/* Support for thunks in symbol table.
Copyright (C) 2003-2023 Free Software Foundation, Inc.
Contributed by Jan Hubicka
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
<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "tree.h"
#include "gimple.h"
#include "predict.h"
#include "target.h"
#include "rtl.h"
#include "alloc-pool.h"
#include "cgraph.h"
#include "symbol-summary.h"
#include "symtab-thunks.h"
#include "lto-streamer.h"
#include "fold-const.h"
#include "gimple-iterator.h"
#include "stor-layout.h"
#include "gimplify-me.h"
#include "varasm.h"
#include "output.h"
#include "cfg.h"
#include "cfghooks.h"
#include "gimple-ssa.h"
#include "gimple-fold.h"
#include "cfgloop.h"
#include "tree-into-ssa.h"
#include "tree-cfg.h"
#include "cfgcleanup.h"
#include "tree-pass.h"
#include "data-streamer.h"
#include "langhooks.h"
/* Used for vtable lookup in thunk adjusting. */
static GTY (()) tree vtable_entry_type;
struct GTY (()) unprocessed_thunk
{
cgraph_node *node;
thunk_info *info;
};
/* To be PCH safe we store thunks into a vector before end of compilation
unit. */
static GTY (()) vec<unprocessed_thunk, va_gc> *thunks;
namespace {
/* Function summary for thunk_infos. */
class GTY((user)) thunk_infos_t: public function_summary <thunk_info *>
{
public:
thunk_infos_t (symbol_table *table, bool ggc):
function_summary<thunk_info *> (table, ggc) { }
/* Hook that is called by summary when a node is duplicated. */
void duplicate (cgraph_node *node,
cgraph_node *node2,
thunk_info *data,
thunk_info *data2) final override;
};
/* Duplication hook. */
void
thunk_infos_t::duplicate (cgraph_node *, cgraph_node *,
thunk_info *src, thunk_info *dst)
{
*dst = *src;
}
} /* anon namespace */
/* Return thunk_info possibly creating new one. */
thunk_info *
thunk_info::get_create (cgraph_node *node)
{
if (!symtab->m_thunks)
{
symtab->m_thunks
= new (ggc_alloc_no_dtor <thunk_infos_t> ())
thunk_infos_t (symtab, true);
symtab->m_thunks->disable_insertion_hook ();
}
return symtab->m_thunks->get_create (node);
}
/* Stream out THIS to OB. */
void
thunk_info::stream_out (lto_simple_output_block *ob)
{
streamer_write_uhwi_stream
(ob->main_stream,
1 + (this_adjusting != 0) * 2
+ (virtual_offset_p != 0) * 4);
streamer_write_uhwi_stream (ob->main_stream, fixed_offset);
streamer_write_uhwi_stream (ob->main_stream, virtual_value);
streamer_write_uhwi_stream (ob->main_stream, indirect_offset);
}
/* Stream in THIS from IB. */
void
thunk_info::stream_in (class lto_input_block *ib)
{
int type = streamer_read_uhwi (ib);
fixed_offset = streamer_read_uhwi (ib);
virtual_value = streamer_read_uhwi (ib);
indirect_offset = streamer_read_uhwi (ib);
this_adjusting = (type & 2);
virtual_offset_p = (type & 4);
}
/* Dump THIS to F. */
void
thunk_info::dump (FILE *f)
{
if (alias)
fprintf (f, " of %s (asm:%s)",
lang_hooks.decl_printable_name (alias, 2),
IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (alias)));
fprintf (f, " fixed offset %i virtual value %i indirect_offset %i "
"has virtual offset %i\n",
(int)fixed_offset,
(int)virtual_value,
(int)indirect_offset,
(int)virtual_offset_p);
}
/* Hash THIS. */
hashval_t
thunk_info::hash ()
{
inchash::hash hstate;
hstate.add_hwi (fixed_offset);
hstate.add_hwi (virtual_value);
hstate.add_flag (this_adjusting);
hstate.add_flag (virtual_offset_p);
return hstate.end ();
}
/* Add unprocessed thunk. */
void
thunk_info::register_early (cgraph_node *node)
{
unprocessed_thunk entry = {node, new (ggc_alloc <thunk_info> ()) thunk_info};
*entry.info = *this;
vec_safe_push (thunks, entry);
}
/* Attach recorded thunks to cgraph_nodes.
