+++ /dev/null
-/* Control flow graph building code for GNU compiler.
- Copyright (C) 1987-2014 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 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/>. */
-
-\f
-#include "config.h"
-#include "system.h"
-#include "coretypes.h"
-#include "tm.h"
-#include "tree.h"
-#include "rtl.h"
-#include "hard-reg-set.h"
-#include "basic-block.h"
-#include "regs.h"
-#include "flags.h"
-#include "function.h"
-#include "except.h"
-#include "expr.h"
-#include "diagnostic-core.h"
-#include "timevar.h"
-#include "sbitmap.h"
-
-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);
-static void compute_outgoing_frequencies (basic_block);
-\f
-/* Return true if insn is something that should be contained inside basic
- block. */
-
-bool
-inside_basic_block_p (const rtx_insn *insn)
-{
- switch (GET_CODE (insn))
- {
- case CODE_LABEL:
- /* Avoid creating of basic block for jumptables. */
- return (NEXT_INSN (insn) == 0
- || ! JUMP_TABLE_DATA_P (NEXT_INSN (insn)));
-
- case JUMP_INSN:
- case CALL_INSN:
- case INSN:
- case DEBUG_INSN:
- return true;
-
- case JUMP_TABLE_DATA:
- case BARRIER:
- case NOTE:
- return false;
-
- default:
- gcc_unreachable ();
- }
-}
-
-/* Return true if INSN may cause control flow transfer, so it should be last in
- the basic block. */
-
-bool
-control_flow_insn_p (const rtx_insn *insn)
-{
- switch (GET_CODE (insn))
- {
- case NOTE:
- case CODE_LABEL:
- case DEBUG_INSN:
- return false;
-
- case JUMP_INSN:
- return true;
-
- case CALL_INSN:
- /* Noreturn and sibling call instructions terminate the basic blocks
- (but only if they happen unconditionally). */
- if ((SIBLING_CALL_P (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. */
- 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;
- if (!cfun->can_throw_non_call_exceptions)
- return false;
- break;
-
- case JUMP_TABLE_DATA:
- case BARRIER:
- /* It is nonsense to reach this when looking for the
- end of basic block, but before dead code is eliminated
- this may happen. */
- return false;
-
- default:
- gcc_unreachable ();
- }
-
- 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)
-{
- gcc_assert (LABEL_P (label));
-
- /* If the label was never emitted, this insn is junk, but avoid a
- crash trying to refer to BLOCK_FOR_INSN (label). This can happen
- as a result of a syntax error and a diagnostic has already been
- printed. */
-
- if (INSN_UID (label) == 0)
- return;
-
- cached_make_edge (edge_cache, src, BLOCK_FOR_INSN (label), flags);
-}
-
-/* Create the edges generated by INSN in REGION. */
-
-void
-rtl_make_eh_edge (sbitmap edge_cache, basic_block src, rtx insn)
-{
- eh_landing_pad lp = get_eh_landing_pad_from_rtx (insn);
-
- if (lp)
- {
- rtx label = lp->landing_pad;
-
- /* 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);
- }
-
- 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. */
-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)
-
-/* 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.
-
- 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;
-
- /* 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->cfg->max_jumptable_ents > 100)
- edge_cache = sbitmap_alloc (last_basic_block_for_fn (cfun));
-
- /* By nature of the way these get numbered, ENTRY_BLOCK_PTR->next_bb block
- is always the entry. */
- if (min == ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb)
- make_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun), min, EDGE_FALLTHRU);
-
- FOR_BB_BETWEEN (bb, min, max->next_bb, next_bb)
- {
- rtx_insn *insn;
- 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)
- {
- bitmap_clear (edge_cache);
- if (update_p)
- {
- FOR_EACH_EDGE (e, ei, bb->succs)
- if (e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun))
- bitmap_set_bit (edge_cache, e->dest->index);
- }
- }
-
- if (LABEL_P (BB_HEAD (bb))
- && LABEL_ALT_ENTRY_P (BB_HEAD (bb)))
- cached_make_edge (NULL, ENTRY_BLOCK_PTR_FOR_FN (cfun), bb, 0);
-
- /* Examine the last instruction of the block, and discover the
- ways we can leave the block. */
-
- insn = BB_END (bb);
- code = GET_CODE (insn);
-
- /* A branch. */
- if (code == JUMP_INSN)
- {
- rtx tmp;
- rtx_jump_table_data *table;
-
- /* Recognize a non-local goto as a branch outside the
- current function. */
- if (find_reg_note (insn, REG_NON_LOCAL_GOTO, NULL_RTX))
