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tree-cfg.c
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tree-cfg.c
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/* Control flow functions for trees.
Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
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 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/>. */
/* Modified by Sun Microsystems 2009 */
#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 "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 "tree-ssa-propagate.h"
#include "value-prof.h"
#include "pointer-set.h"
#include "tree-inline.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;
/* 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 GIMPLE_SWITCHes.
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). */
static struct pointer_map_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 void make_blocks (gimple_seq);
static void factor_computed_gotos (void);
/* Edges. */
static void make_edges (void);
static void make_cond_expr_edges (basic_block);
static void make_gimple_switch_edges (basic_block);
static void make_goto_expr_edges (basic_block);
static edge gimple_redirect_edge_and_branch (edge, basic_block);
static edge gimple_try_redirect_by_replacing_jump (edge, basic_block);
static unsigned int split_critical_edges (void);
/* Various helpers. */
static inline bool stmt_starts_bb_p (gimple, gimple);
static int gimple_verify_flow_info (void);
static void gimple_make_forwarder_block (edge);
static void gimple_cfg2vcg (FILE *);
/* Flowgraph optimization and cleanup. */
static void gimple_merge_blocks (basic_block, basic_block);
static bool gimple_can_merge_blocks_p (basic_block, basic_block);
static void remove_bb (basic_block);
static edge find_taken_edge_computed_goto (basic_block, tree);
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 (gimple, tree);
void
init_empty_tree_cfg_for_function (struct function *fn)
{
/* Initialize the basic block array. */
init_flow (fn);
profile_status_for_function (fn) = PROFILE_ABSENT;
n_basic_blocks_for_function (fn) = NUM_FIXED_BLOCKS;
last_basic_block_for_function (fn) = NUM_FIXED_BLOCKS;
basic_block_info_for_function (fn)
= VEC_alloc (basic_block, gc, initial_cfg_capacity);
VEC_safe_grow_cleared (basic_block, gc,
basic_block_info_for_function (fn),
initial_cfg_capacity);
/* Build a mapping of labels to their associated blocks. */
label_to_block_map_for_function (fn)
= VEC_alloc (basic_block, gc, initial_cfg_capacity);
VEC_safe_grow_cleared (basic_block, gc,
label_to_block_map_for_function (fn),
initial_cfg_capacity);
SET_BASIC_BLOCK_FOR_FUNCTION (fn, ENTRY_BLOCK,
ENTRY_BLOCK_PTR_FOR_FUNCTION (fn));
SET_BASIC_BLOCK_FOR_FUNCTION (fn, EXIT_BLOCK,
EXIT_BLOCK_PTR_FOR_FUNCTION (fn));
ENTRY_BLOCK_PTR_FOR_FUNCTION (fn)->next_bb
= EXIT_BLOCK_PTR_FOR_FUNCTION (fn);
EXIT_BLOCK_PTR_FOR_FUNCTION (fn)->prev_bb
= ENTRY_BLOCK_PTR_FOR_FUNCTION (fn);
}
void
init_empty_tree_cfg (void)
{
init_empty_tree_cfg_for_function (cfun);
}
/*---------------------------------------------------------------------------
Create basic blocks
---------------------------------------------------------------------------*/
/* Entry point to the CFG builder for trees. SEQ is the sequence of
statements to be added to the flowgraph. */
static void
build_gimple_cfg (gimple_seq seq)
{
/* Register specific gimple functions. */
gimple_register_cfg_hooks ();
memset ((void *) &cfg_stats, 0, sizeof (cfg_stats));
init_empty_tree_cfg ();
found_computed_goto = 0;
make_blocks (seq);
/* 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 == NUM_FIXED_BLOCKS)