All this is done only to avoid need to stream summaries to PCH. */
void
thunk_info::process_early_thunks ()
{
unprocessed_thunk *e;
unsigned int i;
if (!thunks)
return;
FOR_EACH_VEC_ELT (*thunks, i, e)
{
*thunk_info::get_create (e->node) = *e->info;
}
vec_free (thunks);
thunks = NULL;
}
/* Adjust PTR by the constant FIXED_OFFSET, by the vtable offset indicated by
VIRTUAL_OFFSET, and by the indirect offset indicated by INDIRECT_OFFSET, if
it is non-null. THIS_ADJUSTING is nonzero for a this adjusting thunk and zero
for a result adjusting thunk. */
tree
thunk_adjust (gimple_stmt_iterator * bsi,
tree ptr, bool this_adjusting,
HOST_WIDE_INT fixed_offset, tree virtual_offset,
HOST_WIDE_INT indirect_offset)
{
gassign *stmt;
tree ret;
if (this_adjusting
&& fixed_offset != 0)
{
stmt = gimple_build_assign
(ptr, fold_build_pointer_plus_hwi_loc (input_location,
ptr,
fixed_offset));
gsi_insert_after (bsi, stmt, GSI_NEW_STMT);
}
if (!vtable_entry_type && (virtual_offset || indirect_offset != 0))
{
tree vfunc_type = make_node (FUNCTION_TYPE);
TREE_TYPE (vfunc_type) = integer_type_node;
TYPE_ARG_TYPES (vfunc_type) = NULL_TREE;
layout_type (vfunc_type);
vtable_entry_type = build_pointer_type (vfunc_type);
}
/* If there's a virtual offset, look up that value in the vtable and
adjust the pointer again. */
if (virtual_offset)
{
tree vtabletmp;
tree vtabletmp2;
tree vtabletmp3;
vtabletmp = create_tmp_reg
(build_pointer_type
(build_pointer_type (vtable_entry_type)), "vptr");
/* The vptr is always at offset zero in the object. */
stmt = gimple_build_assign (vtabletmp,
build1 (NOP_EXPR, TREE_TYPE (vtabletmp),
ptr));
gsi_insert_after (bsi, stmt, GSI_NEW_STMT);
/* Form the vtable address. */
vtabletmp2 = create_tmp_reg (TREE_TYPE (TREE_TYPE (vtabletmp)),
"vtableaddr");
stmt = gimple_build_assign (vtabletmp2,
build_simple_mem_ref (vtabletmp));
gsi_insert_after (bsi, stmt, GSI_NEW_STMT);
/* Find the entry with the vcall offset. */
stmt = gimple_build_assign (vtabletmp2,
fold_build_pointer_plus_loc (input_location,
vtabletmp2,
virtual_offset));
gsi_insert_after (bsi, stmt, GSI_NEW_STMT);
/* Get the offset itself. */
vtabletmp3 = create_tmp_reg (TREE_TYPE (TREE_TYPE (vtabletmp2)),
"vcalloffset");
stmt = gimple_build_assign (vtabletmp3,
build_simple_mem_ref (vtabletmp2));
gsi_insert_after (bsi, stmt, GSI_NEW_STMT);
/* Adjust the `this' pointer. */
ptr = fold_build_pointer_plus_loc (input_location, ptr, vtabletmp3);
ptr = force_gimple_operand_gsi (bsi, ptr, true, NULL_TREE, false,
GSI_CONTINUE_LINKING);
}
/* Likewise for an offset that is stored in the object that contains the
vtable. */
if (indirect_offset != 0)
{
tree offset_ptr, offset_tree;
/* Get the address of the offset. */
offset_ptr
= create_tmp_reg (build_pointer_type
(build_pointer_type (vtable_entry_type)),
"offset_ptr");
stmt = gimple_build_assign (offset_ptr,
build1 (NOP_EXPR, TREE_TYPE (offset_ptr),
ptr));
gsi_insert_after (bsi, stmt, GSI_NEW_STMT);
stmt = gimple_build_assign
(offset_ptr,
fold_build_pointer_plus_hwi_loc (input_location, offset_ptr,
indirect_offset));
gsi_insert_after (bsi, stmt, GSI_NEW_STMT);
/* Get the offset itself. */
offset_tree = create_tmp_reg (TREE_TYPE (TREE_TYPE (offset_ptr)),
"offset");
stmt = gimple_build_assign (offset_tree,
build_simple_mem_ref (offset_ptr));
gsi_insert_after (bsi, stmt, GSI_NEW_STMT);
/* Adjust the `this' pointer. */
ptr = fold_build_pointer_plus_loc (input_location, ptr, offset_tree);
ptr = force_gimple_operand_gsi (bsi, ptr, true, NULL_TREE, false,
GSI_CONTINUE_LINKING);
}
if (!this_adjusting
&& fixed_offset != 0)
/* Adjust the pointer by the constant. */
{
tree ptrtmp;
if (VAR_P (ptr))
ptrtmp = ptr;
else
{
ptrtmp = create_tmp_reg (TREE_TYPE (ptr), "ptr");
stmt = gimple_build_assign (ptrtmp, ptr);
gsi_insert_after (bsi, stmt, GSI_NEW_STMT);
}
ptr = fold_build_pointer_plus_hwi_loc (input_location,
ptrtmp, fixed_offset);
}
/* Emit the statement and gimplify the adjustment expression. */
ret = create_tmp_reg (TREE_TYPE (ptr), "adjusted_this");
stmt = gimple_build_assign (ret, ptr);
gsi_insert_after (bsi, stmt, GSI_NEW_STMT);
return ret;
}
/* Expand thunk NODE to gimple if possible.
