Google Git
Sign in
llvm / llvm-archive / 48649d2c83b557841c9e5c978d9ab5af13cb52e5 / . / llvm-gcc-4.0 / gcc / tree-cfg.c
blob: 82d8275db2333403984abb0a8d0147730785daf0 [file] [log] [blame]
/* Control flow functions for trees.
Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
Contributed by Diego Novillo <dnovillo@redhat.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 2, 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 COPYING. If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "rtl.h"
#include "tm_p.h"
#include "hard-reg-set.h"
#include "basic-block.h"
#include "output.h"
#include "errors.h"
#include "flags.h"
#include "function.h"
#include "expr.h"
#include "ggc.h"
#include "langhooks.h"
#include "diagnostic.h"
#include "tree-flow.h"
#include "timevar.h"
#include "tree-dump.h"
#include "tree-pass.h"
#include "toplev.h"
#include "except.h"
#include "cfgloop.h"
#include "cfglayout.h"
#include "hashtab.h"
/* This file contains functions for building the Control Flow Graph (CFG)
for a function tree. */
/* Local declarations. */
/* Initial capacity for the basic block array. */
static const int initial_cfg_capacity = 20;
/* Mapping of labels to their associated blocks. This can greatly speed up
building of the CFG in code with lots of gotos. */
static GTY(()) varray_type label_to_block_map;
/* This hash table allows us to efficiently lookup all CASE_LABEL_EXPRs
which use a particular edge. The CASE_LABEL_EXPRs are chained together
via their TREE_CHAIN field, which we clear after we're done with the
hash table to prevent problems with duplication of SWITCH_EXPRs.
Access to this list of CASE_LABEL_EXPRs allows us to efficiently
update the case vector in response to edge redirections.
Right now this table is set up and torn down at key points in the
compilation process. It would be nice if we could make the table
more persistent. The key is getting notification of changes to
the CFG (particularly edge removal, creation and redirection). */
struct edge_to_cases_elt
{
/* The edge itself. Necessary for hashing and equality tests. */
edge e;
/* The case labels associated with this edge. We link these up via
their TREE_CHAIN field, then we wipe out the TREE_CHAIN fields
when we destroy the hash table. This prevents problems when copying
SWITCH_EXPRs. */
tree case_labels;
};
static htab_t edge_to_cases;
/* CFG statistics. */
struct cfg_stats_d
{
long num_merged_labels;
};
static struct cfg_stats_d cfg_stats;
/* Nonzero if we found a computed goto while building basic blocks. */
static bool found_computed_goto;
/* Basic blocks and flowgraphs. */
static basic_block create_bb (void *, void *, basic_block);
static void create_block_annotation (basic_block);
static void free_blocks_annotations (void);
static void clear_blocks_annotations (void);
static void make_blocks (tree);
static void factor_computed_gotos (void);
/* Edges. */
static void make_edges (void);
static void make_ctrl_stmt_edges (basic_block);
static void make_exit_edges (basic_block);
static void make_cond_expr_edges (basic_block);
static void make_switch_expr_edges (basic_block);
static void make_goto_expr_edges (basic_block);
static edge tree_redirect_edge_and_branch (edge, basic_block);
static edge tree_try_redirect_by_replacing_jump (edge, basic_block);
static void split_critical_edges (void);
static bool remove_fallthru_edge (VEC(edge) *);
/* Various helpers. */
static inline bool stmt_starts_bb_p (tree, tree);
static int tree_verify_flow_info (void);
static void tree_make_forwarder_block (edge);
static bool tree_forwarder_block_p (basic_block, bool);
static void tree_cfg2vcg (FILE *);
/* Flowgraph optimization and cleanup. */
static void tree_merge_blocks (basic_block, basic_block);
static bool tree_can_merge_blocks_p (basic_block, basic_block);
static void remove_bb (basic_block);
static bool cleanup_control_flow (void);
static bool cleanup_control_expr_graph (basic_block, block_stmt_iterator);
static edge find_taken_edge_cond_expr (basic_block, tree);
static edge find_taken_edge_switch_expr (basic_block, tree);
static tree find_case_label_for_value (tree, tree);
static bool phi_alternatives_equal (basic_block, edge, edge);
static bool cleanup_forwarder_blocks (void);
/*---------------------------------------------------------------------------
Create basic blocks
---------------------------------------------------------------------------*/
/* Entry point to the CFG builder for trees. TP points to the list of
statements to be added to the flowgraph. */
static void
build_tree_cfg (tree *tp)
{
/* Register specific tree functions. */
tree_register_cfg_hooks ();
/* Initialize rbi_pool. */
alloc_rbi_pool ();
/* Initialize the basic block array. */
init_flow ();
profile_status = PROFILE_ABSENT;
n_basic_blocks = 0;
last_basic_block = 0;
VARRAY_BB_INIT (basic_block_info, initial_cfg_capacity, "basic_block_info");
memset ((void *) &cfg_stats, 0, sizeof (cfg_stats));
/* Build a mapping of labels to their associated blocks. */
VARRAY_BB_INIT (label_to_block_map, initial_cfg_capacity,
"label to block map");
ENTRY_BLOCK_PTR->next_bb = EXIT_BLOCK_PTR;
EXIT_BLOCK_PTR->prev_bb = ENTRY_BLOCK_PTR;
found_computed_goto = 0;
make_blocks (*tp);
/* Computed gotos are hell to deal with, especially if there are
lots of them with a large number of destinations. So we factor
them to a common computed goto location before we build the
edge list. After we convert back to normal form, we will un-factor
the computed gotos since factoring introduces an unwanted jump. */
if (found_computed_goto)
factor_computed_gotos ();
/* Make sure there is always at least one block, even if it's empty. */
if (n_basic_blocks == 0)
create_empty_bb (ENTRY_BLOCK_PTR);
create_block_annotation (ENTRY_BLOCK_PTR);
create_block_annotation (EXIT_BLOCK_PTR);
/* Adjust the size of the array. */
VARRAY_GROW (basic_block_info, n_basic_blocks);
/* To speed up statement iterator walks, we first purge dead labels. */
cleanup_dead_labels ();
/* Group case nodes to reduce the number of edges.
We do this after cleaning up dead labels because otherwise we miss
a lot of obvious case merging opportunities. */
group_case_labels ();
/* Create the edges of the flowgraph. */
make_edges ();
/* Debugging dumps. */
/* Write the flowgraph to a VCG file. */
{
int local_dump_flags;
FILE *dump_file = dump_begin (TDI_vcg, &local_dump_flags);
if (dump_file)
{
tree_cfg2vcg (dump_file);
dump_end (TDI_vcg, dump_file);
}
}
/* Dump a textual representation of the flowgraph. */
if (dump_file)
dump_tree_cfg (dump_file, dump_flags);
}
static void
execute_build_cfg (void)
{
build_tree_cfg (&DECL_SAVED_TREE (current_function_decl));
}
struct tree_opt_pass pass_build_cfg =
{
"cfg", /* name */
NULL, /* gate */
execute_build_cfg, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
TV_TREE_CFG, /* tv_id */
PROP_gimple_leh, /* properties_required */
PROP_cfg, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
TODO_verify_stmts, /* todo_flags_finish */
0 /* letter */
};
/* Search the CFG for any computed gotos. If found, factor them to a
common computed goto site. Also record the location of that site so
that we can un-factor the gotos after we have converted back to
normal form. */
static void
factor_computed_gotos (void)
{
basic_block bb;
tree factored_label_decl = NULL;
tree var = NULL;
tree factored_computed_goto_label = NULL;
tree factored_computed_goto = NULL;
/* We know there are one or more computed gotos in this function.
Examine the last statement in each basic block to see if the block
ends with a computed goto. */
FOR_EACH_BB (bb)
{
block_stmt_iterator bsi = bsi_last (bb);
tree last;
if (bsi_end_p (bsi))
continue;
last = bsi_stmt (bsi);
/* Ignore the computed goto we create when we factor the original
computed gotos. */
if (last == factored_computed_goto)
continue;
/* If the last statement is a computed goto, factor it. */
if (computed_goto_p (last))
{
tree assignment;
/* The first time we find a computed goto we need to create
the factored goto block and the variable each original
computed goto will use for their goto destination. */
if (! factored_computed_goto)
{
basic_block new_bb = create_empty_bb (bb);
block_stmt_iterator new_bsi = bsi_start (new_bb);
/* Create the destination of the factored goto. Each original
computed goto will put its desired destination into this
variable and jump to the label we create immediately
below. */
var = create_tmp_var (ptr_type_node, "gotovar");
/* Build a label for the new block which will contain the
factored computed goto. */
factored_label_decl = create_artificial_label ();
factored_computed_goto_label
= build1 (LABEL_EXPR, void_type_node, factored_label_decl);
bsi_insert_after (&new_bsi, factored_computed_goto_label,
BSI_NEW_STMT);
/* Build our new computed goto. */
factored_computed_goto = build1 (GOTO_EXPR, void_type_node, var);
bsi_insert_after (&new_bsi, factored_computed_goto,
BSI_NEW_STMT);
}
/* Copy the original computed goto's destination into VAR. */
assignment = build (MODIFY_EXPR, ptr_type_node,
var, GOTO_DESTINATION (last));
bsi_insert_before (&bsi, assignment, BSI_SAME_STMT);
/* And re-vector the computed goto to the new destination. */
GOTO_DESTINATION (last) = factored_label_decl;
}
}
}
/* Create annotations for a single basic block. */
static void
create_block_annotation (basic_block bb)
{
/* Verify that the tree_annotations field is clear. */
gcc_assert (!bb->tree_annotations);
bb->tree_annotations = ggc_alloc_cleared (sizeof (struct bb_ann_d));
}
/* Free the annotations for all the basic blocks. */
static void free_blocks_annotations (void)
{
clear_blocks_annotations ();
}
/* Clear the annotations for all the basic blocks. */
static void
clear_blocks_annotations (void)
{
basic_block bb;
FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
bb->tree_annotations = NULL;
}
/* Build a flowgraph for the statement_list STMT_LIST. */
static void
make_blocks (tree stmt_list)
