)
module_add_import_initializers ();
return body;
@@ -4321,7 +4321,7 @@ generate_ctor_or_dtor_function (bool initp, unsigned priority,
{
input_location = locus;
- tree body = start_objects (initp, priority);
+ tree body = start_objects (initp, priority, bool (fns));
/* To make sure dynamic construction doesn't access globals from other
compilation units where they might not be yet constructed, for
@@ -4359,7 +4359,9 @@ generate_ctor_or_dtor_function (bool initp, unsigned priority,
if (initp && (flag_sanitize & SANITIZE_ADDRESS))
finish_expr_stmt (asan_dynamic_init_call (/*after_p=*/true));
- /* Close out the function. */
+ /* Close out the function, and arrange for it to be called at init
+ or fini time. (Even module initializer functions need this, as
+ we cannot guarantee the module is imported somewhere in the programq.) */
expand_or_defer_fn (finish_objects (initp, priority, body));
}
@@ -5205,7 +5207,7 @@ c_parse_final_cleanups (void)
push_lang_context (lang_name_c);
if ((c_dialect_objc () && objc_static_init_needed_p ())
- || module_initializer_kind ())
+ || module_global_init_needed () || module_has_import_inits ())
{
// Make sure there's a default priority entry.
if (!static_init_fini_fns[true])
@@ -5871,7 +5873,7 @@ mark_used (tree decl)
tree
vtv_start_verification_constructor_init_function (void)
{
- return start_objects (/*initp=*/true, MAX_RESERVED_INIT_PRIORITY - 1);
+ return start_objects (/*initp=*/true, MAX_RESERVED_INIT_PRIORITY - 1, true);
}
tree
@@ -19026,22 +19026,21 @@ declare_module (module_state *module, location_t from_loc, bool exporting_p,
}
}
-/* +1, we're the primary or a partition. Therefore emitting a
- globally-callable idemportent initializer function.
- -1, we have direct imports. Therefore emitting calls to their
- initializers. */
+/* Return true IFF we must emit a module global initializer function
+ (which will be called by importers' init code). */
-int
-module_initializer_kind ()
+bool
+module_global_init_needed ()
{
- int result = 0;
+ return module_has_cmi_p () && !header_module_p ();
+}
- if (module_has_cmi_p () && !header_module_p ())
- result = +1;
- else if (num_init_calls_needed)
- result = -1;
+/* Return true IFF we have import global inits to call. */
- return result;
+bool
+module_has_import_inits ()
+{
+ return bool (num_init_calls_needed);
}
/* Emit calls to each direct import's global initializer. Including
@@ -3,3 +3,5 @@ export module Foo;
// { dg-module-cmi Foo }
// { dg-final { scan-assembler {_ZGIW3Foo:} } }
+// But it is empty, and so no idempotency bool
+// { dg-final { scan-assembler-not {_ZZ9_ZGIW3FooE9__in_chrg} } }
@@ -5,4 +5,6 @@ export module Bar;
import Foo;
// { dg-final { scan-assembler {_?_ZGIW3Bar:} } }
+// There should be an idempotency check
+// { dg-final { scan-assembler {_ZZ9_ZGIW3BarE9__in_chrg} } }
// { dg-final { scan-assembler {call[ \t]+_?_ZGIW3Foo} { target i?86-*-* x86_64-*-* } } }
--
2.30.2