When FORCE_GIMPLE_THUNK is true, gimple thunk is created and
no assembler is produced.
When OUTPUT_ASM_THUNK is true, also produce assembler for
thunks that are not lowered. */
bool
expand_thunk (cgraph_node *node, bool output_asm_thunks,
bool force_gimple_thunk)
{
thunk_info *info = thunk_info::get (node);
bool this_adjusting = info->this_adjusting;
HOST_WIDE_INT fixed_offset = info->fixed_offset;
HOST_WIDE_INT virtual_value = info->virtual_value;
HOST_WIDE_INT indirect_offset = info->indirect_offset;
tree virtual_offset = NULL;
tree alias = node->callees->callee->decl;
tree thunk_fndecl = node->decl;
tree a;
if (!force_gimple_thunk
&& this_adjusting
&& indirect_offset == 0
&& !DECL_EXTERNAL (alias)
&& !DECL_STATIC_CHAIN (alias)
&& targetm.asm_out.can_output_mi_thunk (thunk_fndecl, fixed_offset,
virtual_value, alias))
{
tree fn_block;
tree restype = TREE_TYPE (TREE_TYPE (thunk_fndecl));
if (!output_asm_thunks)
{
node->analyzed = true;
return false;
}
if (in_lto_p)
node->get_untransformed_body ();
a = DECL_ARGUMENTS (thunk_fndecl);
current_function_decl = thunk_fndecl;
/* Ensure thunks are emitted in their correct sections. */
resolve_unique_section (thunk_fndecl, 0,
flag_function_sections);
DECL_RESULT (thunk_fndecl)
= build_decl (DECL_SOURCE_LOCATION (thunk_fndecl),
RESULT_DECL, 0, restype);
DECL_CONTEXT (DECL_RESULT (thunk_fndecl)) = thunk_fndecl;
/* The back end expects DECL_INITIAL to contain a BLOCK, so we
create one. */
fn_block = make_node (BLOCK);
BLOCK_VARS (fn_block) = a;
DECL_INITIAL (thunk_fndecl) = fn_block;
BLOCK_SUPERCONTEXT (fn_block) = thunk_fndecl;
allocate_struct_function (thunk_fndecl, false);
init_function_start (thunk_fndecl);
cfun->is_thunk = 1;
insn_locations_init ();
set_curr_insn_location (DECL_SOURCE_LOCATION (thunk_fndecl));
prologue_location = curr_insn_location ();
targetm.asm_out.output_mi_thunk (asm_out_file, thunk_fndecl,
fixed_offset, virtual_value, alias);
insn_locations_finalize ();
init_insn_lengths ();
free_after_compilation (cfun);
TREE_ASM_WRITTEN (thunk_fndecl) = 1;
node->thunk = false;
node->analyzed = false;
}
else if (stdarg_p (TREE_TYPE (thunk_fndecl)))
{
error ("generic thunk code fails for method %qD which uses %<...%>",
thunk_fndecl);
TREE_ASM_WRITTEN (thunk_fndecl) = 1;
node->analyzed = true;
return false;
}
else
{
tree restype;
basic_block bb, then_bb, else_bb, return_bb;
gimple_stmt_iterator bsi;
int nargs = 0;
tree arg;
int i;
tree resdecl;
tree restmp = NULL;
gcall *call;
greturn *ret;
bool alias_is_noreturn = TREE_THIS_VOLATILE (alias);
/* We may be called from expand_thunk that releases body except for
DECL_ARGUMENTS. In this case force_gimple_thunk is true. */
if (in_lto_p && !force_gimple_thunk)
node->get_untransformed_body ();
/* We need to force DECL_IGNORED_P when the thunk is created
after early debug was run. */
if (force_gimple_thunk)
DECL_IGNORED_P (thunk_fndecl) = 1;
a = DECL_ARGUMENTS (thunk_fndecl);
current_function_decl = thunk_fndecl;
/* Ensure thunks are emitted in their correct sections. */
resolve_unique_section (thunk_fndecl, 0,
flag_function_sections);
