/* Perform optimizations on tree structure.
Copyright (C) 1998-2021 Free Software Foundation, Inc.
Written by Mark Michell (mark@codesourcery.com).
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
GCC is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3. If not see
. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "target.h"
#include "cp-tree.h"
#include "stringpool.h"
#include "cgraph.h"
#include "debug.h"
#include "tree-inline.h"
#include "tree-iterator.h"
/* Prototypes. */
static void update_cloned_parm (tree, tree, bool);
/* CLONED_PARM is a copy of CLONE, generated for a cloned constructor
or destructor. Update it to ensure that the source-position for
the cloned parameter matches that for the original, and that the
debugging generation code will be able to find the original PARM. */
static void
update_cloned_parm (tree parm, tree cloned_parm, bool first)
{
DECL_ABSTRACT_ORIGIN (cloned_parm) = parm;
/* We may have taken its address. */
TREE_ADDRESSABLE (cloned_parm) = TREE_ADDRESSABLE (parm);
DECL_BY_REFERENCE (cloned_parm) = DECL_BY_REFERENCE (parm);
/* The definition might have different constness. */
TREE_READONLY (cloned_parm) = TREE_READONLY (parm);
TREE_USED (cloned_parm) = !first || TREE_USED (parm);
/* The name may have changed from the declaration. */
DECL_NAME (cloned_parm) = DECL_NAME (parm);
DECL_SOURCE_LOCATION (cloned_parm) = DECL_SOURCE_LOCATION (parm);
TREE_TYPE (cloned_parm) = TREE_TYPE (parm);
DECL_NOT_GIMPLE_REG_P (cloned_parm) = DECL_NOT_GIMPLE_REG_P (parm);
}
/* Like copy_decl_no_change, but handle DECL_OMP_PRIVATIZED_MEMBER
properly. */
static tree
cxx_copy_decl (tree decl, copy_body_data *id)
{
tree copy = copy_decl_no_change (decl, id);
if (VAR_P (decl)
&& DECL_HAS_VALUE_EXPR_P (decl)
&& DECL_ARTIFICIAL (decl)
&& DECL_LANG_SPECIFIC (decl)
&& DECL_OMP_PRIVATIZED_MEMBER (decl))
{
tree expr = DECL_VALUE_EXPR (copy);
walk_tree (&expr, copy_tree_body_r, id, NULL);
SET_DECL_VALUE_EXPR (copy, expr);
}
return copy;
}
/* FN is a function in High GIMPLE form that has a complete body and no
CFG. CLONE is a function whose body is to be set to a copy of FN,
mapping argument declarations according to the ARG_MAP splay_tree. */
static void
clone_body (tree clone, tree fn, void *arg_map)
{
copy_body_data id;
tree stmts;
/* Clone the body, as if we were making an inline call. But, remap
the parameters in the callee to the parameters of caller. */
memset (&id, 0, sizeof (id));
id.src_fn = fn;
id.dst_fn = clone;
id.src_cfun = DECL_STRUCT_FUNCTION (fn);
id.decl_map = static_cast *> (arg_map);
id.copy_decl = cxx_copy_decl;
id.transform_call_graph_edges = CB_CGE_DUPLICATE;
id.transform_new_cfg = true;
id.transform_return_to_modify = false;
/* We're not inside any EH region. */
id.eh_lp_nr = 0;
stmts = DECL_SAVED_TREE (fn);
walk_tree (&stmts, copy_tree_body_r, &id, NULL);
/* Also remap the initializer of any static variables so that they (in
particular, any label addresses) correspond to the base variant rather
than the abstract one. */
if (DECL_NAME (clone) == base_dtor_identifier
|| DECL_NAME (clone) == base_ctor_identifier)
{
unsigned ix;
tree decl;
FOR_EACH_LOCAL_DECL (DECL_STRUCT_FUNCTION (fn), ix, decl)
walk_tree (&DECL_INITIAL (decl), copy_tree_body_r, &id, NULL);
}
append_to_statement_list_force (stmts, &DECL_SAVED_TREE (clone));
}
/* DELETE_DTOR is a delete destructor whose body will be built.
