/* Control flow graph building code for GNU compiler.
Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
- 1999, 2000, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
+ 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008
+ 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
+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
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. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
-/* find_basic_blocks divides the current function's rtl into basic
- blocks and constructs the CFG. The blocks are recorded in the
- basic_block_info array; the CFG exists in the edge structures
- referenced by the blocks.
-
- find_basic_blocks also finds any unreachable loops and deletes them.
-
- Available functionality:
- - CFG construction
- find_basic_blocks */
\f
#include "config.h"
#include "system.h"
#include "output.h"
#include "function.h"
#include "except.h"
+#include "expr.h"
#include "toplev.h"
#include "timevar.h"
+#include "sbitmap.h"
-static int count_basic_blocks (rtx);
-static void find_basic_blocks_1 (rtx);
static void make_edges (basic_block, basic_block, int);
-static void make_label_edge (sbitmap *, basic_block, rtx, int);
+static void make_label_edge (sbitmap, basic_block, rtx, int);
static void find_bb_boundaries (basic_block);
static void compute_outgoing_frequencies (basic_block);
\f
block. */
bool
-inside_basic_block_p (rtx insn)
+inside_basic_block_p (const_rtx insn)
{
switch (GET_CODE (insn))
{
case CALL_INSN:
case INSN:
+ case DEBUG_INSN:
return true;
case BARRIER:
the basic block. */
bool
-control_flow_insn_p (rtx insn)
+control_flow_insn_p (const_rtx insn)
{
- rtx note;
-
switch (GET_CODE (insn))
{
case NOTE:
case CODE_LABEL:
+ case DEBUG_INSN:
return false;
case JUMP_INSN:
|| find_reg_note (insn, REG_NORETURN, 0))
&& GET_CODE (PATTERN (insn)) != COND_EXEC)
return true;
+
/* Call insn may return to the nonlocal goto handler. */
- return ((nonlocal_goto_handler_labels
- && (0 == (note = find_reg_note (insn, REG_EH_REGION,
- NULL_RTX))
- || INTVAL (XEXP (note, 0)) >= 0))
- /* Or may trap. */
- || can_throw_internal (insn));
+ if (can_nonlocal_goto (insn))
+ return true;
+ break;
case INSN:
- return (flag_non_call_exceptions && can_throw_internal (insn));
+ /* Treat trap instructions like noreturn calls (same provision). */
+ if (GET_CODE (PATTERN (insn)) == TRAP_IF
+ && XEXP (PATTERN (insn), 0) == const1_rtx)
+ return true;
+ if (!cfun->can_throw_non_call_exceptions)
+ return false;
+ break;
case BARRIER:
/* It is nonsense to reach barrier when looking for the
- end of basic block, but before dead code is eliminated
- this may happen. */
+ end of basic block, but before dead code is eliminated
+ this may happen. */
return false;
default:
gcc_unreachable ();
}
-}
-/* Count the basic blocks of the function. */
-
-static int
-count_basic_blocks (rtx f)
-{
- int count = 0;
- bool saw_insn = false;
- rtx insn;
-
- for (insn = f; insn; insn = NEXT_INSN (insn))
- {
- /* Code labels and barriers causes current basic block to be
- terminated at previous real insn. */
- if ((LABEL_P (insn) || BARRIER_P (insn))
- && saw_insn)
- count++, saw_insn = false;
-
- /* Start basic block if needed. */
- if (!saw_insn && inside_basic_block_p (insn))
- saw_insn = true;
-
- /* Control flow insn causes current basic block to be terminated. */
- if (saw_insn && control_flow_insn_p (insn))
- count++, saw_insn = false;
