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cfglayout.c
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/* Basic block reordering routines for the GNU compiler.
Copyright (C) 2000, 2001, 2003, 2004, 2005 Free Software Foundation, Inc.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 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, 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "rtl.h"
#include "hard-reg-set.h"
#include "obstack.h"
#include "basic-block.h"
#include "insn-config.h"
#include "output.h"
#include "function.h"
#include "cfglayout.h"
#include "cfgloop.h"
#include "target.h"
#include "ggc.h"
#include "alloc-pool.h"
#include "flags.h"
#include "tree-pass.h"
/* Holds the interesting trailing notes for the function. */
rtx cfg_layout_function_footer, cfg_layout_function_header;
static rtx skip_insns_after_block (basic_block);
static void record_effective_endpoints (void);
static rtx label_for_bb (basic_block);
static void fixup_reorder_chain (void);
static void set_block_levels (tree, int);
static void change_scope (rtx, tree, tree);
void verify_insn_chain (void);
static void fixup_fallthru_exit_predecessor (void);
static tree insn_scope (rtx);
rtx
unlink_insn_chain (rtx first, rtx last)
{
rtx prevfirst = PREV_INSN (first);
rtx nextlast = NEXT_INSN (last);
PREV_INSN (first) = NULL;
NEXT_INSN (last) = NULL;
if (prevfirst)
NEXT_INSN (prevfirst) = nextlast;
if (nextlast)
PREV_INSN (nextlast) = prevfirst;
else
set_last_insn (prevfirst);
if (!prevfirst)
set_first_insn (nextlast);
return first;
}
/* Skip over inter-block insns occurring after BB which are typically
associated with BB (e.g., barriers). If there are any such insns,
we return the last one. Otherwise, we return the end of BB. */
static rtx
skip_insns_after_block (basic_block bb)
{
rtx insn, last_insn, next_head, prev;
next_head = NULL_RTX;
if (bb->next_bb != EXIT_BLOCK_PTR)
next_head = BB_HEAD (bb->next_bb);
for (last_insn = insn = BB_END (bb); (insn = NEXT_INSN (insn)) != 0; )
{
if (insn == next_head)
break;
switch (GET_CODE (insn))
{
case BARRIER:
last_insn = insn;
continue;
case NOTE:
switch (NOTE_LINE_NUMBER (insn))
{
case NOTE_INSN_LOOP_END:
case NOTE_INSN_BLOCK_END:
last_insn = insn;
continue;
case NOTE_INSN_DELETED:
case NOTE_INSN_DELETED_LABEL:
continue;
default:
continue;
break;
}
break;
case CODE_LABEL:
if (NEXT_INSN (insn)
&& JUMP_P (NEXT_INSN (insn))
&& (GET_CODE (PATTERN (NEXT_INSN (insn))) == ADDR_VEC
|| GET_CODE (PATTERN (NEXT_INSN (insn))) == ADDR_DIFF_VEC))
{
insn = NEXT_INSN (insn);
last_insn = insn;
continue;
}
break;
default:
break;
}
break;
}
/* It is possible to hit contradictory sequence. For instance:
jump_insn
NOTE_INSN_LOOP_BEG
barrier
Where barrier belongs to jump_insn, but the note does not. This can be
created by removing the basic block originally following
NOTE_INSN_LOOP_BEG. In such case reorder the notes. */
for (insn = last_insn; insn != BB_END (bb); insn = prev)
{
prev = PREV_INSN (insn);
if (NOTE_P (insn))
switch (NOTE_LINE_NUMBER (insn))
{
case NOTE_INSN_LOOP_END:
case NOTE_INSN_BLOCK_END:
case NOTE_INSN_DELETED:
case NOTE_INSN_DELETED_LABEL:
continue;
default:
reorder_insns (insn, insn, last_insn);
}
}
return last_insn;