- ;
-
- /* Recognize a tablejump and do the right thing. */
- else if (tablejump_p (insn, NULL, &table))
- {
- rtvec vec = table->get_labels ();
- int j;
-
- for (j = GET_NUM_ELEM (vec) - 1; j >= 0; --j)
- make_label_edge (edge_cache, bb,
- XEXP (RTVEC_ELT (vec, j), 0), 0);
-
- /* Some targets (eg, ARM) emit a conditional jump that also
- contains the out-of-range target. Scan for these and
- add an edge if necessary. */
- if ((tmp = single_set (insn)) != NULL
- && SET_DEST (tmp) == pc_rtx
- && GET_CODE (SET_SRC (tmp)) == IF_THEN_ELSE
- && GET_CODE (XEXP (SET_SRC (tmp), 2)) == LABEL_REF)
- make_label_edge (edge_cache, bb,
- XEXP (XEXP (SET_SRC (tmp), 2), 0), 0);
- }
-
- /* If this is a computed jump, then mark it as reaching
- everything on the forced_labels list. */
- else if (computed_jump_p (insn))
- {
- for (rtx_insn_list *x = forced_labels; x; x = x->next ())
- make_label_edge (edge_cache, bb, x->insn (), EDGE_ABNORMAL);
- }
-
- /* Returns create an exit out. */
- else if (returnjump_p (insn))
- cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR_FOR_FN (cfun), 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
- {
- gcc_assert (JUMP_LABEL (insn));
- make_label_edge (edge_cache, bb, JUMP_LABEL (insn), 0);
- }
- }
-
- /* If this is a sibling call insn, then this is in effect a combined call
- and return, and so we need an edge to the exit block. No need to
- worry about EH edges, since we wouldn't have created the sibling call
- in the first place. */
- if (code == CALL_INSN && SIBLING_CALL_P (insn))
- cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR_FOR_FN (cfun),
- EDGE_SIBCALL | EDGE_ABNORMAL);
-
- /* If this is a CALL_INSN, then mark it as reaching the active EH
- 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 || cfun->can_throw_non_call_exceptions)
- {
- /* Add any appropriate EH edges. */
- rtl_make_eh_edge (edge_cache, bb, insn);
-
- if (code == CALL_INSN)
- {
- if (can_nonlocal_goto (insn))
- {
- /* ??? This could be made smarter: in some cases it's
- possible to tell that certain calls will not do a
- nonlocal goto. For example, if the nested functions
- that do the nonlocal 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. */
- for (rtx_insn_list *x = nonlocal_goto_handler_labels;
- x;
- x = x->next ())
- make_label_edge (edge_cache, bb, x->insn (),
- EDGE_ABNORMAL | EDGE_ABNORMAL_CALL);
- }
-
- if (flag_tm)
- {
- rtx note;
- for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
- if (REG_NOTE_KIND (note) == REG_TM)
- make_label_edge (edge_cache, bb, XEXP (note, 0),
- EDGE_ABNORMAL | EDGE_ABNORMAL_CALL);
- }
- }
- }
-
- /* Find out if we can drop through to the next block. */
- insn = NEXT_INSN (insn);
- e = find_edge (bb, EXIT_BLOCK_PTR_FOR_FN (cfun));
- if (e && e->flags & EDGE_FALLTHRU)
- insn = NULL;
-
- while (insn
- && NOTE_P (insn)
- && NOTE_KIND (insn) != NOTE_INSN_BASIC_BLOCK)
- insn = NEXT_INSN (insn);
-
- if (!insn)
- cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR_FOR_FN (cfun),
- EDGE_FALLTHRU);
- else if (bb->next_bb != EXIT_BLOCK_PTR_FOR_FN (cfun))
- {
- if (insn == BB_HEAD (bb->next_bb))
- cached_make_edge (edge_cache, bb, bb->next_bb, EDGE_FALLTHRU);
- }
- }
-
- if (edge_cache)
- sbitmap_free (edge_cache);
-}
-\f
-static void
-mark_tablejump_edge (rtx label)
-{
- basic_block bb;
-
- gcc_assert (LABEL_P (label));
- /* See comment in make_label_edge. */
- if (INSN_UID (label) == 0)
- return;
- bb = BLOCK_FOR_INSN (label);
- SET_STATE (bb, FULL_STATE (bb) | BLOCK_USED_BY_TABLEJUMP);
-}
-
-static void
-purge_dead_tablejump_edges (basic_block bb, rtx_jump_table_data *table)
-{
- rtx_insn *insn = BB_END (bb);
- rtx tmp;
- rtvec vec;
- int j;
- edge_iterator ei;
- edge e;
-
- vec = table->get_labels ();
-
- for (j = GET_NUM_ELEM (vec) - 1; j >= 0; --j)
- mark_tablejump_edge (XEXP (RTVEC_ELT (vec, j), 0));
-
- /* Some targets (eg, ARM) emit a conditional jump that also
- contains the out-of-range target. Scan for these and
- add an edge if necessary. */
- if ((tmp = single_set (insn)) != NULL
- && SET_DEST (tmp) == pc_rtx
- && GET_CODE (SET_SRC (tmp)) == IF_THEN_ELSE
- && GET_CODE (XEXP (SET_SRC (tmp), 2)) == LABEL_REF)
- mark_tablejump_edge (XEXP (XEXP (SET_SRC (tmp), 2), 0));
-
- 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);
- else if (!(e->flags & (EDGE_ABNORMAL | EDGE_EH)))
- {
- remove_edge (e);
- continue;
- }
- ei_next (&ei);
- }
-}
-
-/* Scan basic block BB for possible BB boundaries inside the block
- and create new basic blocks in the progress. */
-
-static void
-find_bb_boundaries (basic_block bb)
-{
- basic_block orig_bb = bb;
- rtx_insn *insn = BB_HEAD (bb);
- rtx_insn *end = BB_END (bb), *x;
- rtx_jump_table_data *table;
- rtx_insn *flow_transfer_insn = NULL;
- edge fallthru = NULL;
-
- if (insn == BB_END (bb))
- return;
-
- if (LABEL_P (insn))
- insn = NEXT_INSN (insn);
-
- /* Scan insn chain and try to find new basic block boundaries. */
- while (1)
- {
- enum rtx_code code = GET_CODE (insn);
-
- /* 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;
-
- /* 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;
- if (code == CODE_LABEL && LABEL_ALT_ENTRY_P (insn))
- make_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun), bb, 0);
- }
- else if (code == BARRIER)
- {
- /* __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))
- flow_transfer_insn = insn;
- if (insn == end)
- break;
- insn = NEXT_INSN (insn);
- }
-
- /* In case expander replaced normal insn by sequence terminating by
- 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;
-
- /* 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
- be dead. */
- purge_dead_edges (bb);
-
- /* purge_dead_edges doesn't handle tablejump's, but if we have split the
- basic block, we might need to kill some edges. */
- if (bb != orig_bb && tablejump_p (BB_END (bb), NULL, &table))
- purge_dead_tablejump_edges (bb, table);
-}
-
-/* Assume that frequency of basic block B is known. Compute frequencies
- and probabilities of outgoing edges. */
-
-static void
-compute_outgoing_frequencies (basic_block b)
-{
- edge e, f;
- edge_iterator ei;
-
- if (EDGE_COUNT (b->succs) == 2)
- {
- rtx note = find_reg_note (BB_END (b), REG_BR_PROB, NULL);
- int probability;
-
- if (note)
- {
- probability = XINT (note, 0);
- e = BRANCH_EDGE (b);
- e->probability = probability;
- e->count = apply_probability (b->count, probability);
- f = FALLTHRU_EDGE (b);
- f->probability = REG_BR_PROB_BASE - probability;
- f->count = b->count - e->count;
- return;
- }
- else
- {
- guess_outgoing_edge_probabilities (b);
- }
- }
- else if (single_succ_p (b))
- {
- e = single_succ_edge (b);
- e->probability = REG_BR_PROB_BASE;
- e->count = b->count;
- return;
- }
- else
- {
- /* We rely on BBs with more than two successors to have sane probabilities
- and do not guess them here. For BBs terminated by switch statements
- expanded to jump-table jump, we have done the right thing during
- expansion. For EH edges, we still guess the probabilities here. */
- bool complex_edge = false;
- FOR_EACH_EDGE (e, ei, b->succs)
- if (e->flags & EDGE_COMPLEX)
- {
- complex_edge = true;
- break;
- }
- if (complex_edge)
- guess_outgoing_edge_probabilities (b);
- }
-
- if (b->count)
- FOR_EACH_EDGE (e, ei, b->succs)
- e->count = apply_probability (b->count, e->probability);
-}
-
-/* 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)
-{
- basic_block bb, min, max;
-
- FOR_EACH_BB_FN (bb, cfun)
- SET_STATE (bb,
- bitmap_bit_p (blocks, bb->index) ? BLOCK_TO_SPLIT : BLOCK_ORIGINAL);
-
- FOR_EACH_BB_FN (bb, cfun)
- if (STATE (bb) == BLOCK_TO_SPLIT)
- find_bb_boundaries (bb);
-
- FOR_EACH_BB_FN (bb, cfun)
- if (STATE (bb) != BLOCK_ORIGINAL)
- break;
-
- min = max = bb;
- for (; bb != EXIT_BLOCK_PTR_FOR_FN (cfun); bb = bb->next_bb)
- if (STATE (bb) != BLOCK_ORIGINAL)
- max = bb;
-
- /* Now re-scan and wire in all edges. This expect simple (conditional)
- jumps at the end of each new basic blocks. */
- make_edges (min, max, 1);
-
- /* Update branch probabilities. Expect only (un)conditional jumps
- to be created with only the forward edges. */
- if (profile_status_for_fn (cfun) != PROFILE_ABSENT)
- FOR_BB_BETWEEN (bb, min, max->next_bb, next_bb)
- {
- edge e;
- edge_iterator ei;
-
- if (STATE (bb) == BLOCK_ORIGINAL)
- continue;
- if (STATE (bb) == BLOCK_NEW)
- {
- bb->count = 0;
- bb->frequency = 0;
- FOR_EACH_EDGE (e, ei, bb->preds)
- {
- bb->count += e->count;
- bb->frequency += EDGE_FREQUENCY (e);
- }
- }
-
- compute_outgoing_frequencies (bb);
- }
-
- FOR_EACH_BB_FN (bb, cfun)
- SET_STATE (bb, 0);
-}
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