- }
-
- if (saw_insn)
- count++;
-
- /* The rest of the compiler works a bit smoother when we don't have to
- check for the edge case of do-nothing functions with no basic blocks. */
- if (count == 0)
- {
- emit_insn (gen_rtx_USE (VOIDmode, const0_rtx));
- count = 1;
- }
-
- return count;
+ return can_throw_internal (insn);
}
+
\f
/* Create an edge between two basic blocks. FLAGS are auxiliary information
about the edge that is accumulated between calls. */
/* Create an edge from a basic block to a label. */
static void
-make_label_edge (sbitmap *edge_cache, basic_block src, rtx label, int flags)
+make_label_edge (sbitmap edge_cache, basic_block src, rtx label, int flags)
{
gcc_assert (LABEL_P (label));
/* Create the edges generated by INSN in REGION. */
void
-rtl_make_eh_edge (sbitmap *edge_cache, basic_block src, rtx insn)
+rtl_make_eh_edge (sbitmap edge_cache, basic_block src, rtx insn)
{
- int is_call = CALL_P (insn) ? EDGE_ABNORMAL_CALL : 0;
- rtx handlers, i;
+ eh_landing_pad lp = get_eh_landing_pad_from_rtx (insn);
- handlers = reachable_handlers (insn);
+ if (lp)
+ {
+ rtx label = lp->landing_pad;
- for (i = handlers; i; i = XEXP (i, 1))
- make_label_edge (edge_cache, src, XEXP (i, 0),
- EDGE_ABNORMAL | EDGE_EH | is_call);
+ /* During initial rtl generation, use the post_landing_pad. */
+ if (label == NULL)
+ {
+ gcc_assert (lp->post_landing_pad);
+ label = label_rtx (lp->post_landing_pad);
+ }
- free_INSN_LIST_list (&handlers);
+ make_label_edge (edge_cache, src, label,
+ EDGE_ABNORMAL | EDGE_EH
+ | (CALL_P (insn) ? EDGE_ABNORMAL_CALL : 0));
+ }
}
-/* Identify the edges between basic blocks MIN to MAX.
+/* States of basic block as seen by find_many_sub_basic_blocks. */
+enum state {
+ /* Basic blocks created via split_block belong to this state.
+ make_edges will examine these basic blocks to see if we need to
+ create edges going out of them. */
+ BLOCK_NEW = 0,
+
+ /* Basic blocks that do not need examining belong to this state.
+ These blocks will be left intact. In particular, make_edges will
+ not create edges going out of these basic blocks. */
+ BLOCK_ORIGINAL,
+
+ /* Basic blocks that may need splitting (due to a label appearing in
+ the middle, etc) belong to this state. After splitting them,
+ make_edges will create edges going out of them as needed. */
+ BLOCK_TO_SPLIT
+};
+
+#define STATE(BB) (enum state) ((size_t) (BB)->aux)
+#define SET_STATE(BB, STATE) ((BB)->aux = (void *) (size_t) (STATE))
+
+/* Used internally by purge_dead_tablejump_edges, ORed into state. */
+#define BLOCK_USED_BY_TABLEJUMP 32
+#define FULL_STATE(BB) ((size_t) (BB)->aux)
- NONLOCAL_LABEL_LIST is a list of non-local labels in the function. Blocks
- that are otherwise unreachable may be reachable with a non-local goto.
+/* Identify the edges going out of basic blocks between MIN and MAX,
+ inclusive, that have their states set to BLOCK_NEW or
+ BLOCK_TO_SPLIT.
- BB_EH_END is an array indexed by basic block number in which we record
- the list of exception regions active at the end of the basic block. */
+ UPDATE_P should be nonzero if we are updating CFG and zero if we
+ are building CFG from scratch. */
static void
make_edges (basic_block min, basic_block max, int update_p)
{
basic_block bb;
- sbitmap *edge_cache = NULL;
+ sbitmap edge_cache = NULL;
/* Heavy use of computed goto in machine-generated code can lead to
nearly fully-connected CFGs. In that case we spend a significant