COMPLETE_DTOR is the corresponding complete destructor. */
static void
build_delete_destructor_body (tree delete_dtor, tree complete_dtor)
{
tree parm = DECL_ARGUMENTS (delete_dtor);
tree virtual_size = cxx_sizeof (current_class_type);
/* Call the delete function. */
tree call_delete = build_op_delete_call (DELETE_EXPR, current_class_ptr,
virtual_size,
/*global_p=*/false,
/*placement=*/NULL_TREE,
/*alloc_fn=*/NULL_TREE,
tf_warning_or_error);
tree op = get_callee_fndecl (call_delete);
if (op && DECL_P (op) && destroying_delete_p (op))
{
/* The destroying delete will handle calling complete_dtor. */
add_stmt (call_delete);
}
else
{
/* Call the corresponding complete destructor. */
gcc_assert (complete_dtor);
tree call_dtor = build_cxx_call (complete_dtor, 1, &parm,
tf_warning_or_error);
/* Operator delete must be called, whether or not the dtor throws. */
add_stmt (build2 (TRY_FINALLY_EXPR, void_type_node,
call_dtor, call_delete));
}
/* Return the address of the object.
??? How is it useful to return an invalid address? */
if (targetm.cxx.cdtor_returns_this ())
{
tree val = DECL_ARGUMENTS (delete_dtor);
val = build2 (MODIFY_EXPR, TREE_TYPE (val),
DECL_RESULT (delete_dtor), val);
add_stmt (build_stmt (0, RETURN_EXPR, val));
}
}
/* Return name of comdat group for complete and base ctor (or dtor)
that have the same body. If dtor is virtual, deleting dtor goes
into this comdat group as well. */
static tree
cdtor_comdat_group (tree complete, tree base)
{
tree complete_name = DECL_ASSEMBLER_NAME (complete);
tree base_name = DECL_ASSEMBLER_NAME (base);
char *grp_name;
const char *p, *q;
bool diff_seen = false;
size_t idx;
gcc_assert (IDENTIFIER_LENGTH (complete_name)
== IDENTIFIER_LENGTH (base_name));
grp_name = XALLOCAVEC (char, IDENTIFIER_LENGTH (complete_name) + 1);
p = IDENTIFIER_POINTER (complete_name);
q = IDENTIFIER_POINTER (base_name);
for (idx = 0; idx < IDENTIFIER_LENGTH (complete_name); idx++)
if (p[idx] == q[idx])
grp_name[idx] = p[idx];
else
{
gcc_assert (!diff_seen
&& idx > 0
&& (p[idx - 1] == 'C' || p[idx - 1] == 'D'
|| p[idx - 1] == 'I')
&& p[idx] == '1'
&& q[idx] == '2');
grp_name[idx] = '5';
diff_seen = true;
}
grp_name[idx] = '\0';
gcc_assert (diff_seen);
return get_identifier (grp_name);
}
/* Returns true iff we can make the base and complete [cd]tor aliases of
the same symbol rather than separate functions. */
static bool
can_alias_cdtor (tree fn)
{
/* If aliases aren't supported by the assembler, fail. */
if (!TARGET_SUPPORTS_ALIASES)
return false;
/* We can't use an alias if there are virtual bases. */
if (CLASSTYPE_VBASECLASSES (DECL_CONTEXT (fn)))
return false;
gcc_assert (DECL_MAYBE_IN_CHARGE_CDTOR_P (fn));
/* Don't use aliases for weak/linkonce definitions unless we can put both
symbols in the same COMDAT group. */
return (DECL_INTERFACE_KNOWN (fn)
&& (SUPPORTS_ONE_ONLY || !DECL_WEAK (fn))
&& (!DECL_ONE_ONLY (fn)
|| (HAVE_COMDAT_GROUP && DECL_WEAK (fn))));
}
/* FN is a [cd]tor, fns is a pointer to an array of length 3. Fill fns
with pointers to the base, complete, and deleting variants. */
static void
populate_clone_array (tree fn, tree *fns)
{
tree clone;
fns[0] = NULL_TREE;
fns[1] = NULL_TREE;
fns[2] = NULL_TREE;