create_empty_bb (ENTRY_BLOCK_PTR);
/* Adjust the size of the array. */
if (VEC_length (basic_block, basic_block_info) < (size_t) n_basic_blocks)
VEC_safe_grow_cleared (basic_block, gc, 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 ();
cleanup_dead_labels ();
/* Debugging dumps. */
/* Write the flowgraph to a VCG file. */
{
int local_dump_flags;
FILE *vcg_file = dump_begin (TDI_vcg, &local_dump_flags);
if (vcg_file)
{
gimple_cfg2vcg (vcg_file);
dump_end (TDI_vcg, vcg_file);
}
}
#ifdef ENABLE_CHECKING
verify_stmts ();
#endif
}
static unsigned int
execute_build_cfg (void)
{
gimple_seq body = gimple_body (current_function_decl);
build_gimple_cfg (body);
gimple_set_body (current_function_decl, NULL);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Scope blocks:\n");
dump_scope_blocks (dump_file, dump_flags);
}
return 0;
}
struct gimple_opt_pass pass_build_cfg =
{
{
GIMPLE_PASS,
"cfg", /* name */
gate_generate_rtl, /* 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_cleanup_cfg
| TODO_dump_func /* todo_flags_finish */
}
};
/* Return true if T is a computed goto. */
static bool
computed_goto_p (gimple t)
{
return (gimple_code (t) == GIMPLE_GOTO
&& TREE_CODE (gimple_goto_dest (t)) != LABEL_DECL);
}
/* 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;
gimple factored_computed_goto_label = NULL;
gimple 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)
{
gimple_stmt_iterator gsi = gsi_last_bb (bb);
gimple last;
if (gsi_end_p (gsi))
continue;
last = gsi_stmt (gsi);
/* 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))
{
gimple 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);
gimple_stmt_iterator new_gsi = gsi_start_bb (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
= gimple_build_label (factored_label_decl);
gsi_insert_after (&new_gsi, factored_computed_goto_label,
GSI_NEW_STMT);
/* Build our new computed goto. */
factored_computed_goto = gimple_build_goto (var);
gsi_insert_after (&new_gsi, factored_computed_goto, GSI_NEW_STMT);
}
/* Copy the original computed goto's destination into VAR. */
assignment = gimple_build_assign (var, gimple_goto_dest (last));
gsi_insert_before (&gsi, assignment, GSI_SAME_STMT);
/* And re-vector the computed goto to the new destination. */
gimple_goto_set_dest (last, factored_label_decl);
}
}
}
/* Build a flowgraph for the sequence of stmts SEQ. */
static void
make_blocks (gimple_seq seq)
{
gimple_stmt_iterator i = gsi_start (seq);
gimple stmt = NULL;
bool start_new_block = true;
bool first_stmt_of_seq = true;
basic_block bb = ENTRY_BLOCK_PTR;
while (!gsi_end_p (i))
{
gimple prev_stmt;
prev_stmt = stmt;
stmt = gsi_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_seq)
seq = gsi_split_seq_before (&i);
bb = create_basic_block (seq, NULL, bb);
start_new_block = false;
}
/* Now add STMT to BB and create the subgraphs for special statement
codes. */
gimple_set_bb (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;
gsi_next (&i);
first_stmt_of_seq = 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->il.gimple = GGC_CNEW (struct gimple_bb_info);
set_bb_seq (bb, h ? (gimple_seq) h : gimple_seq_alloc ());
/* 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 == VEC_length (basic_block, basic_block_info))
{
size_t new_size = last_basic_block + (last_basic_block + 3) / 4;
VEC_safe_grow_cleared (basic_block, gc, basic_block_info, new_size);
}
/* Add the newly created block to the array. */
SET_BASIC_BLOCK (last_basic_block, bb);
n_basic_blocks++;
last_basic_block++;
return bb;
}
/*---------------------------------------------------------------------------
Edge creation
---------------------------------------------------------------------------*/