amount of time searching the edge lists for duplicates. */
- if (forced_labels || cfun->max_jumptable_ents > 100)
- {
- edge_cache = sbitmap_vector_alloc (last_basic_block, last_basic_block);
- sbitmap_vector_zero (edge_cache, last_basic_block);
-
- if (update_p)
- FOR_BB_BETWEEN (bb, min, max->next_bb, next_bb)
- {
- edge e;
- edge_iterator ei;
-
- FOR_EACH_EDGE (e, ei, bb->succs)
- if (e->dest != EXIT_BLOCK_PTR)
- SET_BIT (edge_cache[bb->index], e->dest->index);
- }
- }
+ if (forced_labels || cfun->cfg->max_jumptable_ents > 100)
+ edge_cache = sbitmap_alloc (last_basic_block);
/* By nature of the way these get numbered, ENTRY_BLOCK_PTR->next_bb block
is always the entry. */
if (min == ENTRY_BLOCK_PTR->next_bb)
- cached_make_edge (edge_cache, ENTRY_BLOCK_PTR, min,
- EDGE_FALLTHRU);
+ make_edge (ENTRY_BLOCK_PTR, min, EDGE_FALLTHRU);
FOR_BB_BETWEEN (bb, min, max->next_bb, next_bb)
{
rtx insn, x;
enum rtx_code code;
edge e;
+ edge_iterator ei;
+
+ if (STATE (bb) == BLOCK_ORIGINAL)
+ continue;
+
+ /* If we have an edge cache, cache edges going out of BB. */
+ if (edge_cache)
+ {
+ sbitmap_zero (edge_cache);
+ if (update_p)
+ {
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (e->dest != EXIT_BLOCK_PTR)
+ SET_BIT (edge_cache, e->dest->index);
+ }
+ }
if (LABEL_P (BB_HEAD (bb))
&& LABEL_ALT_ENTRY_P (BB_HEAD (bb)))
{
rtx tmp;
- /* Recognize exception handling placeholders. */
- if (GET_CODE (PATTERN (insn)) == RESX)
- rtl_make_eh_edge (edge_cache, bb, insn);
-
/* Recognize a non-local goto as a branch outside the
current function. */
- else if (find_reg_note (insn, REG_NON_LOCAL_GOTO, NULL_RTX))
+ if (find_reg_note (insn, REG_NON_LOCAL_GOTO, NULL_RTX))
;
/* Recognize a tablejump and do the right thing. */
else if (returnjump_p (insn))
cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR, 0);
+ /* Recognize asm goto and do the right thing. */
+ else if ((tmp = extract_asm_operands (PATTERN (insn))) != NULL)
+ {
+ int i, n = ASM_OPERANDS_LABEL_LENGTH (tmp);
+ for (i = 0; i < n; ++i)
+ make_label_edge (edge_cache, bb,
+ XEXP (ASM_OPERANDS_LABEL (tmp, i), 0), 0);
+ }
+
/* Otherwise, we have a plain conditional or unconditional jump. */
else
{
handler for this CALL_INSN. If we're handling non-call
exceptions then any insn can reach any of the active handlers.
Also mark the CALL_INSN as reaching any nonlocal goto handler. */
- else if (code == CALL_INSN || flag_non_call_exceptions)
+ else if (code == CALL_INSN || cfun->can_throw_non_call_exceptions)
{
/* Add any appropriate EH edges. */
rtl_make_eh_edge (edge_cache, bb, insn);
gotos do not have their addresses taken, then only calls to
those functions or to other nested functions that use them
could possibly do nonlocal gotos. */
-
- /* We do know that a REG_EH_REGION note with a value less
- than 0 is guaranteed not to perform a non-local goto. */
- rtx note = find_reg_note (insn, REG_EH_REGION, NULL_RTX);
-
- if (!note || INTVAL (XEXP (note, 0)) >= 0)
+ if (can_nonlocal_goto (insn))
for (x = nonlocal_goto_handler_labels; x; x = XEXP (x, 1))
make_label_edge (edge_cache, bb, XEXP (x, 0),
EDGE_ABNORMAL | EDGE_ABNORMAL_CALL);
while (insn
&& NOTE_P (insn)
- && NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK)
+ && NOTE_KIND (insn) != NOTE_INSN_BASIC_BLOCK)
insn = NEXT_INSN (insn);
if (!insn)
sbitmap_vector_free (edge_cache);
}
\f
-/* Find all basic blocks of the function whose first insn is F.