bitmap_obstack_initialize (NULL);
if (info->virtual_offset_p)
virtual_offset = size_int (virtual_value);
/* Build the return declaration for the function. */
restype = TREE_TYPE (TREE_TYPE (thunk_fndecl));
if (DECL_RESULT (thunk_fndecl) == NULL_TREE)
{
resdecl = build_decl (input_location, RESULT_DECL, 0, restype);
DECL_ARTIFICIAL (resdecl) = 1;
DECL_IGNORED_P (resdecl) = 1;
DECL_CONTEXT (resdecl) = thunk_fndecl;
DECL_RESULT (thunk_fndecl) = resdecl;
}
else
resdecl = DECL_RESULT (thunk_fndecl);
profile_count cfg_count = node->count;
if (!cfg_count.initialized_p ())
cfg_count = profile_count::from_gcov_type
(BB_FREQ_MAX).guessed_local ();
bb = then_bb = else_bb = return_bb
= init_lowered_empty_function (thunk_fndecl, true, cfg_count);
bsi = gsi_start_bb (bb);
/* Build call to the function being thunked. */
if (!VOID_TYPE_P (restype)
&& (!alias_is_noreturn
|| TREE_ADDRESSABLE (restype)
|| TREE_CODE (TYPE_SIZE_UNIT (restype)) != INTEGER_CST))
{
if (DECL_BY_REFERENCE (resdecl))
{
restmp = gimple_fold_indirect_ref (resdecl);
if (!restmp)
restmp = build2 (MEM_REF,
TREE_TYPE (TREE_TYPE (resdecl)),
resdecl,
build_int_cst (TREE_TYPE (resdecl), 0));
}
else if (!is_gimple_reg_type (restype))
{
if (aggregate_value_p (resdecl, TREE_TYPE (thunk_fndecl)))
{
restmp = resdecl;
if (VAR_P (restmp))
{
add_local_decl (cfun, restmp);
BLOCK_VARS (DECL_INITIAL (current_function_decl))
= restmp;
}
}
else
restmp = create_tmp_var (restype, "retval");
}
else
restmp = create_tmp_reg (restype, "retval");
}
for (arg = a; arg; arg = DECL_CHAIN (arg))
nargs++;
auto_vec<tree> vargs (nargs);
i = 0;
arg = a;
if (this_adjusting)
{
vargs.quick_push (thunk_adjust (&bsi, a, 1, fixed_offset,
virtual_offset, indirect_offset));
arg = DECL_CHAIN (a);
i = 1;
}
if (nargs)
for (; i < nargs; i++, arg = DECL_CHAIN (arg))
{
tree tmp = arg;
DECL_NOT_GIMPLE_REG_P (arg) = 0;
if (!is_gimple_val (arg))
{
tmp = create_tmp_reg (TYPE_MAIN_VARIANT
(TREE_TYPE (arg)), "arg");
gimple *stmt = gimple_build_assign (tmp, arg);
gsi_insert_after (&bsi, stmt, GSI_NEW_STMT);
}
vargs.quick_push (tmp);
}
call = gimple_build_call_vec (build_fold_addr_expr_loc (0, alias), vargs);
node->callees->call_stmt = call;
gimple_call_set_from_thunk (call, true);
if (DECL_STATIC_CHAIN (alias))
{
tree p = DECL_STRUCT_FUNCTION (alias)->static_chain_decl;
tree type = TREE_TYPE (p);
tree decl = build_decl (DECL_SOURCE_LOCATION (thunk_fndecl),
PARM_DECL, create_tmp_var_name ("CHAIN"),
type);
DECL_ARTIFICIAL (decl) = 1;
DECL_IGNORED_P (decl) = 1;
TREE_USED (decl) = 1;
DECL_CONTEXT (decl) = thunk_fndecl;
DECL_ARG_TYPE (decl) = type;
TREE_READONLY (decl) = 1;
struct function *sf = DECL_STRUCT_FUNCTION (thunk_fndecl);
sf->static_chain_decl = decl;
gimple_call_set_chain (call, decl);
}
/* Return slot optimization is always possible and in fact required to
return values with DECL_BY_REFERENCE. */
if (aggregate_value_p (resdecl, TREE_TYPE (thunk_fndecl))
&& (!is_gimple_reg_type (TREE_TYPE (resdecl))
|| DECL_BY_REFERENCE (resdecl)))
gimple_call_set_return_slot_opt (call, true);
if (restmp)
{
gimple_call_set_lhs (call, restmp);