}
/* Locate or create a label for a given basic block. */
static rtx
label_for_bb (basic_block bb)
{
rtx label = BB_HEAD (bb);
if (!LABEL_P (label))
{
if (dump_file)
fprintf (dump_file, "Emitting label for block %d\n", bb->index);
label = block_label (bb);
}
return label;
}
/* Locate the effective beginning and end of the insn chain for each
block, as defined by skip_insns_after_block above. */
static void
record_effective_endpoints (void)
{
rtx next_insn;
basic_block bb;
rtx insn;
for (insn = get_insns ();
insn
&& NOTE_P (insn)
&& NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK;
insn = NEXT_INSN (insn))
continue;
/* No basic blocks at all? */
gcc_assert (insn);
if (PREV_INSN (insn))
cfg_layout_function_header =
unlink_insn_chain (get_insns (), PREV_INSN (insn));
else
cfg_layout_function_header = NULL_RTX;
next_insn = get_insns ();
FOR_EACH_BB (bb)
{
rtx end;
if (PREV_INSN (BB_HEAD (bb)) && next_insn != BB_HEAD (bb))
bb->il.rtl->header = unlink_insn_chain (next_insn,
PREV_INSN (BB_HEAD (bb)));
end = skip_insns_after_block (bb);
if (NEXT_INSN (BB_END (bb)) && BB_END (bb) != end)
bb->il.rtl->footer = unlink_insn_chain (NEXT_INSN (BB_END (bb)), end);
next_insn = NEXT_INSN (BB_END (bb));
}
cfg_layout_function_footer = next_insn;
if (cfg_layout_function_footer)
cfg_layout_function_footer = unlink_insn_chain (cfg_layout_function_footer, get_last_insn ());
}
DEF_VEC_I(int);
DEF_VEC_ALLOC_I(int,heap);
/* Data structures representing mapping of INSN_LOCATOR into scope blocks, line
numbers and files. In order to be GGC friendly we need to use separate
varrays. This also slightly improve the memory locality in binary search.
The _locs array contains locators where the given property change. The
block_locators_blocks contains the scope block that is used for all insn
locator greater than corresponding block_locators_locs value and smaller
than the following one. Similarly for the other properties. */
static VEC(int,heap) *block_locators_locs;
static GTY(()) VEC(tree,gc) *block_locators_blocks;
static VEC(int,heap) *line_locators_locs;
static VEC(int,heap) *line_locators_lines;
static VEC(int,heap) *file_locators_locs;
static GTY(()) varray_type file_locators_files;
int prologue_locator;
int epilogue_locator;
/* During the RTL expansion the lexical blocks and line numbers are
represented via INSN_NOTEs. Replace them by representation using
INSN_LOCATORs. */
void
insn_locators_initialize (void)
{
tree block = NULL;
tree last_block = NULL;
rtx insn, next;
int loc = 0;
int line_number = 0, last_line_number = 0;
const char *file_name = NULL, *last_file_name = NULL;
prologue_locator = epilogue_locator = 0;
block_locators_locs = VEC_alloc (int, heap, 32);
block_locators_blocks = VEC_alloc (tree, gc, 32);
line_locators_locs = VEC_alloc (int, heap, 32);
line_locators_lines = VEC_alloc (int, heap, 32);
file_locators_locs = VEC_alloc (int, heap, 32);
VARRAY_CHAR_PTR_INIT (file_locators_files, 32, "file_locators_files");
for (insn = get_insns (); insn; insn = next)
{
int active = 0;
next = NEXT_INSN (insn);
if (NOTE_P (insn))
{
gcc_assert (NOTE_LINE_NUMBER (insn) != NOTE_INSN_BLOCK_BEG
&& NOTE_LINE_NUMBER (insn) != NOTE_INSN_BLOCK_END);
if (NOTE_LINE_NUMBER (insn) > 0)