{
tree_stmt_iterator i = tsi_start (stmt_list);
tree stmt = NULL;
bool start_new_block = true;
bool first_stmt_of_list = true;
basic_block bb = ENTRY_BLOCK_PTR;
while (!tsi_end_p (i))
{
tree prev_stmt;
prev_stmt = stmt;
stmt = tsi_stmt (i);
/* If the statement starts a new basic block or if we have determined
in a previous pass that we need to create a new block for STMT, do
so now. */
if (start_new_block || stmt_starts_bb_p (stmt, prev_stmt))
{
if (!first_stmt_of_list)
stmt_list = tsi_split_statement_list_before (&i);
bb = create_basic_block (stmt_list, NULL, bb);
start_new_block = false;
}
/* Now add STMT to BB and create the subgraphs for special statement
codes. */
set_bb_for_stmt (stmt, bb);
if (computed_goto_p (stmt))
found_computed_goto = true;
/* If STMT is a basic block terminator, set START_NEW_BLOCK for the
next iteration. */
if (stmt_ends_bb_p (stmt))
start_new_block = true;
tsi_next (&i);
first_stmt_of_list = false;
}
}
/* Create and return a new empty basic block after bb AFTER. */
static basic_block
create_bb (void *h, void *e, basic_block after)
{
basic_block bb;
gcc_assert (!e);
/* Create and initialize a new basic block. Since alloc_block uses
ggc_alloc_cleared to allocate a basic block, we do not have to
clear the newly allocated basic block here. */
bb = alloc_block ();
bb->index = last_basic_block;
bb->flags = BB_NEW;
bb->stmt_list = h ? h : alloc_stmt_list ();
/* Add the new block to the linked list of blocks. */
link_block (bb, after);
/* Grow the basic block array if needed. */
if ((size_t) last_basic_block == VARRAY_SIZE (basic_block_info))
{
size_t new_size = last_basic_block + (last_basic_block + 3) / 4;
VARRAY_GROW (basic_block_info, new_size);
}
/* Add the newly created block to the array. */
BASIC_BLOCK (last_basic_block) = bb;
create_block_annotation (bb);
n_basic_blocks++;
last_basic_block++;
initialize_bb_rbi (bb);
return bb;
}
/*---------------------------------------------------------------------------
Edge creation
---------------------------------------------------------------------------*/
/* Fold COND_EXPR_COND of each COND_EXPR. */
/* APPLE LOCAL mainline 4506977 */
void
fold_cond_expr_cond (void)
{
basic_block bb;
FOR_EACH_BB (bb)
{
tree stmt = last_stmt (bb);
if (stmt
&& TREE_CODE (stmt) == COND_EXPR)
{
tree cond = fold (COND_EXPR_COND (stmt));
if (integer_zerop (cond))
COND_EXPR_COND (stmt) = integer_zero_node;
else if (integer_onep (cond))
COND_EXPR_COND (stmt) = integer_one_node;
}
}
}
/* Join all the blocks in the flowgraph. */
static void
make_edges (void)
{
basic_block bb;
/* Create an edge from entry to the first block with executable
statements in it. */
make_edge (ENTRY_BLOCK_PTR, BASIC_BLOCK (0), EDGE_FALLTHRU);
/* Traverse the basic block array placing edges. */
FOR_EACH_BB (bb)
{
tree first = first_stmt (bb);
tree last = last_stmt (bb);
if (first)
{
/* Edges for statements that always alter flow control. */
if (is_ctrl_stmt (last))
make_ctrl_stmt_edges (bb);
/* Edges for statements that sometimes alter flow control. */
if (is_ctrl_altering_stmt (last))
make_exit_edges (bb);
}
/* Finally, if no edges were created above, this is a regular
basic block that only needs a fallthru edge. */
if (EDGE_COUNT (bb->succs) == 0)
make_edge (bb, bb->next_bb, EDGE_FALLTHRU);
}
/* We do not care about fake edges, so remove any that the CFG
builder inserted for completeness. */
remove_fake_exit_edges ();
/* Fold COND_EXPR_COND of each COND_EXPR. */
fold_cond_expr_cond ();
/* Clean up the graph and warn for unreachable code. */
cleanup_tree_cfg ();
}
/* Create edges for control statement at basic block BB. */
static void
make_ctrl_stmt_edges (basic_block bb)
{
tree last = last_stmt (bb);
gcc_assert (last);
switch (TREE_CODE (last))
{
case GOTO_EXPR:
make_goto_expr_edges (bb);
break;
case RETURN_EXPR:
make_edge (bb, EXIT_BLOCK_PTR, 0);
break;
case COND_EXPR:
make_cond_expr_edges (bb);
break;
case SWITCH_EXPR:
make_switch_expr_edges (bb);
break;
case RESX_EXPR:
make_eh_edges (last);
/* Yet another NORETURN hack. */
if (EDGE_COUNT (bb->succs) == 0)
make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE);
break;
default:
gcc_unreachable ();
}
}
/* Create exit edges for statements in block BB that alter the flow of
control. Statements that alter the control flow are 'goto', 'return'
and calls to non-returning functions. */
static void
make_exit_edges (basic_block bb)
{
tree last = last_stmt (bb), op;
gcc_assert (last);
switch (TREE_CODE (last))
{
case CALL_EXPR:
/* If this function receives a nonlocal goto, then we need to
make edges from this call site to all the nonlocal goto
handlers. */
if (TREE_SIDE_EFFECTS (last)
&& current_function_has_nonlocal_label)
make_goto_expr_edges (bb);
/* If this statement has reachable exception handlers, then
create abnormal edges to them. */
make_eh_edges (last);
/* Some calls are known not to return. For such calls we create
a fake edge.
We really need to revamp how we build edges so that it's not
such a bloody pain to avoid creating edges for this case since
all we do is remove these edges when we're done building the
CFG. */
if (call_expr_flags (last) & ECF_NORETURN)
{
make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE);
return;
}
/* Don't forget the fall-thru edge. */
make_edge (bb, bb->next_bb, EDGE_FALLTHRU);
break;
case MODIFY_EXPR:
/* A MODIFY_EXPR may have a CALL_EXPR on its RHS and the CALL_EXPR
may have an abnormal edge. Search the RHS for this case and
create any required edges. */
op = get_call_expr_in (last);
if (op && TREE_SIDE_EFFECTS (op)
&& current_function_has_nonlocal_label)
make_goto_expr_edges (bb);
make_eh_edges (last);
make_edge (bb, bb->next_bb, EDGE_FALLTHRU);
break;
default:
gcc_unreachable ();
}
}
/* Create the edges for a COND_EXPR starting at block BB.
At this point, both clauses must contain only simple gotos. */
static void
make_cond_expr_edges (basic_block bb)
{
tree entry = last_stmt (bb);
basic_block then_bb, else_bb;
tree then_label, else_label;
gcc_assert (entry);
gcc_assert (TREE_CODE (entry) == COND_EXPR);
/* Entry basic blocks for each component. */
then_label = GOTO_DESTINATION (COND_EXPR_THEN (entry));
else_label = GOTO_DESTINATION (COND_EXPR_ELSE (entry));
then_bb = label_to_block (then_label);
else_bb = label_to_block (else_label);
make_edge (bb, then_bb, EDGE_TRUE_VALUE);
make_edge (bb, else_bb, EDGE_FALSE_VALUE);
}
/* Hashing routine for EDGE_TO_CASES. */
static hashval_t
edge_to_cases_hash (const void *p)
{
edge e = ((struct edge_to_cases_elt *)p)->e;
/* Hash on the edge itself (which is a pointer). */
return htab_hash_pointer (e);
}
/* Equality routine for EDGE_TO_CASES, edges are unique, so testing
for equality is just a pointer comparison. */
static int
edge_to_cases_eq (const void *p1, const void *p2)
{
edge e1 = ((struct edge_to_cases_elt *)p1)->e;
edge e2 = ((struct edge_to_cases_elt *)p2)->e;
return e1 == e2;
}
/* Called for each element in the hash table (P) as we delete the
edge to cases hash table.
Clear all the TREE_CHAINs to prevent problems with copying of
SWITCH_EXPRs and structure sharing rules, then free the hash table
element. */
static void
edge_to_cases_cleanup (void *p)
{
struct edge_to_cases_elt *elt = p;
tree t, next;
for (t = elt->case_labels; t; t = next)
{
next = TREE_CHAIN (t);
TREE_CHAIN (t) = NULL;
}
free (p);
}
/* Start recording information mapping edges to case labels. */
static void
start_recording_case_labels (void)
{
gcc_assert (edge_to_cases == NULL);
edge_to_cases = htab_create (37,
edge_to_cases_hash,
edge_to_cases_eq,
edge_to_cases_cleanup);
}
/* Return nonzero if we are recording information for case labels. */
static bool
recording_case_labels_p (void)
{
return (edge_to_cases != NULL);
}
/* Stop recording information mapping edges to case labels and
remove any information we have recorded. */
static void
end_recording_case_labels (void)
{
htab_delete (edge_to_cases);
edge_to_cases = NULL;
}
/* Record that CASE_LABEL (a CASE_LABEL_EXPR) references edge E. */
static void
record_switch_edge (edge e, tree case_label)
{
struct edge_to_cases_elt *elt;
void **slot;
/* Build a hash table element so we can see if E is already
in the table. */
elt = xmalloc (sizeof (struct edge_to_cases_elt));
elt->e = e;
elt->case_labels = case_label;
slot = htab_find_slot (edge_to_cases, elt, INSERT);
if (*slot == NULL)
{
/* E was not in the hash table. Install E into the hash table. */
*slot = (void *)elt;
}
else
{
/* E was already in the hash table. Free ELT as we do not need it
anymore. */
free (elt);
/* Get the entry stored in the hash table. */
elt = (struct edge_to_cases_elt *) *slot;
/* Add it to the chain of CASE_LABEL_EXPRs referencing E. */
TREE_CHAIN (case_label) = elt->case_labels;
elt->case_labels = case_label;
}
}
/* If we are inside a {start,end}_recording_cases block, then return
a chain of CASE_LABEL_EXPRs from T which reference E.
Otherwise return NULL. */
static tree
get_cases_for_edge (edge e, tree t)
{
struct edge_to_cases_elt elt, *elt_p;
void **slot;
size_t i, n;
tree vec;
/* If we are not recording cases, then we do not have CASE_LABEL_EXPR
chains available. Return NULL so the caller can detect this case. */
if (!recording_case_labels_p ())
return NULL;
restart:
elt.e = e;
elt.case_labels = NULL;
slot = htab_find_slot (edge_to_cases, &elt, NO_INSERT);
if (slot)
{
elt_p = (struct edge_to_cases_elt *)*slot;
return elt_p->case_labels;
}
/* If we did not find E in the hash table, then this must be the first
time we have been queried for information about E & T. Add all the
elements from T to the hash table then perform the query again. */
vec = SWITCH_LABELS (t);
n = TREE_VEC_LENGTH (vec);
for (i = 0; i < n; i++)
{
tree lab = CASE_LABEL (TREE_VEC_ELT (vec, i));
basic_block label_bb = label_to_block (lab);
record_switch_edge (find_edge (e->src, label_bb), TREE_VEC_ELT (vec, i));
}
goto restart;
}
/* Create the edges for a SWITCH_EXPR starting at block BB.
