/* 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, 2007 Free Software Foundation, Inc.
+ 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008
+ Free Software Foundation, Inc.
This file is part of GCC.
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"
-static int count_basic_blocks (const_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 find_bb_boundaries (basic_block);
case CALL_INSN:
case INSN:
+ case DEBUG_INSN:
return true;
case BARRIER:
bool
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:
/* Treat trap instructions like noreturn calls (same provision). */
if (GET_CODE (PATTERN (insn)) == TRAP_IF
&& XEXP (PATTERN (insn), 0) == const1_rtx)
return true;
-
- return (flag_non_call_exceptions && can_throw_internal (insn));
+ if (!flag_non_call_exceptions)
+ return false;
+ break;
case BARRIER:
/* It is nonsense to reach barrier when looking for the
default:
gcc_unreachable ();
}
-}
-
-/* Count the basic blocks of the function. */
-
-static int
-count_basic_blocks (const_rtx f)
-{
- int count = NUM_FIXED_BLOCKS;
- bool saw_insn = false;
- const_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 == NUM_FIXED_BLOCKS)
- {
- emit_use (const0_rtx);
- count = NUM_FIXED_BLOCKS + 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. */
void
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));
+ }
}
/* States of basic block as seen by find_many_sub_basic_blocks. */
{
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
{
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);
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:
- /* 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 (NOTE_INSN_BASIC_BLOCK_P (insn))
- {
- 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 = NUM_FIXED_BLOCKS;
- 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. */
-
- basic_block_info = VEC_alloc (basic_block, gc, n_basic_blocks);
- VEC_safe_grow_cleared (basic_block, gc, basic_block_info, n_basic_blocks);
- SET_BASIC_BLOCK (ENTRY_BLOCK, ENTRY_BLOCK_PTR);
- SET_BASIC_BLOCK (EXIT_BLOCK, EXIT_BLOCK_PTR);
-
- find_basic_blocks_1 (f);
-
- profile_status = PROFILE_ABSENT;
-
- /* Tell make_edges to examine every block for out-going edges. */
- FOR_EACH_BB (bb)
- SET_STATE (bb, BLOCK_NEW);
-
- /* 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
static void
mark_tablejump_edge (rtx label)
{
{
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 = 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;
-
- /* 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;
+ /* __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))