FOR_EACH_CLONE (clone, fn)
if (DECL_NAME (clone) == complete_dtor_identifier
|| DECL_NAME (clone) == complete_ctor_identifier)
fns[1] = clone;
else if (DECL_NAME (clone) == base_dtor_identifier
|| DECL_NAME (clone) == base_ctor_identifier)
fns[0] = clone;
else if (DECL_NAME (clone) == deleting_dtor_identifier)
fns[2] = clone;
else
gcc_unreachable ();
}
/* FN is a constructor or destructor, and there are FUNCTION_DECLs
cloned from it nearby. Instead of cloning this body, leave it
alone and create tiny one-call bodies for the cloned
FUNCTION_DECLs. These clones are sibcall candidates, and their
resulting code will be very thunk-esque. */
static bool
maybe_thunk_body (tree fn, bool force)
{
tree bind, block, call, clone, clone_result, fn_parm, fn_parm_typelist;
tree last_arg, modify, *args;
int parmno, vtt_parmno, max_parms;
tree fns[3];
if (!force && !flag_declone_ctor_dtor)
return 0;
/* If function accepts variable arguments, give up. */
last_arg = tree_last (TYPE_ARG_TYPES (TREE_TYPE (fn)));
if (last_arg != void_list_node)
return 0;
/* If we got this far, we've decided to turn the clones into thunks. */
/* We're going to generate code for fn, so it is no longer "abstract."
Also make the unified ctor/dtor private to either the translation unit
(for non-vague linkage ctors) or the COMDAT group (otherwise). */
populate_clone_array (fn, fns);
/* Can happen during error recovery (c++/71464). */
if (!fns[0] || !fns[1])
return 0;
/* Don't use thunks if the base clone omits inherited parameters. */
if (ctor_omit_inherited_parms (fns[0]))
return 0;
DECL_ABSTRACT_P (fn) = false;
if (!DECL_WEAK (fn))
{
TREE_PUBLIC (fn) = false;
DECL_EXTERNAL (fn) = false;
DECL_INTERFACE_KNOWN (fn) = true;
}
else if (HAVE_COMDAT_GROUP)
{
/* At eof, defer creation of mangling aliases temporarily. */
bool save_defer_mangling_aliases = defer_mangling_aliases;
defer_mangling_aliases = true;
tree comdat_group = cdtor_comdat_group (fns[1], fns[0]);
defer_mangling_aliases = save_defer_mangling_aliases;
cgraph_node::get_create (fns[0])->set_comdat_group (comdat_group);
cgraph_node::get_create (fns[1])->add_to_same_comdat_group
(cgraph_node::get_create (fns[0]));
symtab_node::get (fn)->add_to_same_comdat_group
(symtab_node::get (fns[0]));
if (fns[2])
/* If *[CD][12]* dtors go into the *[CD]5* comdat group and dtor is
virtual, it goes into the same comdat group as well. */
cgraph_node::get_create (fns[2])->add_to_same_comdat_group
(symtab_node::get (fns[0]));
/* Emit them now that the thunks are same comdat group aliases. */
if (!save_defer_mangling_aliases)
generate_mangling_aliases ();
TREE_PUBLIC (fn) = false;
DECL_EXTERNAL (fn) = false;
DECL_INTERFACE_KNOWN (fn) = true;
/* function_and_variable_visibility doesn't want !PUBLIC decls to
have these flags set. */
DECL_WEAK (fn) = false;
DECL_COMDAT (fn) = false;
}
/* Find the vtt_parm, if present. */
for (vtt_parmno = -1, parmno = 0, fn_parm = DECL_ARGUMENTS (fn);
fn_parm;
++parmno, fn_parm = TREE_CHAIN (fn_parm))
{
if (DECL_ARTIFICIAL (fn_parm)
&& DECL_NAME (fn_parm) == vtt_parm_identifier)
{
/* Compensate for removed in_charge parameter. */
vtt_parmno = parmno;
break;
}
}
/* Allocate an argument buffer for build_cxx_call().