{
expanded_location xloc;
NOTE_EXPANDED_LOCATION (xloc, insn);
line_number = xloc.line;
file_name = xloc.file;
}
}
else
active = (active_insn_p (insn)
&& GET_CODE (PATTERN (insn)) != ADDR_VEC
&& GET_CODE (PATTERN (insn)) != ADDR_DIFF_VEC);
check_block_change (insn, &block);
if (active
|| !next
|| (!prologue_locator && file_name))
{
if (last_block != block)
{
loc++;
VEC_safe_push (int, heap, block_locators_locs, loc);
VEC_safe_push (tree, gc, block_locators_blocks, block);
last_block = block;
}
if (last_line_number != line_number)
{
loc++;
VEC_safe_push (int, heap, line_locators_locs, loc);
VEC_safe_push (int, heap, line_locators_lines, line_number);
last_line_number = line_number;
}
if (last_file_name != file_name)
{
loc++;
VEC_safe_push (int, heap, file_locators_locs, loc);
VARRAY_PUSH_CHAR_PTR (file_locators_files, (char *) file_name);
last_file_name = file_name;
}
if (!prologue_locator && file_name)
prologue_locator = loc;
if (!next)
epilogue_locator = loc;
if (active)
INSN_LOCATOR (insn) = loc;
}
}
/* Tag the blocks with a depth number so that change_scope can find
the common parent easily. */
set_block_levels (DECL_INITIAL (cfun->decl), 0);
free_block_changes ();
}
struct tree_opt_pass pass_insn_locators_initialize =
{
"locators", /* name */
NULL, /* gate */
insn_locators_initialize, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
0, /* tv_id */
0, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
TODO_dump_func, /* todo_flags_finish */
0 /* letter */
};
/* For each lexical block, set BLOCK_NUMBER to the depth at which it is
found in the block tree. */
static void
set_block_levels (tree block, int level)
{
while (block)
{
BLOCK_NUMBER (block) = level;
set_block_levels (BLOCK_SUBBLOCKS (block), level + 1);
block = BLOCK_CHAIN (block);
}
}
/* Return sope resulting from combination of S1 and S2. */
static tree
choose_inner_scope (tree s1, tree s2)
{
if (!s1)
return s2;
if (!s2)
return s1;
if (BLOCK_NUMBER (s1) > BLOCK_NUMBER (s2))
return s1;
return s2;
}
/* Emit lexical block notes needed to change scope from S1 to S2. */
static void
change_scope (rtx orig_insn, tree s1, tree s2)
{
rtx insn = orig_insn;
tree com = NULL_TREE;
tree ts1 = s1, ts2 = s2;
tree s;
while (ts1 != ts2)
{
gcc_assert (ts1 && ts2);
if (BLOCK_NUMBER (ts1) > BLOCK_NUMBER (ts2))
ts1 = BLOCK_SUPERCONTEXT (ts1);
else if (BLOCK_NUMBER (ts1) < BLOCK_NUMBER (ts2))
ts2 = BLOCK_SUPERCONTEXT (ts2);
else
{
ts1 = BLOCK_SUPERCONTEXT (ts1);
ts2 = BLOCK_SUPERCONTEXT (ts2);
}
}
com = ts1;
/* Close scopes. */
s = s1;
while (s != com)
{
rtx note = emit_note_before (NOTE_INSN_BLOCK_END, insn);
NOTE_BLOCK (note) = s;
s = BLOCK_SUPERCONTEXT (s);
}
/* Open scopes. */
s = s2;
while (s != com)
{
insn = emit_note_before (NOTE_INSN_BLOCK_BEG, insn);
NOTE_BLOCK (insn) = s;
s = BLOCK_SUPERCONTEXT (s);
}
}
/* Return lexical scope block insn belong to. */
static tree
insn_scope (rtx insn)
{
int max = VEC_length (int, block_locators_locs);
int min = 0;
int loc = INSN_LOCATOR (insn);
/* When block_locators_locs was initialized, the pro- and epilogue
insns didn't exist yet and can therefore not be found this way.
But we know that they belong to the outer most block of the
current function.
