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Diffstat (limited to 'gcc/cfgcleanup.c')
| -rw-r--r-- | gcc/cfgcleanup.c | 2785 |
1 files changed, 2785 insertions, 0 deletions
diff --git a/gcc/cfgcleanup.c b/gcc/cfgcleanup.c new file mode 100644 index 000000000..0a6449800 --- /dev/null +++ b/gcc/cfgcleanup.c @@ -0,0 +1,2785 @@ +/* Control flow optimization code for GNU compiler. + Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, + 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2010 + 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/>. */ + +/* This file contains optimizer of the control flow. The main entry point is + cleanup_cfg. Following optimizations are performed: + + - Unreachable blocks removal + - Edge forwarding (edge to the forwarder block is forwarded to its + successor. Simplification of the branch instruction is performed by + underlying infrastructure so branch can be converted to simplejump or + eliminated). + - Cross jumping (tail merging) + - Conditional jump-around-simplejump simplification + - Basic block merging. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "tm.h" +#include "rtl.h" +#include "hard-reg-set.h" +#include "regs.h" +#include "timevar.h" +#include "output.h" +#include "insn-config.h" +#include "flags.h" +#include "recog.h" +#include "diagnostic-core.h" +#include "cselib.h" +#include "params.h" +#include "tm_p.h" +#include "target.h" +#include "cfglayout.h" +#include "emit-rtl.h" +#include "tree-pass.h" +#include "cfgloop.h" +#include "expr.h" +#include "df.h" +#include "dce.h" +#include "dbgcnt.h" + +#define FORWARDER_BLOCK_P(BB) ((BB)->flags & BB_FORWARDER_BLOCK) + +/* Set to true when we are running first pass of try_optimize_cfg loop. */ +static bool first_pass; + +/* Set to true if crossjumps occured in the latest run of try_optimize_cfg. */ +static bool crossjumps_occured; + +/* Set to true if we couldn't run an optimization due to stale liveness + information; we should run df_analyze to enable more opportunities. */ +static bool block_was_dirty; + +static bool try_crossjump_to_edge (int, edge, edge); +static bool try_crossjump_bb (int, basic_block); +static bool outgoing_edges_match (int, basic_block, basic_block); +static bool old_insns_match_p (int, rtx, rtx); + +static void merge_blocks_move_predecessor_nojumps (basic_block, basic_block); +static void merge_blocks_move_successor_nojumps (basic_block, basic_block); +static bool try_optimize_cfg (int); +static bool try_simplify_condjump (basic_block); +static bool try_forward_edges (int, basic_block); +static edge thread_jump (edge, basic_block); +static bool mark_effect (rtx, bitmap); +static void notice_new_block (basic_block); +static void update_forwarder_flag (basic_block); +static int mentions_nonequal_regs (rtx *, void *); +static void merge_memattrs (rtx, rtx); + +/* Set flags for newly created block. */ + +static void +notice_new_block (basic_block bb) +{ + if (!bb) + return; + + if (forwarder_block_p (bb)) + bb->flags |= BB_FORWARDER_BLOCK; +} + +/* Recompute forwarder flag after block has been modified. */ + +static void +update_forwarder_flag (basic_block bb) +{ + if (forwarder_block_p (bb)) + bb->flags |= BB_FORWARDER_BLOCK; + else + bb->flags &= ~BB_FORWARDER_BLOCK; +} + +/* Simplify a conditional jump around an unconditional jump. + Return true if something changed. */ + +static bool +try_simplify_condjump (basic_block cbranch_block) +{ + basic_block jump_block, jump_dest_block, cbranch_dest_block; + edge cbranch_jump_edge, cbranch_fallthru_edge; + rtx cbranch_insn; + + /* Verify that there are exactly two successors. */ + if (EDGE_COUNT (cbranch_block->succs) != 2) + return false; + + /* Verify that we've got a normal conditional branch at the end + of the block. */ + cbranch_insn = BB_END (cbranch_block); + if (!any_condjump_p (cbranch_insn)) + return false; + + cbranch_fallthru_edge = FALLTHRU_EDGE (cbranch_block); + cbranch_jump_edge = BRANCH_EDGE (cbranch_block); + + /* The next block must not have multiple predecessors, must not + be the last block in the function, and must contain just the + unconditional jump. */ + jump_block = cbranch_fallthru_edge->dest; + if (!single_pred_p (jump_block) + || jump_block->next_bb == EXIT_BLOCK_PTR + || !FORWARDER_BLOCK_P (jump_block)) + return false; + jump_dest_block = single_succ (jump_block); + + /* If we are partitioning hot/cold basic blocks, we don't want to + mess up unconditional or indirect jumps that cross between hot + and cold sections. + + Basic block partitioning may result in some jumps that appear to + be optimizable (or blocks that appear to be mergeable), but which really + must be left untouched (they are required to make it safely across + partition boundaries). See the comments at the top of + bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */ + + if (BB_PARTITION (jump_block) != BB_PARTITION (jump_dest_block) + || (cbranch_jump_edge->flags & EDGE_CROSSING)) + return false; + + /* The conditional branch must target the block after the + unconditional branch. */ + cbranch_dest_block = cbranch_jump_edge->dest; + + if (cbranch_dest_block == EXIT_BLOCK_PTR + || !can_fallthru (jump_block, cbranch_dest_block)) + return false; + + /* Invert the conditional branch. */ + if (!invert_jump (cbranch_insn, block_label (jump_dest_block), 0)) + return false; + + if (dump_file) + fprintf (dump_file, "Simplifying condjump %i around jump %i\n", + INSN_UID (cbranch_insn), INSN_UID (BB_END (jump_block))); + + /* Success. Update the CFG to match. Note that after this point + the edge variable names appear backwards; the redirection is done + this way to preserve edge profile data. */ + cbranch_jump_edge = redirect_edge_succ_nodup (cbranch_jump_edge, + cbranch_dest_block); + cbranch_fallthru_edge = redirect_edge_succ_nodup (cbranch_fallthru_edge, + jump_dest_block); + cbranch_jump_edge->flags |= EDGE_FALLTHRU; + cbranch_fallthru_edge->flags &= ~EDGE_FALLTHRU; + update_br_prob_note (cbranch_block); + + /* Delete the block with the unconditional jump, and clean up the mess. */ + delete_basic_block (jump_block); + tidy_fallthru_edge (cbranch_jump_edge); + update_forwarder_flag (cbranch_block); + + return true; +} + +/* Attempt to prove that operation is NOOP using CSElib or mark the effect + on register. Used by jump threading. */ + +static bool +mark_effect (rtx exp, regset nonequal) +{ + int regno; + rtx dest; + switch (GET_CODE (exp)) + { + /* In case we do clobber the register, mark it as equal, as we know the + value is dead so it don't have to match. */ + case CLOBBER: + if (REG_P (XEXP (exp, 0))) + { + dest = XEXP (exp, 0); + regno = REGNO (dest); + CLEAR_REGNO_REG_SET (nonequal, regno); + if (regno < FIRST_PSEUDO_REGISTER) + { + int n = hard_regno_nregs[regno][GET_MODE (dest)]; + while (--n > 0) + CLEAR_REGNO_REG_SET (nonequal, regno + n); + } + } + return false; + + case SET: + if (rtx_equal_for_cselib_p (SET_DEST (exp), SET_SRC (exp))) + return false; + dest = SET_DEST (exp); + if (dest == pc_rtx) + return false; + if (!REG_P (dest)) + return true; + regno = REGNO (dest); + SET_REGNO_REG_SET (nonequal, regno); + if (regno < FIRST_PSEUDO_REGISTER) + { + int n = hard_regno_nregs[regno][GET_MODE (dest)]; + while (--n > 0) + SET_REGNO_REG_SET (nonequal, regno + n); + } + return false; + + default: + return false; + } +} + +/* Return nonzero if X is a register set in regset DATA. + Called via for_each_rtx. */ +static int +mentions_nonequal_regs (rtx *x, void *data) +{ + regset nonequal = (regset) data; + if (REG_P (*x)) + { + int regno; + + regno = REGNO (*x); + if (REGNO_REG_SET_P (nonequal, regno)) + return 1; + if (regno < FIRST_PSEUDO_REGISTER) + { + int n = hard_regno_nregs[regno][GET_MODE (*x)]; + while (--n > 0) + if (REGNO_REG_SET_P (nonequal, regno + n)) + return 1; + } + } + return 0; +} +/* Attempt to prove that the basic block B will have no side effects and + always continues in the same edge if reached via E. Return the edge + if exist, NULL otherwise. */ + +static edge +thread_jump (edge e, basic_block b) +{ + rtx set1, set2, cond1, cond2, insn; + enum rtx_code code1, code2, reversed_code2; + bool reverse1 = false; + unsigned i; + regset nonequal; + bool failed = false; + reg_set_iterator rsi; + + if (b->flags & BB_NONTHREADABLE_BLOCK) + return NULL; + + /* At the moment, we do handle only conditional jumps, but later we may + want to extend this code to tablejumps and others. */ + if (EDGE_COUNT (e->src->succs) != 2) + return NULL; + if (EDGE_COUNT (b->succs) != 2) + { + b->flags |= BB_NONTHREADABLE_BLOCK; + return NULL; + } + + /* Second branch must end with onlyjump, as we will eliminate the jump. */ + if (!any_condjump_p (BB_END (e->src))) + return NULL; + + if (!any_condjump_p (BB_END (b)) || !onlyjump_p (BB_END (b))) + { + b->flags |= BB_NONTHREADABLE_BLOCK; + return NULL; + } + + set1 = pc_set (BB_END (e->src)); + set2 = pc_set (BB_END (b)); + if (((e->flags & EDGE_FALLTHRU) != 0) + != (XEXP (SET_SRC (set1), 1) == pc_rtx)) + reverse1 = true; + + cond1 = XEXP (SET_SRC (set1), 0); + cond2 = XEXP (SET_SRC (set2), 0); + if (reverse1) + code1 = reversed_comparison_code (cond1, BB_END (e->src)); + else + code1 = GET_CODE (cond1); + + code2 = GET_CODE (cond2); + reversed_code2 = reversed_comparison_code (cond2, BB_END (b)); + + if (!comparison_dominates_p (code1, code2) + && !comparison_dominates_p (code1, reversed_code2)) + return