/* Fold COND_EXPR_COND of each COND_EXPR. */
void
fold_cond_expr_cond (void)
{
basic_block bb;
FOR_EACH_BB (bb)
{
gimple stmt = last_stmt (bb);
if (stmt && gimple_code (stmt) == GIMPLE_COND)
{
tree cond;
bool zerop, onep;
fold_defer_overflow_warnings ();
cond = fold_binary (gimple_cond_code (stmt), boolean_type_node,
gimple_cond_lhs (stmt), gimple_cond_rhs (stmt));
if (cond)
{
zerop = integer_zerop (cond);
onep = integer_onep (cond);
}
else
zerop = onep = false;
fold_undefer_overflow_warnings (zerop || onep,
stmt,
WARN_STRICT_OVERFLOW_CONDITIONAL);
if (zerop)
gimple_cond_make_false (stmt);
else if (onep)
gimple_cond_make_true (stmt);
}
}
}
/* Join all the blocks in the flowgraph. */
static void
make_edges (void)
{
basic_block bb;
struct omp_region *cur_region = NULL;
/* Create an edge from entry to the first block with executable
statements in it. */
make_edge (ENTRY_BLOCK_PTR, BASIC_BLOCK (NUM_FIXED_BLOCKS), EDGE_FALLTHRU);
/* Traverse the basic block array placing edges. */
FOR_EACH_BB (bb)
{
gimple last = last_stmt (bb);
bool fallthru;
if (last)
{
enum gimple_code code = gimple_code (last);
switch (code)
{
case GIMPLE_GOTO:
make_goto_expr_edges (bb);
fallthru = false;
break;
case GIMPLE_RETURN:
make_edge (bb, EXIT_BLOCK_PTR, 0);
fallthru = false;
break;
case GIMPLE_COND:
make_cond_expr_edges (bb);
fallthru = false;
break;
case GIMPLE_SWITCH:
make_gimple_switch_edges (bb);
fallthru = false;
break;
case GIMPLE_RESX:
make_eh_edges (last);
fallthru = false;
break;
case GIMPLE_CALL:
/* If this function receives a nonlocal goto, then we need to
make edges from this call site to all the nonlocal goto
handlers. */
if (stmt_can_make_abnormal_goto (last))
make_abnormal_goto_edges (bb, true);
/* If this statement has reachable exception handlers, then
create abnormal edges to them. */
make_eh_edges (last);
/* Some calls are known not to return. */
fallthru = !(gimple_call_flags (last) & ECF_NORETURN);
break;
case GIMPLE_ASSIGN:
/* A GIMPLE_ASSIGN may throw internally and thus be considered
control-altering. */
if (is_ctrl_altering_stmt (last))
{
make_eh_edges (last);
}
fallthru = true;
break;
case GIMPLE_OMP_PARALLEL:
case GIMPLE_OMP_TASK:
case GIMPLE_OMP_FOR:
case GIMPLE_OMP_SINGLE:
case GIMPLE_OMP_MASTER:
case GIMPLE_OMP_ORDERED:
case GIMPLE_OMP_CRITICAL:
case GIMPLE_OMP_SECTION:
cur_region = new_omp_region (bb, code, cur_region);
fallthru = true;
break;
case GIMPLE_OMP_SECTIONS:
cur_region = new_omp_region (bb, code, cur_region);
fallthru = true;
break;
case GIMPLE_OMP_SECTIONS_SWITCH:
fallthru = false;
break;
case GIMPLE_OMP_ATOMIC_LOAD:
case GIMPLE_OMP_ATOMIC_STORE:
fallthru = true;
break;
case GIMPLE_OMP_RETURN:
/* In the case of a GIMPLE_OMP_SECTION, the edge will go
somewhere other than the next block. This will be
created later. */
cur_region->exit = bb;
fallthru = cur_region->type != GIMPLE_OMP_SECTION;
cur_region = cur_region->outer;
break;
case GIMPLE_OMP_CONTINUE:
cur_region->cont = bb;
switch (cur_region->type)
{
case GIMPLE_OMP_FOR:
/* Mark all GIMPLE_OMP_FOR and GIMPLE_OMP_CONTINUE
succs edges as abnormal to prevent splitting
them. */
single_succ_edge (cur_region->entry)->flags |= EDGE_ABNORMAL;
/* Make the loopback edge. */
make_edge (bb, single_succ (cur_region->entry),
EDGE_ABNORMAL);
/* Create an edge from GIMPLE_OMP_FOR to exit, which
corresponds to the case that the body of the loop
is not executed at all. */
make_edge (cur_region->entry, bb->next_bb, EDGE_ABNORMAL);
make_edge (bb, bb->next_bb, EDGE_FALLTHRU | EDGE_ABNORMAL);
fallthru = false;
break;
case GIMPLE_OMP_SECTIONS:
/* Wire up the edges into and out of the nested sections. */