Without this test, the prologue would be put inside the block of
the first valid instruction in the function and when that first
insn is part of an inlined function then the low_pc of that
inlined function is messed up. Likewise for the epilogue and
the last valid instruction. */
if (loc == prologue_locator || loc == epilogue_locator)
return DECL_INITIAL (cfun->decl);
if (!max || !loc)
return NULL;
while (1)
{
int pos = (min + max) / 2;
int tmp = VEC_index (int, block_locators_locs, pos);
if (tmp <= loc && min != pos)
min = pos;
else if (tmp > loc && max != pos)
max = pos;
else
{
min = pos;
break;
}
}
return VEC_index (tree, block_locators_blocks, min);
}
/* Return line number of the statement specified by the locator. */
int
locator_line (int loc)
{
int max = VEC_length (int, line_locators_locs);
int min = 0;
if (!max || !loc)
return 0;
while (1)
{
int pos = (min + max) / 2;
int tmp = VEC_index (int, line_locators_locs, pos);
if (tmp <= loc && min != pos)
min = pos;
else if (tmp > loc && max != pos)
max = pos;
else
{
min = pos;
break;
}
}
return VEC_index (int, line_locators_lines, min);
}
/* Return line number of the statement that produced this insn. */
int
insn_line (rtx insn)
{
return locator_line (INSN_LOCATOR (insn));
}
/* Return source file of the statement specified by LOC. */
const char *
locator_file (int loc)
{
int max = VEC_length (int, file_locators_locs);
int min = 0;
if (!max || !loc)
return NULL;
while (1)
{
int pos = (min + max) / 2;
int tmp = VEC_index (int, file_locators_locs, pos);
if (tmp <= loc && min != pos)
min = pos;
else if (tmp > loc && max != pos)
max = pos;
else
{
min = pos;
break;
}
}
return VARRAY_CHAR_PTR (file_locators_files, min);
}
/* Return source file of the statement that produced this insn. */
const char *
insn_file (rtx insn)
{
return locator_file (INSN_LOCATOR (insn));
}
/* Rebuild all the NOTE_INSN_BLOCK_BEG and NOTE_INSN_BLOCK_END notes based
on the scope tree and the newly reordered instructions. */
void
reemit_insn_block_notes (void)
{
tree cur_block = DECL_INITIAL (cfun->decl);
rtx insn, note;
insn = get_insns ();
if (!active_insn_p (insn))
insn = next_active_insn (insn);
for (; insn; insn = next_active_insn (insn))
{
tree this_block;
/* Avoid putting scope notes between jump table and its label. */
if (JUMP_P (insn)
&& (GET_CODE (PATTERN (insn)) == ADDR_VEC
|| GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC))
continue;
this_block = insn_scope (insn);
/* For sequences compute scope resulting from merging all scopes
of instructions nested inside. */
if (GET_CODE (PATTERN (insn)) == SEQUENCE)
{
int i;
rtx body = PATTERN (insn);
this_block = NULL;
for (i = 0; i < XVECLEN (body, 0); i++)
this_block = choose_inner_scope (this_block,
insn_scope (XVECEXP (body, 0, i)));
}
if (! this_block)
continue;
if (this_block != cur_block)
{
change_scope (insn, cur_block, this_block);
cur_block = this_block;
}
}
/* change_scope emits before the insn, not after. */
note = emit_note (NOTE_INSN_DELETED);
change_scope (note, cur_block, DECL_INITIAL (cfun->decl));
delete_insn (note);
reorder_blocks ();
}
/* Given a reorder chain, rearrange the code to match. */
static void
fixup_reorder_chain (void)
{
basic_block bb, prev_bb;
int index;