-
- Collect and return a list of labels whose addresses are taken. This
- will be used in make_edges for use with computed gotos. */
-
-static void
-find_basic_blocks_1 (rtx f)
-{
- rtx insn, next;
- rtx bb_note = NULL_RTX;
- rtx head = NULL_RTX;
- rtx end = NULL_RTX;
- basic_block prev = ENTRY_BLOCK_PTR;
-
- /* We process the instructions in a slightly different way than we did
- previously. This is so that we see a NOTE_BASIC_BLOCK after we have
- closed out the previous block, so that it gets attached at the proper
- place. Since this form should be equivalent to the previous,
- count_basic_blocks continues to use the old form as a check. */
-
- for (insn = f; insn; insn = next)
- {
- enum rtx_code code = GET_CODE (insn);
-
- next = NEXT_INSN (insn);
-
- if ((LABEL_P (insn) || BARRIER_P (insn))
- && head)
- {
- prev = create_basic_block_structure (head, end, bb_note, prev);
- head = end = NULL_RTX;
- bb_note = NULL_RTX;
- }
-
- if (inside_basic_block_p (insn))
- {
- if (head == NULL_RTX)
- head = insn;
- end = insn;
- }
-
- if (head && control_flow_insn_p (insn))
- {
- prev = create_basic_block_structure (head, end, bb_note, prev);
- head = end = NULL_RTX;
- bb_note = NULL_RTX;
- }
-
- switch (code)
- {
- case NOTE:
- {
- int kind = NOTE_LINE_NUMBER (insn);
-
- /* Look for basic block notes with which to keep the
- basic_block_info pointers stable. Unthread the note now;
- we'll put it back at the right place in create_basic_block.
- Or not at all if we've already found a note in this block. */
- if (kind == NOTE_INSN_BASIC_BLOCK)
- {
- if (bb_note == NULL_RTX)
- bb_note = insn;
- else
- next = delete_insn (insn);
- }
- break;
- }
-
- case CODE_LABEL:
- case JUMP_INSN:
- case CALL_INSN:
- case INSN:
- case BARRIER:
- break;
-
- default:
- gcc_unreachable ();
- }
- }
-
- if (head != NULL_RTX)
- create_basic_block_structure (head, end, bb_note, prev);
- else if (bb_note)
- delete_insn (bb_note);
-
- gcc_assert (last_basic_block == n_basic_blocks);
-
- clear_aux_for_blocks ();
-}
-
-
-/* Find basic blocks of the current function.
- F is the first insn of the function. */
-
-void
-find_basic_blocks (rtx f)
-{
- basic_block bb;
-
- timevar_push (TV_CFG);
-
- /* Flush out existing data. */
- if (basic_block_info != NULL)
- {
- clear_edges ();
-
- /* Clear bb->aux on all extant basic blocks. We'll use this as a
- tag for reuse during create_basic_block, just in case some pass
- copies around basic block notes improperly. */
- FOR_EACH_BB (bb)
- bb->aux = NULL;
-
- basic_block_info = NULL;
- }
-
- n_basic_blocks = count_basic_blocks (f);
- last_basic_block = 0;
- ENTRY_BLOCK_PTR->next_bb = EXIT_BLOCK_PTR;
- EXIT_BLOCK_PTR->prev_bb = ENTRY_BLOCK_PTR;
-
- /* Size the basic block table. The actual structures will be allocated
- by find_basic_blocks_1, since we want to keep the structure pointers
- stable across calls to find_basic_blocks. */
- /* ??? This whole issue would be much simpler if we called find_basic_blocks
- exactly once, and thereafter we don't have a single long chain of
- instructions at all until close to the end of compilation when we
- actually lay them out. */
-
- VARRAY_BB_INIT (basic_block_info, n_basic_blocks, "basic_block_info");
-
- find_basic_blocks_1 (f);
-
- profile_status = PROFILE_ABSENT;
-
- /* Discover the edges of our cfg. */
- make_edges (ENTRY_BLOCK_PTR->next_bb, EXIT_BLOCK_PTR->prev_bb, 0);
-
- /* Do very simple cleanup now, for the benefit of code that runs between
- here and cleanup_cfg, e.g. thread_prologue_and_epilogue_insns. */
- tidy_fallthru_edges ();
-
-#ifdef ENABLE_CHECKING
- verify_flow_info ();
-#endif
- timevar_pop (TV_CFG);
-}
-\f
-/* State of basic block as seen by find_many_sub_basic_blocks. */