{
basic_block switch_bb = single_succ (cur_region->entry);
struct omp_region *i;
for (i = cur_region->inner; i ; i = i->next)
{
gcc_assert (i->type == GIMPLE_OMP_SECTION);
make_edge (switch_bb, i->entry, 0);
make_edge (i->exit, bb, EDGE_FALLTHRU);
}
/* Make the loopback edge to the block with
GIMPLE_OMP_SECTIONS_SWITCH. */
make_edge (bb, switch_bb, 0);
/* Make the edge from the switch to exit. */
make_edge (switch_bb, bb->next_bb, 0);
fallthru = false;
}
break;
default:
gcc_unreachable ();
}
break;
default:
gcc_assert (!stmt_ends_bb_p (last));
fallthru = true;
}
}
else
fallthru = true;
if (fallthru)
make_edge (bb, bb->next_bb, EDGE_FALLTHRU);
}
if (root_omp_region)
free_omp_regions ();
/* Fold COND_EXPR_COND of each COND_EXPR. */
fold_cond_expr_cond ();
}
/* Create the edges for a GIMPLE_COND starting at block BB. */
static void
make_cond_expr_edges (basic_block bb)
{
gimple entry = last_stmt (bb);
gimple then_stmt, else_stmt;
basic_block then_bb, else_bb;
tree then_label, else_label;
edge e;
gcc_assert (entry);
gcc_assert (gimple_code (entry) == GIMPLE_COND);
/* Entry basic blocks for each component. */
then_label = gimple_cond_true_label (entry);
else_label = gimple_cond_false_label (entry);
then_bb = label_to_block (then_label);
else_bb = label_to_block (else_label);
then_stmt = first_stmt (then_bb);
else_stmt = first_stmt (else_bb);
e = make_edge (bb, then_bb, EDGE_TRUE_VALUE);
e->goto_locus = gimple_location (then_stmt);
if (e->goto_locus)
e->goto_block = gimple_block (then_stmt);
e = make_edge (bb, else_bb, EDGE_FALSE_VALUE);
if (e)
{
e->goto_locus = gimple_location (else_stmt);
if (e->goto_locus)
e->goto_block = gimple_block (else_stmt);
}
/* We do not need the labels anymore. */
gimple_cond_set_true_label (entry, NULL_TREE);
gimple_cond_set_false_label (entry, NULL_TREE);
}
/* 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 bool
edge_to_cases_cleanup (const void *key ATTRIBUTE_UNUSED, void **value,
void *data ATTRIBUTE_UNUSED)
{
tree t, next;
for (t = (tree) *value; t; t = next)
{
next = TREE_CHAIN (t);
TREE_CHAIN (t) = NULL;
}
*value = NULL;
return false;
}
/* Start recording information mapping edges to case labels. */
void
start_recording_case_labels (void)
{
gcc_assert (edge_to_cases == NULL);
edge_to_cases = pointer_map_create ();
}
/* 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. */
void
end_recording_case_labels (void)
{
pointer_map_traverse (edge_to_cases, edge_to_cases_cleanup, NULL);
pointer_map_destroy (edge_to_cases);
edge_to_cases = NULL;
}
/* 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, gimple t)
{
void **slot;
size_t i, n;
/* 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;
slot = pointer_map_contains (edge_to_cases, e);
if (slot)
return (tree) *slot;
/* 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. */
n = gimple_switch_num_labels (t);
for (i = 0; i < n; i++)
{
tree elt = gimple_switch_label (t, i);
tree lab = CASE_LABEL (elt);
basic_block label_bb = label_to_block (lab);
edge this_edge = find_edge (e->src, label_bb);
/* Add it to the chain of CASE_LABEL_EXPRs referencing E, or create
a new chain. */
slot = pointer_map_insert (edge_to_cases, this_edge);
TREE_CHAIN (elt) = (tree) *slot;
*slot = elt;
}
return (tree) *pointer_map_contains (edge_to_cases, e);
}
/* Create the edges for a GIMPLE_SWITCH starting at block BB. */
static void
make_gimple_switch_edges (basic_block bb)
{
gimple entry = last_stmt (bb);
size_t i, n;
n = gimple_switch_num_labels (entry);
for (i = 0; i < n; ++i)
{
tree lab = CASE_LABEL (gimple_switch_label (entry, 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_fn (struct function *ifun, 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)