rtx insn = NULL;
if (cfg_layout_function_header)
{
set_first_insn (cfg_layout_function_header);
insn = cfg_layout_function_header;
while (NEXT_INSN (insn))
insn = NEXT_INSN (insn);
}
/* First do the bulk reordering -- rechain the blocks without regard to
the needed changes to jumps and labels. */
for (bb = ENTRY_BLOCK_PTR->next_bb, index = 0;
bb != 0;
bb = bb->aux, index++)
{
if (bb->il.rtl->header)
{
if (insn)
NEXT_INSN (insn) = bb->il.rtl->header;
else
set_first_insn (bb->il.rtl->header);
PREV_INSN (bb->il.rtl->header) = insn;
insn = bb->il.rtl->header;
while (NEXT_INSN (insn))
insn = NEXT_INSN (insn);
}
if (insn)
NEXT_INSN (insn) = BB_HEAD (bb);
else
set_first_insn (BB_HEAD (bb));
PREV_INSN (BB_HEAD (bb)) = insn;
insn = BB_END (bb);
if (bb->il.rtl->footer)
{
NEXT_INSN (insn) = bb->il.rtl->footer;
PREV_INSN (bb->il.rtl->footer) = insn;
while (NEXT_INSN (insn))
insn = NEXT_INSN (insn);
}
}
gcc_assert (index == n_basic_blocks);
NEXT_INSN (insn) = cfg_layout_function_footer;
if (cfg_layout_function_footer)
PREV_INSN (cfg_layout_function_footer) = insn;
while (NEXT_INSN (insn))
insn = NEXT_INSN (insn);
set_last_insn (insn);
#ifdef ENABLE_CHECKING
verify_insn_chain ();
#endif
delete_dead_jumptables ();
/* Now add jumps and labels as needed to match the blocks new
outgoing edges. */
for (bb = ENTRY_BLOCK_PTR->next_bb; bb ; bb = bb->aux)
{
edge e_fall, e_taken, e;
rtx bb_end_insn;
basic_block nb;
edge_iterator ei;
if (EDGE_COUNT (bb->succs) == 0)
continue;
/* Find the old fallthru edge, and another non-EH edge for
a taken jump. */
e_taken = e_fall = NULL;
FOR_EACH_EDGE (e, ei, bb->succs)
if (e->flags & EDGE_FALLTHRU)
e_fall = e;
else if (! (e->flags & EDGE_EH))
e_taken = e;
bb_end_insn = BB_END (bb);
if (JUMP_P (bb_end_insn))
{
if (any_condjump_p (bb_end_insn))
{
/* If the old fallthru is still next, nothing to do. */
if (bb->aux == e_fall->dest
|| e_fall->dest == EXIT_BLOCK_PTR)
continue;
/* The degenerated case of conditional jump jumping to the next
instruction can happen on target having jumps with side
effects.
Create temporarily the duplicated edge representing branch.
It will get unidentified by force_nonfallthru_and_redirect
that would otherwise get confused by fallthru edge not pointing
to the next basic block. */
if (!e_taken)
{
rtx note;
edge e_fake;
bool redirected;
e_fake = unchecked_make_edge (bb, e_fall->dest, 0);
redirected = redirect_jump (BB_END (bb),
block_label (bb), 0);
gcc_assert (redirected);
note = find_reg_note (BB_END (bb), REG_BR_PROB, NULL_RTX);
if (note)
{
int prob = INTVAL (XEXP (note, 0));
e_fake->probability = prob;
e_fake->count = e_fall->count * prob / REG_BR_PROB_BASE;
e_fall->probability -= e_fall->probability;
e_fall->count -= e_fake->count;
if (e_fall->probability < 0)
e_fall->probability = 0;
if (e_fall->count < 0)
e_fall->count = 0;
}
}
/* There is one special case: if *neither* block is next,
such as happens at the very end of a function, then we'll
need to add a new unconditional jump. Choose the taken
edge based on known or assumed probability. */
else if (bb->aux != e_taken->dest)
{
rtx note = find_reg_note (bb_end_insn, REG_BR_PROB, 0);
if (note
&& INTVAL (XEXP (note, 0)) < REG_BR_PROB_BASE / 2
&& invert_jump (bb_end_insn,