NULL; + + /* Ensure that the comparison operators are equivalent. + ??? This is far too pessimistic. We should allow swapped operands, + different CCmodes, or for example comparisons for interval, that + dominate even when operands are not equivalent. */ + if (!rtx_equal_p (XEXP (cond1, 0), XEXP (cond2, 0)) + || !rtx_equal_p (XEXP (cond1, 1), XEXP (cond2, 1))) + return NULL; + + /* Short circuit cases where block B contains some side effects, as we can't + safely bypass it. */ + for (insn = NEXT_INSN (BB_HEAD (b)); insn != NEXT_INSN (BB_END (b)); + insn = NEXT_INSN (insn)) + if (INSN_P (insn) && side_effects_p (PATTERN (insn))) + { + b->flags |= BB_NONTHREADABLE_BLOCK; + return NULL; + } + + cselib_init (0); + + /* First process all values computed in the source basic block. */ + for (insn = NEXT_INSN (BB_HEAD (e->src)); + insn != NEXT_INSN (BB_END (e->src)); + insn = NEXT_INSN (insn)) + if (INSN_P (insn)) + cselib_process_insn (insn); + + nonequal = BITMAP_ALLOC (NULL); + CLEAR_REG_SET (nonequal); + + /* Now assume that we've continued by the edge E to B and continue + processing as if it were same basic block. + Our goal is to prove that whole block is an NOOP. */ + + for (insn = NEXT_INSN (BB_HEAD (b)); + insn != NEXT_INSN (BB_END (b)) && !failed; + insn = NEXT_INSN (insn)) + { + if (INSN_P (insn)) + { + rtx pat = PATTERN (insn); + + if (GET_CODE (pat) == PARALLEL) + { + for (i = 0; i < (unsigned)XVECLEN (pat, 0); i++) + failed |= mark_effect (XVECEXP (pat, 0, i), nonequal); + } + else + failed |= mark_effect (pat, nonequal); + } + + cselib_process_insn (insn); + } + + /* Later we should clear nonequal of dead registers. So far we don't + have life information in cfg_cleanup. */ + if (failed) + { + b->flags |= BB_NONTHREADABLE_BLOCK; + goto failed_exit; + } + + /* cond2 must not mention any register that is not equal to the + former block. */ + if (for_each_rtx (&cond2, mentions_nonequal_regs, nonequal)) + goto failed_exit; + + EXECUTE_IF_SET_IN_REG_SET (nonequal, 0, i, rsi) + goto failed_exit; + + BITMAP_FREE (nonequal); + cselib_finish (); + if ((comparison_dominates_p (code1, code2) != 0) + != (XEXP (SET_SRC (set2), 1) == pc_rtx)) + return BRANCH_EDGE (b); + else + return FALLTHRU_EDGE (b); + +failed_exit: + BITMAP_FREE (nonequal); + cselib_finish (); + return NULL; +} + +/* Attempt to forward edges leaving basic block B. + Return true if successful. */ + +static bool +try_forward_edges (int mode, basic_block b) +{ + bool changed = false; + edge_iterator ei; + edge e, *threaded_edges = NULL; + + /* If we are partitioning hot/cold basic blocks, we don't want to + mess up unconditional or indirect jumps that cross between hot + and cold sections. + + Basic block partitioning may result in some jumps that appear to + be optimizable (or blocks that appear to be mergeable), but which really + must be left untouched (they are required to make it safely across + partition boundaries). See the comments at the top of + bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */ + + if (find_reg_note (BB_END (b), REG_CROSSING_JUMP, NULL_RTX)) + return false; + + for (ei = ei_start (b->succs); (e = ei_safe_edge (ei)); ) + { + basic_block target, first; + int counter, goto_locus; + bool threaded = false; + int nthreaded_edges = 0; + bool may_thread = first_pass || (b->flags & BB_MODIFIED) != 0; + + /* Skip complex edges because we don't know how to update them. + + Still handle fallthru edges, as we can succeed to forward fallthru + edge to the same place as the branch edge of conditional branch + and turn conditional branch to an unconditional branch. */ + if (e->flags & EDGE_COMPLEX) + { + ei_next (&ei); + continue; + } + + target = first = e->dest; + counter = NUM_FIXED_BLOCKS; + goto_locus = e->goto_locus; + + /* If we are partitioning hot/cold basic_blocks, we don't want to mess + up jumps that cross between hot/cold sections. + + Basic block partitioning may result in some jumps that appear + to be optimizable (or blocks that appear to be mergeable), but which + really must be left untouched (they are required to make it safely + across partition boundaries). See the comments at the top of + bb-reorder.c:partition_hot_cold_basic_blocks for complete + details. */ + + if (first != EXIT_BLOCK_PTR + && find_reg_note (BB_END (first), REG_CROSSING_JUMP, NULL_RTX)) + return false; + + while (counter < n_basic_blocks) + { + basic_block new_target = NULL; + bool new_target_threaded = false; + may_thread |= (target->flags & BB_MODIFIED) != 0; + + if (FORWARDER_BLOCK_P (target) + && !(single_succ_edge (target)->flags & EDGE_CROSSING) + && single_succ (target) != EXIT_BLOCK_PTR) + { + /* Bypass trivial infinite loops. */ + new_target = single_succ (target); + if (target == new_target) + counter = n_basic_blocks; + else if (!optimize) + { + /* When not optimizing, ensure that edges or forwarder + blocks with different locus are not optimized out. */ + int new_locus = single_succ_edge (target)->goto_locus; + int locus = goto_locus; + + if (new_locus && locus && !locator_eq (new_locus, locus)) + new_target = NULL; + else + { + rtx last; + + if (new_locus) + locus = new_locus; + + last = BB_END (target); + if (DEBUG_INSN_P (last)) + last = prev_nondebug_insn (last); + + new_locus = last && INSN_P (last) + ? INSN_LOCATOR (last) : 0; + + if (new_locus && locus && !locator_eq (new_locus, locus)) + new_target = NULL; + else + { + if (new_locus) + locus = new_locus; + + goto_locus = locus; + } + } + } + } + + /* Allow to thread only over one edge at time to simplify updating + of probabilities. */ + else if ((mode & CLEANUP_THREADING) && may_thread) + { + edge t = thread_jump (e, target); + if (t) + { + if (!threaded_edges) + threaded_edges = XNEWVEC (edge, n_basic_blocks); + else + { + int i; + + /* Detect an infinite loop across blocks not + including the start block. */ + for (i = 0; i < nthreaded_edges; ++i) + if (threaded_edges[i] == t) + break; + if (i < nthreaded_edges) + { + counter = n_basic_blocks; + break; + } + } + + /* Detect an infinite loop across the start block. */ + if (t->dest == b) + break; + + gcc_assert (nthreaded_edges < n_basic_blocks - NUM_FIXED_BLOCKS); + threaded_edges[nthreaded_edges++] = t; + + new_target = t->dest; + new_target_threaded = true; + } + } + + if (!new_target) + break; + + counter++; + target = new_target; + threaded |= new_target_threaded; + } + + if (counter >= n_basic_blocks) + { + if (dump_file) + fprintf (dump_file, "Infinite loop in BB %i.\n", + target->index); + } + else if (target == first) + ; /* We didn't do anything. */ + else + { + /* Save the values now, as the edge may get removed. */ + gcov_type edge_count = e->count; + int edge_probability = e->probability; + int edge_frequency; + int n = 0; + + e->goto_locus = goto_locus; + + /* Don't force if target is exit block. */ + if (threaded && target != EXIT_BLOCK_PTR) + { + notice_new_block (redirect_edge_and_branch_force (e, target)); + if (dump_file) + fprintf (dump_file, "Conditionals threaded.\n"); + } + else if (!redirect_edge_and_branch (e, target)) + { + if (dump_file) + fprintf (dump_file, + "Forwarding edge %i->%i to %i failed.\n", + b->index, e->dest->index, target->index); + ei_next (&ei); + continue; + } + + /* We successfully forwarded the edge. Now update profile + data: for each edge we traversed in the chain, remove + the original edge's execution count. */ + edge_frequency = ((edge_probability * b->frequency + + REG_BR_PROB_BASE / 2) + / REG_BR_PROB_BASE); + + if (!FORWARDER_BLOCK_P (b) && forwarder_block_p (b)) + b->flags |= BB_FORWARDER_BLOCK; + + do + { + edge t; + + if (!single_succ_p (first)) + { + gcc_assert (n < nthreaded_edges); + t = threaded_edges [n++]; + gcc_assert (t->src == first); + update_bb_profile_for_threading (first, edge_frequency, + edge_count, t); + update_br_prob_note (first); + } + else + { + first->count -= edge_count; + if (first->count < 0) + first->count = 0; + first->frequency -= edge_frequency; + if (first->frequency < 0) + first->frequency = 0; + /* It is possible that as the result of + threading we've removed edge as it is + threaded to the fallthru edge. Avoid + getting out of sync. */ + if (n < nthreaded_edges + && first == threaded_edges [n]->src) + n++; + t = single_succ_edge (first); + } + + t->count -= edge_count; + if (t->count < 0) + t->count = 0; + first = t->dest; + } + while (first != target); + + changed = true; + continue; + } + ei_next (&ei); + } + + if (threaded_edges) + free (threaded_edges); + return changed; +} + + +/* Blocks A and B are to be merged into a single block. A has no incoming + fallthru edge, so it can be moved before B without adding or modifying + any jumps (aside from the jump from A to B). */ + +static void +merge_blocks_move_predecessor_nojumps (basic_block a, basic_block b) +{ + rtx barrier; + + /* If we are partitioning hot/cold basic blocks, we don't want to + mess up unconditional or indirect jumps that cross between hot + and cold sections. + + Basic block partitioning may result in some jumps that appear to + be optimizable (or blocks that appear to be mergeable), but which really + must be left untouched (they are required to make it safely across + partition boundaries). See the comments at the top of + bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */ + + if (BB_PARTITION (a) != BB_PARTITION (b)) + return; + + barrier = next_nonnote_insn (BB_END (a)); + gcc_assert (BARRIER_P (barrier)); + delete_insn (barrier); + + /* Scramble the insn chain. */ + if (BB_END (a) != PREV_INSN (BB_HEAD (b))) + reorder_insns_nobb (BB_HEAD (a), BB_END (a), PREV_INSN (BB_HEAD (b))); + df_set_bb_dirty (a); + + if (dump_file) + fprintf (dump_file, "Moved block %d before %d and merged.