At this point, the switch body has been lowered and the
SWITCH_LABELS filled in, so this is in effect a multi-way branch. */
static void
make_switch_expr_edges (basic_block bb)
{
tree entry = last_stmt (bb);
size_t i, n;
tree vec;
vec = SWITCH_LABELS (entry);
n = TREE_VEC_LENGTH (vec);
for (i = 0; i < n; ++i)
{
tree lab = CASE_LABEL (TREE_VEC_ELT (vec, i));
basic_block label_bb = label_to_block (lab);
make_edge (bb, label_bb, 0);
}
}
/* Return the basic block holding label DEST. */
basic_block
label_to_block (tree dest)
{
int uid = LABEL_DECL_UID (dest);
/* We would die hard when faced by an undefined label. Emit a label to
the very first basic block. This will hopefully make even the dataflow
and undefined variable warnings quite right. */
if ((errorcount || sorrycount) && uid < 0)
{
block_stmt_iterator bsi = bsi_start (BASIC_BLOCK (0));
tree stmt;
stmt = build1 (LABEL_EXPR, void_type_node, dest);
bsi_insert_before (&bsi, stmt, BSI_NEW_STMT);
uid = LABEL_DECL_UID (dest);
}
return VARRAY_BB (label_to_block_map, uid);
}
/* Create edges for a goto statement at block BB. */
static void
make_goto_expr_edges (basic_block bb)
{
tree goto_t, dest;
basic_block target_bb;
int for_call;
block_stmt_iterator last = bsi_last (bb);
goto_t = bsi_stmt (last);
/* If the last statement is not a GOTO (i.e., it is a RETURN_EXPR,
CALL_EXPR or MODIFY_EXPR), then the edge is an abnormal edge resulting
from a nonlocal goto. */
if (TREE_CODE (goto_t) != GOTO_EXPR)
{
dest = error_mark_node;
for_call = 1;
}
else
{
dest = GOTO_DESTINATION (goto_t);
for_call = 0;
/* A GOTO to a local label creates normal edges. */
if (simple_goto_p (goto_t))
{
edge e = make_edge (bb, label_to_block (dest), EDGE_FALLTHRU);
#ifdef USE_MAPPED_LOCATION
e->goto_locus = EXPR_LOCATION (goto_t);
#else
e->goto_locus = EXPR_LOCUS (goto_t);
#endif
bsi_remove (&last);
return;
}
/* Nothing more to do for nonlocal gotos. */
if (TREE_CODE (dest) == LABEL_DECL)
return;
/* Computed gotos remain. */
}
/* Look for the block starting with the destination label. In the
case of a computed goto, make an edge to any label block we find
in the CFG. */
FOR_EACH_BB (target_bb)
{
block_stmt_iterator bsi;
for (bsi = bsi_start (target_bb); !bsi_end_p (bsi); bsi_next (&bsi))
{
tree target = bsi_stmt (bsi);
if (TREE_CODE (target) != LABEL_EXPR)
break;
if (
/* Computed GOTOs. Make an edge to every label block that has
been marked as a potential target for a computed goto. */
(FORCED_LABEL (LABEL_EXPR_LABEL (target)) && for_call == 0)
/* Nonlocal GOTO target. Make an edge to every label block
that has been marked as a potential target for a nonlocal
goto. */
|| (DECL_NONLOCAL (LABEL_EXPR_LABEL (target)) && for_call == 1))
{
make_edge (bb, target_bb, EDGE_ABNORMAL);
break;
}
}
}
/* Degenerate case of computed goto with no labels. */
if (!for_call && EDGE_COUNT (bb->succs) == 0)
make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE);
}
/*---------------------------------------------------------------------------
Flowgraph analysis
---------------------------------------------------------------------------*/
/* Remove unreachable blocks and other miscellaneous clean up work. */
bool
cleanup_tree_cfg (void)
{
bool retval = false;
timevar_push (TV_TREE_CLEANUP_CFG);
retval = cleanup_control_flow ();
retval |= delete_unreachable_blocks ();
/* cleanup_forwarder_blocks can redirect edges out of SWITCH_EXPRs,
which can get expensive. So we want to enable recording of edge
to CASE_LABEL_EXPR mappings around the call to
cleanup_forwarder_blocks. */
start_recording_case_labels ();
retval |= cleanup_forwarder_blocks ();
end_recording_case_labels ();
#ifdef ENABLE_CHECKING
if (retval)
{
gcc_assert (!cleanup_control_flow ());
gcc_assert (!delete_unreachable_blocks ());
gcc_assert (!cleanup_forwarder_blocks ());
}
#endif
/* Merging the blocks creates no new opportunities for the other
optimizations, so do it here. */
retval |= merge_seq_blocks ();
compact_blocks ();
#ifdef ENABLE_CHECKING
verify_flow_info ();
#endif
timevar_pop (TV_TREE_CLEANUP_CFG);
return retval;
}
/* Cleanup useless labels in basic blocks. This is something we wish
to do early because it allows us to group case labels before creating
the edges for the CFG, and it speeds up block statement iterators in
all passes later on.
We only run this pass once, running it more than once is probably not
profitable. */
/* A map from basic block index to the leading label of that block. */
static tree *label_for_bb;
/* Callback for for_each_eh_region. Helper for cleanup_dead_labels. */
static void
update_eh_label (struct eh_region *region)
{
tree old_label = get_eh_region_tree_label (region);
if (old_label)
{
tree new_label;
basic_block bb = label_to_block (old_label);
/* ??? After optimizing, there may be EH regions with labels
that have already been removed from the function body, so
there is no basic block for them. */
if (! bb)
return;
new_label = label_for_bb[bb->index];
set_eh_region_tree_label (region, new_label);
}
}
/* Given LABEL return the first label in the same basic block. */
static tree
main_block_label (tree label)
{
basic_block bb = label_to_block (label);
/* label_to_block possibly inserted undefined label into the chain. */
if (!label_for_bb[bb->index])
label_for_bb[bb->index] = label;
return label_for_bb[bb->index];
}
/* Cleanup redundant labels. This is a three-step process:
1) Find the leading label for each block.
2) Redirect all references to labels to the leading labels.
3) Cleanup all useless labels. */
void
cleanup_dead_labels (void)
{
basic_block bb;
label_for_bb = xcalloc (last_basic_block, sizeof (tree));
/* Find a suitable label for each block. We use the first user-defined
label if there is one, or otherwise just the first label we see. */
FOR_EACH_BB (bb)
{
block_stmt_iterator i;
for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
{
tree label, stmt = bsi_stmt (i);
if (TREE_CODE (stmt) != LABEL_EXPR)
break;
label = LABEL_EXPR_LABEL (stmt);
/* If we have not yet seen a label for the current block,
remember this one and see if there are more labels. */
if (! label_for_bb[bb->index])
{
label_for_bb[bb->index] = label;
continue;
}
/* If we did see a label for the current block already, but it
is an artificially created label, replace it if the current
label is a user defined label. */
if (! DECL_ARTIFICIAL (label)
&& DECL_ARTIFICIAL (label_for_bb[bb->index]))
{
label_for_bb[bb->index] = label;
break;
}
}
}
/* Now redirect all jumps/branches to the selected label.
First do so for each block ending in a control statement. */
FOR_EACH_BB (bb)
{
tree stmt = last_stmt (bb);
if (!stmt)
continue;
switch (TREE_CODE (stmt))
{
case COND_EXPR:
{
tree true_branch, false_branch;
true_branch = COND_EXPR_THEN (stmt);
false_branch = COND_EXPR_ELSE (stmt);
GOTO_DESTINATION (true_branch)
= main_block_label (GOTO_DESTINATION (true_branch));
GOTO_DESTINATION (false_branch)
= main_block_label (GOTO_DESTINATION (false_branch));
break;
}
case SWITCH_EXPR:
{
size_t i;
tree vec = SWITCH_LABELS (stmt);
size_t n = TREE_VEC_LENGTH (vec);
/* Replace all destination labels. */
for (i = 0; i < n; ++i)
{
tree elt = TREE_VEC_ELT (vec, i);
tree label = main_block_label (CASE_LABEL (elt));
CASE_LABEL (elt) = label;
}
break;
}
/* We have to handle GOTO_EXPRs until they're removed, and we don't
remove them until after we've created the CFG edges. */
case GOTO_EXPR:
if (! computed_goto_p (stmt))
{
GOTO_DESTINATION (stmt)
= main_block_label (GOTO_DESTINATION (stmt));
break;
}
default:
break;
}
}
for_each_eh_region (update_eh_label);
/* Finally, purge dead labels. All user-defined labels and labels that
can be the target of non-local gotos are preserved. */
FOR_EACH_BB (bb)
{
block_stmt_iterator i;
tree label_for_this_bb = label_for_bb[bb->index];
if (! label_for_this_bb)
continue;
for (i = bsi_start (bb); !bsi_end_p (i); )
{
tree label, stmt = bsi_stmt (i);
if (TREE_CODE (stmt) != LABEL_EXPR)
break;
label = LABEL_EXPR_LABEL (stmt);
if (label == label_for_this_bb
|| ! DECL_ARTIFICIAL (label)
|| DECL_NONLOCAL (label))
bsi_next (&i);
else
bsi_remove (&i);
}
}
free (label_for_bb);
}
/* Look for blocks ending in a multiway branch (a SWITCH_EXPR in GIMPLE),
and scan the sorted vector of cases. Combine the ones jumping to the
same label.
Eg. three separate entries 1: 2: 3: become one entry 1..3: */
void
group_case_labels (void)
{
basic_block bb;
FOR_EACH_BB (bb)
{
tree stmt = last_stmt (bb);
if (stmt && TREE_CODE (stmt) == SWITCH_EXPR)
{
tree labels = SWITCH_LABELS (stmt);
int old_size = TREE_VEC_LENGTH (labels);
int i, j, new_size = old_size;
tree default_case = TREE_VEC_ELT (labels, old_size - 1);
tree default_label;
/* The default label is always the last case in a switch
statement after gimplification. */
default_label = CASE_LABEL (default_case);
/* Look for possible opportunities to merge cases.
Ignore the last element of the label vector because it
must be the default case. */
i = 0;
while (i < old_size - 1)
{
tree base_case, base_label, base_high, type;
base_case = TREE_VEC_ELT (labels, i);
gcc_assert (base_case);
base_label = CASE_LABEL (base_case);
/* Discard cases that have the same destination as the
default case. */
if (base_label == default_label)
{
TREE_VEC_ELT (labels, i) = NULL_TREE;
i++;
new_size--;
continue;
}
type = TREE_TYPE (CASE_LOW (base_case));
base_high = CASE_HIGH (base_case) ?
CASE_HIGH (base_case) : CASE_LOW (base_case);
i++;
/* Try to merge case labels. Break out when we reach the end
of the label vector or when we cannot merge the next case
label with the current one. */
while (i < old_size - 1)
{
tree merge_case = TREE_VEC_ELT (labels, i);
tree merge_label = CASE_LABEL (merge_case);
tree t = int_const_binop (PLUS_EXPR, base_high,
integer_one_node, 1);
/* Merge the cases if they jump to the same place,
and their ranges are consecutive. */
if (merge_label == base_label
&& tree_int_cst_equal (CASE_LOW (merge_case), t))
{
base_high = CASE_HIGH (merge_case) ?
CASE_HIGH (merge_case) : CASE_LOW (merge_case);
CASE_HIGH (base_case) = base_high;
TREE_VEC_ELT (labels, i) = NULL_TREE;
new_size--;
i++;
}
else
break;
}
}
/* Compress the case labels in the label vector, and adjust the
length of the vector. */
for (i = 0, j = 0; i < new_size; i++)
{
while (! TREE_VEC_ELT (labels, j))
j++;
TREE_VEC_ELT (labels, i) = TREE_VEC_ELT (labels, j++);
}
TREE_VEC_LENGTH (labels) = new_size;
}
}
}
/* Checks whether we can merge block B into block A. */
static bool
tree_can_merge_blocks_p (basic_block a, basic_block b)
{
tree stmt;
block_stmt_iterator bsi;
if (EDGE_COUNT (a->succs) != 1)
return false;
if (EDGE_SUCC (a, 0)->flags & EDGE_ABNORMAL)
return false;
if (EDGE_SUCC (a, 0)->dest != b)
return false;
if (EDGE_COUNT (b->preds) > 1)
return false;
if (b == EXIT_BLOCK_PTR)
return false;
/* If A ends by a statement causing exceptions or something similar, we
cannot merge the blocks. */
stmt = last_stmt (a);
if (stmt && stmt_ends_bb_p (stmt))
return false;
/* Do not allow a block with only a non-local label to be merged. */
if (stmt && TREE_CODE (stmt) == LABEL_EXPR
&& DECL_NONLOCAL (LABEL_EXPR_LABEL (stmt)))
return false;
/* There may be no phi nodes at the start of b. Most of these degenerate
phi nodes should be cleaned up by kill_redundant_phi_nodes. */
if (phi_nodes (b))
return false;
/* Do not remove user labels. */
for (bsi = bsi_start (b); !bsi_end_p (bsi); bsi_next (&bsi))
{
stmt = bsi_stmt (bsi);
if (TREE_CODE (stmt) != LABEL_EXPR)
break;
if (!DECL_ARTIFICIAL (LABEL_EXPR_LABEL (stmt)))
return false;
}
return true;
}
/* Merge block B into block A. */
static void
tree_merge_blocks (basic_block a, basic_block b)
{
block_stmt_iterator bsi;
tree_stmt_iterator last;
if (dump_file)
fprintf (dump_file, "Merging blocks %d and %d\n", a->index, b->index);
/* Ensure that B follows A. */
move_block_after (b, a);
gcc_assert (EDGE_SUCC (a, 0)->flags & EDGE_FALLTHRU);
gcc_assert (!last_stmt (a) || !stmt_ends_bb_p (last_stmt (a)));
/* Remove labels from B and set bb_for_stmt to A for other statements. */
for (bsi = bsi_start (b); !bsi_end_p (bsi);)
{
if (TREE_CODE (bsi_stmt (bsi)) == LABEL_EXPR)
bsi_remove (&bsi);
else
{
set_bb_for_stmt (bsi_stmt (bsi), a);
bsi_next (&bsi);
}
}
/* Merge the chains. */
last = tsi_last (a->stmt_list);
tsi_link_after (&last, b->stmt_list, TSI_NEW_STMT);
b->stmt_list = NULL;
}
/* Walk the function tree removing unnecessary statements.