(e_fall->dest == EXIT_BLOCK_PTR
? NULL_RTX
: label_for_bb (e_fall->dest)), 0))
{
e_fall->flags &= ~EDGE_FALLTHRU;
#ifdef ENABLE_CHECKING
gcc_assert (could_fall_through
(e_taken->src, e_taken->dest));
#endif
e_taken->flags |= EDGE_FALLTHRU;
update_br_prob_note (bb);
e = e_fall, e_fall = e_taken, e_taken = e;
}
}
/* If the "jumping" edge is a crossing edge, and the fall
through edge is non-crossing, leave things as they are. */
else if ((e_taken->flags & EDGE_CROSSING)
&& !(e_fall->flags & EDGE_CROSSING))
continue;
/* Otherwise we can try to invert the jump. This will
basically never fail, however, keep up the pretense. */
else if (invert_jump (bb_end_insn,
(e_fall->dest == EXIT_BLOCK_PTR
? NULL_RTX
: label_for_bb (e_fall->dest)), 0))
{
e_fall->flags &= ~EDGE_FALLTHRU;
#ifdef ENABLE_CHECKING
gcc_assert (could_fall_through
(e_taken->src, e_taken->dest));
#endif
e_taken->flags |= EDGE_FALLTHRU;
update_br_prob_note (bb);
continue;
}
}
else
{
/* Otherwise we have some return, switch or computed
jump. In the 99% case, there should not have been a
fallthru edge. */
gcc_assert (returnjump_p (bb_end_insn) || !e_fall);
continue;
}
}
else
{
/* No fallthru implies a noreturn function with EH edges, or
something similarly bizarre. In any case, we don't need to
do anything. */
if (! e_fall)
continue;
/* If the fallthru block is still next, nothing to do. */
if (bb->aux == e_fall->dest)
continue;
/* A fallthru to exit block. */
if (e_fall->dest == EXIT_BLOCK_PTR)
continue;
}
/* We got here if we need to add a new jump insn. */
nb = force_nonfallthru (e_fall);
if (nb)
{
nb->il.rtl->visited = 1;
nb->aux = bb->aux;
bb->aux = nb;
/* Don't process this new block. */
bb = nb;
/* Make sure new bb is tagged for correct section (same as
fall-thru source, since you cannot fall-throu across
section boundaries). */
BB_COPY_PARTITION (e_fall->src, single_pred (bb));
if (flag_reorder_blocks_and_partition
&& targetm.have_named_sections
&& JUMP_P (BB_END (bb))
&& !any_condjump_p (BB_END (bb))
&& (EDGE_SUCC (bb, 0)->flags & EDGE_CROSSING))
REG_NOTES (BB_END (bb)) = gen_rtx_EXPR_LIST
(REG_CROSSING_JUMP, NULL_RTX, REG_NOTES (BB_END (bb)));
}
}
/* Put basic_block_info in the new order. */
if (dump_file)
{
fprintf (dump_file, "Reordered sequence:\n");
for (bb = ENTRY_BLOCK_PTR->next_bb, index = 0;
bb;
bb = bb->aux, index++)
{
fprintf (dump_file, " %i ", index);
if (get_bb_original (bb))
fprintf (dump_file, "duplicate of %i ",
get_bb_original (bb)->index);
else if (forwarder_block_p (bb)
&& !LABEL_P (BB_HEAD (bb)))
fprintf (dump_file, "compensation ");
else
fprintf (dump_file, "bb %i ", bb->index);
fprintf (dump_file, " [%i]\n", bb->frequency);
}
}
prev_bb = ENTRY_BLOCK_PTR;
bb = ENTRY_BLOCK_PTR->next_bb;
index = 0;
for (; bb; prev_bb = bb, bb = bb->aux, index ++)
{
bb->index = index;
BASIC_BLOCK (index) = bb;
bb->prev_bb = prev_bb;
prev_bb->next_bb = bb;
}
prev_bb->next_bb = EXIT_BLOCK_PTR;
EXIT_BLOCK_PTR->prev_bb = prev_bb;
/* Annoying special case - jump around dead jumptables left in the code. */
FOR_EACH_BB (bb)
{
edge e;
edge_iterator ei;
FOR_EACH_EDGE (e, ei, bb->succs)
if (e->flags & EDGE_FALLTHRU)
break;
if (e && !can_fallthru (e->src, e->dest))
force_nonfallthru (e);
}
}
/* Perform sanity checks on the insn chain.