\n", + a->index, b->index); + + /* Swap the records for the two blocks around. */ + + unlink_block (a); + link_block (a, b->prev_bb); + + /* Now blocks A and B are contiguous. Merge them. */ + merge_blocks (a, b); +} + +/* Blocks A and B are to be merged into a single block. B has no outgoing + fallthru edge, so it can be moved after A without adding or modifying + any jumps (aside from the jump from A to B). */ + +static void +merge_blocks_move_successor_nojumps (basic_block a, basic_block b) +{ + rtx barrier, real_b_end; + rtx label, table; + + /* If we are partitioning hot/cold basic blocks, we don't want to + mess up unconditional or indirect jumps that cross between hot + and cold sections. + + Basic block partitioning may result in some jumps that appear to + be optimizable (or blocks that appear to be mergeable), but which really + must be left untouched (they are required to make it safely across + partition boundaries). See the comments at the top of + bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */ + + if (BB_PARTITION (a) != BB_PARTITION (b)) + return; + + real_b_end = BB_END (b); + + /* If there is a jump table following block B temporarily add the jump table + to block B so that it will also be moved to the correct location. */ + if (tablejump_p (BB_END (b), &label, &table) + && prev_active_insn (label) == BB_END (b)) + { + BB_END (b) = table; + } + + /* There had better have been a barrier there. Delete it. */ + barrier = NEXT_INSN (BB_END (b)); + if (barrier && BARRIER_P (barrier)) + delete_insn (barrier); + + + /* Scramble the insn chain. */ + reorder_insns_nobb (BB_HEAD (b), BB_END (b), BB_END (a)); + + /* Restore the real end of b. */ + BB_END (b) = real_b_end; + + if (dump_file) + fprintf (dump_file, "Moved block %d after %d and merged.\n", + b->index, a->index); + + /* Now blocks A and B are contiguous. Merge them. */ + merge_blocks (a, b); +} + +/* Attempt to merge basic blocks that are potentially non-adjacent. + Return NULL iff the attempt failed, otherwise return basic block + where cleanup_cfg should continue. Because the merging commonly + moves basic block away or introduces another optimization + possibility, return basic block just before B so cleanup_cfg don't + need to iterate. + + It may be good idea to return basic block before C in the case + C has been moved after B and originally appeared earlier in the + insn sequence, but we have no information available about the + relative ordering of these two. Hopefully it is not too common. */ + +static basic_block +merge_blocks_move (edge e, basic_block b, basic_block c, int mode) +{ + basic_block next; + + /* If we are partitioning hot/cold basic blocks, we don't want to + mess up unconditional or indirect jumps that cross between hot + and cold sections. + + Basic block partitioning may result in some jumps that appear to + be optimizable (or blocks that appear to be mergeable), but which really + must be left untouched (they are required to make it safely across + partition boundaries). See the comments at the top of + bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */ + + if (BB_PARTITION (b) != BB_PARTITION (c)) + return NULL; + + /* If B has a fallthru edge to C, no need to move anything. */ + if (e->flags & EDGE_FALLTHRU) + { + int b_index = b->index, c_index = c->index; + merge_blocks (b, c); + update_forwarder_flag (b); + + if (dump_file) + fprintf (dump_file, "Merged %d and %d without moving.\n", + b_index, c_index); + + return b->prev_bb == ENTRY_BLOCK_PTR ? b : b->prev_bb; + } + + /* Otherwise we will need to move code around. Do that only if expensive + transformations are allowed. */ + else if (mode & CLEANUP_EXPENSIVE) + { + edge tmp_edge, b_fallthru_edge; + bool c_has_outgoing_fallthru; + bool b_has_incoming_fallthru; + + /* Avoid overactive code motion, as the forwarder blocks should be + eliminated by edge redirection instead. One exception might have + been if B is a forwarder block and C has no fallthru edge, but + that should be cleaned up by bb-reorder instead. */ + if (FORWARDER_BLOCK_P (b) || FORWARDER_BLOCK_P (c)) + return NULL; + + /* We must make sure to not munge nesting of lexical blocks, + and loop notes. This is done by squeezing out all the notes + and leaving them there to lie. Not ideal, but functional. */ + + tmp_edge = find_fallthru_edge (c->succs); + c_has_outgoing_fallthru = (tmp_edge != NULL); + + tmp_edge = find_fallthru_edge (b->preds); + b_has_incoming_fallthru = (tmp_edge != NULL); + b_fallthru_edge = tmp_edge; + next = b->prev_bb; + if (next == c) + next = next->prev_bb; + + /* Otherwise, we're going to try to move C after B. If C does + not have an outgoing fallthru, then it can be moved + immediately after B without introducing or modifying jumps. */ + if (! c_has_outgoing_fallthru) + { + merge_blocks_move_successor_nojumps (b, c); + return next == ENTRY_BLOCK_PTR ? next->next_bb : next; + } + + /* If B does not have an incoming fallthru, then it can be moved + immediately before C without introducing or modifying jumps. + C cannot be the first block, so we do not have to worry about + accessing a non-existent block. */ + + if (b_has_incoming_fallthru) + { + basic_block bb; + + if (b_fallthru_edge->src == ENTRY_BLOCK_PTR) + return NULL; + bb = force_nonfallthru (b_fallthru_edge); + if (bb) + notice_new_block (bb); + } + + merge_blocks_move_predecessor_nojumps (b, c); + return next == ENTRY_BLOCK_PTR ? next->next_bb : next; + } + + return NULL; +} + + +/* Removes the memory attributes of MEM expression + if they are not equal. */ + +void +merge_memattrs (rtx x, rtx y) +{ + int i; + int j; + enum rtx_code code; + const char *fmt; + + if (x == y) + return; + if (x == 0 || y == 0) + return; + + code = GET_CODE (x); + + if (code != GET_CODE (y)) + return; + + if (GET_MODE (x) != GET_MODE (y)) + return; + + if (code == MEM && MEM_ATTRS (x) != MEM_ATTRS (y)) + { + if (! MEM_ATTRS (x)) + MEM_ATTRS (y) = 0; + else if (! MEM_ATTRS (y)) + MEM_ATTRS (x) = 0; + else + { + rtx mem_size; + + if (MEM_ALIAS_SET (x) != MEM_ALIAS_SET (y)) + { + set_mem_alias_set (x, 0); + set_mem_alias_set (y, 0); + } + + if (! mem_expr_equal_p (MEM_EXPR (x), MEM_EXPR (y))) + { + set_mem_expr (x, 0); + set_mem_expr (y, 0); + set_mem_offset (x, 0); + set_mem_offset (y, 0); + } + else if (MEM_OFFSET (x) != MEM_OFFSET (y)) + { + set_mem_offset (x, 0); + set_mem_offset (y, 0); + } + + if (!MEM_SIZE (x)) + mem_size = NULL_RTX; + else if (!MEM_SIZE (y)) + mem_size = NULL_RTX; + else + mem_size = GEN_INT (MAX (INTVAL (MEM_SIZE (x)), + INTVAL (MEM_SIZE (y)))); + set_mem_size (x, mem_size); + set_mem_size (y, mem_size); + + set_mem_align (x, MIN (MEM_ALIGN (x), MEM_ALIGN (y))); + set_mem_align (y, MEM_ALIGN (x)); + } + } + + fmt = GET_RTX_FORMAT (code); + for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) + { + switch (fmt[i]) + { + case 'E': + /* Two vectors must have the same length. */ + if (XVECLEN (x, i) != XVECLEN (y, i)) + return; + + for (j = 0; j < XVECLEN (x, i); j++) + merge_memattrs (XVECEXP (x, i, j), XVECEXP (y, i, j)); + + break; + + case 'e': + merge_memattrs (XEXP (x, i), XEXP (y, i)); + } + } + return; +} + + +/* Return true if I1 and I2 are equivalent and thus can be crossjumped. */ + +static bool +old_insns_match_p (int mode ATTRIBUTE_UNUSED, rtx i1, rtx i2) +{ + rtx p1, p2; + + /* Verify that I1 and I2 are equivalent. */ + if (GET_CODE (i1) != GET_CODE (i2)) + return false; + + /* __builtin_unreachable() may lead to empty blocks (ending with + NOTE_INSN_BASIC_BLOCK). They may be crossjumped. */ + if (NOTE_INSN_BASIC_BLOCK_P (i1) && NOTE_INSN_BASIC_BLOCK_P (i2)) + return true; + + p1 = PATTERN (i1); + p2 = PATTERN (i2); + + if (GET_CODE (p1) != GET_CODE (p2)) + return false; + + /* If this is a CALL_INSN, compare register usage information. + If we don't check this on stack register machines, the two + CALL_INSNs might be merged leaving reg-stack.c with mismatching + numbers of stack registers in the same basic block. + If we don't check this on machines with delay slots, a delay slot may + be filled that clobbers a parameter expected by the subroutine. + + ??? We take the simple route for now and assume that if they're + equal, they were constructed identically. + + Also check for identical exception regions. */ + + if (CALL_P (i1)) + { + /* Ensure the same EH region. */ + rtx n1 = find_reg_note (i1, REG_EH_REGION, 0); + rtx n2 = find_reg_note (i2, REG_EH_REGION, 0); + + if (!n1 && n2) + return false; + + if (n1 && (!n2 || XEXP (n1, 0) != XEXP (n2, 0))) + return false; + + if (!rtx_equal_p (CALL_INSN_FUNCTION_USAGE (i1), + CALL_INSN_FUNCTION_USAGE (i2)) + || SIBLING_CALL_P (i1) != SIBLING_CALL_P (i2)) + return false; + } + +#ifdef STACK_REGS + /* If cross_jump_death_matters is not 0, the insn's mode + indicates whether or not the insn contains any stack-like + regs. */ + + if ((mode & CLEANUP_POST_REGSTACK) && stack_regs_mentioned (i1)) + { + /* If register stack conversion has already been done, then + death notes must also be compared before it is certain that + the two instruction streams