gcc_assert (useless_type_conversion_p (TREE_TYPE (restmp),
TREE_TYPE (TREE_TYPE (alias))));
}
gsi_insert_after (&bsi, call, GSI_NEW_STMT);
if (!alias_is_noreturn)
{
if (restmp && !this_adjusting
&& (fixed_offset || virtual_offset))
{
tree true_label = NULL_TREE;
if (TREE_CODE (TREE_TYPE (restmp)) == POINTER_TYPE)
{
gimple *stmt;
edge e;
/* If the return type is a pointer, we need to
protect against NULL. We know there will be an
adjustment, because that's why we're emitting a
thunk. */
then_bb = create_basic_block (NULL, bb);
then_bb->count = cfg_count - cfg_count / 16;
return_bb = create_basic_block (NULL, then_bb);
return_bb->count = cfg_count;
else_bb = create_basic_block (NULL, else_bb);
else_bb->count = cfg_count / 16;
add_bb_to_loop (then_bb, bb->loop_father);
add_bb_to_loop (return_bb, bb->loop_father);
add_bb_to_loop (else_bb, bb->loop_father);
remove_edge (single_succ_edge (bb));
true_label = gimple_block_label (then_bb);
stmt = gimple_build_cond (NE_EXPR, restmp,
build_zero_cst (TREE_TYPE (restmp)),
NULL_TREE, NULL_TREE);
gsi_insert_after (&bsi, stmt, GSI_NEW_STMT);
e = make_edge (bb, then_bb, EDGE_TRUE_VALUE);
e->probability = profile_probability::guessed_always () / 16;
e = make_edge (bb, else_bb, EDGE_FALSE_VALUE);
e->probability = profile_probability::guessed_always () / 16;
make_single_succ_edge (return_bb,
EXIT_BLOCK_PTR_FOR_FN (cfun), 0);
make_single_succ_edge (then_bb, return_bb, EDGE_FALLTHRU);
e = make_edge (else_bb, return_bb, EDGE_FALLTHRU);
e->probability = profile_probability::always ();
bsi = gsi_last_bb (then_bb);
}
restmp = thunk_adjust (&bsi, restmp, /*this_adjusting=*/0,
fixed_offset, virtual_offset,
indirect_offset);
if (true_label)
{
gimple *stmt;
bsi = gsi_last_bb (else_bb);
stmt = gimple_build_assign (restmp,
build_zero_cst
(TREE_TYPE (restmp)));
gsi_insert_after (&bsi, stmt, GSI_NEW_STMT);
bsi = gsi_last_bb (return_bb);
}
}
else
{
gimple_call_set_tail (call, true);
cfun->tail_call_marked = true;
}
/* Build return value. */
if (!DECL_BY_REFERENCE (resdecl))
ret = gimple_build_return (restmp);
else
ret = gimple_build_return (resdecl);
gsi_insert_after (&bsi, ret, GSI_NEW_STMT);
}
else
{
gimple_call_set_ctrl_altering (call, true);
gimple_call_set_tail (call, true);
cfun->tail_call_marked = true;
remove_edge (single_succ_edge (bb));
}
cfun->gimple_df->in_ssa_p = true;
update_max_bb_count ();
profile_status_for_fn (cfun)
= cfg_count.initialized_p () && cfg_count.ipa_p ()
? PROFILE_READ : PROFILE_GUESSED;
/* FIXME: C++ FE should stop setting TREE_ASM_WRITTEN on thunks. */
TREE_ASM_WRITTEN (thunk_fndecl) = false;
cfun->cfg->full_profile = true;
delete_unreachable_blocks ();
update_ssa (TODO_update_ssa);
checking_verify_flow_info ();
free_dominance_info (CDI_DOMINATORS);
/* Since we want to emit the thunk, we explicitly mark its name as
referenced. */
node->thunk = false;
node->lowered = true;
bitmap_obstack_release (NULL);
}
current_function_decl = NULL;
set_cfun (NULL);
return true;
}
void
symtab_thunks_cc_finalize (void)
{
vtable_entry_type = NULL;
}
#include "gt-symtab-thunks.h"