1. Check that next/prev pointers are consistent in both the forward and
reverse direction.
2. Count insns in chain, going both directions, and check if equal.
3. Check that get_last_insn () returns the actual end of chain. */
void
verify_insn_chain (void)
{
rtx x, prevx, nextx;
int insn_cnt1, insn_cnt2;
for (prevx = NULL, insn_cnt1 = 1, x = get_insns ();
x != 0;
prevx = x, insn_cnt1++, x = NEXT_INSN (x))
gcc_assert (PREV_INSN (x) == prevx);
gcc_assert (prevx == get_last_insn ());
for (nextx = NULL, insn_cnt2 = 1, x = get_last_insn ();
x != 0;
nextx = x, insn_cnt2++, x = PREV_INSN (x))
gcc_assert (NEXT_INSN (x) == nextx);
gcc_assert (insn_cnt1 == insn_cnt2);
}
/* If we have assembler epilogues, the block falling through to exit must
be the last one in the reordered chain when we reach final. Ensure
that this condition is met. */
static void
fixup_fallthru_exit_predecessor (void)
{
edge e;
edge_iterator ei;
basic_block bb = NULL;
/* This transformation is not valid before reload, because we might
separate a call from the instruction that copies the return
value. */
gcc_assert (reload_completed);
FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds)
if (e->flags & EDGE_FALLTHRU)
bb = e->src;
if (bb && bb->aux)
{
basic_block c = ENTRY_BLOCK_PTR->next_bb;
/* If the very first block is the one with the fall-through exit
edge, we have to split that block. */
if (c == bb)
{
bb = split_block (bb, NULL)->dest;
bb->aux = c->aux;
c->aux = bb;
bb->il.rtl->footer = c->il.rtl->footer;
c->il.rtl->footer = NULL;
}
while (c->aux != bb)
c = c->aux;
c->aux = bb->aux;
while (c->aux)
c = c->aux;
c->aux = bb;
bb->aux = NULL;
}
}
/* Return true in case it is possible to duplicate the basic block BB. */
/* We do not want to declare the function in a header file, since it should
only be used through the cfghooks interface, and we do not want to move
it to cfgrtl.c since it would require also moving quite a lot of related
code. */
extern bool cfg_layout_can_duplicate_bb_p (basic_block);
bool
cfg_layout_can_duplicate_bb_p (basic_block bb)
{
/* Do not attempt to duplicate tablejumps, as we need to unshare
the dispatch table. This is difficult to do, as the instructions
computing jump destination may be hoisted outside the basic block. */
if (tablejump_p (BB_END (bb), NULL, NULL))
return false;
/* Do not duplicate blocks containing insns that can't be copied. */
if (targetm.cannot_copy_insn_p)
{
rtx insn = BB_HEAD (bb);
while (1)
{
if (INSN_P (insn) && targetm.cannot_copy_insn_p (insn))
return false;
if (insn == BB_END (bb))
break;
insn = NEXT_INSN (insn);
}
}
return true;
}
rtx
duplicate_insn_chain (rtx from, rtx to)
{
rtx insn, last;
/* Avoid updating of boundaries of previous basic block. The
note will get removed from insn stream in fixup. */
last = emit_note (NOTE_INSN_DELETED);
/* Create copy at the end of INSN chain. The chain will
be reordered later. */
for (insn = from; insn != NEXT_INSN (to); insn = NEXT_INSN (insn))
{
switch (GET_CODE (insn))
{
case INSN:
case CALL_INSN:
case JUMP_INSN:
/* Avoid copying of dispatch tables. We never duplicate
tablejumps, so this can hit only in case the table got
moved far from original jump. */
if (GET_CODE (PATTERN (insn)) == ADDR_VEC
|| GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
break;
emit_copy_of_insn_after (insn, get_last_insn ());
break;