match. */ + + rtx note; + HARD_REG_SET i1_regset, i2_regset; + + CLEAR_HARD_REG_SET (i1_regset); + CLEAR_HARD_REG_SET (i2_regset); + + for (note = REG_NOTES (i1); note; note = XEXP (note, 1)) + if (REG_NOTE_KIND (note) == REG_DEAD && STACK_REG_P (XEXP (note, 0))) + SET_HARD_REG_BIT (i1_regset, REGNO (XEXP (note, 0))); + + for (note = REG_NOTES (i2); note; note = XEXP (note, 1)) + if (REG_NOTE_KIND (note) == REG_DEAD && STACK_REG_P (XEXP (note, 0))) + SET_HARD_REG_BIT (i2_regset, REGNO (XEXP (note, 0))); + + if (!hard_reg_set_equal_p (i1_regset, i2_regset)) + return false; + } +#endif + + if (reload_completed + ? rtx_renumbered_equal_p (p1, p2) : rtx_equal_p (p1, p2)) + return true; + + return false; +} + +/* When comparing insns I1 and I2 in flow_find_cross_jump or + flow_find_head_matching_sequence, ensure the notes match. */ + +static void +merge_notes (rtx i1, rtx i2) +{ + /* If the merged insns have different REG_EQUAL notes, then + remove them. */ + rtx equiv1 = find_reg_equal_equiv_note (i1); + rtx equiv2 = find_reg_equal_equiv_note (i2); + + if (equiv1 && !equiv2) + remove_note (i1, equiv1); + else if (!equiv1 && equiv2) + remove_note (i2, equiv2); + else if (equiv1 && equiv2 + && !rtx_equal_p (XEXP (equiv1, 0), XEXP (equiv2, 0))) + { + remove_note (i1, equiv1); + remove_note (i2, equiv2); + } +} + +/* Look through the insns at the end of BB1 and BB2 and find the longest + sequence that are equivalent. Store the first insns for that sequence + in *F1 and *F2 and return the sequence length. + + To simplify callers of this function, if the blocks match exactly, + store the head of the blocks in *F1 and *F2. */ + +int +flow_find_cross_jump (basic_block bb1, basic_block bb2, rtx *f1, rtx *f2) +{ + rtx i1, i2, last1, last2, afterlast1, afterlast2; + int ninsns = 0; + + /* Skip simple jumps at the end of the blocks. Complex jumps still + need to be compared for equivalence, which we'll do below. */ + + i1 = BB_END (bb1); + last1 = afterlast1 = last2 = afterlast2 = NULL_RTX; + if (onlyjump_p (i1) + || (returnjump_p (i1) && !side_effects_p (PATTERN (i1)))) + { + last1 = i1; + i1 = PREV_INSN (i1); + } + + i2 = BB_END (bb2); + if (onlyjump_p (i2) + || (returnjump_p (i2) && !side_effects_p (PATTERN (i2)))) + { + last2 = i2; + /* Count everything except for unconditional jump as insn. */ + if (!simplejump_p (i2) && !returnjump_p (i2) && last1) + ninsns++; + i2 = PREV_INSN (i2); + } + + while (true) + { + /* Ignore notes. */ + while (!NONDEBUG_INSN_P (i1) && i1 != BB_HEAD (bb1)) + i1 = PREV_INSN (i1); + + while (!NONDEBUG_INSN_P (i2) && i2 != BB_HEAD (bb2)) + i2 = PREV_INSN (i2); + + if (i1 == BB_HEAD (bb1) || i2 == BB_HEAD (bb2)) + break; + + if (!old_insns_match_p (0, i1, i2)) + break; + + merge_memattrs (i1, i2); + + /* Don't begin a cross-jump with a NOTE insn. */ + if (INSN_P (i1)) + { + merge_notes (i1, i2); + + afterlast1 = last1, afterlast2 = last2; + last1 = i1, last2 = i2; + ninsns++; + } + + i1 = PREV_INSN (i1); + i2 = PREV_INSN (i2); + } + +#ifdef HAVE_cc0 + /* Don't allow the insn after a compare to be shared by + cross-jumping unless the compare is also shared. */ + if (ninsns && reg_mentioned_p (cc0_rtx, last1) && ! sets_cc0_p (last1)) + last1 = afterlast1, last2 = afterlast2, ninsns--; +#endif + + /* Include preceding notes and labels in the cross-jump. One, + this may bring us to the head of the blocks as requested above. + Two, it keeps line number notes as matched as may be. */ + if (ninsns) + { + while (last1 != BB_HEAD (bb1) && !NONDEBUG_INSN_P (PREV_INSN (last1))) + last1 = PREV_INSN (last1); + + if (last1 != BB_HEAD (bb1) && LABEL_P (PREV_INSN (last1))) + last1 = PREV_INSN (last1); + + while (last2 != BB_HEAD (bb2) && !NONDEBUG_INSN_P (PREV_INSN (last2))) + last2 = PREV_INSN (last2); + + if (last2 != BB_HEAD (bb2) && LABEL_P (PREV_INSN (last2))) + last2 = PREV_INSN (last2); + + *f1 = last1; + *f2 = last2; + } + + return ninsns; +} + +/* Like flow_find_cross_jump, except start looking for a matching sequence from + the head of the two blocks. Do not include jumps at the end. + If STOP_AFTER is nonzero, stop after finding that many matching + instructions. */ + +int +flow_find_head_matching_sequence (basic_block bb1, basic_block bb2, rtx *f1, + rtx *f2, int stop_after) +{ + rtx i1, i2, last1, last2, beforelast1, beforelast2; + int ninsns = 0; + edge e; + edge_iterator ei; + int nehedges1 = 0, nehedges2 = 0; + + FOR_EACH_EDGE (e, ei, bb1->succs) + if (e->flags & EDGE_EH) + nehedges1++; + FOR_EACH_EDGE (e, ei, bb2->succs) + if (e->flags & EDGE_EH) + nehedges2++; + + i1 = BB_HEAD (bb1); + i2 = BB_HEAD (bb2); + last1 = beforelast1 = last2 = beforelast2 = NULL_RTX; + + while (true) + { + /* Ignore notes, except NOTE_INSN_EPILOGUE_BEG. */ + while (!NONDEBUG_INSN_P (i1) && i1 != BB_END (bb1)) + { + if (NOTE_P (i1) && NOTE_KIND (i1) == NOTE_INSN_EPILOGUE_BEG) + break; + i1 = NEXT_INSN (i1); + } + + while (!NONDEBUG_INSN_P (i2) && i2 != BB_END (bb2)) + { + if (NOTE_P (i2) && NOTE_KIND (i2) == NOTE_INSN_EPILOGUE_BEG) + break; + i2 = NEXT_INSN (i2); + } + + if ((i1 == BB_END (bb1) && !NONDEBUG_INSN_P (i1)) + || (i2 == BB_END (bb2) && !NONDEBUG_INSN_P (i2))) + break; + + if (NOTE_P (i1) || NOTE_P (i2) + || JUMP_P (i1) || JUMP_P (i2)) + break; + + /* A sanity check to make sure we're not merging insns with different + effects on EH. If only one of them ends a basic block, it shouldn't + have an EH edge; if both end a basic block, there should be the same + number of EH edges. */ + if ((i1 == BB_END (bb1) && i2 != BB_END (bb2) + && nehedges1 > 0) + || (i2 == BB_END (bb2) && i1 != BB_END (bb1) + && nehedges2 > 0) + || (i1 == BB_END (bb1) && i2 == BB_END (bb2) + && nehedges1 != nehedges2)) + break; + + if (!old_insns_match_p (0, i1, i2)) + break; + + merge_memattrs (i1, i2); + + /* Don't begin a cross-jump with a NOTE insn. */ + if (INSN_P (i1)) + { + merge_notes (i1, i2); + + beforelast1 = last1, beforelast2 = last2; + last1 = i1, last2 = i2; + ninsns++; + } + + if (i1 == BB_END (bb1) || i2 == BB_END (bb2) + || (stop_after > 0 && ninsns == stop_after)) + break; + + i1 = NEXT_INSN (i1); + i2 = NEXT_INSN (i2); + } + +#ifdef HAVE_cc0 + /* Don't allow a compare to be shared by cross-jumping unless the insn + after the compare is also shared. */ + if (ninsns && reg_mentioned_p (cc0_rtx, last1) && sets_cc0_p (last1)) + last1 = beforelast1, last2 = beforelast2, ninsns--; +#endif + + if (ninsns) + { + *f1 = last1; + *f2 = last2; + } + + return ninsns; +} + +/* Return true iff outgoing edges of BB1 and BB2 match, together with + the branch instruction. This means that if we commonize the control + flow before end of the basic block, the semantic remains unchanged. + + We may assume that there exists one edge with a common destination. */ + +static bool +outgoing_edges_match (int mode, basic_block bb1, basic_block bb2) +{ + int nehedges1 = 0, nehedges2 = 0; + edge fallthru1 = 0, fallthru2 = 0; + edge e1, e2; + edge_iterator ei; + + /* If BB1 has only one successor, we may be looking at either an + unconditional jump, or a fake edge to exit. */ + if (single_succ_p (bb1) + && (single_succ_edge (bb1)->flags & (EDGE_COMPLEX | EDGE_FAKE)) == 0 + && (!JUMP_P (BB_END (bb1)) || simplejump_p (BB_END (bb1)))) + return (single_succ_p (bb2) + && (single_succ_edge (bb2)->flags + & (EDGE_COMPLEX | EDGE_FAKE)) == 0 + && (!JUMP_P (BB_END (bb2)) || simplejump_p (BB_END (bb2)))); + + /* Match conditional jumps - this may get tricky when fallthru and branch + edges are crossed. */ + if (EDGE_COUNT (bb1->succs) == 2 + && any_condjump_p (BB_END (bb1)) + && onlyjump_p (BB_END (bb1))) + { + edge b1, f1, b2, f2; + bool reverse, match; + rtx set1, set2, cond1, cond2; + enum rtx_code code1, code2; + + if (EDGE_COUNT (bb2->succs) != 2 + || !any_condjump_p (BB_END (bb2)) + || !onlyjump_p (BB_END (bb2))) + return false; + + b1 = BRANCH_EDGE (bb1); + b2 = BRANCH_EDGE (bb2); + f1 = FALLTHRU_EDGE (bb1); + f2 = FALLTHRU_EDGE (bb2); + + /* Get around possible forwarders on fallthru edges. Other cases + should be optimized out already. */ + if (FORWARDER_BLOCK_P (f1->dest)) + f1 = single_succ_edge (f1->dest); + + if (FORWARDER_BLOCK_P (f2->dest)) + f2 = single_succ_edge (f2->dest); + + /* To simplify use of this function, return false if there are + unneeded forwarder blocks. These will get eliminated later + during cleanup_cfg. */ + if (FORWARDER_BLOCK_P (f1->dest) + || FORWARDER_BLOCK_P (f2->dest) + || FORWARDER_BLOCK_P (b1->dest) + || FORWARDER_BLOCK_P (b2->dest)) + return false; + + if (f1->dest == f2->dest && b1->dest == b2->dest) + reverse = false; + else if (f1->dest == b2->dest && b1->dest == f2->dest) + reverse = true; + else + return false; + + set1 = pc_set (BB_END (bb1)); + set2 = pc_set (BB_END (bb2)); + if ((XEXP (SET_SRC (set1), 1) == pc_rtx) + != (XEXP (SET_SRC (set2), 1) == pc_rtx)) + reverse = !reverse; + + cond1 = XEXP (SET_SRC (set1), 0); + cond2 = XEXP (SET_SRC (set2), 0); + code1 = GET_CODE (cond1); + if (reverse) + code2 = reversed_comparison_code (cond2, BB_END (bb2)); + else + code2 = GET_CODE (cond2); + + if (code2 == UNKNOWN) + return false; + + /* Verify codes and operands match. */ + match = ((code1 == code2 + && rtx_renumbered_equal_p (XEXP (cond1, 0), XEXP (cond2, 0)) + && rtx_renumbered_equal_p (XEXP (cond1, 1), XEXP (cond2, 1))) + || (code1 == swap_condition (code2) + && rtx_renumbered_equal_p (XEXP (cond1, 1), + XEXP (cond2, 0)) + && rtx_renumbered_equal_p (XEXP (cond1, 0), + XEXP (cond2, 1)))); + + /* If we return true, we will join the blocks. Which means that + we will only have one branch prediction bit to work with. Thus + we require the existing branches to have probabilities that are + roughly similar. */ + if (match + && optimize_bb_for_speed_p (bb1) + && optimize_bb_for_speed_p (bb2)) + { + int prob2; + + if (b1->dest == b2->dest) + prob2 = b2->probability; + else + /* Do not use f2 probability as f2 may be forwarded. */ + prob2 = REG_BR_PROB_BASE - b2->probability; + + /* Fail if the difference in probabilities is greater than 50%. + This rules out two well-predicted branches with opposite + outcomes. */ + if (abs (b1->probability - prob2) > REG_BR_PROB_BASE / 2) + { + if (dump_file) + fprintf (dump_file, + "Outcomes of branch in bb %i and %i differ too much (%i %i)\n", + bb1->index, bb2->index, b1->probability, prob2); + + return false; + } + } + + if (dump_file && match) + fprintf (dump_file, "Conditionals in bb %i and %i match.