* Empty statement nodes are removed
* Unnecessary TRY_FINALLY and TRY_CATCH blocks are removed
* Unnecessary COND_EXPRs are removed
* Some unnecessary BIND_EXPRs are removed
Clearly more work could be done. The trick is doing the analysis
and removal fast enough to be a net improvement in compile times.
Note that when we remove a control structure such as a COND_EXPR
BIND_EXPR, or TRY block, we will need to repeat this optimization pass
to ensure we eliminate all the useless code. */
struct rus_data
{
tree *last_goto;
bool repeat;
bool may_throw;
bool may_branch;
bool has_label;
};
static void remove_useless_stmts_1 (tree *, struct rus_data *);
static bool
remove_useless_stmts_warn_notreached (tree stmt)
{
if (EXPR_HAS_LOCATION (stmt))
{
location_t loc = EXPR_LOCATION (stmt);
if (LOCATION_LINE (loc) > 0)
{
warning ("%Hwill never be executed", &loc);
return true;
}
}
switch (TREE_CODE (stmt))
{
case STATEMENT_LIST:
{
tree_stmt_iterator i;
for (i = tsi_start (stmt); !tsi_end_p (i); tsi_next (&i))
if (remove_useless_stmts_warn_notreached (tsi_stmt (i)))
return true;
}
break;
case COND_EXPR:
if (remove_useless_stmts_warn_notreached (COND_EXPR_COND (stmt)))
return true;
if (remove_useless_stmts_warn_notreached (COND_EXPR_THEN (stmt)))
return true;
if (remove_useless_stmts_warn_notreached (COND_EXPR_ELSE (stmt)))
return true;
break;
case TRY_FINALLY_EXPR:
case TRY_CATCH_EXPR:
if (remove_useless_stmts_warn_notreached (TREE_OPERAND (stmt, 0)))
return true;
if (remove_useless_stmts_warn_notreached (TREE_OPERAND (stmt, 1)))
return true;
break;
case CATCH_EXPR:
return remove_useless_stmts_warn_notreached (CATCH_BODY (stmt));
case EH_FILTER_EXPR:
return remove_useless_stmts_warn_notreached (EH_FILTER_FAILURE (stmt));
case BIND_EXPR:
return remove_useless_stmts_warn_notreached (BIND_EXPR_BLOCK (stmt));
default:
/* Not a live container. */
break;
}
return false;
}
static void
remove_useless_stmts_cond (tree *stmt_p, struct rus_data *data)
{
tree then_clause, else_clause, cond;
bool save_has_label, then_has_label, else_has_label;
save_has_label = data->has_label;
data->has_label = false;
data->last_goto = NULL;
remove_useless_stmts_1 (&COND_EXPR_THEN (*stmt_p), data);
then_has_label = data->has_label;
data->has_label = false;
data->last_goto = NULL;
remove_useless_stmts_1 (&COND_EXPR_ELSE (*stmt_p), data);
else_has_label = data->has_label;
data->has_label = save_has_label | then_has_label | else_has_label;
then_clause = COND_EXPR_THEN (*stmt_p);
else_clause = COND_EXPR_ELSE (*stmt_p);
cond = fold (COND_EXPR_COND (*stmt_p));
/* If neither arm does anything at all, we can remove the whole IF. */
if (!TREE_SIDE_EFFECTS (then_clause) && !TREE_SIDE_EFFECTS (else_clause))
{
*stmt_p = build_empty_stmt ();
data->repeat = true;
}
/* If there are no reachable statements in an arm, then we can
zap the entire conditional. */
else if (integer_nonzerop (cond) && !else_has_label)
{
if (warn_notreached)
remove_useless_stmts_warn_notreached (else_clause);
*stmt_p = then_clause;
data->repeat = true;
}
else if (integer_zerop (cond) && !then_has_label)
{
if (warn_notreached)
remove_useless_stmts_warn_notreached (then_clause);
*stmt_p = else_clause;
data->repeat = true;
}
/* Check a couple of simple things on then/else with single stmts. */
else
{
tree then_stmt = expr_only (then_clause);
tree else_stmt = expr_only (else_clause);
/* Notice branches to a common destination. */
if (then_stmt && else_stmt
&& TREE_CODE (then_stmt) == GOTO_EXPR
&& TREE_CODE (else_stmt) == GOTO_EXPR
&& (GOTO_DESTINATION (then_stmt) == GOTO_DESTINATION (else_stmt)))
{
*stmt_p = then_stmt;
data->repeat = true;
}
/* If the THEN/ELSE clause merely assigns a value to a variable or
parameter which is already known to contain that value, then
remove the useless THEN/ELSE clause. */
else if (TREE_CODE (cond) == VAR_DECL || TREE_CODE (cond) == PARM_DECL)
{
if (else_stmt
&& TREE_CODE (else_stmt) == MODIFY_EXPR
&& TREE_OPERAND (else_stmt, 0) == cond
&& integer_zerop (TREE_OPERAND (else_stmt, 1)))
COND_EXPR_ELSE (*stmt_p) = alloc_stmt_list ();
}
else if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
&& (TREE_CODE (TREE_OPERAND (cond, 0)) == VAR_DECL
|| TREE_CODE (TREE_OPERAND (cond, 0)) == PARM_DECL)
&& TREE_CONSTANT (TREE_OPERAND (cond, 1)))
{
tree stmt = (TREE_CODE (cond) == EQ_EXPR
? then_stmt : else_stmt);
tree *location = (TREE_CODE (cond) == EQ_EXPR
? &COND_EXPR_THEN (*stmt_p)
: &COND_EXPR_ELSE (*stmt_p));
if (stmt
&& TREE_CODE (stmt) == MODIFY_EXPR
&& TREE_OPERAND (stmt, 0) == TREE_OPERAND (cond, 0)
&& TREE_OPERAND (stmt, 1) == TREE_OPERAND (cond, 1))
*location = alloc_stmt_list ();
}
}
/* Protect GOTOs in the arm of COND_EXPRs from being removed. They
would be re-introduced during lowering. */
data->last_goto = NULL;
}
static void
remove_useless_stmts_tf (tree *stmt_p, struct rus_data *data)
{
bool save_may_branch, save_may_throw;
bool this_may_branch, this_may_throw;
/* Collect may_branch and may_throw information for the body only. */
save_may_branch = data->may_branch;
save_may_throw = data->may_throw;
data->may_branch = false;
data->may_throw = false;
data->last_goto = NULL;
remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 0), data);
this_may_branch = data->may_branch;
this_may_throw = data->may_throw;
data->may_branch |= save_may_branch;
data->may_throw |= save_may_throw;
data->last_goto = NULL;
remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 1), data);
/* If the body is empty, then we can emit the FINALLY block without
the enclosing TRY_FINALLY_EXPR. */
if (!TREE_SIDE_EFFECTS (TREE_OPERAND (*stmt_p, 0)))
{
*stmt_p = TREE_OPERAND (*stmt_p, 1);
data->repeat = true;
}
/* If the handler is empty, then we can emit the TRY block without
the enclosing TRY_FINALLY_EXPR. */
else if (!TREE_SIDE_EFFECTS (TREE_OPERAND (*stmt_p, 1)))
{
*stmt_p = TREE_OPERAND (*stmt_p, 0);
data->repeat = true;
}
/* If the body neither throws, nor branches, then we can safely
string the TRY and FINALLY blocks together. */
else if (!this_may_branch && !this_may_throw)
{
tree stmt = *stmt_p;
*stmt_p = TREE_OPERAND (stmt, 0);
append_to_statement_list (TREE_OPERAND (stmt, 1), stmt_p);
data->repeat = true;
}
}
static void
remove_useless_stmts_tc (tree *stmt_p, struct rus_data *data)
{
bool save_may_throw, this_may_throw;
tree_stmt_iterator i;
tree stmt;
/* Collect may_throw information for the body only. */
save_may_throw = data->may_throw;
data->may_throw = false;
data->last_goto = NULL;
remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 0), data);
this_may_throw = data->may_throw;
data->may_throw = save_may_throw;
/* If the body cannot throw, then we can drop the entire TRY_CATCH_EXPR. */
if (!this_may_throw)
{
if (warn_notreached)
remove_useless_stmts_warn_notreached (TREE_OPERAND (*stmt_p, 1));
*stmt_p = TREE_OPERAND (*stmt_p, 0);
data->repeat = true;
return;
}
/* Process the catch clause specially. We may be able to tell that
no exceptions propagate past this point. */
this_may_throw = true;
i = tsi_start (TREE_OPERAND (*stmt_p, 1));
stmt = tsi_stmt (i);
data->last_goto = NULL;
switch (TREE_CODE (stmt))
{
case CATCH_EXPR:
for (; !tsi_end_p (i); tsi_next (&i))
{
stmt = tsi_stmt (i);
/* If we catch all exceptions, then the body does not
propagate exceptions past this point. */
if (CATCH_TYPES (stmt) == NULL)
this_may_throw = false;
data->last_goto = NULL;
remove_useless_stmts_1 (&CATCH_BODY (stmt), data);
}
break;
case EH_FILTER_EXPR:
if (EH_FILTER_MUST_NOT_THROW (stmt))
this_may_throw = false;
else if (EH_FILTER_TYPES (stmt) == NULL)
this_may_throw = false;
remove_useless_stmts_1 (&EH_FILTER_FAILURE (stmt), data);
break;
default:
/* Otherwise this is a cleanup. */
remove_useless_stmts_1 (&TREE_OPERAND (*stmt_p, 1), data);
/* If the cleanup is empty, then we can emit the TRY block without
the enclosing TRY_CATCH_EXPR. */
if (!TREE_SIDE_EFFECTS (TREE_OPERAND (*stmt_p, 1)))
{
*stmt_p = TREE_OPERAND (*stmt_p, 0);
data->repeat = true;
}
break;
}
data->may_throw |= this_may_throw;
}
static void
remove_useless_stmts_bind (tree *stmt_p, struct rus_data *data)
{
tree block;
/* First remove anything underneath the BIND_EXPR. */
remove_useless_stmts_1 (&BIND_EXPR_BODY (*stmt_p), data);
/* If the BIND_EXPR has no variables, then we can pull everything
up one level and remove the BIND_EXPR, unless this is the toplevel
BIND_EXPR for the current function or an inlined function.
When this situation occurs we will want to apply this
optimization again. */
block = BIND_EXPR_BLOCK (*stmt_p);
if (BIND_EXPR_VARS (*stmt_p) == NULL_TREE
&& *stmt_p != DECL_SAVED_TREE (current_function_decl)
&& (! block
|| ! BLOCK_ABSTRACT_ORIGIN (block)
|| (TREE_CODE (BLOCK_ABSTRACT_ORIGIN (block))
!= FUNCTION_DECL)))
{
*stmt_p = BIND_EXPR_BODY (*stmt_p);
data->repeat = true;
}
}
static void
remove_useless_stmts_goto (tree *stmt_p, struct rus_data *data)
{
tree dest = GOTO_DESTINATION (*stmt_p);
data->may_branch = true;
data->last_goto = NULL;
/* Record the last goto expr, so that we can delete it if unnecessary. */
if (TREE_CODE (dest) == LABEL_DECL)
data->last_goto = stmt_p;
}
static void
remove_useless_stmts_label (tree *stmt_p, struct rus_data *data)
{
tree label = LABEL_EXPR_LABEL (*stmt_p);
data->has_label = true;
/* We do want to jump across non-local label receiver code. */
if (DECL_NONLOCAL (label))
data->last_goto = NULL;
else if (data->last_goto && GOTO_DESTINATION (*data->last_goto) == label)
{
*data->last_goto = build_empty_stmt ();
data->repeat = true;
}
/* ??? Add something here to delete unused labels. */
}
/* If the function is "const" or "pure", then clear TREE_SIDE_EFFECTS on its
decl. This allows us to eliminate redundant or useless
calls to "const" functions.