{
gimple_stmt_iterator gsi = gsi_start_bb (BASIC_BLOCK (NUM_FIXED_BLOCKS));
gimple stmt;
stmt = gimple_build_label (dest);
gsi_insert_before (&gsi, stmt, GSI_NEW_STMT);
uid = LABEL_DECL_UID (dest);
}
if (VEC_length (basic_block, ifun->cfg->x_label_to_block_map)
<= (unsigned int) uid)
return NULL;
return VEC_index (basic_block, ifun->cfg->x_label_to_block_map, uid);
}
/* Create edges for an abnormal goto statement at block BB. If FOR_CALL
is true, the source statement is a CALL_EXPR instead of a GOTO_EXPR. */
void
make_abnormal_goto_edges (basic_block bb, bool for_call)
{
basic_block target_bb;
gimple_stmt_iterator gsi;
FOR_EACH_BB (target_bb)
for (gsi = gsi_start_bb (target_bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
gimple label_stmt = gsi_stmt (gsi);
tree target;
if (gimple_code (label_stmt) != GIMPLE_LABEL)
break;
target = gimple_label_label (label_stmt);
/* Make an edge to every label block that has been marked as a
potential target for a computed goto or a non-local goto. */
if ((FORCED_LABEL (target) && !for_call)
|| (DECL_NONLOCAL (target) && for_call))
{
make_edge (bb, target_bb, EDGE_ABNORMAL);
break;
}
}
}
/* Create edges for a goto statement at block BB. */
static void
make_goto_expr_edges (basic_block bb)
{
gimple_stmt_iterator last = gsi_last_bb (bb);
gimple goto_t = gsi_stmt (last);
/* A simple GOTO creates normal edges. */
if (simple_goto_p (goto_t))
{
tree dest = gimple_goto_dest (goto_t);
edge e = make_edge (bb, label_to_block (dest), EDGE_FALLTHRU);
e->goto_locus = gimple_location (goto_t);
if (e->goto_locus)
e->goto_block = gimple_block (goto_t);
gsi_remove (&last, true);
return;
}
/* A computed GOTO creates abnormal edges. */
make_abnormal_goto_edges (bb, false);
}
/*---------------------------------------------------------------------------
Flowgraph analysis
---------------------------------------------------------------------------*/
/* 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 rerun this pass after CFG is created, to get rid of the labels that
are no longer referenced. After then we do not run it any more, since
(almost) no new labels should be created. */
/* A map from basic block index to the leading label of that block. */
static struct label_record
{
/* The label. */
tree label;
/* True if the label is referenced from somewhere. */
bool used;
} *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].label;
label_for_bb[bb->index].used = true;
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);
tree main_label = label_for_bb[bb->index].label;
/* label_to_block possibly inserted undefined label into the chain. */
if (!main_label)
{
label_for_bb[bb->index].label = label;
main_label = label;
}
label_for_bb[bb->index].used = true;
return main_label;
}
/* 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 = XCNEWVEC (struct label_record, last_basic_block);
/* 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)
{
gimple_stmt_iterator i;
for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
{
tree label;
gimple stmt = gsi_stmt (i);
if (gimple_code (stmt) != GIMPLE_LABEL)
break;
label = gimple_label_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)
{
label_for_bb[bb->index].label = 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))
{
label_for_bb[bb->index].label = 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)
{
gimple stmt = last_stmt (bb);
if (!stmt)
continue;
switch (gimple_code (stmt))
{
case GIMPLE_COND:
{
tree true_label = gimple_cond_true_label (stmt);
tree false_label = gimple_cond_false_label (stmt);