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tree-pass.h (make_pass_ipa_comdats): New pass.

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* tree-pass.h (make_pass_ipa_comdats): New pass.
	* timevar.def (TV_IPA_COMDATS): New timevar.
	* passes.def (pass_ipa_comdats): Add.
	* Makefile.in (OBJS): Add ipa-comdats.o
	* ipa-comdats.c: New file.

	* g++.dg/ipa/comdat.C: New file.

From-SVN: r210597
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Jan Hubicka 2014-05-19 02:58:43 +02:00 committed by Jan Hubicka
parent 449cdb37f0
commit a04d9035ec
8 changed files with 421 additions and 0 deletions
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8
gcc/ChangeLog
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@ -1,3 +1,11 @@
2014-05-17 Jan Hubicka <hubicka@ucw.cz>
* tree-pass.h (make_pass_ipa_comdats): New pass.
* timevar.def (TV_IPA_COMDATS): New timevar.
* passes.def (pass_ipa_comdats): Add.
* Makefile.in (OBJS): Add ipa-comdats.o
* ipa-comdats.c: New file.
2014-05-17 Jan Hubicka <hubicka@ucw.cz>
* ipa.c (update_visibility_by_resolution_info): New function.

1
gcc/Makefile.in
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@ -1269,6 +1269,7 @@ OBJS = \
ipa-devirt.o \
ipa-split.o \
ipa-inline.o \
ipa-comdats.o \
ipa-inline-analysis.o \
ipa-inline-transform.o \
ipa-profile.o \