Make sure it is large enough for any of the clones. */
max_parms = 0;
FOR_EACH_CLONE (clone, fn)
{
int length = list_length (DECL_ARGUMENTS (fn));
if (length > max_parms)
max_parms = length;
}
args = XALLOCAVEC (tree, max_parms);
/* We know that any clones immediately follow FN in TYPE_FIELDS. */
FOR_EACH_CLONE (clone, fn)
{
tree clone_parm;
/* If we've already generated a body for this clone, avoid
duplicating it. (Is it possible for a clone-list to grow after we
first see it?) */
if (DECL_SAVED_TREE (clone) || TREE_ASM_WRITTEN (clone))
continue;
/* Start processing the function. */
start_preparsed_function (clone, NULL_TREE, SF_PRE_PARSED);
if (clone == fns[2])
{
for (clone_parm = DECL_ARGUMENTS (clone); clone_parm;
clone_parm = TREE_CHAIN (clone_parm))
DECL_ABSTRACT_ORIGIN (clone_parm) = NULL_TREE;
/* Build the delete destructor by calling complete destructor and
delete function. */
build_delete_destructor_body (clone, fns[1]);
}
else
{
/* Walk parameter lists together, creating parameter list for
call to original function. */
for (parmno = 0,
fn_parm = DECL_ARGUMENTS (fn),
fn_parm_typelist = TYPE_ARG_TYPES (TREE_TYPE (fn)),
clone_parm = DECL_ARGUMENTS (clone);
fn_parm;
++parmno,
fn_parm = TREE_CHAIN (fn_parm))
{
if (parmno == vtt_parmno && ! DECL_HAS_VTT_PARM_P (clone))
{
gcc_assert (fn_parm_typelist);
/* Clobber argument with formal parameter type. */
args[parmno]
= convert (TREE_VALUE (fn_parm_typelist),
null_pointer_node);
}
else if (parmno == 1 && DECL_HAS_IN_CHARGE_PARM_P (fn))
{
tree in_charge
= copy_node (in_charge_arg_for_name (DECL_NAME (clone)));
args[parmno] = in_charge;
}
/* Map other parameters to their equivalents in the cloned
function. */
else
{
gcc_assert (clone_parm);
DECL_ABSTRACT_ORIGIN (clone_parm) = NULL;
args[parmno] = clone_parm;
/* Clear TREE_ADDRESSABLE on thunk arguments. */
TREE_ADDRESSABLE (clone_parm) = 0;
clone_parm = TREE_CHAIN (clone_parm);
}
if (fn_parm_typelist)
fn_parm_typelist = TREE_CHAIN (fn_parm_typelist);
}
/* We built this list backwards; fix now. */
mark_used (fn);
call = build_cxx_call (fn, parmno, args, tf_warning_or_error);
/* Arguments passed to the thunk by invisible reference should
be transmitted to the callee unchanged. Do not create a
temporary and invoke the copy constructor. The thunking
transformation must not introduce any constructor calls. */
CALL_FROM_THUNK_P (call) = 1;
block = make_node (BLOCK);
if (targetm.cxx.cdtor_returns_this ())
{
clone_result = DECL_RESULT (clone);
modify = build2 (MODIFY_EXPR, TREE_TYPE (clone_result),
clone_result, call);
modify = build1 (RETURN_EXPR, void_type_node, modify);
add_stmt (modify);
}
else
{
add_stmt (call);
}
bind = c_build_bind_expr (DECL_SOURCE_LOCATION (clone),
block, cur_stmt_list);
DECL_SAVED_TREE (clone) = push_stmt_list ();
add_stmt (bind);
}
DECL_ABSTRACT_ORIGIN (clone) = NULL;