\n", + bb1->index, bb2->index); + + return match; + } + + /* Generic case - we are seeing a computed jump, table jump or trapping + instruction. */ + + /* Check whether there are tablejumps in the end of BB1 and BB2. + Return true if they are identical. */ + { + rtx label1, label2; + rtx table1, table2; + + if (tablejump_p (BB_END (bb1), &label1, &table1) + && tablejump_p (BB_END (bb2), &label2, &table2) + && GET_CODE (PATTERN (table1)) == GET_CODE (PATTERN (table2))) + { + /* The labels should never be the same rtx. If they really are same + the jump tables are same too. So disable crossjumping of blocks BB1 + and BB2 because when deleting the common insns in the end of BB1 + by delete_basic_block () the jump table would be deleted too. */ + /* If LABEL2 is referenced in BB1->END do not do anything + because we would loose information when replacing + LABEL1 by LABEL2 and then LABEL2 by LABEL1 in BB1->END. */ + if (label1 != label2 && !rtx_referenced_p (label2, BB_END (bb1))) + { + /* Set IDENTICAL to true when the tables are identical. */ + bool identical = false; + rtx p1, p2; + + p1 = PATTERN (table1); + p2 = PATTERN (table2); + if (GET_CODE (p1) == ADDR_VEC && rtx_equal_p (p1, p2)) + { + identical = true; + } + else if (GET_CODE (p1) == ADDR_DIFF_VEC + && (XVECLEN (p1, 1) == XVECLEN (p2, 1)) + && rtx_equal_p (XEXP (p1, 2), XEXP (p2, 2)) + && rtx_equal_p (XEXP (p1, 3), XEXP (p2, 3))) + { + int i; + + identical = true; + for (i = XVECLEN (p1, 1) - 1; i >= 0 && identical; i--) + if (!rtx_equal_p (XVECEXP (p1, 1, i), XVECEXP (p2, 1, i))) + identical = false; + } + + if (identical) + { + replace_label_data rr; + bool match; + + /* Temporarily replace references to LABEL1 with LABEL2 + in BB1->END so that we could compare the instructions. */ + rr.r1 = label1; + rr.r2 = label2; + rr.update_label_nuses = false; + for_each_rtx (&BB_END (bb1), replace_label, &rr); + + match = old_insns_match_p (mode, BB_END (bb1), BB_END (bb2)); + if (dump_file && match) + fprintf (dump_file, + "Tablejumps in bb %i and %i match.\n", + bb1->index, bb2->index); + + /* Set the original label in BB1->END because when deleting + a block whose end is a tablejump, the tablejump referenced + from the instruction is deleted too. */ + rr.r1 = label2; + rr.r2 = label1; + for_each_rtx (&BB_END (bb1), replace_label, &rr); + + return match; + } + } + return false; + } + } + + /* First ensure that the instructions match. There may be many outgoing + edges so this test is generally cheaper. */ + if (!old_insns_match_p (mode, BB_END (bb1), BB_END (bb2))) + return false; + + /* Search the outgoing edges, ensure that the counts do match, find possible + fallthru and exception handling edges since these needs more + validation. */ + if (EDGE_COUNT (bb1->succs) != EDGE_COUNT (bb2->succs)) + return false; + + FOR_EACH_EDGE (e1, ei, bb1->succs) + { + e2 = EDGE_SUCC (bb2, ei.index); + + if (e1->flags & EDGE_EH) + nehedges1++; + + if (e2->flags & EDGE_EH) + nehedges2++; + + if (e1->flags & EDGE_FALLTHRU) + fallthru1 = e1; + if (e2->flags & EDGE_FALLTHRU) + fallthru2 = e2; + } + + /* If number of edges of various types does not match, fail. */ + if (nehedges1 != nehedges2 + || (fallthru1 != 0) != (fallthru2 != 0)) + return false; + + /* fallthru edges must be forwarded to the same destination. */ + if (fallthru1) + { + basic_block d1 = (forwarder_block_p (fallthru1->dest) + ? single_succ (fallthru1->dest): fallthru1->dest); + basic_block d2 = (forwarder_block_p (fallthru2->dest) + ? single_succ (fallthru2->dest): fallthru2->dest); + + if (d1 != d2) + return false; + } + + /* Ensure the same EH region. */ + { + rtx n1 = find_reg_note (BB_END (bb1), REG_EH_REGION, 0); + rtx n2 = find_reg_note (BB_END (bb2), REG_EH_REGION, 0); + + if (!n1 && n2) + return false; + + if (n1 && (!n2 || XEXP (n1, 0) != XEXP (n2, 0))) + return false; + } + + /* The same checks as in try_crossjump_to_edge. It is required for RTL + version of sequence abstraction. */ + FOR_EACH_EDGE (e1, ei, bb2->succs) + { + edge e2; + edge_iterator ei; + basic_block d1 = e1->dest; + + if (FORWARDER_BLOCK_P (d1)) + d1 = EDGE_SUCC (d1, 0)->dest; + + FOR_EACH_EDGE (e2, ei, bb1->succs) + { + basic_block d2 = e2->dest; + if (FORWARDER_BLOCK_P (d2)) + d2 = EDGE_SUCC (d2, 0)->dest; + if (d1 == d2) + break; + } + + if (!e2) + return false; + } + + return true; +} + +/* Returns true if BB basic block has a preserve label. */ + +static bool +block_has_preserve_label (basic_block bb) +{ + return (bb + && block_label (bb) + && LABEL_PRESERVE_P (block_label (bb))); +} + +/* E1 and E2 are edges with the same destination block. Search their + predecessors for common code. If found, redirect control flow from + (maybe the middle of) E1->SRC to (maybe the middle of) E2->SRC. */ + +static bool +try_crossjump_to_edge (int mode, edge e1, edge e2) +{ + int nmatch; + basic_block src1 = e1->src, src2 = e2->src; + basic_block redirect_to, redirect_from, to_remove; + rtx newpos1, newpos2; + edge s; + edge_iterator ei; + + newpos1 = newpos2 = NULL_RTX; + + /* If we have partitioned hot/cold basic blocks, it is a bad idea + to try this optimization. + + Basic block partitioning may result in some jumps that appear to + be optimizable (or blocks that appear to be mergeable), but which really + must be left untouched (they are required to make it safely across + partition boundaries). See the comments at the top of + bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */ + + if (flag_reorder_blocks_and_partition && reload_completed) + return false; + + /* Search backward through forwarder blocks. We don't need to worry + about multiple entry or chained forwarders, as they will be optimized + away. We do this to look past the unconditional jump following a + conditional jump that is required due to the current CFG shape. */ + if (single_pred_p (src1) + && FORWARDER_BLOCK_P (src1)) + e1 = single_pred_edge (src1), src1 = e1->src; + + if (single_pred_p (src2) + && FORWARDER_BLOCK_P (src2)) + e2 = single_pred_edge (src2), src2 = e2->src; + + /* Nothing to do if we reach ENTRY, or a common source block. */ + if (src1 == ENTRY_BLOCK_PTR || src2 == ENTRY_BLOCK_PTR) + return false; + if (src1 == src2) + return false; + + /* Seeing more than 1 forwarder blocks would confuse us later... */ + if (FORWARDER_BLOCK_P (e1->dest) + && FORWARDER_BLOCK_P (single_succ (e1->dest))) + return false; + + if (FORWARDER_BLOCK_P (e2->dest) + && FORWARDER_BLOCK_P (single_succ (e2->dest))) + return false; + + /* Likewise with dead code (possibly newly created by the other optimizations + of cfg_cleanup). */ + if (EDGE_COUNT (src1->preds) == 0 || EDGE_COUNT (src2->preds) == 0) + return false; + + /* Look for the common insn sequence, part the first ... */ + if (!outgoing_edges_match (mode, src1, src2)) + return false; + + /* ... and part the second. */ + nmatch = flow_find_cross_jump (src1, src2, &newpos1, &newpos2); + + /* Don't proceed with the crossjump unless we found a sufficient number + of matching instructions or the 'from' block was totally matched + (such that its predecessors will hopefully be redirected and the + block removed). */ + if ((nmatch < PARAM_VALUE (PARAM_MIN_CROSSJUMP_INSNS)) + && (newpos1 != BB_HEAD (src1))) + return false; + + /* Avoid deleting preserve label when redirecting ABNORMAL edges. */ + if (block_has_preserve_label (e1->dest) + && (e1->flags & EDGE_ABNORMAL)) + return false; + + /* Here we know that the insns in the end of SRC1 which are common with SRC2 + will be deleted. + If we have tablejumps in the end of SRC1 and SRC2 + they have been already compared for equivalence in outgoing_edges_match () + so replace the references to TABLE1 by references to TABLE2. */ + { + rtx label1, label2; + rtx table1, table2; + + if (tablejump_p (BB_END (src1), &label1, &table1) + && tablejump_p (BB_END (src2), &label2, &table2) + && label1 != label2) + { + replace_label_data rr; + rtx insn; + + /* Replace references to LABEL1 with LABEL2. */ + rr.r1 = label1; + rr.r2 = label2; + rr.update_label_nuses = true; + for (insn = get_insns (); insn; insn = NEXT_INSN (insn)) + { + /* Do not replace the label in SRC1->END because when deleting + a block whose end is a tablejump, the tablejump referenced + from the instruction is deleted too. */ + if (insn != BB_END (src1)) + for_each_rtx (&insn, replace_label, &rr); + } + } + } + + /* Avoid splitting if possible. We must always split when SRC2 has + EH predecessor edges, or we may end up with basic blocks with both + normal and EH predecessor edges. */ + if (newpos2 == BB_HEAD (src2) + && !