387
gcc/ipa-comdats.c Normal file
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@ -0,0 +1,387 @@
/* Localize comdats.
Copyright (C) 2014 Free Software Foundation, Inc.
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/>. */
/* This is very simple pass that looks for static symbols that are used
exlusively by symbol within one comdat group. In this case it makes
sense to bring the symbol itself into the group to avoid dead code
that would arrise when the comdat group from current unit is replaced
by a different copy. Consider for example:
static int q(void)
{
....
}
inline int t(void)
{
return q();
}
if Q is used only by T, it makes sense to put Q into T's comdat group.
The pass solve simple dataflow across the callgraph trying to prove what
symbols are used exclusively from a given comdat group.
The implementation maintains a queue linked by AUX pointer terminated by
pointer value 1. Lattice values are NULL for TOP, actual comdat group, or
ERROR_MARK_NODE for bottom.
TODO: When symbol is used only by comdat symbols, but from different groups,
it would make sense to produce a new comdat group for it with anonymous name.
TODO2: We can't mix variables and functions within one group. Currently
we just give up on references of symbols of different types. We also should
handle this by anonymous comdat group section. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "cgraph.h"
#include "tree-pass.h"
#include "pointer-set.h"
/* Main dataflow loop propagating comdat groups across
the symbol table. All references to SYMBOL are examined
and NEWGROUP is updated accordingly. MAP holds current lattice
values for individual symbols. */
tree
propagate_comdat_group (struct symtab_node *symbol,
tree newgroup, pointer_map <tree> &map)
{
int i;
struct ipa_ref *ref;
/* Walk all references to SYMBOL, recursively dive into aliases. */
for (i = 0;
ipa_ref_list_referring_iterate (&symbol->ref_list, i, ref)
&& newgroup != error_mark_node; i++)
{
struct symtab_node *symbol2 = ref->referring;
if (ref->use == IPA_REF_ALIAS)
{
newgroup = propagate_comdat_group (symbol2, newgroup, map);
continue;
}
/* One COMDAT group can not hold both variables and functions at
a same time. For now we just go to BOTTOM, in future we may
invent special comdat groups for this case. */
if (symbol->type != symbol2->type)
{
newgroup = error_mark_node;
break;
}
/* If we see inline clone, its comdat group actually
corresponds to the comdat group of the function it is inlined
to. */
if (cgraph_node * cn = dyn_cast <cgraph_node *> (symbol2))
{
if (cn->global.inlined_to)
symbol2 = cn->global.inlined_to;
}
/* The actual merge operation. */
tree *val2 = map.contains (symbol2);
if (val2 && *val2 != newgroup)
{
if (!newgroup)
newgroup = *val2;
else
newgroup = error_mark_node;
}
}
/* If we analyze function, walk also callers. */
cgraph_node *cnode = dyn_cast <cgraph_node *> (symbol);
if (cnode)
for (struct cgraph_edge * edge = cnode->callers;
edge && newgroup != error_mark_node; edge = edge->next_caller)
{
struct symtab_node *symbol2 = edge->caller;
/* If we see inline clone, its comdat group actually
corresponds to the comdat group of the function it is inlined
to. */
if (cgraph_node * cn = dyn_cast <cgraph_node *> (symbol2))
{
if (cn->global.inlined_to)
symbol2 = cn->global.inlined_to;
}
/* The actual merge operation. */
tree *val2 = map.contains (symbol2);
if (val2 && *val2 != newgroup)
{
if (!newgroup)
newgroup = *val2;
else
newgroup = error_mark_node;
}
}
return newgroup;
}
/* Add all references of SYMBOL that are defined into queue started by FIRST
and linked by AUX pointer (unless they are already enqueued).
Walk recursively inlined functions. */
void
enqueue_references (symtab_node **first,
symtab_node *symbol)
{
int i;
struct ipa_ref *ref;
for (i = 0; ipa_ref_list_reference_iterate (&symbol->ref_list, i, ref); i++)
{
symtab_node *node = symtab_alias_ultimate_target (ref->referred, NULL);
if (!node->aux && node->definition)
{
node->aux = *first;
*first = node;
}
}
if (cgraph_node *cnode = dyn_cast <cgraph_node *> (symbol))
{
struct cgraph_edge *edge;
for (edge = cnode->callees; edge; edge = edge->next_callee)
if (!edge->inline_failed)
enqueue_references (first, edge->callee);
else
{
symtab_node *node = symtab_alias_ultimate_target (edge->callee,
NULL);
if (!node->aux && node->definition)
{
node->aux = *first;
*first = node;
}
}
}
}
/* Set comdat group of SYMBOL to GROUP.
Callback for symtab_for_node_and_aliases. */
bool
set_comdat_group (symtab_node *symbol,
void *head_p)
{
symtab_node *head = (symtab_node *)head_p;
gcc_assert (!DECL_COMDAT_GROUP (symbol->decl));
DECL_COMDAT_GROUP (symbol->decl) = DECL_COMDAT_GROUP (head->decl);
symtab_add_to_same_comdat_group (symbol, head);
return false;
}
/* The actual pass with the main dataflow loop. */
static unsigned int
ipa_comdats (void)
{
pointer_map<tree> map;
pointer_map<symtab_node *> comdat_head_map;
symtab_node *symbol;
bool comdat_group_seen = false;
symtab_node *first = (symtab_node *) (void *) 1;
/* Start the dataflow by assigning comdat group to symbols that are in comdat
groups already. All other externally visible symbols must stay, we use
ERROR_MARK_NODE as bottom for the propagation. */
FOR_EACH_DEFINED_SYMBOL (symbol)
if (!symtab_real_symbol_p (symbol))
;
else if (DECL_COMDAT_GROUP (symbol->decl))
{
*map.insert (symbol) = DECL_COMDAT_GROUP (symbol->decl);
*comdat_head_map.insert (DECL_COMDAT_GROUP (symbol->decl)) = symbol;
comdat_group_seen = true;
/* Mark the symbol so we won't waste time visiting it for dataflow. */
symbol->aux = (symtab_node *) (void *) 1;
}
/* See symbols that can not be privatized to comdats; that is externally
visible symbols or otherwise used ones. We also do not want to mangle
user section names. */
else if (symbol->externally_visible
|| symbol->force_output
|| symbol->used_from_other_partition
|| TREE_THIS_VOLATILE (symbol->decl)
|| DECL_SECTION_NAME (symbol->decl)
|| (TREE_CODE (symbol->decl) == FUNCTION_DECL
&& (DECL_STATIC_CONSTRUCTOR (symbol->decl)
|| DECL_STATIC_DESTRUCTOR (symbol->decl))))
{
*map.insert (symtab_alias_ultimate_target (symbol, NULL)) = error_mark_node;
/* Mark the symbol so we won't waste time visiting it for dataflow. */
symbol->aux = (symtab_node *) (void *) 1;
}
else
{
/* Enqueue symbol for dataflow. */
symbol->aux = first;
first = symbol;
}
if (!comdat_group_seen)
{
FOR_EACH_DEFINED_SYMBOL (symbol)
symbol->aux = NULL;
return 0;
}
/* The actual dataflow. */
while (first != (void *) 1)
{
tree group = NULL;
tree newgroup, *val;
symbol = first;
first = (symtab_node *)first->aux;
/* Get current lattice value of SYMBOL. */
val = map.contains (symbol);
if (val)
group = *val;
/* If it is bottom, there is nothing to do; do not clear AUX
so we won't re-queue the symbol. */
if (group == error_mark_node)
continue;
newgroup = propagate_comdat_group (symbol, group, map);
/* If nothing changed, proceed to next symbol. */
if (newgroup == group)
{
symbol->aux = NULL;
continue;
}
/* Update lattice value and enqueue all references for re-visiting. */
gcc_assert (newgroup);
if (val)
*val = newgroup;
else
*map.insert (symbol) = newgroup;
enqueue_references (&first, symbol);
/* We may need to revisit the symbol unless it is BOTTOM. */
if (newgroup != error_mark_node)
symbol->aux = NULL;
}
/* Finally assign symbols to the sections. */
FOR_EACH_DEFINED_SYMBOL (symbol)
{
symbol->aux = NULL;
if (!DECL_COMDAT_GROUP (symbol->decl)
&& !symbol->alias
&& symtab_real_symbol_p (symbol))
{
tree group = *map.contains (symbol);
if (group == error_mark_node)
continue;
if (dump_file)
{
fprintf (dump_file, "Localizing symbol\n");
dump_symtab_node (dump_file, symbol);
fprintf (dump_file, "To group: %s\n", IDENTIFIER_POINTER (group));
}
symtab_for_node_and_aliases (symbol, set_comdat_group,
*comdat_head_map.contains (group), true);
}
}
return 0;
}
namespace {
const pass_data pass_data_ipa_comdats =
{
IPA_PASS, /* type */
"comdats", /* name */
OPTGROUP_NONE, /* optinfo_flags */
true, /* has_execute */
TV_IPA_COMDATS, /* tv_id */
0, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
0, /* todo_flags_finish */
};
class pass_ipa_comdats : public ipa_opt_pass_d
{
public:
pass_ipa_comdats (gcc::context *ctxt)
: ipa_opt_pass_d (pass_data_ipa_comdats, ctxt,
NULL, /* generate_summary */
NULL, /* write_summary */
NULL, /* read_summary */
NULL, /* write_optimization_summary */
NULL, /* read_optimization_summary */
NULL, /* stmt_fixup */
0, /* function_transform_todo_flags_start */
NULL, /* function_transform */
NULL) /* variable_transform */
{}
/* opt_pass methods: */
virtual bool gate (function *);
virtual unsigned int execute (function *) { return ipa_comdats (); }
}; // class pass_ipa_comdats
bool
pass_ipa_comdats::gate (function *)
{
return optimize;
}
} // anon namespace
ipa_opt_pass_d *
make_pass_ipa_comdats (gcc::context *ctxt)
{
return new pass_ipa_comdats (ctxt);
}