expand_or_defer_fn (finish_function (/*inline_p=*/false));
}
return 1;
}
/* FN is a function that has a complete body. Clone the body as
necessary. Returns nonzero if there's no longer any need to
process the main body. */
bool
maybe_clone_body (tree fn)
{
tree comdat_group = NULL_TREE;
tree clone;
tree fns[3];
bool first = true;
int idx;
bool need_alias = false;
/* We only clone constructors and destructors. */
if (!DECL_MAYBE_IN_CHARGE_CDTOR_P (fn))
return 0;
populate_clone_array (fn, fns);
/* Remember if we can't have multiple clones for some reason. We need to
check this before we remap local static initializers in clone_body. */
if (!tree_versionable_function_p (fn))
need_alias = true;
/* We know that any clones immediately follow FN in the TYPE_FIELDS
list. */
push_to_top_level ();
for (idx = 0; idx < 3; idx++)
{
tree parm;
tree clone_parm;
clone = fns[idx];
if (!clone)
continue;
/* Update CLONE's source position information to match FN's. */
DECL_SOURCE_LOCATION (clone) = DECL_SOURCE_LOCATION (fn);
DECL_DECLARED_INLINE_P (clone) = DECL_DECLARED_INLINE_P (fn);
DECL_DECLARED_CONSTEXPR_P (clone) = DECL_DECLARED_CONSTEXPR_P (fn);
DECL_COMDAT (clone) = DECL_COMDAT (fn);
DECL_WEAK (clone) = DECL_WEAK (fn);
/* We don't copy the comdat group from fn to clone because the assembler
name of fn was corrupted by write_mangled_name by adding *INTERNAL*
to it. By doing so, it also corrupted the comdat group. */
if (DECL_ONE_ONLY (fn))
cgraph_node::get_create (clone)->set_comdat_group (cxx_comdat_group (clone));
DECL_USE_TEMPLATE (clone) = DECL_USE_TEMPLATE (fn);
DECL_EXTERNAL (clone) = DECL_EXTERNAL (fn);
DECL_INTERFACE_KNOWN (clone) = DECL_INTERFACE_KNOWN (fn);
DECL_NOT_REALLY_EXTERN (clone) = DECL_NOT_REALLY_EXTERN (fn);
TREE_PUBLIC (clone) = TREE_PUBLIC (fn);
DECL_VISIBILITY (clone) = DECL_VISIBILITY (fn);
DECL_VISIBILITY_SPECIFIED (clone) = DECL_VISIBILITY_SPECIFIED (fn);
DECL_DLLIMPORT_P (clone) = DECL_DLLIMPORT_P (fn);
DECL_ATTRIBUTES (clone) = copy_list (DECL_ATTRIBUTES (fn));
DECL_DISREGARD_INLINE_LIMITS (clone) = DECL_DISREGARD_INLINE_LIMITS (fn);
set_decl_section_name (clone, fn);
/* Adjust the parameter names and locations. */
parm = DECL_ARGUMENTS (fn);
clone_parm = DECL_ARGUMENTS (clone);
/* Update the `this' parameter, which is always first. */
update_cloned_parm (parm, clone_parm, first);
parm = DECL_CHAIN (parm);
clone_parm = DECL_CHAIN (clone_parm);
if (DECL_HAS_IN_CHARGE_PARM_P (fn))
parm = DECL_CHAIN (parm);
if (DECL_HAS_VTT_PARM_P (fn))
parm = DECL_CHAIN (parm);
if (DECL_HAS_VTT_PARM_P (clone))
clone_parm = DECL_CHAIN (clone_parm);
for (; parm && clone_parm;
parm = DECL_CHAIN (parm), clone_parm = DECL_CHAIN (clone_parm))
/* Update this parameter. */
update_cloned_parm (parm, clone_parm, first);
}
bool can_alias = can_alias_cdtor (fn);
/* If we decide to turn clones into thunks, they will branch to fn.