Gimplifier already does the same operation, but we may notice functions
being const and pure once their calls has been gimplified, so we need
to update the flag. */
static void
update_call_expr_flags (tree call)
{
tree decl = get_callee_fndecl (call);
if (!decl)
return;
if (call_expr_flags (call) & (ECF_CONST | ECF_PURE))
TREE_SIDE_EFFECTS (call) = 0;
if (TREE_NOTHROW (decl))
TREE_NOTHROW (call) = 1;
}
/* T is CALL_EXPR. Set current_function_calls_* flags. */
void
notice_special_calls (tree t)
{
int flags = call_expr_flags (t);
if (flags & ECF_MAY_BE_ALLOCA)
current_function_calls_alloca = true;
if (flags & ECF_RETURNS_TWICE)
current_function_calls_setjmp = true;
}
/* Clear flags set by notice_special_calls. Used by dead code removal
to update the flags. */
void
clear_special_calls (void)
{
current_function_calls_alloca = false;
current_function_calls_setjmp = false;
}
static void
remove_useless_stmts_1 (tree *tp, struct rus_data *data)
{
tree t = *tp, op;
switch (TREE_CODE (t))
{
case COND_EXPR:
remove_useless_stmts_cond (tp, data);
break;
case TRY_FINALLY_EXPR:
remove_useless_stmts_tf (tp, data);
break;
case TRY_CATCH_EXPR:
remove_useless_stmts_tc (tp, data);
break;
case BIND_EXPR:
remove_useless_stmts_bind (tp, data);
break;
case GOTO_EXPR:
remove_useless_stmts_goto (tp, data);
break;
case LABEL_EXPR:
remove_useless_stmts_label (tp, data);
break;
case RETURN_EXPR:
fold_stmt (tp);
data->last_goto = NULL;
data->may_branch = true;
break;
case CALL_EXPR:
fold_stmt (tp);
data->last_goto = NULL;
notice_special_calls (t);
update_call_expr_flags (t);
if (tree_could_throw_p (t))
data->may_throw = true;
break;
case MODIFY_EXPR:
data->last_goto = NULL;
fold_stmt (tp);
op = get_call_expr_in (t);
if (op)
{
update_call_expr_flags (op);
notice_special_calls (op);
}
if (tree_could_throw_p (t))
data->may_throw = true;
break;
case STATEMENT_LIST:
{
tree_stmt_iterator i = tsi_start (t);
while (!tsi_end_p (i))
{
t = tsi_stmt (i);
if (IS_EMPTY_STMT (t))
{
tsi_delink (&i);
continue;
}
remove_useless_stmts_1 (tsi_stmt_ptr (i), data);
t = tsi_stmt (i);
if (TREE_CODE (t) == STATEMENT_LIST)
{
tsi_link_before (&i, t, TSI_SAME_STMT);
tsi_delink (&i);
}
else
tsi_next (&i);
}
}
break;
case ASM_EXPR:
fold_stmt (tp);
data->last_goto = NULL;
break;
default:
data->last_goto = NULL;
break;
}
}
static void
remove_useless_stmts (void)
{
struct rus_data data;
clear_special_calls ();
do
{
memset (&data, 0, sizeof (data));
remove_useless_stmts_1 (&DECL_SAVED_TREE (current_function_decl), &data);
}
while (data.repeat);
}
struct tree_opt_pass pass_remove_useless_stmts =
{
"useless", /* name */
NULL, /* gate */
remove_useless_stmts, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
0, /* tv_id */
PROP_gimple_any, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
TODO_dump_func, /* todo_flags_finish */
0 /* letter */
};
/* Remove obviously useless statements in basic block BB. */
static void
cfg_remove_useless_stmts_bb (basic_block bb)
{
block_stmt_iterator bsi;
tree stmt = NULL_TREE;
tree cond, var = NULL_TREE, val = NULL_TREE;
struct var_ann_d *ann;
/* Check whether we come here from a condition, and if so, get the
condition. */
if (EDGE_COUNT (bb->preds) != 1
|| !(EDGE_PRED (bb, 0)->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
return;
cond = COND_EXPR_COND (last_stmt (EDGE_PRED (bb, 0)->src));
if (TREE_CODE (cond) == VAR_DECL || TREE_CODE (cond) == PARM_DECL)
{
var = cond;
val = (EDGE_PRED (bb, 0)->flags & EDGE_FALSE_VALUE
? boolean_false_node : boolean_true_node);
}
else if (TREE_CODE (cond) == TRUTH_NOT_EXPR
&& (TREE_CODE (TREE_OPERAND (cond, 0)) == VAR_DECL
|| TREE_CODE (TREE_OPERAND (cond, 0)) == PARM_DECL))
{
var = TREE_OPERAND (cond, 0);
val = (EDGE_PRED (bb, 0)->flags & EDGE_FALSE_VALUE
? boolean_true_node : boolean_false_node);
}
else
{
if (EDGE_PRED (bb, 0)->flags & EDGE_FALSE_VALUE)
cond = invert_truthvalue (cond);
if (TREE_CODE (cond) == EQ_EXPR
&& (TREE_CODE (TREE_OPERAND (cond, 0)) == VAR_DECL
|| TREE_CODE (TREE_OPERAND (cond, 0)) == PARM_DECL)
&& (TREE_CODE (TREE_OPERAND (cond, 1)) == VAR_DECL
|| TREE_CODE (TREE_OPERAND (cond, 1)) == PARM_DECL
|| TREE_CONSTANT (TREE_OPERAND (cond, 1))))
{
var = TREE_OPERAND (cond, 0);
val = TREE_OPERAND (cond, 1);
}
else
return;
}
/* Only work for normal local variables. */
ann = var_ann (var);
if (!ann
|| ann->may_aliases
|| TREE_ADDRESSABLE (var))
return;
if (! TREE_CONSTANT (val))
{
ann = var_ann (val);
if (!ann
|| ann->may_aliases
|| TREE_ADDRESSABLE (val))
return;
}
/* Ignore floating point variables, since comparison behaves weird for
them. */
if (FLOAT_TYPE_P (TREE_TYPE (var)))
return;
for (bsi = bsi_start (bb); !bsi_end_p (bsi);)
{
stmt = bsi_stmt (bsi);
/* If the THEN/ELSE clause merely assigns a value to a variable/parameter
which is already known to contain that value, then remove the useless
THEN/ELSE clause. */
if (TREE_CODE (stmt) == MODIFY_EXPR
&& TREE_OPERAND (stmt, 0) == var
&& operand_equal_p (val, TREE_OPERAND (stmt, 1), 0))
{
bsi_remove (&bsi);
continue;
}
/* Invalidate the var if we encounter something that could modify it.
Likewise for the value it was previously set to. Note that we only
consider values that are either a VAR_DECL or PARM_DECL so we
can test for conflict very simply. */
if (TREE_CODE (stmt) == ASM_EXPR
|| (TREE_CODE (stmt) == MODIFY_EXPR
&& (TREE_OPERAND (stmt, 0) == var
|| TREE_OPERAND (stmt, 0) == val)))
return;
bsi_next (&bsi);
}
}
/* A CFG-aware version of remove_useless_stmts. */
void
cfg_remove_useless_stmts (void)
{
basic_block bb;
#ifdef ENABLE_CHECKING
verify_flow_info ();
#endif
FOR_EACH_BB (bb)
{
cfg_remove_useless_stmts_bb (bb);
}
}
/* Remove PHI nodes associated with basic block BB and all edges out of BB. */
static void
remove_phi_nodes_and_edges_for_unreachable_block (basic_block bb)
{
tree phi;
/* Since this block is no longer reachable, we can just delete all
of its PHI nodes. */
phi = phi_nodes (bb);
while (phi)
{
tree next = PHI_CHAIN (phi);
remove_phi_node (phi, NULL_TREE, bb);
phi = next;
}
/* Remove edges to BB's successors. */
while (EDGE_COUNT (bb->succs) > 0)
remove_edge (EDGE_SUCC (bb, 0));
}
/* Remove statements of basic block BB. */
static void
remove_bb (basic_block bb)
{
block_stmt_iterator i;
source_locus loc = 0;
if (dump_file)
{
fprintf (dump_file, "Removing basic block %d\n", bb->index);
if (dump_flags & TDF_DETAILS)
{
dump_bb (bb, dump_file, 0);
fprintf (dump_file, "\n");
}
}
/* Remove all the instructions in the block. */
for (i = bsi_start (bb); !bsi_end_p (i);)
{
tree stmt = bsi_stmt (i);
if (TREE_CODE (stmt) == LABEL_EXPR
&& FORCED_LABEL (LABEL_EXPR_LABEL (stmt)))
{
basic_block new_bb = bb->prev_bb;
block_stmt_iterator new_bsi = bsi_start (new_bb);
bsi_remove (&i);
bsi_insert_before (&new_bsi, stmt, BSI_NEW_STMT);
}
else
{
release_defs (stmt);
set_bb_for_stmt (stmt, NULL);
bsi_remove (&i);
}
/* Don't warn for removed gotos. Gotos are often removed due to
jump threading, thus resulting in bogus warnings. Not great,
since this way we lose warnings for gotos in the original
program that are indeed unreachable. */
if (TREE_CODE (stmt) != GOTO_EXPR && EXPR_HAS_LOCATION (stmt) && !loc)
{
source_locus t;
#ifdef USE_MAPPED_LOCATION
t = EXPR_LOCATION (stmt);
#else
t = EXPR_LOCUS (stmt);
#endif
if (t && LOCATION_LINE (*t) > 0)
loc = t;
}
}
/* If requested, give a warning that the first statement in the
block is unreachable. We walk statements backwards in the
loop above, so the last statement we process is the first statement
in the block. */
if (warn_notreached && loc)
#ifdef USE_MAPPED_LOCATION
warning ("%Hwill never be executed", &loc);
#else
warning ("%Hwill never be executed", loc);
#endif
remove_phi_nodes_and_edges_for_unreachable_block (bb);
}
/* A list of all the noreturn calls passed to modify_stmt.