(EDGE_PRED (src2, 0)->flags & EDGE_EH)) + redirect_to = src2; + else + { + if (newpos2 == BB_HEAD (src2)) + { + /* Skip possible basic block header. */ + if (LABEL_P (newpos2)) + newpos2 = NEXT_INSN (newpos2); + while (DEBUG_INSN_P (newpos2)) + newpos2 = NEXT_INSN (newpos2); + if (NOTE_P (newpos2)) + newpos2 = NEXT_INSN (newpos2); + while (DEBUG_INSN_P (newpos2)) + newpos2 = NEXT_INSN (newpos2); + } + + if (dump_file) + fprintf (dump_file, "Splitting bb %i before %i insns\n", + src2->index, nmatch); + redirect_to = split_block (src2, PREV_INSN (newpos2))->dest; + } + + if (dump_file) + fprintf (dump_file, + "Cross jumping from bb %i to bb %i; %i common insns\n", + src1->index, src2->index, nmatch); + + /* We may have some registers visible through the block. */ + df_set_bb_dirty (redirect_to); + + /* Recompute the frequencies and counts of outgoing edges. */ + FOR_EACH_EDGE (s, ei, redirect_to->succs) + { + edge s2; + edge_iterator ei; + basic_block d = s->dest; + + if (FORWARDER_BLOCK_P (d)) + d = single_succ (d); + + FOR_EACH_EDGE (s2, ei, src1->succs) + { + basic_block d2 = s2->dest; + if (FORWARDER_BLOCK_P (d2)) + d2 = single_succ (d2); + if (d == d2) + break; + } + + s->count += s2->count; + + /* Take care to update possible forwarder blocks. We verified + that there is no more than one in the chain, so we can't run + into infinite loop. */ + if (FORWARDER_BLOCK_P (s->dest)) + { + single_succ_edge (s->dest)->count += s2->count; + s->dest->count += s2->count; + s->dest->frequency += EDGE_FREQUENCY (s); + } + + if (FORWARDER_BLOCK_P (s2->dest)) + { + single_succ_edge (s2->dest)->count -= s2->count; + if (single_succ_edge (s2->dest)->count < 0) + single_succ_edge (s2->dest)->count = 0; + s2->dest->count -= s2->count; + s2->dest->frequency -= EDGE_FREQUENCY (s); + if (s2->dest->frequency < 0) + s2->dest->frequency = 0; + if (s2->dest->count < 0) + s2->dest->count = 0; + } + + if (!redirect_to->frequency && !src1->frequency) + s->probability = (s->probability + s2->probability) / 2; + else + s->probability + = ((s->probability * redirect_to->frequency + + s2->probability * src1->frequency) + / (redirect_to->frequency + src1->frequency)); + } + + /* Adjust count and frequency for the block. An earlier jump + threading pass may have left the profile in an inconsistent + state (see update_bb_profile_for_threading) so we must be + prepared for overflows. */ + redirect_to->count += src1->count; + redirect_to->frequency += src1->frequency; + if (redirect_to->frequency > BB_FREQ_MAX) + redirect_to->frequency = BB_FREQ_MAX; + update_br_prob_note (redirect_to); + + /* Edit SRC1 to go to REDIRECT_TO at NEWPOS1. */ + + /* Skip possible basic block header. */ + if (LABEL_P (newpos1)) + newpos1 = NEXT_INSN (newpos1); + + while (DEBUG_INSN_P (newpos1)) + newpos1 = NEXT_INSN (newpos1); + + if (NOTE_INSN_BASIC_BLOCK_P (newpos1)) + newpos1 = NEXT_INSN (newpos1); + + while (DEBUG_INSN_P (newpos1)) + newpos1 = NEXT_INSN (newpos1); + + redirect_from = split_block (src1, PREV_INSN (newpos1))->src; + to_remove = single_succ (redirect_from); + + redirect_edge_and_branch_force (single_succ_edge (redirect_from), redirect_to); + delete_basic_block (to_remove); + + update_forwarder_flag (redirect_from); + if (redirect_to != src2) + update_forwarder_flag (src2); + + return true; +} + +/* Search the predecessors of BB for common insn sequences. When found, + share code between them by redirecting control flow. Return true if + any changes made. */ + +static bool +try_crossjump_bb (int mode, basic_block bb) +{ + edge e, e2, fallthru; + bool changed; + unsigned max, ix, ix2; + basic_block ev, ev2; + + /* Nothing to do if there is not at least two incoming edges. */ + if (EDGE_COUNT (bb->preds) < 2) + return false; + + /* Don't crossjump if this block ends in a computed jump, + unless we are optimizing for size. */ + if (optimize_bb_for_size_p (bb) + && bb != EXIT_BLOCK_PTR + && computed_jump_p (BB_END (bb))) + return false; + + /* If we are partitioning hot/cold basic blocks, we don't want to + mess up unconditional or indirect jumps that cross between hot + and cold sections. + + Basic block partitioning may result in some jumps that appear to + be optimizable (or blocks that appear to be mergeable), but which really + must be left untouched (they are required to make it safely across + partition boundaries). See the comments at the top of + bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */ + + if (BB_PARTITION (EDGE_PRED (bb, 0)->src) != + BB_PARTITION (EDGE_PRED (bb, 1)->src) + || (EDGE_PRED (bb, 0)->flags & EDGE_CROSSING)) + return false; + + /* It is always cheapest to redirect a block that ends in a branch to + a block that falls through into BB, as that adds no branches to the + program. We'll try that combination first. */ + fallthru = NULL; + max = PARAM_VALUE (PARAM_MAX_CROSSJUMP_EDGES); + + if (EDGE_COUNT (bb->preds) > max) + return false; + + fallthru = find_fallthru_edge (bb->preds); + + changed = false; + for (ix = 0, ev = bb; ix < EDGE_COUNT (ev->preds); ) + { + e = EDGE_PRED (ev, ix); + ix++; + + /* As noted above, first try with the fallthru predecessor (or, a + fallthru predecessor if we are in cfglayout mode). */ + if (fallthru) + { + /* Don't combine the fallthru edge into anything else. + If there is a match, we'll do it the other way around. */ + if (e == fallthru) + continue; + /* If nothing changed since the last attempt, there is nothing + we can do. */ + if (!first_pass + && !((e->src->flags & BB_MODIFIED) + || (fallthru->src->flags & BB_MODIFIED))) + continue; + + if (try_crossjump_to_edge (mode, e, fallthru)) + { + changed = true; + ix = 0; + ev = bb; + continue; + } + } + + /* Non-obvious work limiting check: Recognize that we're going + to call try_crossjump_bb on every basic block. So if we have + two blocks with lots of outgoing edges (a switch) and they + share lots of common destinations, then we would do the + cross-jump check once for each common destination. + + Now, if the blocks actually are cross-jump candidates, then + all of their destinations will be shared. Which means that + we only need check them for cross-jump candidacy once. We + can eliminate redundant checks of crossjump(A,B) by arbitrarily + choosing to do the check from the block for which the edge + in question is the first successor of A. */ + if (EDGE_SUCC (e->src, 0) != e) + continue; + + for (ix2 = 0, ev2 = bb; ix2 < EDGE_COUNT (ev2->preds); ) + { + e2 = EDGE_PRED (ev2, ix2); + ix2++; + + if (e2 == e) + continue; + + /* We've already checked the fallthru edge above. */ + if (e2 == fallthru) + continue; + + /* The "first successor" check above only prevents multiple + checks of crossjump(A,B). In order to prevent redundant + checks of crossjump(B,A), require that A be the block + with the lowest index. */ + if (e->src->index > e2->src->index) + continue; + + /* If nothing changed since the last attempt, there is nothing + we can do. */ + if (!first_pass + && !((e->src->flags & BB_MODIFIED) + || (e2->src->flags & BB_MODIFIED))) + continue; + + if (try_crossjump_to_edge (mode, e, e2)) + { + changed = true; + ev2 = bb; + ix = 0; + break; + } + } + } + + if (changed) + crossjumps_occured = true; + + return changed; +} + +/* Search the successors of BB for common insn sequences. When found, + share code between them by moving it across the basic block + boundary. Return true if any changes made. */ + +static bool +try_head_merge_bb (basic_block bb) +{ + basic_block final_dest_bb = NULL; + int max_match = INT_MAX; + edge e0; + rtx *headptr, *currptr, *nextptr; + bool changed, moveall; + unsigned ix; + rtx e0_last_head, cond, move_before; + unsigned nedges = EDGE_COUNT (bb->succs); + rtx jump = BB_END (bb); + regset live, live_union; + + /* Nothing to do if there is not at least two outgoing edges. */ + if (nedges < 2) + return false; + + /* Don't crossjump if this block ends in a computed jump, + unless we are optimizing for size. */ + if (optimize_bb_for_size_p (bb) + && bb != EXIT_BLOCK_PTR + && computed_jump_p (BB_END (bb))) + return false; + + cond = get_condition (jump, &move_before, true, false); + if (cond == NULL_RTX) + { +#ifdef HAVE_cc0 + if (reg_mentioned_p (cc0_rtx, jump)) + move_before = prev_nonnote_nondebug_insn (jump); + else +#endif + move_before = jump; + } + + for (ix = 0; ix < nedges; ix++) + if (EDGE_SUCC (bb, ix)->dest == EXIT_BLOCK_PTR) + return false; + + for (ix = 0; ix < nedges; ix++) + { + edge e = EDGE_SUCC (bb, ix); + basic_block other_bb = e->dest; + + if (df_get_bb_dirty (other_bb)) + { + block_was_dirty = true; + return false; + } + + if (e->flags & EDGE_ABNORMAL) + return false; + + /* Normally, all destination blocks must only be reachable from this + block, i.e. they must have one incoming edge. + + There is one special case we can handle, that of multiple consecutive + jumps where the first jumps to one of the targets of the second jump. + This happens frequently in switch statements for default labels. + The structure is as follows: + FINAL_DEST_BB + .... + if (cond) jump A; + fall through + BB + jump with targets A, B, C, D... + A + has two incoming edges, from FINAL_DEST_BB and BB + + In this case, we can try to move the