-enum state {BLOCK_NEW = 0, BLOCK_ORIGINAL, BLOCK_TO_SPLIT};
-
-#define STATE(BB) (enum state) ((size_t) (BB)->aux)
-#define SET_STATE(BB, STATE) ((BB)->aux = (void *) (size_t) (STATE))
-
-/* Used internally by purge_dead_tablejump_edges, ORed into state. */
-#define BLOCK_USED_BY_TABLEJUMP 32
-#define FULL_STATE(BB) ((size_t) (BB)->aux)
-
static void
mark_tablejump_edge (rtx label)
{
for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
{
if (FULL_STATE (e->dest) & BLOCK_USED_BY_TABLEJUMP)
- SET_STATE (e->dest, FULL_STATE (e->dest)
- & ~(size_t) BLOCK_USED_BY_TABLEJUMP);
+ SET_STATE (e->dest, FULL_STATE (e->dest)
+ & ~(size_t) BLOCK_USED_BY_TABLEJUMP);
else if (!(e->flags & (EDGE_ABNORMAL | EDGE_EH)))
- {
- remove_edge (e);
- continue;
- }
+ {
+ remove_edge (e);
+ continue;
+ }
ei_next (&ei);
}
}
{
basic_block orig_bb = bb;
rtx insn = BB_HEAD (bb);
- rtx end = BB_END (bb);
+ rtx end = BB_END (bb), x;
rtx table;
rtx flow_transfer_insn = NULL_RTX;
edge fallthru = NULL;
{
enum rtx_code code = GET_CODE (insn);
- /* On code label, split current basic block. */
- if (code == CODE_LABEL)
+ /* In case we've previously seen an insn that effects a control
+ flow transfer, split the block. */
+ if ((flow_transfer_insn || code == CODE_LABEL)
+ && inside_basic_block_p (insn))
{
fallthru = split_block (bb, PREV_INSN (insn));
if (flow_transfer_insn)
- BB_END (bb) = flow_transfer_insn;
+ {
+ BB_END (bb) = flow_transfer_insn;
+
+ /* Clean up the bb field for the insns between the blocks. */
+ for (x = NEXT_INSN (flow_transfer_insn);
+ x != BB_HEAD (fallthru->dest);
+ x = NEXT_INSN (x))
+ if (!BARRIER_P (x))
+ set_block_for_insn (x, NULL);
+ }
bb = fallthru->dest;
remove_edge (fallthru);
flow_transfer_insn = NULL_RTX;
- if (LABEL_ALT_ENTRY_P (insn))
+ if (code == CODE_LABEL && LABEL_ALT_ENTRY_P (insn))
make_edge (ENTRY_BLOCK_PTR, bb, 0);
}
-
- /* In case we've previously seen an insn that effects a control
- flow transfer, split the block. */
- if (flow_transfer_insn && inside_basic_block_p (insn))
+ else if (code == BARRIER)
{
- fallthru = split_block (bb, PREV_INSN (insn));
- BB_END (bb) = flow_transfer_insn;
- bb = fallthru->dest;
- remove_edge (fallthru);
- flow_transfer_insn = NULL_RTX;
+ /* __builtin_unreachable () may cause a barrier to be emitted in
+ the middle of a BB. We need to split it in the same manner as
+ if the barrier were preceded by a control_flow_insn_p insn. */
+ if (!flow_transfer_insn)
+ flow_transfer_insn = prev_nonnote_insn_bb (insn);
}
if (control_flow_insn_p (insn))
return and barrier, or possibly other sequence not behaving like
ordinary jump, we need to take care and move basic block boundary. */
if (flow_transfer_insn)
- BB_END (bb) = flow_transfer_insn;
+ {
+ BB_END (bb) = flow_transfer_insn;
+
+ /* Clean up the bb field for the insns that do not belong to BB. */
+ x = flow_transfer_insn;
+ while (x != end)
+ {
+ x = NEXT_INSN (x);
+ if (!BARRIER_P (x))
+ set_block_for_insn (x, NULL);
+ }
+ }
/* We've possibly replaced the conditional jump by conditional jump
followed by cleanup at fallthru edge, so the outgoing edges may
}
}
- if (EDGE_COUNT (b->succs) == 1)
+ if (single_succ_p (b))
{
- e = EDGE_SUCC (b, 0);
+ e = single_succ_edge (b);
e->probability = REG_BR_PROB_BASE;
e->count = b->count;
return;
/ REG_BR_PROB_BASE);
}
-/* Assume that someone emitted code with control flow instructions to the
- basic block. Update the data structure. */
+/* Assume that some pass has inserted labels or control flow
+ instructions within a basic block. Split basic blocks as needed
+ and create edges. */
void
find_many_sub_basic_blocks (sbitmap blocks)
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