cleanup_control_flow uses it to detect cases where a mid-block
indirect call has been turned into a noreturn call. When this
happens, all the instructions after the call are no longer
reachable and must be deleted as dead. */
VEC(tree) *modified_noreturn_calls;
/* Try to remove superfluous control structures. */
static bool
cleanup_control_flow (void)
{
basic_block bb;
block_stmt_iterator bsi;
bool retval = false;
tree stmt;
/* Detect cases where a mid-block call is now known not to return. */
while (VEC_length (tree, modified_noreturn_calls))
{
stmt = VEC_pop (tree, modified_noreturn_calls);
bb = bb_for_stmt (stmt);
if (bb != NULL && last_stmt (bb) != stmt && noreturn_call_p (stmt))
split_block (bb, stmt);
}
FOR_EACH_BB (bb)
{
bsi = bsi_last (bb);
if (bsi_end_p (bsi))
continue;
stmt = bsi_stmt (bsi);
if (TREE_CODE (stmt) == COND_EXPR
|| TREE_CODE (stmt) == SWITCH_EXPR)
retval |= cleanup_control_expr_graph (bb, bsi);
/* Check for indirect calls that have been turned into
noreturn calls. */
if (noreturn_call_p (stmt) && remove_fallthru_edge (bb->succs))
{
free_dominance_info (CDI_DOMINATORS);
retval = true;
}
}
return retval;
}
/* Disconnect an unreachable block in the control expression starting
at block BB. */
static bool
cleanup_control_expr_graph (basic_block bb, block_stmt_iterator bsi)
{
edge taken_edge;
bool retval = false;
tree expr = bsi_stmt (bsi), val;
if (EDGE_COUNT (bb->succs) > 1)
{
edge e;
edge_iterator ei;
switch (TREE_CODE (expr))
{
case COND_EXPR:
val = COND_EXPR_COND (expr);
break;
case SWITCH_EXPR:
val = SWITCH_COND (expr);
if (TREE_CODE (val) != INTEGER_CST)
return false;
break;
default:
gcc_unreachable ();
}
taken_edge = find_taken_edge (bb, val);
if (!taken_edge)
return false;
/* Remove all the edges except the one that is always executed. */
for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
{
if (e != taken_edge)
{
taken_edge->probability += e->probability;
taken_edge->count += e->count;
remove_edge (e);
retval = true;
}
else
ei_next (&ei);
}
if (taken_edge->probability > REG_BR_PROB_BASE)
taken_edge->probability = REG_BR_PROB_BASE;
}
else
taken_edge = EDGE_SUCC (bb, 0);
bsi_remove (&bsi);
taken_edge->flags = EDGE_FALLTHRU;
/* We removed some paths from the cfg. */
free_dominance_info (CDI_DOMINATORS);
return retval;
}
/* Remove any fallthru edge from EV. Return true if an edge was removed. */
static bool
remove_fallthru_edge (VEC(edge) *ev)
{
edge_iterator ei;
edge e;
FOR_EACH_EDGE (e, ei, ev)
if ((e->flags & EDGE_FALLTHRU) != 0)
{
remove_edge (e);
return true;
}
return false;
}
/* Given a basic block BB ending with COND_EXPR or SWITCH_EXPR, and a
predicate VAL, return the edge that will be taken out of the block.
If VAL does not match a unique edge, NULL is returned. */
edge
find_taken_edge (basic_block bb, tree val)
{
tree stmt;
stmt = last_stmt (bb);
gcc_assert (stmt);
gcc_assert (is_ctrl_stmt (stmt));
gcc_assert (val);
if (TREE_CODE (val) != INTEGER_CST)
return NULL;
if (TREE_CODE (stmt) == COND_EXPR)
return find_taken_edge_cond_expr (bb, val);
if (TREE_CODE (stmt) == SWITCH_EXPR)
return find_taken_edge_switch_expr (bb, val);
gcc_unreachable ();
}
/* Given a constant value VAL and the entry block BB to a COND_EXPR
statement, determine which of the two edges will be taken out of the
block. Return NULL if either edge may be taken. */
static edge
find_taken_edge_cond_expr (basic_block bb, tree val)
{
edge true_edge, false_edge;
extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
gcc_assert (TREE_CODE (val) == INTEGER_CST);
return (zero_p (val) ? false_edge : true_edge);
}
/* Given an INTEGER_CST VAL and the entry block BB to a SWITCH_EXPR
statement, determine which edge will be taken out of the block. Return
NULL if any edge may be taken. */
static edge
find_taken_edge_switch_expr (basic_block bb, tree val)
{
tree switch_expr, taken_case;
basic_block dest_bb;
edge e;
switch_expr = last_stmt (bb);
taken_case = find_case_label_for_value (switch_expr, val);
dest_bb = label_to_block (CASE_LABEL (taken_case));
e = find_edge (bb, dest_bb);
gcc_assert (e);
return e;
}
/* Return the CASE_LABEL_EXPR that SWITCH_EXPR will take for VAL.
We can make optimal use here of the fact that the case labels are
sorted: We can do a binary search for a case matching VAL. */
static tree
find_case_label_for_value (tree switch_expr, tree val)
{
tree vec = SWITCH_LABELS (switch_expr);
size_t low, high, n = TREE_VEC_LENGTH (vec);
tree default_case = TREE_VEC_ELT (vec, n - 1);
for (low = -1, high = n - 1; high - low > 1; )
{
size_t i = (high + low) / 2;
tree t = TREE_VEC_ELT (vec, i);
int cmp;
/* Cache the result of comparing CASE_LOW and val. */
cmp = tree_int_cst_compare (CASE_LOW (t), val);
if (cmp > 0)
high = i;
else
low = i;
if (CASE_HIGH (t) == NULL)
{
/* A singe-valued case label. */
if (cmp == 0)
return t;
}
else
{
/* A case range. We can only handle integer ranges. */
if (cmp <= 0 && tree_int_cst_compare (CASE_HIGH (t), val) >= 0)
return t;
}
}
return default_case;
}
/* If all the PHI nodes in DEST have alternatives for E1 and E2 and
those alternatives are equal in each of the PHI nodes, then return
true, else return false. */
static bool
phi_alternatives_equal (basic_block dest, edge e1, edge e2)
{
int n1 = e1->dest_idx;
int n2 = e2->dest_idx;
tree phi;
for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi))
{
tree val1 = PHI_ARG_DEF (phi, n1);
tree val2 = PHI_ARG_DEF (phi, n2);
gcc_assert (val1 != NULL_TREE);
gcc_assert (val2 != NULL_TREE);
if (!operand_equal_for_phi_arg_p (val1, val2))
return false;
}
return true;
}
/*---------------------------------------------------------------------------
Debugging functions
---------------------------------------------------------------------------*/
/* Dump tree-specific information of block BB to file OUTF. */
void
tree_dump_bb (basic_block bb, FILE *outf, int indent)
{
dump_generic_bb (outf, bb, indent, TDF_VOPS);
}
/* Dump a basic block on stderr. */
void
debug_tree_bb (basic_block bb)
{
dump_bb (bb, stderr, 0);
}
/* Dump basic block with index N on stderr. */
basic_block
debug_tree_bb_n (int n)
{
debug_tree_bb (BASIC_BLOCK (n));
return BASIC_BLOCK (n);
}
/* Dump the CFG on stderr.
FLAGS are the same used by the tree dumping functions
(see TDF_* in tree.h). */
void
debug_tree_cfg (int flags)
{
dump_tree_cfg (stderr, flags);
}
/* Dump the program showing basic block boundaries on the given FILE.
FLAGS are the same used by the tree dumping functions (see TDF_* in
tree.h). */
void
dump_tree_cfg (FILE *file, int flags)
{
if (flags & TDF_DETAILS)
{
const char *funcname
= lang_hooks.decl_printable_name (current_function_decl, 2);
fputc ('\n', file);
fprintf (file, ";; Function %s\n\n", funcname);
fprintf (file, ";; \n%d basic blocks, %d edges, last basic block %d.\n\n",
n_basic_blocks, n_edges, last_basic_block);
brief_dump_cfg (file);
fprintf (file, "\n");
}
if (flags & TDF_STATS)
dump_cfg_stats (file);
dump_function_to_file (current_function_decl, file, flags | TDF_BLOCKS);
}
/* Dump CFG statistics on FILE. */
void
dump_cfg_stats (FILE *file)
{
static long max_num_merged_labels = 0;
unsigned long size, total = 0;
int n_edges;
basic_block bb;
const char * const fmt_str = "%-30s%-13s%12s\n";
const char * const fmt_str_1 = "%-30s%13d%11lu%c\n";
const char * const fmt_str_3 = "%-43s%11lu%c\n";
const char *funcname
= lang_hooks.decl_printable_name (current_function_decl, 2);
fprintf (file, "\nCFG Statistics for %s\n\n", funcname);
fprintf (file, "---------------------------------------------------------\n");
fprintf (file, fmt_str, "", " Number of ", "Memory");
fprintf (file, fmt_str, "", " instances ", "used ");
fprintf (file, "---------------------------------------------------------\n");
size = n_basic_blocks * sizeof (struct basic_block_def);
total += size;
fprintf (file, fmt_str_1, "Basic blocks", n_basic_blocks,
SCALE (size), LABEL (size));
n_edges = 0;
FOR_EACH_BB (bb)
n_edges += EDGE_COUNT (bb->succs);
size = n_edges * sizeof (struct edge_def);
total += size;
fprintf (file, fmt_str_1, "Edges", n_edges, SCALE (size), LABEL (size));
size = n_basic_blocks * sizeof (struct bb_ann_d);
total += size;
fprintf (file, fmt_str_1, "Basic block annotations", n_basic_blocks,
SCALE (size), LABEL (size));
fprintf (file, "---------------------------------------------------------\n");
fprintf (file, fmt_str_3, "Total memory used by CFG data", SCALE (total),
LABEL (total));
fprintf (file, "---------------------------------------------------------\n");
fprintf (file, "\n");
if (cfg_stats.num_merged_labels > max_num_merged_labels)
max_num_merged_labels = cfg_stats.num_merged_labels;
fprintf (file, "Coalesced label blocks: %ld (Max so far: %ld)\n",
cfg_stats.num_merged_labels, max_num_merged_labels);
fprintf (file, "\n");
}
/* Dump CFG statistics on stderr. Keep extern so that it's always
linked in the final executable. */
void
debug_cfg_stats (void)
{
dump_cfg_stats (stderr);
}
/* Dump the flowgraph to a .vcg FILE. */
static void
tree_cfg2vcg (FILE *file)
{
edge e;
edge_iterator ei;
basic_block bb;
const char *funcname
= lang_hooks.decl_printable_name (current_function_decl, 2);
/* Write the file header. */
fprintf (file, "graph: { title: \"%s\"\n", funcname);
fprintf (file, "node: { title: \"ENTRY\" label: \"ENTRY\" }\n");
fprintf (file, "node: { title: \"EXIT\" label: \"EXIT\" }\n");
/* Write blocks and edges. */
FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR->succs)
{
fprintf (file, "edge: { sourcename: \"ENTRY\" targetname: \"%d\"",
e->dest->index);
if (e->flags & EDGE_FAKE)
fprintf (file, " linestyle: dotted priority: 10");
else
fprintf (file, " linestyle: solid priority: 100");
fprintf (file, " }\n");
}
fputc ('\n', file);
FOR_EACH_BB (bb)
{
enum tree_code head_code, end_code;
const char *head_name, *end_name;
int head_line = 0;
int end_line = 0;
tree first = first_stmt (bb);
tree last = last_stmt (bb);
if (first)
{
head_code = TREE_CODE (first);
head_name = tree_code_name[head_code];
head_line = get_lineno (first);
}
else
head_name = "no-statement";
if (last)
{
end_code = TREE_CODE (last);
end_name = tree_code_name[end_code];
end_line = get_lineno (last);
}
else
end_name = "no-statement";
fprintf (file, "node: { title: \"%d\" label: \"#%d\\n%s (%d)\\n%s (%d)\"}\n",
bb->index, bb->index, head_name, head_line, end_name,
end_line);
FOR_EACH_EDGE (e, ei, bb->succs)
{
if (e->dest == EXIT_BLOCK_PTR)
fprintf (file, "edge: { sourcename: \"%d\" targetname: \"EXIT\"", bb->index);
else
fprintf (file, "edge: { sourcename: \"%d\" targetname: \"%d\"", bb->index, e->dest->index);
if (e->flags & EDGE_FAKE)
fprintf (file, " priority: 10 linestyle: dotted");
else
fprintf (file, " priority: 100 linestyle: solid");
fprintf (file, " }\n");
}
if (bb->next_bb != EXIT_BLOCK_PTR)
fputc ('\n', file);
}
fputs ("}\n\n", file);
}
/*---------------------------------------------------------------------------
Miscellaneous helpers
---------------------------------------------------------------------------*/
/* Return true if T represents a stmt that always transfers control. */
bool
is_ctrl_stmt (tree t)
{
return (TREE_CODE (t) == COND_EXPR
|| TREE_CODE (t) == SWITCH_EXPR
|| TREE_CODE (t) == GOTO_EXPR
|| TREE_CODE (t) == RETURN_EXPR
|| TREE_CODE (t) == RESX_EXPR);
}
/* Return true if T is a statement that may alter the flow of control
(e.g., a call to a non-returning function). */
bool
is_ctrl_altering_stmt (tree t)
{
tree call;
gcc_assert (t);
call = get_call_expr_in (t);
if (call)
{
/* A non-pure/const CALL_EXPR alters flow control if the current
function has nonlocal labels. */
if (TREE_SIDE_EFFECTS (call) && current_function_has_nonlocal_label)
return true;
/* A CALL_EXPR also alters control flow if it does not return. */
if (call_expr_flags (call) & ECF_NORETURN)
return true;
}
/* If a statement can throw, it alters control flow. */
return tree_can_throw_internal (t);
}
/* Return true if T is a computed goto. */
bool
computed_goto_p (tree t)
{
return (TREE_CODE (t) == GOTO_EXPR
&& TREE_CODE (GOTO_DESTINATION (t)) != LABEL_DECL);
}
/* Checks whether EXPR is a simple local goto. */
bool
simple_goto_p (tree expr)
{
return (TREE_CODE (expr) == GOTO_EXPR
&& TREE_CODE (GOTO_DESTINATION (expr)) == LABEL_DECL);
}
/* Return true if T should start a new basic block. PREV_T is the
statement preceding T. It is used when T is a label or a case label.