4
gcc/passes.def
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@ -110,6 +110,10 @@ along with GCC; see the file COPYING3. If not see
NEXT_PASS (pass_ipa_inline);
NEXT_PASS (pass_ipa_pure_const);
NEXT_PASS (pass_ipa_reference);
/* Comdat privatization come last, as direct references to comdat local
symbols are not allowed outside of the comdat group. Privatizing early
would result in missed optimizations due to this restriction. */
NEXT_PASS (pass_ipa_comdats);
TERMINATE_PASS_LIST ()
/* Simple IPA passes executed after the regular passes. In WHOPR mode the

4
gcc/testsuite/ChangeLog
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@ -1,3 +1,7 @@
2014-05-17 Jan Hubicka <hubicka@ucw.cz>
* g++.dg/ipa/comdat.C: New file.
2014-05-18 Eric Botcazou <ebotcazou@adacore.com>
* gnat.dg/volatile12.ad[sb]: New test.

15
gcc/testsuite/g++.dg/ipa/comdat.C Normal file
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@ -0,0 +1,15 @@
/* { dg-do compile { target *-*-linux* *-*-gnu* } } */
/* { dg-options "-O2 -fdump-ipa-comdats" } */
#include <stdio.h>
__attribute__ ((noinline))
static int q(void)
{
return printf ("test");
}
inline int t(void)
{
return q();
}
int (*f)()=t;
/* { dg-final { scan-ipa-dump-times "Localizing symbol" 1 "comdats" } } */
/* { dg-final { cleanup-ipa-dump "comdats" } } */

1
gcc/timevar.def
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@ -71,6 +71,7 @@ DEFTIMEVAR (TV_IPA_DEVIRT , "ipa devirtualization")
DEFTIMEVAR (TV_IPA_CONSTANT_PROP , "ipa cp")
DEFTIMEVAR (TV_IPA_INLINING , "ipa inlining heuristics")
DEFTIMEVAR (TV_IPA_FNSPLIT , "ipa function splitting")
DEFTIMEVAR (TV_IPA_COMDATS , "ipa comdats")
DEFTIMEVAR (TV_IPA_OPT , "ipa various optimizations")
DEFTIMEVAR (TV_IPA_LTO_GIMPLE_IN , "ipa lto gimple in")
DEFTIMEVAR (TV_IPA_LTO_GIMPLE_OUT , "ipa lto gimple out")

1
gcc/tree-pass.h
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@ -472,6 +472,7 @@ extern simple_ipa_opt_pass *make_pass_ipa_tm (gcc::context *ctxt);
extern simple_ipa_opt_pass *make_pass_omp_simd_clone (gcc::context *ctxt);
extern ipa_opt_pass_d *make_pass_ipa_profile (gcc::context *ctxt);
extern ipa_opt_pass_d *make_pass_ipa_cdtor_merge (gcc::context *ctxt);
extern ipa_opt_pass_d *make_pass_ipa_comdats (gcc::context *ctxt);
extern gimple_opt_pass *make_pass_cleanup_cfg_post_optimizing (gcc::context
*ctxt);