Must have original function available to call. */
if (!can_alias && maybe_thunk_body (fn, need_alias))
{
pop_from_top_level ();
/* We still need to emit the original function. */
return 0;
}
/* Emit the DWARF1 abstract instance. */
(*debug_hooks->deferred_inline_function) (fn);
/* We know that any clones immediately follow FN in the TYPE_FIELDS. */
for (idx = 0; idx < 3; idx++)
{
tree parm;
tree clone_parm;
int parmno;
hash_map *decl_map;
bool alias = false;
clone = fns[idx];
if (!clone)
continue;
/* Start processing the function. */
start_preparsed_function (clone, NULL_TREE, SF_PRE_PARSED);
/* Tell cgraph if both ctors or both dtors are known to have
the same body. */
if (can_alias
&& fns[0]
&& idx == 1
&& cgraph_node::get_create (fns[0])->create_same_body_alias
(clone, fns[0]))
{
alias = true;
if (DECL_ONE_ONLY (fns[0]))
{
/* For comdat base and complete cdtors put them
into the same, *[CD]5* comdat group instead of
*[CD][12]*. */
comdat_group = cdtor_comdat_group (fns[1], fns[0]);
cgraph_node::get_create (fns[0])->set_comdat_group (comdat_group);
if (symtab_node::get (clone)->same_comdat_group)
symtab_node::get (clone)->remove_from_same_comdat_group ();
symtab_node::get (clone)->add_to_same_comdat_group
(symtab_node::get (fns[0]));
}
}
/* Build the delete destructor by calling complete destructor
and delete function. */
if (idx == 2)
{
build_delete_destructor_body (clone, fns[1]);
/* If *[CD][12]* dtors go into the *[CD]5* comdat group and dtor is
virtual, it goes into the same comdat group as well. */
if (comdat_group)
cgraph_node::get_create (clone)->add_to_same_comdat_group
(symtab_node::get (fns[0]));
}
else if (alias)
/* No need to populate body. */ ;
else
{
/* If we can't have multiple copies of FN (say, because there's a
static local initialized with the address of a label), we need
to use an alias for the complete variant. */
if (idx == 1 && need_alias)
{
if (DECL_STRUCT_FUNCTION (fn)->cannot_be_copied_set)
sorry (DECL_STRUCT_FUNCTION (fn)->cannot_be_copied_reason, fn);
else
sorry ("making multiple clones of %qD", fn);
}
/* Remap the parameters. */
decl_map = new hash_map;
for (parmno = 0,
parm = DECL_ARGUMENTS (fn),
clone_parm = DECL_ARGUMENTS (clone);
parm;
++parmno,
parm = DECL_CHAIN (parm))
{
/* Map the in-charge parameter to an appropriate constant. */
if (DECL_HAS_IN_CHARGE_PARM_P (fn) && parmno == 1)
{
tree in_charge;
in_charge = in_charge_arg_for_name (DECL_NAME (clone));
decl_map->put (parm, in_charge);
}
else if (DECL_ARTIFICIAL (parm)
&& DECL_NAME (parm) == vtt_parm_identifier)
{
/* For a subobject constructor or destructor, the next
argument is the VTT parameter. Remap the VTT_PARM
from the CLONE to this parameter. */
if (DECL_HAS_VTT_PARM_P (clone))
{
DECL_ABSTRACT_ORIGIN (clone_parm) = parm;
decl_map->put (parm, clone_parm);
clone_parm = DECL_CHAIN (clone_parm);
}
/* Otherwise, map the VTT parameter to `NULL'. */
else
{
tree t
= fold_convert (TREE_TYPE (parm), null_pointer_node);
decl_map->put (parm, t);
}
}
/* Map other parameters to their equivalents in the cloned
function. */
else
{
tree replacement;
if (clone_parm)
{
replacement = clone_parm;
clone_parm = DECL_CHAIN (clone_parm);
}
else
{
/* Inheriting ctors can omit parameters from the base
clone. Replace them with null lvalues. */
tree reftype = build_reference_type (TREE_TYPE (parm));
replacement = fold_convert (reftype, null_pointer_node);
replacement = convert_from_reference (replacement);
}
decl_map->put (parm, replacement);
}
}
if (targetm.cxx.cdtor_returns_this ())
{
parm = DECL_RESULT (fn);
clone_parm = DECL_RESULT (clone);
decl_map->put (parm, clone_parm);
}
/* Clone the body. */
clone_body (clone, fn, decl_map);
/* Clean up. */
delete decl_map;
}
/* The clone can throw iff the original function can throw. */
cp_function_chain->can_throw = !TREE_NOTHROW (fn);
/* Now, expand this function into RTL, if appropriate. */
finish_function (/*inline_p=*/false);
BLOCK_ABSTRACT_ORIGIN (DECL_INITIAL (clone)) = DECL_INITIAL (fn);
if (alias)
{
if (expand_or_defer_fn_1 (clone))
emit_associated_thunks (clone);
/* We didn't generate a body, so remove the empty one. */
DECL_SAVED_TREE (clone) = NULL_TREE;
}
else
expand_or_defer_fn (clone);
first = false;
}
pop_from_top_level ();
/* We don't need to process the original function any further. */
return 1;
}