Labels should only start a new basic block if their previous statement
wasn't a label. Otherwise, sequence of labels would generate
unnecessary basic blocks that only contain a single label. */
static inline bool
stmt_starts_bb_p (tree t, tree prev_t)
{
enum tree_code code;
if (t == NULL_TREE)
return false;
/* LABEL_EXPRs start a new basic block only if the preceding
statement wasn't a label of the same type. This prevents the
creation of consecutive blocks that have nothing but a single
label. */
code = TREE_CODE (t);
if (code == LABEL_EXPR)
{
/* Nonlocal and computed GOTO targets always start a new block. */
if (code == LABEL_EXPR
&& (DECL_NONLOCAL (LABEL_EXPR_LABEL (t))
|| FORCED_LABEL (LABEL_EXPR_LABEL (t))))
return true;
if (prev_t && TREE_CODE (prev_t) == code)
{
if (DECL_NONLOCAL (LABEL_EXPR_LABEL (prev_t)))
return true;
cfg_stats.num_merged_labels++;
return false;
}
else
return true;
}
return false;
}
/* Return true if T should end a basic block. */
bool
stmt_ends_bb_p (tree t)
{
return is_ctrl_stmt (t) || is_ctrl_altering_stmt (t);
}
/* Add gotos that used to be represented implicitly in the CFG. */
void
disband_implicit_edges (void)
{
basic_block bb;
block_stmt_iterator last;
edge e;
edge_iterator ei;
tree stmt, label;
FOR_EACH_BB (bb)
{
last = bsi_last (bb);
stmt = last_stmt (bb);
if (stmt && TREE_CODE (stmt) == COND_EXPR)
{
/* Remove superfluous gotos from COND_EXPR branches. Moved
from cfg_remove_useless_stmts here since it violates the
invariants for tree--cfg correspondence and thus fits better
here where we do it anyway. */
e = find_edge (bb, bb->next_bb);
if (e)
{
if (e->flags & EDGE_TRUE_VALUE)
COND_EXPR_THEN (stmt) = build_empty_stmt ();
else if (e->flags & EDGE_FALSE_VALUE)
COND_EXPR_ELSE (stmt) = build_empty_stmt ();
else
gcc_unreachable ();
e->flags |= EDGE_FALLTHRU;
}
continue;
}
if (stmt && TREE_CODE (stmt) == RETURN_EXPR)
{
/* Remove the RETURN_EXPR if we may fall though to the exit
instead. */
gcc_assert (EDGE_COUNT (bb->succs) == 1);
gcc_assert (EDGE_SUCC (bb, 0)->dest == EXIT_BLOCK_PTR);
if (bb->next_bb == EXIT_BLOCK_PTR
&& !TREE_OPERAND (stmt, 0))
{
bsi_remove (&last);
EDGE_SUCC (bb, 0)->flags |= EDGE_FALLTHRU;
}
continue;
}
/* There can be no fallthru edge if the last statement is a control
one. */
if (stmt && is_ctrl_stmt (stmt))
continue;
/* Find a fallthru edge and emit the goto if necessary. */
FOR_EACH_EDGE (e, ei, bb->succs)
if (e->flags & EDGE_FALLTHRU)
break;
if (!e || e->dest == bb->next_bb)
continue;
gcc_assert (e->dest != EXIT_BLOCK_PTR);
label = tree_block_label (e->dest);
stmt = build1 (GOTO_EXPR, void_type_node, label);
#ifdef USE_MAPPED_LOCATION
SET_EXPR_LOCATION (stmt, e->goto_locus);
#else
SET_EXPR_LOCUS (stmt, e->goto_locus);
#endif
bsi_insert_after (&last, stmt, BSI_NEW_STMT);
e->flags &= ~EDGE_FALLTHRU;
}
}
/* Remove block annotations and other datastructures. */
void
delete_tree_cfg_annotations (void)
{
basic_block bb;
if (n_basic_blocks > 0)
free_blocks_annotations ();
label_to_block_map = NULL;
free_rbi_pool ();
FOR_EACH_BB (bb)
bb->rbi = NULL;
}
/* Return the first statement in basic block BB. */
tree
first_stmt (basic_block bb)
{
block_stmt_iterator i = bsi_start (bb);
return !bsi_end_p (i) ? bsi_stmt (i) : NULL_TREE;
}
/* Return the last statement in basic block BB. */
tree
last_stmt (basic_block bb)
{
block_stmt_iterator b = bsi_last (bb);
return !bsi_end_p (b) ? bsi_stmt (b) : NULL_TREE;
}
/* Return a pointer to the last statement in block BB. */
tree *
last_stmt_ptr (basic_block bb)
{
block_stmt_iterator last = bsi_last (bb);
return !bsi_end_p (last) ? bsi_stmt_ptr (last) : NULL;
}
/* Return the last statement of an otherwise empty block. Return NULL
if the block is totally empty, or if it contains more than one
statement. */
tree
last_and_only_stmt (basic_block bb)
{
block_stmt_iterator i = bsi_last (bb);
tree last, prev;
if (bsi_end_p (i))
return NULL_TREE;
last = bsi_stmt (i);
bsi_prev (&i);
if (bsi_end_p (i))
return last;
/* Empty statements should no longer appear in the instruction stream.
Everything that might have appeared before should be deleted by
remove_useless_stmts, and the optimizers should just bsi_remove
instead of smashing with build_empty_stmt.
Thus the only thing that should appear here in a block containing
one executable statement is a label. */
prev = bsi_stmt (i);
if (TREE_CODE (prev) == LABEL_EXPR)
return last;
else
return NULL_TREE;
}
/* Mark BB as the basic block holding statement T. */
void
set_bb_for_stmt (tree t, basic_block bb)
{
if (TREE_CODE (t) == PHI_NODE)
PHI_BB (t) = bb;
else if (TREE_CODE (t) == STATEMENT_LIST)
{
tree_stmt_iterator i;
for (i = tsi_start (t); !tsi_end_p (i); tsi_next (&i))
set_bb_for_stmt (tsi_stmt (i), bb);
}
else
{
stmt_ann_t ann = get_stmt_ann (t);
ann->bb = bb;
/* If the statement is a label, add the label to block-to-labels map
so that we can speed up edge creation for GOTO_EXPRs. */
if (TREE_CODE (t) == LABEL_EXPR)
{
int uid;
t = LABEL_EXPR_LABEL (t);
uid = LABEL_DECL_UID (t);
if (uid == -1)
{
LABEL_DECL_UID (t) = uid = cfun->last_label_uid++;
if (VARRAY_SIZE (label_to_block_map) <= (unsigned) uid)
VARRAY_GROW (label_to_block_map, 3 * uid / 2);
}
else
/* We're moving an existing label. Make sure that we've
removed it from the old block. */
gcc_assert (!bb || !VARRAY_BB (label_to_block_map, uid));
VARRAY_BB (label_to_block_map, uid) = bb;
}
}
}
/* Finds iterator for STMT. */
extern block_stmt_iterator
bsi_for_stmt (tree stmt)
{
block_stmt_iterator bsi;
for (bsi = bsi_start (bb_for_stmt (stmt)); !bsi_end_p (bsi); bsi_next (&bsi))
if (bsi_stmt (bsi) == stmt)
return bsi;
gcc_unreachable ();
}
/* Insert statement (or statement list) T before the statement
pointed-to by iterator I. M specifies how to update iterator I
after insertion (see enum bsi_iterator_update). */
void
bsi_insert_before (block_stmt_iterator *i, tree t, enum bsi_iterator_update m)
{
set_bb_for_stmt (t, i->bb);
tsi_link_before (&i->tsi, t, m);
modify_stmt (t);
}
/* Insert statement (or statement list) T after the statement
pointed-to by iterator I. M specifies how to update iterator I
after insertion (see enum bsi_iterator_update). */
void
bsi_insert_after (block_stmt_iterator *i, tree t, enum bsi_iterator_update m)
{
set_bb_for_stmt (t, i->bb);
tsi_link_after (&i->tsi, t, m);
modify_stmt (t);
}
/* Remove the statement pointed to by iterator I. The iterator is updated
to the next statement. */
void
bsi_remove (block_stmt_iterator *i)
{
tree t = bsi_stmt (*i);
set_bb_for_stmt (t, NULL);
tsi_delink (&i->tsi);
}
/* Move the statement at FROM so it comes right after the statement at TO. */
void
bsi_move_after (block_stmt_iterator *from, block_stmt_iterator *to)
{
tree stmt = bsi_stmt (*from);
bsi_remove (from);
bsi_insert_after (to, stmt, BSI_SAME_STMT);
}
/* Move the statement at FROM so it comes right before the statement at TO. */
void
bsi_move_before (block_stmt_iterator *from, block_stmt_iterator *to)
{
tree stmt = bsi_stmt (*from);
bsi_remove (from);
bsi_insert_before (to, stmt, BSI_SAME_STMT);
}
/* Move the statement at FROM to the end of basic block BB. */
void
bsi_move_to_bb_end (block_stmt_iterator *from, basic_block bb)
{
block_stmt_iterator last = bsi_last (bb);
/* Have to check bsi_end_p because it could be an empty block. */
if (!bsi_end_p (last) && is_ctrl_stmt (bsi_stmt (last)))
bsi_move_before (from, &last);
else
bsi_move_after (from, &last);
}
/* Replace the contents of the statement pointed to by iterator BSI
with STMT. If PRESERVE_EH_INFO is true, the exception handling
information of the original statement is preserved. */
void
bsi_replace (const block_stmt_iterator *bsi, tree stmt, bool preserve_eh_info)
{
int eh_region;
tree orig_stmt = bsi_stmt (*bsi);
SET_EXPR_LOCUS (stmt, EXPR_LOCUS (orig_stmt));
set_bb_for_stmt (stmt, bsi->bb);
/* Preserve EH region information from the original statement, if
requested by the caller. */
if (preserve_eh_info)
{
eh_region = lookup_stmt_eh_region (orig_stmt);
if (eh_region >= 0)
add_stmt_to_eh_region (stmt, eh_region);
}
*bsi_stmt_ptr (*bsi) = stmt;
modify_stmt (stmt);
}
/* Insert the statement pointed-to by BSI into edge E. Every attempt
is made to place the statement in an existing basic block, but
sometimes that isn't possible. When it isn't possible, the edge is
split and the statement is added to the new block.