insns through BB and into + FINAL_DEST_BB. */ + if (EDGE_COUNT (other_bb->preds) != 1) + { + edge incoming_edge, incoming_bb_other_edge; + edge_iterator ei; + + if (final_dest_bb != NULL + || EDGE_COUNT (other_bb->preds) != 2) + return false; + + /* We must be able to move the insns across the whole block. */ + move_before = BB_HEAD (bb); + while (!NONDEBUG_INSN_P (move_before)) + move_before = NEXT_INSN (move_before); + + if (EDGE_COUNT (bb->preds) != 1) + return false; + incoming_edge = EDGE_PRED (bb, 0); + final_dest_bb = incoming_edge->src; + if (EDGE_COUNT (final_dest_bb->succs) != 2) + return false; + FOR_EACH_EDGE (incoming_bb_other_edge, ei, final_dest_bb->succs) + if (incoming_bb_other_edge != incoming_edge) + break; + if (incoming_bb_other_edge->dest != other_bb) + return false; + } + } + + e0 = EDGE_SUCC (bb, 0); + e0_last_head = NULL_RTX; + changed = false; + + for (ix = 1; ix < nedges; ix++) + { + edge e = EDGE_SUCC (bb, ix); + rtx e0_last, e_last; + int nmatch; + + nmatch = flow_find_head_matching_sequence (e0->dest, e->dest, + &e0_last, &e_last, 0); + if (nmatch == 0) + return false; + + if (nmatch < max_match) + { + max_match = nmatch; + e0_last_head = e0_last; + } + } + + /* If we matched an entire block, we probably have to avoid moving the + last insn. */ + if (max_match > 0 + && e0_last_head == BB_END (e0->dest) + && (find_reg_note (e0_last_head, REG_EH_REGION, 0) + || control_flow_insn_p (e0_last_head))) + { + max_match--; + if (max_match == 0) + return false; + do + e0_last_head = prev_real_insn (e0_last_head); + while (DEBUG_INSN_P (e0_last_head)); + } + + if (max_match == 0) + return false; + + /* We must find a union of the live registers at each of the end points. */ + live = BITMAP_ALLOC (NULL); + live_union = BITMAP_ALLOC (NULL); + + currptr = XNEWVEC (rtx, nedges); + headptr = XNEWVEC (rtx, nedges); + nextptr = XNEWVEC (rtx, nedges); + + for (ix = 0; ix < nedges; ix++) + { + int j; + basic_block merge_bb = EDGE_SUCC (bb, ix)->dest; + rtx head = BB_HEAD (merge_bb); + + while (!NONDEBUG_INSN_P (head)) + head = NEXT_INSN (head); + headptr[ix] = head; + currptr[ix] = head; + + /* Compute the end point and live information */ + for (j = 1; j < max_match; j++) + do + head = NEXT_INSN (head); + while (!NONDEBUG_INSN_P (head)); + simulate_backwards_to_point (merge_bb, live, head); + IOR_REG_SET (live_union, live); + } + + /* If we're moving across two blocks, verify the validity of the + first move, then adjust the target and let the loop below deal + with the final move. */ + if (final_dest_bb != NULL) + { + rtx move_upto; + + moveall = can_move_insns_across (currptr[0], e0_last_head, move_before, + jump, e0->dest, live_union, + NULL, &move_upto); + if (!moveall) + { + if (move_upto == NULL_RTX) + goto out; + + while (e0_last_head != move_upto) + { + df_simulate_one_insn_backwards (e0->dest, e0_last_head, + live_union); + e0_last_head = PREV_INSN (e0_last_head); + } + } + if (e0_last_head == NULL_RTX) + goto out; + + jump = BB_END (final_dest_bb); + cond = get_condition (jump, &move_before, true, false); + if (cond == NULL_RTX) + { +#ifdef HAVE_cc0 + if (reg_mentioned_p (cc0_rtx, jump)) + move_before = prev_nonnote_nondebug_insn (jump); + else +#endif + move_before = jump; + } + } + + do + { + rtx move_upto; + moveall = can_move_insns_across (currptr[0], e0_last_head, + move_before, jump, e0->dest, live_union, + NULL, &move_upto); + if (!moveall && move_upto == NULL_RTX) + { + if (jump == move_before) + break; + + /* Try again, using a different insertion point. */ + move_before = jump; + +#ifdef HAVE_cc0 + /* Don't try moving before a cc0 user, as that may invalidate + the cc0. */ + if (reg_mentioned_p (cc0_rtx, jump)) + break; +#endif + + continue; + } + + if (final_dest_bb && !moveall) + /* We haven't checked whether a partial move would be OK for the first + move, so we have to fail this case. */ + break; + + changed = true; + for (;;) + { + if (currptr[0] == move_upto) + break; + for (ix = 0; ix < nedges; ix++) + { + rtx curr = currptr[ix]; + do + curr = NEXT_INSN (curr); + while (!NONDEBUG_INSN_P (curr)); + currptr[ix] = curr; + } + } + + /* If we can't currently move all of the identical insns, remember + each insn after the range that we'll merge. */ + if (!moveall) + for (ix = 0; ix < nedges; ix++) + { + rtx curr = currptr[ix]; + do + curr = NEXT_INSN (curr); + while (!NONDEBUG_INSN_P (curr)); + nextptr[ix] = curr; + } + + reorder_insns (headptr[0], currptr[0], PREV_INSN (move_before)); + df_set_bb_dirty (EDGE_SUCC (bb, 0)->dest); + if (final_dest_bb != NULL) + df_set_bb_dirty (final_dest_bb); + df_set_bb_dirty (bb); + for (ix = 1; ix < nedges; ix++) + { + df_set_bb_dirty (EDGE_SUCC (bb, ix)->dest); + delete_insn_chain (headptr[ix], currptr[ix], false); + } + if (!moveall) + { + if (jump == move_before) + break; + + /* For the unmerged insns, try a different insertion point. */ + move_before = jump; + +#ifdef HAVE_cc0 + /* Don't try moving before a cc0 user, as that may invalidate + the cc0. */ + if (reg_mentioned_p (cc0_rtx, jump)) + break; +#endif + + for (ix = 0; ix < nedges; ix++) + currptr[ix] = headptr[ix] = nextptr[ix]; + } + } + while (!moveall); + + out: + free (currptr); + free (headptr); + free (nextptr); + + crossjumps_occured |= changed; + + return changed; +} + +/* Return true if BB contains just bb note, or bb note followed + by only DEBUG_INSNs. */ + +static bool +trivially_empty_bb_p (basic_block bb) +{ + rtx insn = BB_END (bb); + + while (1) + { + if (insn == BB_HEAD (bb)) + return true; + if (!DEBUG_INSN_P (insn)) + return false; + insn = PREV_INSN (insn); + } +} + +/* Do simple CFG optimizations - basic block merging, simplifying of jump + instructions etc. Return nonzero if changes were made. */ + +static bool +try_optimize_cfg (int mode) +{ + bool changed_overall = false; + bool changed; + int iterations = 0; + basic_block bb, b, next; + + if (mode & (CLEANUP_CROSSJUMP | CLEANUP_THREADING)) + clear_bb_flags (); + + crossjumps_occured = false; + + FOR_EACH_BB (bb) + update_forwarder_flag (bb); + + if (! targetm.cannot_modify_jumps_p ()) + { + first_pass = true; + /* Attempt to merge blocks as made possible by edge removal. If + a block has only one successor, and the successor has only + one predecessor, they may be combined. */ + do + { + block_was_dirty = false; + changed = false; + iterations++; + + if (dump_file) + fprintf (dump_file, + "\n\ntry_optimize_cfg iteration %i\n\n", + iterations); + + for (b = ENTRY_BLOCK_PTR->next_bb; b != EXIT_BLOCK_PTR;) + { + basic_block c; + edge s; + bool changed_here = false; + + /* Delete trivially dead basic blocks. This is either + blocks with no predecessors, or empty blocks with no + successors. However if the empty block with no + successors is the successor of the ENTRY_BLOCK, it is + kept. This ensures that the ENTRY_BLOCK will have a + successor which is a precondition for many RTL + passes. Empty blocks may result from expanding + __builtin_unreachable (). */ + if (EDGE_COUNT (b->preds) == 0 + || (EDGE_COUNT (b->succs) == 0 + && trivially_empty_bb_p (b) + && single_succ_edge (ENTRY_BLOCK_PTR)->dest != b)) + { + c = b->prev_bb; + if (EDGE_COUNT (b->preds) > 0) + { + edge e; + edge_iterator ei; + + if (current_ir_type () == IR_RTL_CFGLAYOUT) + { + if (b->il.rtl->footer + && BARRIER_P (b->il.rtl->footer)) + FOR_EACH_EDGE (e, ei, b->preds) + if ((e->flags & EDGE_FALLTHRU) + && e->src->il.rtl->footer == NULL) + { + if (b->il.rtl->footer) + { + e->src->il.rtl->footer = b->il.rtl->footer; + b->il.rtl->footer = NULL; + } + else + { + start_sequence (); + e->src->il.rtl->footer = emit_barrier (); + end_sequence (); + } + } + } + else + { + rtx last = get_last_bb_insn (b); + if (last && BARRIER_P (last)) + FOR_EACH_EDGE (e, ei, b->preds) + if ((e->flags & EDGE_FALLTHRU)) + emit_barrier_after (BB_END (e->src)); + } + } + delete_basic_block (b); + changed = true; + /* Avoid trying to remove ENTRY_BLOCK_PTR. */ + b = (c == ENTRY_BLOCK_PTR ? c->next_bb : c); + continue; + } + + /* Remove code labels no longer used. */ + if (single_pred_p (b) + && (single_pred_edge (b)->flags & EDGE_FALLTHRU) + && !(single_pred_edge (b)->flags & EDGE_COMPLEX) + && LABEL_P (BB_HEAD (b)) + /* If the previous block ends with a branch to this + block, we can't delete the label. Normally this + is a condjump that is yet to be simplified, but + if CASE_DROPS_THRU, this can be a tablejump with + some element going to the same place as the + default (fallthru). */ + && (single_pred (b) == ENTRY_BLOCK_PTR + || !JUMP_P (BB_END (single_pred (b))) + || ! label_is_jump_target_p (BB_HEAD (b), + BB_END (single_pred (b))))) + { + rtx label = BB_HEAD (b); + + delete_insn_chain (label, label, false); + /* If the case label is undeletable, move it after the + BASIC_BLOCK note. */ + if (NOTE_KIND (BB_HEAD (b)) == NOTE_INSN_DELETED_LABEL) + { + rtx bb_note = NEXT_INSN (BB_HEAD (b)); + + reorder_insns_nobb (label, label, bb_note); + BB_HEAD (b) = bb_note; + if (BB_END (b) == bb_note) + BB_END (b) = label; + } + if (dump_file) + fprintf (dump_file, "Deleted label in block %i.\n", + b->index); + } + + /* If we fall through an empty block, we can remove it. */ + if (!(mode & CLEANUP_CFGLAYOUT) + && single_pred_p (b) + && (single_pred_edge (b)->flags & EDGE_FALLTHRU) + && !LABEL_P (BB_HEAD (b)) + && FORWARDER_BLOCK_P (b) + /* Note that forwarder_block_p true ensures that + there is a successor for this block. */ + && (single_succ_edge (b)->flags & EDGE_FALLTHRU) + && n_basic_blocks > NUM_FIXED_BLOCKS + 1) + { + if (dump_file) + fprintf (dump_file, + "Deleting fallthru block %i.\n", + b->index); + + c = b->prev_bb == ENTRY_BLOCK_PTR ? b->next_bb : b->prev_bb; + redirect_edge_succ_nodup (single_pred_edge (b), + single_succ (b)); + delete_basic_block (b); + changed = true; + b = c; + continue; + } + + /* Merge B with its single successor, if any. */ + if (single_succ_p (b) + && (s = single_succ_edge (b)) + && !(s->flags & EDGE_COMPLEX) + && (c = s->dest) != EXIT_BLOCK_PTR + && single_pred_p (c) + && b != c) + { + /* When not in cfg_layout mode use code aware of reordering + INSN. This code possibly creates new basic blocks so it + does not fit merge_blocks interface and is kept here in + hope that it will become useless once more of compiler + is transformed to use cfg_layout mode. */ + + if ((mode & CLEANUP_CFGLAYOUT) + && can_merge_blocks_p (b, c)) + { + merge_blocks (b, c); + update_forwarder_flag (b); + changed_here = true; + } + else if (!(mode & CLEANUP_CFGLAYOUT) + /* If the jump insn has side effects, + we can't kill the edge. */ + && (!JUMP_P (BB_END (b)) + || (reload_completed + ? simplejump_p (BB_END (b)) + : (onlyjump_p (BB_END (b)) + && !tablejump_p (BB_END (b), + NULL, NULL)))) + && (next = merge_blocks_move (s, b, c, mode))) + { + b = next; + changed_here = true; + } + } + + /* Simplify branch over branch. */ + if ((mode & CLEANUP_EXPENSIVE) + && !(mode & CLEANUP_CFGLAYOUT) + && try_simplify_condjump (b)) + changed_here = true; + + /* If B has a single outgoing edge, but uses a + non-trivial jump instruction without side-effects, we + can either delete the jump entirely, or replace it + with a simple unconditional jump. */ + if (single_succ_p (b) + && single_succ (b) != EXIT_BLOCK_PTR + && onlyjump_p (BB_END (b)) + && !find_reg_note (BB_END (b), REG_CROSSING_JUMP, NULL_RTX) + && try_redirect_by_replacing_jump (single_succ_edge (b), + single_succ (b), + (mode & CLEANUP_CFGLAYOUT) != 0)) + { + update_forwarder_flag (b); + changed_here = true; + } + + /* Simplify branch to branch. */ + if (try_forward_edges (mode, b)) + changed_here = true; + + /* Look for shared code between blocks. */ + if ((mode & CLEANUP_CROSSJUMP) + && try_crossjump_bb (mode, b)) + changed_here = true; + + if ((mode & CLEANUP_CROSSJUMP) + /* This can lengthen register lifetimes. Do it only after + reload. */ + && reload_completed + && try_head_merge_bb (b)) + changed_here = true; + + /* Don't get confused by the index shift caused by + deleting blocks. */ + if (!changed_here) + b = b->next_bb; + else + changed = true; + } + + if ((mode & CLEANUP_CROSSJUMP) + && try_crossjump_bb (mode, EXIT_BLOCK_PTR)) + changed = true; + + if (block_was_dirty) + { + /* This should only be set by head-merging. */ + gcc_assert (mode & CLEANUP_CROSSJUMP); + df_analyze (); + } + +#ifdef ENABLE_CHECKING + if (changed) + verify_flow_info (); +#endif + + changed_overall |= changed; + first_pass = false; + } + while (changed); + } + + FOR_ALL_BB (b) + b->flags &= ~(BB_FORWARDER_BLOCK | BB_NONTHREADABLE_BLOCK); + + return changed_overall; +} + +/* Delete all unreachable basic blocks. */ + +bool +delete_unreachable_blocks (void) +{ + bool changed = false; + basic_block b, prev_bb; + + find_unreachable_blocks (); + + /* When we're in GIMPLE mode and there may be debug insns, we should + delete blocks in reverse dominator order, so as to get a chance + to substitute all released DEFs into debug stmts. If we don't + have dominators information, walking blocks backward gets us a + better chance of retaining most debug information than + otherwise. */ + if (MAY_HAVE_DEBUG_STMTS && current_ir_type () == IR_GIMPLE + && dom_info_available_p (CDI_DOMINATORS)) + { + for (b = EXIT_BLOCK_PTR->prev_bb; b != ENTRY_BLOCK_PTR; b = prev_bb) + { + prev_bb = b->prev_bb; + + if (!(b->flags & BB_REACHABLE)) + { + /* Speed up the removal of blocks that don't dominate + others. Walking backwards, this should be the common + case. */ + if (!first_dom_son (CDI_DOMINATORS, b)) + delete_basic_block (b); + else + { + VEC (basic_block, heap) *h + = get_all_dominated_blocks (CDI_DOMINATORS, b); + + while (VEC_length (basic_block, h)) + { + b = VEC_pop (basic_block, h); + + prev_bb = b->prev_bb; + + gcc_assert (!(b->flags & BB_REACHABLE)); + + delete_basic_block (b); + } + + VEC_free (basic_block, heap, h); + } + + changed = true; + } + } + } + else + { + for (b = EXIT_BLOCK_PTR->prev_bb; b != ENTRY_BLOCK_PTR; b = prev_bb) + { + prev_bb = b->prev_bb; + + if (!(b->flags & BB_REACHABLE)) + { + delete_basic_block (b); + changed = true; + } + } + } + + if (changed) + tidy_fallthru_edges (); + return changed; +} + +/* Delete any jump tables never referenced. We can't delete them at the + time of removing tablejump insn as they are referenced by the preceding + insns computing the destination, so we delay deleting and garbagecollect + them once life information is computed. */ +void +delete_dead_jumptables (void) +{ + basic_block bb; + + /* A dead jump table does not belong to any basic block. Scan insns + between two adjacent basic blocks. */ + FOR_EACH_BB (bb) + { + rtx insn, next; + + for (insn = NEXT_INSN (BB_END (bb)); + insn && !NOTE_INSN_BASIC_BLOCK_P (insn); + insn = next) + { + next = NEXT_INSN (insn); + if (LABEL_P (insn) + && LABEL_NUSES (insn) == LABEL_PRESERVE_P (insn) + && JUMP_TABLE_DATA_P (next)) + { + rtx label = insn, jump = next; + + if (dump_file) + fprintf (dump_file, "Dead jumptable %i removed\n", + INSN_UID (insn)); + + next = NEXT_INSN (next); + delete_insn (jump); + delete_insn (label); + } + } + } +} + + +/* Tidy the CFG by deleting unreachable code and whatnot. */ + +bool +cleanup_cfg (int mode) +{ + bool changed = false; + + /* Set the cfglayout mode flag here. We could update all the callers + but that is just inconvenient, especially given that we eventually + want to have cfglayout mode as the default. */ + if (current_ir_type () == IR_RTL_CFGLAYOUT) + mode |= CLEANUP_CFGLAYOUT; + + timevar_push (TV_CLEANUP_CFG); + if (delete_unreachable_blocks ()) + { + changed = true; + /* We've possibly created trivially dead code. Cleanup it right + now to introduce more opportunities for try_optimize_cfg. */ + if (!(mode & (CLEANUP_NO_INSN_DEL)) + && !reload_completed) + delete_trivially_dead_insns (get_insns (), max_reg_num ()); + } + + compact_blocks (); + + /* To tail-merge blocks ending in the same noreturn function (e.g. + a call to abort) we have to insert fake edges to exit. Do this + here once. The fake edges do not interfere with any other CFG + cleanups. */ + if (mode & CLEANUP_CROSSJUMP) + add_noreturn_fake_exit_edges (); + + if (!dbg_cnt (cfg_cleanup)) + return changed; + + while (try_optimize_cfg (mode)) + { + delete_unreachable_blocks (), changed = true; + if (!(mode & CLEANUP_NO_INSN_DEL)) + { + /* Try to remove some trivially dead insns when doing an expensive + cleanup. But delete_trivially_dead_insns doesn't work after + reload (it only handles pseudos) and run_fast_dce is too costly + to run in every iteration. + + For effective cross jumping, we really want to run a fast DCE to + clean up any dead conditions, or they get in the way of performing + useful tail merges. + + Other transformations in cleanup_cfg are not so sensitive to dead + code, so delete_trivially_dead_insns or even doing nothing at all + is good enough. */ + if ((mode & CLEANUP_EXPENSIVE) && !reload_completed + && !delete_trivially_dead_insns (get_insns (), max_reg_num ())) + break; + if ((mode & CLEANUP_CROSSJUMP) && crossjumps_occured) + run_fast_dce (); + } + else + break; + } + + if (mode & CLEANUP_CROSSJUMP) + remove_fake_exit_edges (); + + /* Don't call delete_dead_jumptables in cfglayout mode, because + that function assumes that jump tables are in the insns stream. + But we also don't _have_ to delete dead jumptables in cfglayout + mode because we shouldn't even be looking at things that are + not in a basic block. Dead jumptables are cleaned up when + going out of cfglayout mode. */ + if (!(mode & CLEANUP_CFGLAYOUT)) + delete_dead_jumptables (); + + timevar_pop (TV_CLEANUP_CFG); + + return changed; +} + +static unsigned int +rest_of_handle_jump (void) +{ + if (crtl->tail_call_emit) + fixup_tail_calls (); + return 0; +} + +struct rtl_opt_pass pass_jump = +{ + { + RTL_PASS, + "sibling", /* name */ + NULL, /* gate */ + rest_of_handle_jump, /* execute */ + NULL, /* sub */ + NULL, /* next */ + 0, /* static_pass_number */ + TV_JUMP, /* tv_id */ + 0, /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + TODO_ggc_collect, /* todo_flags_start */ + TODO_verify_flow, /* todo_flags_finish */ + } +}; + + +static unsigned int +rest_of_handle_jump2 (void) +{ + delete_trivially_dead_insns (get_insns (), max_reg_num ()); + if (dump_file) + dump_flow_info (dump_file, dump_flags); + cleanup_cfg ((optimize ? CLEANUP_EXPENSIVE : 0) + | (flag_thread_jumps ? CLEANUP_THREADING : 0)); + return 0; +} + + +struct rtl_opt_pass pass_jump2 = +{ + { + RTL_PASS, + "jump", /* name */ + NULL, /* gate */ + rest_of_handle_jump2, /* execute */ + NULL, /* sub */ + NULL, /* next */ + 0, /* static_pass_number */ + TV_JUMP, /* tv_id */ + 0, /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + TODO_ggc_collect, /* todo_flags_start */ + TODO_dump_func | TODO_verify_rtl_sharing,/* todo_flags_finish */ + } +}; + + |