In all cases, the returned *BSI points to the correct location. The
return value is true if insertion should be done after the location,
or false if it should be done before the location. If new basic block
has to be created, it is stored in *NEW_BB. */
static bool
tree_find_edge_insert_loc (edge e, block_stmt_iterator *bsi,
basic_block *new_bb)
{
basic_block dest, src;
tree tmp;
dest = e->dest;
restart:
/* If the destination has one predecessor which has no PHI nodes,
insert there. Except for the exit block.
The requirement for no PHI nodes could be relaxed. Basically we
would have to examine the PHIs to prove that none of them used
the value set by the statement we want to insert on E. That
hardly seems worth the effort. */
if (EDGE_COUNT (dest->preds) == 1
&& ! phi_nodes (dest)
&& dest != EXIT_BLOCK_PTR)
{
*bsi = bsi_start (dest);
if (bsi_end_p (*bsi))
return true;
/* Make sure we insert after any leading labels. */
tmp = bsi_stmt (*bsi);
while (TREE_CODE (tmp) == LABEL_EXPR)
{
bsi_next (bsi);
if (bsi_end_p (*bsi))
break;
tmp = bsi_stmt (*bsi);
}
if (bsi_end_p (*bsi))
{
*bsi = bsi_last (dest);
return true;
}
else
return false;
}
/* If the source has one successor, the edge is not abnormal and
the last statement does not end a basic block, insert there.
Except for the entry block. */
src = e->src;
if ((e->flags & EDGE_ABNORMAL) == 0
&& EDGE_COUNT (src->succs) == 1
&& src != ENTRY_BLOCK_PTR)
{
*bsi = bsi_last (src);
if (bsi_end_p (*bsi))
return true;
tmp = bsi_stmt (*bsi);
if (!stmt_ends_bb_p (tmp))
return true;
/* Insert code just before returning the value. We may need to decompose
the return in the case it contains non-trivial operand. */
if (TREE_CODE (tmp) == RETURN_EXPR)
{
tree op = TREE_OPERAND (tmp, 0);
if (!is_gimple_val (op))
{
gcc_assert (TREE_CODE (op) == MODIFY_EXPR);
bsi_insert_before (bsi, op, BSI_NEW_STMT);
TREE_OPERAND (tmp, 0) = TREE_OPERAND (op, 0);
}
bsi_prev (bsi);
return true;
}
}
/* Otherwise, create a new basic block, and split this edge. */
dest = split_edge (e);
if (new_bb)
*new_bb = dest;
e = EDGE_PRED (dest, 0);
goto restart;
}
/* This routine will commit all pending edge insertions, creating any new
basic blocks which are necessary. */
void
bsi_commit_edge_inserts (void)
{
basic_block bb;
edge e;
edge_iterator ei;
bsi_commit_one_edge_insert (EDGE_SUCC (ENTRY_BLOCK_PTR, 0), NULL);
FOR_EACH_BB (bb)
FOR_EACH_EDGE (e, ei, bb->succs)
bsi_commit_one_edge_insert (e, NULL);
}
/* Commit insertions pending at edge E. If a new block is created, set NEW_BB
to this block, otherwise set it to NULL. */
void
bsi_commit_one_edge_insert (edge e, basic_block *new_bb)
{
if (new_bb)
*new_bb = NULL;
if (PENDING_STMT (e))
{
block_stmt_iterator bsi;
tree stmt = PENDING_STMT (e);
PENDING_STMT (e) = NULL_TREE;
if (tree_find_edge_insert_loc (e, &bsi, new_bb))
bsi_insert_after (&bsi, stmt, BSI_NEW_STMT);
else
bsi_insert_before (&bsi, stmt, BSI_NEW_STMT);
}
}
/* Add STMT to the pending list of edge E. No actual insertion is
made until a call to bsi_commit_edge_inserts () is made. */
void
bsi_insert_on_edge (edge e, tree stmt)
{
append_to_statement_list (stmt, &PENDING_STMT (e));
}
/* Similar to bsi_insert_on_edge+bsi_commit_edge_inserts. If a new
block has to be created, it is returned. */
basic_block
bsi_insert_on_edge_immediate (edge e, tree stmt)
{
block_stmt_iterator bsi;
basic_block new_bb = NULL;
gcc_assert (!PENDING_STMT (e));
if (tree_find_edge_insert_loc (e, &bsi, &new_bb))
bsi_insert_after (&bsi, stmt, BSI_NEW_STMT);
else
bsi_insert_before (&bsi, stmt, BSI_NEW_STMT);
return new_bb;
}
/*---------------------------------------------------------------------------
Tree specific functions for CFG manipulation
---------------------------------------------------------------------------*/
/* Reinstall those PHI arguments queued in OLD_EDGE to NEW_EDGE. */
static void
reinstall_phi_args (edge new_edge, edge old_edge)
{
tree var, phi;
if (!PENDING_STMT (old_edge))
return;
for (var = PENDING_STMT (old_edge), phi = phi_nodes (new_edge->dest);
var && phi;
var = TREE_CHAIN (var), phi = PHI_CHAIN (phi))
{
tree result = TREE_PURPOSE (var);
tree arg = TREE_VALUE (var);
gcc_assert (result == PHI_RESULT (phi));
add_phi_arg (phi, arg, new_edge);
}
PENDING_STMT (old_edge) = NULL;
}
/* Split a (typically critical) edge EDGE_IN. Return the new block.
Abort on abnormal edges. */
static basic_block
tree_split_edge (edge edge_in)
{
basic_block new_bb, after_bb, dest, src;
edge new_edge, e;
/* Abnormal edges cannot be split. */
gcc_assert (!(edge_in->flags & EDGE_ABNORMAL));
src = edge_in->src;
dest = edge_in->dest;
/* Place the new block in the block list. Try to keep the new block
near its "logical" location. This is of most help to humans looking
at debugging dumps. */
if (dest->prev_bb && find_edge (dest->prev_bb, dest))
after_bb = edge_in->src;
else
after_bb = dest->prev_bb;
new_bb = create_empty_bb (after_bb);
new_bb->frequency = EDGE_FREQUENCY (edge_in);
new_bb->count = edge_in->count;
new_edge = make_edge (new_bb, dest, EDGE_FALLTHRU);
new_edge->probability = REG_BR_PROB_BASE;
new_edge->count = edge_in->count;
e = redirect_edge_and_branch (edge_in, new_bb);
gcc_assert (e);
reinstall_phi_args (new_edge, e);
return new_bb;
}
/* Return true when BB has label LABEL in it. */
static bool
has_label_p (basic_block bb, tree label)
{
block_stmt_iterator bsi;
for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
{
tree stmt = bsi_stmt (bsi);
if (TREE_CODE (stmt) != LABEL_EXPR)
return false;
if (LABEL_EXPR_LABEL (stmt) == label)
return true;
}
return false;
}
/* Callback for walk_tree, check that all elements with address taken are
properly noticed as such. The DATA is an int* that is 1 if TP was seen
inside a PHI node. */
static tree
verify_expr (tree *tp, int *walk_subtrees, void *data ATTRIBUTE_UNUSED)
{
tree t = *tp, x;
bool in_phi = (data != NULL);
if (TYPE_P (t))
*walk_subtrees = 0;
/* Check operand N for being valid GIMPLE and give error MSG if not.
We check for constants explicitly since they are not considered
gimple invariants if they overflowed. */
#define CHECK_OP(N, MSG) \
do { if (!CONSTANT_CLASS_P (TREE_OPERAND (t, N)) \
&& !is_gimple_val (TREE_OPERAND (t, N))) \
{ error (MSG); return TREE_OPERAND (t, N); }} while (0)
switch (TREE_CODE (t))
{
case SSA_NAME:
if (SSA_NAME_IN_FREE_LIST (t))
{
error ("SSA name in freelist but still referenced");
return *tp;
}
break;
case MODIFY_EXPR:
x = TREE_OPERAND (t, 0);
if (TREE_CODE (x) == BIT_FIELD_REF
&& is_gimple_reg (TREE_OPERAND (x, 0)))
{
error ("GIMPLE register modified with BIT_FIELD_REF");
return t;
}
break;
case ADDR_EXPR:
/* ??? tree-ssa-alias.c may have overlooked dead PHI nodes, missing
dead PHIs that take the address of something. But if the PHI
result is dead, the fact that it takes the address of anything
is irrelevant. Because we can not tell from here if a PHI result
is dead, we just skip this check for PHIs altogether. This means
we may be missing "valid" checks, but what can you do?
This was PR19217. */
if (in_phi)
break;
/* Skip any references (they will be checked when we recurse down the
tree) and ensure that any variable used as a prefix is marked
addressable. */
for (x = TREE_OPERAND (t, 0);
handled_component_p (x);
x = TREE_OPERAND (x, 0))
;
if (TREE_CODE (x) != VAR_DECL && TREE_CODE (x) != PARM_DECL)
return NULL;
if (!TREE_ADDRESSABLE (x))
{
error ("address taken, but ADDRESSABLE bit not set");
return x;
}
break;
case COND_EXPR:
x = COND_EXPR_COND (t);
if (TREE_CODE (TREE_TYPE (x)) != BOOLEAN_TYPE)
{
error ("non-boolean used in condition");
return x;
}
break;
case NOP_EXPR:
case CONVERT_EXPR:
case FIX_TRUNC_EXPR:
case FIX_CEIL_EXPR:
case FIX_FLOOR_EXPR:
case FIX_ROUND_EXPR:
case FLOAT_EXPR:
case NEGATE_EXPR:
case ABS_EXPR:
case BIT_NOT_EXPR:
case NON_LVALUE_EXPR:
case TRUTH_NOT_EXPR:
CHECK_OP (0, "Invalid operand to unary operator");
break;
case REALPART_EXPR:
case IMAGPART_EXPR:
case COMPONENT_REF:
case ARRAY_REF:
case ARRAY_RANGE_REF:
case BIT_FIELD_REF:
case VIEW_CONVERT_EXPR:
/* We have a nest of references. Verify that each of the operands
that determine where to reference is either a constant or a variable,
verify that the base is valid, and then show we've already checked
the subtrees. */
while (handled_component_p (t))
{
if (TREE_CODE (t) == COMPONENT_REF && TREE_OPERAND (t, 2))
CHECK_OP (2, "Invalid COMPONENT_REF offset operator");
else if (TREE_CODE (t) == ARRAY_REF
|| TREE_CODE (t) == ARRAY_RANGE_REF)
{
CHECK_OP (1, "Invalid array index.");
if (TREE_OPERAND (t, 2))
CHECK_OP (2, "Invalid array lower bound.");
if (TREE_OPERAND (t, 3))
CHECK_OP (3, "Invalid array stride.");
}
else if (TREE_CODE (t) == BIT_FIELD_REF)
{
CHECK_OP (1, "Invalid operand to BIT_FIELD_REF");
CHECK_OP (2, "Invalid operand to BIT_FIELD_REF");
}
t = TREE_OPERAND (t, 0);
}
if (!CONSTANT_CLASS_P (t) && !is_gimple_lvalue (t))
{
error ("Invalid reference prefix.");
return t;
}
*walk_subtrees = 0;
break;
case LT_EXPR:
case LE_EXPR:
case GT_EXPR:
case GE_EXPR:
case EQ_EXPR:
case NE_EXPR:
case UNORDERED_EXPR:
case ORDERED_EXPR:
case UNLT_EXPR:
case UNLE_EXPR:
case UNGT_EXPR:
case UNGE_EXPR:
case UNEQ_EXPR:
case LTGT_EXPR:
case PLUS_EXPR: