diff options
author | obrien <obrien@FreeBSD.org> | 2002-02-01 18:16:02 +0000 |
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committer | obrien <obrien@FreeBSD.org> | 2002-02-01 18:16:02 +0000 |
commit | c9ab9ae440a8066b2c2b85b157b1fdadcf09916a (patch) | |
tree | 086d9d6c8fbd4fc8fe4495059332f66bc0f8d12b /contrib/gcc/cfgcleanup.c | |
parent | 2ecfd8bd04b63f335c1ec6295740a4bfd97a4fa6 (diff) | |
download | FreeBSD-src-c9ab9ae440a8066b2c2b85b157b1fdadcf09916a.zip FreeBSD-src-c9ab9ae440a8066b2c2b85b157b1fdadcf09916a.tar.gz |
Enlist the FreeBSD-CURRENT users as testers of what is to become Gcc 3.1.0.
These bits are taken from the FSF anoncvs repo on 1-Feb-2002 08:20 PST.
Diffstat (limited to 'contrib/gcc/cfgcleanup.c')
-rw-r--r-- | contrib/gcc/cfgcleanup.c | 1753 |
1 files changed, 1753 insertions, 0 deletions
diff --git a/contrib/gcc/cfgcleanup.c b/contrib/gcc/cfgcleanup.c new file mode 100644 index 0000000..13c5a8e --- /dev/null +++ b/contrib/gcc/cfgcleanup.c @@ -0,0 +1,1753 @@ +/* Control flow optimization code for GNU compiler. + Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, + 1999, 2000, 2001 Free Software Foundation, Inc. + +This file is part of GCC. + +GCC is free software; you can redistribute it and/or modify it under +the terms of the GNU General Public License as published by the Free +Software Foundation; either version 2, or (at your option) any later +version. + +GCC is distributed in the hope that it will be useful, but WITHOUT ANY +WARRANTY; without even the implied warranty of MERCHANTABILITY or +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +for more details. + +You should have received a copy of the GNU General Public License +along with GCC; see the file COPYING. If not, write to the Free +Software Foundation, 59 Temple Place - Suite 330, Boston, MA +02111-1307, USA. */ + +/* This file contains optimizer of the control flow. The main entrypoint is + cleanup_cfg. Following optimizations are performed: + + - Unreachable blocks removal + - Edge forwarding (edge to the forwarder block is forwarded to it's + 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 "rtl.h" +#include "hard-reg-set.h" +#include "basic-block.h" +#include "timevar.h" +#include "output.h" +#include "insn-config.h" +#include "flags.h" +#include "recog.h" +#include "toplev.h" +#include "cselib.h" +#include "tm_p.h" + +#include "obstack.h" + +/* cleanup_cfg maintains following flags for each basic block. */ + +enum bb_flags +{ + /* Set if life info needs to be recomputed for given BB. */ + BB_UPDATE_LIFE = 1, + /* Set if BB is the forwarder block to avoid too many + forwarder_block_p calls. */ + BB_FORWARDER_BLOCK = 2 +}; + +#define BB_FLAGS(BB) (enum bb_flags) (BB)->aux +#define BB_SET_FLAG(BB, FLAG) \ + (BB)->aux = (void *) (long) ((enum bb_flags) (BB)->aux | (FLAG)) +#define BB_CLEAR_FLAG(BB, FLAG) \ + (BB)->aux = (void *) (long) ((enum bb_flags) (BB)->aux & ~(FLAG)) + +#define FORWARDER_BLOCK_P(BB) (BB_FLAGS (BB) & BB_FORWARDER_BLOCK) + +static bool try_crossjump_to_edge PARAMS ((int, edge, edge)); +static bool try_crossjump_bb PARAMS ((int, basic_block)); +static bool outgoing_edges_match PARAMS ((int, + basic_block, basic_block)); +static int flow_find_cross_jump PARAMS ((int, basic_block, basic_block, + rtx *, rtx *)); +static bool insns_match_p PARAMS ((int, rtx, rtx)); + +static bool delete_unreachable_blocks PARAMS ((void)); +static bool label_is_jump_target_p PARAMS ((rtx, rtx)); +static bool tail_recursion_label_p PARAMS ((rtx)); +static void merge_blocks_move_predecessor_nojumps PARAMS ((basic_block, + basic_block)); +static void merge_blocks_move_successor_nojumps PARAMS ((basic_block, + basic_block)); +static bool merge_blocks PARAMS ((edge,basic_block,basic_block, + int)); +static bool try_optimize_cfg PARAMS ((int)); +static bool try_simplify_condjump PARAMS ((basic_block)); +static bool try_forward_edges PARAMS ((int, basic_block)); +static edge thread_jump PARAMS ((int, edge, basic_block)); +static bool mark_effect PARAMS ((rtx, bitmap)); +static void notice_new_block PARAMS ((basic_block)); +static void update_forwarder_flag PARAMS ((basic_block)); + +/* Set flags for newly created block. */ + +static void +notice_new_block (bb) + basic_block bb; +{ + if (!bb) + return; + + BB_SET_FLAG (bb, BB_UPDATE_LIFE); + if (forwarder_block_p (bb)) + BB_SET_FLAG (bb, BB_FORWARDER_BLOCK); +} + +/* Recompute forwarder flag after block has been modified. */ + +static void +update_forwarder_flag (bb) + basic_block bb; +{ + if (forwarder_block_p (bb)) + BB_SET_FLAG (bb, BB_FORWARDER_BLOCK); + else + BB_CLEAR_FLAG (bb, BB_FORWARDER_BLOCK); +} + +/* Simplify a conditional jump around an unconditional jump. + Return true if something changed. */ + +static bool +try_simplify_condjump (cbranch_block) + 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 (!cbranch_block->succ + || !cbranch_block->succ->succ_next + || cbranch_block->succ->succ_next->succ_next) + return false; + + /* Verify that we've got a normal conditional branch at the end + of the block. */ + cbranch_insn = cbranch_block->end; + 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 (jump_block->pred->pred_next + || jump_block->index == n_basic_blocks - 1 + || !FORWARDER_BLOCK_P (jump_block)) + return false; + jump_dest_block = jump_block->succ->dest; + + /* The conditional branch must target the block after the + unconditional branch. */ + cbranch_dest_block = cbranch_jump_edge->dest; + + if (!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 (rtl_dump_file) + fprintf (rtl_dump_file, "Simplifying condjump %i around jump %i\n", + INSN_UID (cbranch_insn), INSN_UID (jump_block->end)); + + /* 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. */ + flow_delete_block (jump_block); + tidy_fallthru_edge (cbranch_jump_edge, cbranch_block, cbranch_dest_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 (exp, nonequal) + 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; + } +} +/* Attempt to prove that the basic block B will have no side effects and + allways continues in the same edge if reached via E. Return the edge + if exist, NULL otherwise. */ + +static edge +thread_jump (mode, e, b) + int mode; + edge e; + basic_block b; +{ + rtx set1, set2, cond1, cond2, insn; + enum rtx_code code1, code2, reversed_code2; + bool reverse1 = false; + int i; + regset nonequal; + bool failed = false; + + /* At the moment, we do handle only conditional jumps, but later we may + want to extend this code to tablejumps and others. */ + if (!e->src->succ->succ_next || e->src->succ->succ_next->succ_next) + return NULL; + if (!b->succ || !b->succ->succ_next || b->succ->succ_next->succ_next) + return NULL; + + /* Second branch must end with onlyjump, as we will eliminate the jump. */ + if (!any_condjump_p (e->src->end) || !any_condjump_p (b->end) + || !onlyjump_p (b->end)) + return NULL; + + set1 = pc_set (e->src->end); + set2 = pc_set (b->end); + 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, e->src->end); + else + code1 = GET_CODE (cond1); + + code2 = GET_CODE (cond2); + reversed_code2 = reversed_comparison_code (cond2, b->end); + + 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 pesimistic. 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 (b->head); insn != NEXT_INSN (b->end); + insn = NEXT_INSN (insn)) + if (INSN_P (insn) && side_effects_p (PATTERN (insn))) + return NULL; + + cselib_init (); + + /* First process all values computed in the source basic block. */ + for (insn = NEXT_INSN (e->src->head); insn != NEXT_INSN (e->src->end); + insn = NEXT_INSN (insn)) + if (INSN_P (insn)) + cselib_process_insn (insn); + + nonequal = BITMAP_XMALLOC(); + 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 (b->head); insn != NEXT_INSN (b->end) && !failed; + insn = NEXT_INSN (insn)) + { + if (INSN_P (insn)) + { + rtx pat = PATTERN (insn); + + if (GET_CODE (pat) == PARALLEL) + { + for (i = 0; i < 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) + goto failed_exit; + + /* In case liveness information is available, we need to prove equivalence + only of the live values. */ + if (mode & CLEANUP_UPDATE_LIFE) + AND_REG_SET (nonequal, b->global_live_at_end); + + EXECUTE_IF_SET_IN_REG_SET (nonequal, 0, i, goto failed_exit;); + + BITMAP_XFREE (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_XFREE (nonequal); + cselib_finish (); + return NULL; +} + +/* Attempt to forward edges leaving basic block B. + Return true if successful. */ + +static bool +try_forward_edges (mode, b) + basic_block b; + int mode; +{ + bool changed = false; + edge e, next, *threaded_edges = NULL; + + for (e = b->succ; e; e = next) + { + basic_block target, first; + int counter; + bool threaded = false; + int nthreaded_edges = 0; + + next = e->succ_next; + + /* 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) + continue; + + target = first = e->dest; + counter = 0; + + while (counter < n_basic_blocks) + { + basic_block new_target = NULL; + bool new_target_threaded = false; + + if (FORWARDER_BLOCK_P (target) + && target->succ->dest != EXIT_BLOCK_PTR) + { + /* Bypass trivial infinite loops. */ + if (target == target->succ->dest) + counter = n_basic_blocks; + new_target = target->succ->dest; + } + + /* Allow to thread only over one edge at time to simplify updating + of probabilities. */ + else if (mode & CLEANUP_THREADING) + { + edge t = thread_jump (mode, e, target); + if (t) + { + if (!threaded_edges) + threaded_edges = xmalloc (sizeof (*threaded_edges) + * 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; + + if (nthreaded_edges >= n_basic_blocks) + abort (); + threaded_edges[nthreaded_edges++] = t; + + new_target = t->dest; + new_target_threaded = true; + } + } + + if (!new_target) + break; + + /* Avoid killing of loop pre-headers, as it is the place loop + optimizer wants to hoist code to. + + For fallthru forwarders, the LOOP_BEG note must appear between + the header of block and CODE_LABEL of the loop, for non forwarders + it must appear before the JUMP_INSN. */ + if (mode & CLEANUP_PRE_LOOP) + { + rtx insn = (target->succ->flags & EDGE_FALLTHRU + ? target->head : prev_nonnote_insn (target->end)); + + if (GET_CODE (insn) != NOTE) + insn = NEXT_INSN (insn); + + for (; insn && GET_CODE (insn) != CODE_LABEL && !INSN_P (insn); + insn = NEXT_INSN (insn)) + if (GET_CODE (insn) == NOTE + && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG) + break; + + if (GET_CODE (insn) == NOTE) + break; + } + + counter++; + target = new_target; + threaded |= new_target_threaded; + } + + if (counter >= n_basic_blocks) + { + if (rtl_dump_file) + fprintf (rtl_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; + + /* 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 (rtl_dump_file) + fprintf (rtl_dump_file, "Conditionals threaded.\n"); + } + else if (!redirect_edge_and_branch (e, target)) + { + if (rtl_dump_file) + fprintf (rtl_dump_file, + "Forwarding edge %i->%i to %i failed.\n", + b->index, e->dest->index, target->index); + 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)) + BB_SET_FLAG (b, BB_FORWARDER_BLOCK); + BB_SET_FLAG (b, BB_UPDATE_LIFE); + + do + { + edge t; + + first->count -= edge_count; + if (first->count < 0) + first->count = 0; + first->frequency -= edge_frequency; + if (first->frequency < 0) + first->frequency = 0; + if (first->succ->succ_next) + { + edge e; + int prob; + if (n >= nthreaded_edges) + abort (); + t = threaded_edges [n++]; + if (t->src != first) + abort (); + if (first->frequency) + prob = edge_frequency * REG_BR_PROB_BASE / first->frequency; + else + prob = 0; + if (prob > t->probability) + prob = t->probability; + t->probability -= prob; + prob = REG_BR_PROB_BASE - prob; + if (prob <= 0) + { + first->succ->probability = REG_BR_PROB_BASE; + first->succ->succ_next->probability = 0; + } + else + for (e = first->succ; e; e = e->succ_next) + e->probability = ((e->probability * REG_BR_PROB_BASE) + / (double) prob); + update_br_prob_note (first); + } + else + { + /* 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 = first->succ; + } + + t->count -= edge_count; + if (t->count < 0) + t->count = 0; + first = t->dest; + } + while (first != target); + + changed = true; + } + } + + if (threaded_edges) + free (threaded_edges); + return changed; +} + +/* Return true if LABEL is a target of JUMP_INSN. This applies only + to non-complex jumps. That is, direct unconditional, conditional, + and tablejumps, but not computed jumps or returns. It also does + not apply to the fallthru case of a conditional jump. */ + +static bool +label_is_jump_target_p (label, jump_insn) + rtx label, jump_insn; +{ + rtx tmp = JUMP_LABEL (jump_insn); + + if (label == tmp) + return true; + + if (tmp != NULL_RTX + && (tmp = NEXT_INSN (tmp)) != NULL_RTX + && GET_CODE (tmp) == JUMP_INSN + && (tmp = PATTERN (tmp), + GET_CODE (tmp) == ADDR_VEC + || GET_CODE (tmp) == ADDR_DIFF_VEC)) + { + rtvec vec = XVEC (tmp, GET_CODE (tmp) == ADDR_DIFF_VEC); + int i, veclen = GET_NUM_ELEM (vec); + + for (i = 0; i < veclen; ++i) + if (XEXP (RTVEC_ELT (vec, i), 0) == label) + return true; + } + + return false; +} + +/* Return true if LABEL is used for tail recursion. */ + +static bool +tail_recursion_label_p (label) + rtx label; +{ + rtx x; + + for (x = tail_recursion_label_list; x; x = XEXP (x, 1)) + if (label == XEXP (x, 0)) + return true; + + return false; +} + +/* 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 (a, b) + basic_block a, b; +{ + rtx barrier; + int index; + + barrier = next_nonnote_insn (a->end); + if (GET_CODE (barrier) != BARRIER) + abort (); + delete_insn (barrier); + + /* Move block and loop notes out of the chain so that we do not + disturb their order. + + ??? A better solution would be to squeeze out all the non-nested notes + and adjust the block trees appropriately. Even better would be to have + a tighter connection between block trees and rtl so that this is not + necessary. */ + if (squeeze_notes (&a->head, &a->end)) + abort (); + + /* Scramble the insn chain. */ + if (a->end != PREV_INSN (b->head)) + reorder_insns_nobb (a->head, a->end, PREV_INSN (b->head)); + BB_SET_FLAG (a, BB_UPDATE_LIFE); + + if (rtl_dump_file) + fprintf (rtl_dump_file, "Moved block %d before %d and merged.\n", + a->index, b->index); + + /* Swap the records for the two blocks around. Although we are deleting B, + A is now where B was and we want to compact the BB array from where + A used to be. */ + BASIC_BLOCK (a->index) = b; + BASIC_BLOCK (b->index) = a; + index = a->index; + a->index = b->index; + b->index = index; + + /* Now blocks A and B are contiguous. Merge them. */ + merge_blocks_nomove (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 (a, b) + basic_block a, b; +{ + rtx barrier, real_b_end; + + real_b_end = b->end; + barrier = NEXT_INSN (b->end); + + /* Recognize a jump table following block B. */ + if (barrier + && GET_CODE (barrier) == CODE_LABEL + && NEXT_INSN (barrier) + && GET_CODE (NEXT_INSN (barrier)) == JUMP_INSN + && (GET_CODE (PATTERN (NEXT_INSN (barrier))) == ADDR_VEC + || GET_CODE (PATTERN (NEXT_INSN (barrier))) == ADDR_DIFF_VEC)) + { + /* Temporarily add the table jump insn to b, so that it will also + be moved to the correct location. */ + b->end = NEXT_INSN (barrier); + barrier = NEXT_INSN (b->end); + } + + /* There had better have been a barrier there. Delete it. */ + if (barrier && GET_CODE (barrier) == BARRIER) + delete_insn (barrier); + + /* Move block and loop notes out of the chain so that we do not + disturb their order. + + ??? A better solution would be to squeeze out all the non-nested notes + and adjust the block trees appropriately. Even better would be to have + a tighter connection between block trees and rtl so that this is not + necessary. */ + if (squeeze_notes (&b->head, &b->end)) + abort (); + + /* Scramble the insn chain. */ + reorder_insns_nobb (b->head, b->end, a->end); + + /* Restore the real end of b. */ + b->end = real_b_end; + + /* Now blocks A and B are contiguous. Merge them. */ + merge_blocks_nomove (a, b); + BB_SET_FLAG (a, BB_UPDATE_LIFE); + + if (rtl_dump_file) + fprintf (rtl_dump_file, "Moved block %d after %d and merged.\n", + b->index, a->index); +} + +/* Attempt to merge basic blocks that are potentially non-adjacent. + Return true iff the attempt succeeded. */ + +static bool +merge_blocks (e, b, c, mode) + edge e; + basic_block b, c; + int mode; +{ + /* If C has a tail recursion label, do not merge. There is no + edge recorded from the call_placeholder back to this label, as + that would make optimize_sibling_and_tail_recursive_calls more + complex for no gain. */ + if ((mode & CLEANUP_PRE_SIBCALL) + && GET_CODE (c->head) == CODE_LABEL + && tail_recursion_label_p (c->head)) + return false; + + /* 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; + /* We need to update liveness in case C already has broken liveness + or B ends by conditional jump to next instructions that will be + removed. */ + if ((BB_FLAGS (c) & BB_UPDATE_LIFE) + || GET_CODE (b->end) == JUMP_INSN) + BB_SET_FLAG (b, BB_UPDATE_LIFE); + merge_blocks_nomove (b, c); + update_forwarder_flag (b); + + if (rtl_dump_file) + fprintf (rtl_dump_file, "Merged %d and %d without moving.\n", + b_index, c_index); + + return true; + } + + /* 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 false; + + /* 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. */ + + for (tmp_edge = c->succ; tmp_edge; tmp_edge = tmp_edge->succ_next) + if (tmp_edge->flags & EDGE_FALLTHRU) + break; + + c_has_outgoing_fallthru = (tmp_edge != NULL); + + for (tmp_edge = b->pred; tmp_edge; tmp_edge = tmp_edge->pred_next) + if (tmp_edge->flags & EDGE_FALLTHRU) + break; + + b_has_incoming_fallthru = (tmp_edge != NULL); + b_fallthru_edge = tmp_edge; + + /* 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 true; + } + + /* 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 false; + bb = force_nonfallthru (b_fallthru_edge); + if (bb) + notice_new_block (bb); + else + BB_SET_FLAG (b_fallthru_edge->src, BB_UPDATE_LIFE); + } + + merge_blocks_move_predecessor_nojumps (b, c); + return true; + } + + return false; +} + + +/* Return true if I1 and I2 are equivalent and thus can be crossjumped. */ + +static bool +insns_match_p (mode, i1, i2) + int mode ATTRIBUTE_UNUSED; + rtx i1, i2; +{ + rtx p1, p2; + + /* Verify that I1 and I2 are equivalent. */ + if (GET_CODE (i1) != GET_CODE (i2)) + return false; + + 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. */ + + if (GET_CODE (i1) == CALL_INSN + && !rtx_equal_p (CALL_INSN_FUNCTION_USAGE (i1), + CALL_INSN_FUNCTION_USAGE (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))); + + GO_IF_HARD_REG_EQUAL (i1_regset, i2_regset, done); + + return false; + + done: + ; + } +#endif + + if (reload_completed + ? ! rtx_renumbered_equal_p (p1, p2) : ! rtx_equal_p (p1, p2)) + { + /* The following code helps take care of G++ cleanups. */ + rtx equiv1 = find_reg_equal_equiv_note (i1); + rtx equiv2 = find_reg_equal_equiv_note (i2); + + if (equiv1 && equiv2 + /* If the equivalences are not to a constant, they may + reference pseudos that no longer exist, so we can't + use them. */ + && (! reload_completed + || (CONSTANT_P (XEXP (equiv1, 0)) + && rtx_equal_p (XEXP (equiv1, 0), XEXP (equiv2, 0))))) + { + rtx s1 = single_set (i1); + rtx s2 = single_set (i2); + if (s1 != 0 && s2 != 0 + && rtx_renumbered_equal_p (SET_DEST (s1), SET_DEST (s2))) + { + validate_change (i1, &SET_SRC (s1), XEXP (equiv1, 0), 1); + validate_change (i2, &SET_SRC (s2), XEXP (equiv2, 0), 1); + if (! rtx_renumbered_equal_p (p1, p2)) + cancel_changes (0); + else if (apply_change_group ()) + return true; + } + } + + return false; + } + + return true; +} + +/* 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. */ + +static int +flow_find_cross_jump (mode, bb1, bb2, f1, f2) + int mode ATTRIBUTE_UNUSED; + basic_block bb1, bb2; + rtx *f1, *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 = bb1->end; + 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 = bb2->end; + 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 (!active_insn_p (i1) && i1 != bb1->head) + i1 = PREV_INSN (i1); + + while (!active_insn_p (i2) && i2 != bb2->head) + i2 = PREV_INSN (i2); + + if (i1 == bb1->head || i2 == bb2->head) + break; + + if (!insns_match_p (mode, i1, i2)) + break; + + /* Don't begin a cross-jump with a USE or CLOBBER insn. */ + if (active_insn_p (i1)) + { + /* 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); + } + + 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 != bb1->head && !active_insn_p (PREV_INSN (last1))) + last1 = PREV_INSN (last1); + + if (last1 != bb1->head && GET_CODE (PREV_INSN (last1)) == CODE_LABEL) + last1 = PREV_INSN (last1); + + while (last2 != bb2->head && !active_insn_p (PREV_INSN (last2))) + last2 = PREV_INSN (last2); + + if (last2 != bb2->head && GET_CODE (PREV_INSN (last2)) == CODE_LABEL) + last2 = PREV_INSN (last2); + + *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 (mode, bb1, bb2) + int mode; + basic_block bb1; + basic_block bb2; +{ + int nehedges1 = 0, nehedges2 = 0; + edge fallthru1 = 0, fallthru2 = 0; + edge e1, e2; + + /* If BB1 has only one successor, we may be looking at either an + unconditional jump, or a fake edge to exit. */ + if (bb1->succ && !bb1->succ->succ_next + && !(bb1->succ->flags & (EDGE_COMPLEX | EDGE_FAKE))) + return (bb2->succ && !bb2->succ->succ_next + && (bb2->succ->flags & (EDGE_COMPLEX | EDGE_FAKE)) == 0); + + /* Match conditional jumps - this may get tricky when fallthru and branch + edges are crossed. */ + if (bb1->succ + && bb1->succ->succ_next + && !bb1->succ->succ_next->succ_next + && any_condjump_p (bb1->end) + && onlyjump_p (bb1->end)) + { + edge b1, f1, b2, f2; + bool reverse, match; + rtx set1, set2, cond1, cond2; + enum rtx_code code1, code2; + + if (!bb2->succ + || !bb2->succ->succ_next + || bb1->succ->succ_next->succ_next + || !any_condjump_p (bb2->end) + || !onlyjump_p (bb1->end)) + 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 = f1->dest->succ; + + if (FORWARDER_BLOCK_P (f2->dest)) + f2 = f2->dest->succ; + + /* 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 (bb1->end); + set2 = pc_set (bb2->end); + 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, bb2->end); + 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_size + && bb1->frequency > BB_FREQ_MAX / 1000 + && bb2->frequency > BB_FREQ_MAX / 1000) + { + 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 5%. */ + if (abs (b1->probability - prob2) > REG_BR_PROB_BASE / 20) + { + if (rtl_dump_file) + fprintf (rtl_dump_file, + "Outcomes of branch in bb %i and %i differs to much (%i %i)\n", + bb1->index, bb2->index, b1->probability, prob2); + + return false; + } + } + + if (rtl_dump_file && match) + fprintf (rtl_dump_file, "Conditionals in bb %i and %i match.\n", + bb1->index, bb2->index); + + return match; + } + + /* Generic case - we are seeing an computed jump, table jump or trapping + instruction. */ + + /* First ensure that the instructions match. There may be many outgoing + edges so this test is generally cheaper. + ??? Currently the tablejumps will never match, as they do have + different tables. */ + if (!insns_match_p (mode, bb1->end, bb2->end)) + return false; + + /* Search the outgoing edges, ensure that the counts do match, find possible + fallthru and exception handling edges since these needs more + validation. */ + for (e1 = bb1->succ, e2 = bb2->succ; e1 && e2; + e1 = e1->succ_next, e2 = e2->succ_next) + { + 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 (e1 || e2 + || 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) + ? fallthru1->dest->succ->dest: fallthru1->dest); + basic_block d2 = (forwarder_block_p (fallthru2->dest) + ? fallthru2->dest->succ->dest: fallthru2->dest); + + if (d1 != d2) + return false; + } + + /* In case we do have EH edges, ensure we are in the same region. */ + if (nehedges1) + { + rtx n1 = find_reg_note (bb1->end, REG_EH_REGION, 0); + rtx n2 = find_reg_note (bb2->end, REG_EH_REGION, 0); + + if (XEXP (n1, 0) != XEXP (n2, 0)) + return false; + } + + /* We don't need to match the rest of edges as above checks should be enought + to ensure that they are equivalent. */ + return true; +} + +/* 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 (mode, e1, e2) + int mode; + edge e1, e2; +{ + int nmatch; + basic_block src1 = e1->src, src2 = e2->src; + basic_block redirect_to; + rtx newpos1, newpos2; + edge s; + rtx last; + rtx label; + + /* 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 (src1->pred + && !src1->pred->pred_next + && FORWARDER_BLOCK_P (src1)) + e1 = src1->pred, src1 = e1->src; + + if (src2->pred + && !src2->pred->pred_next + && FORWARDER_BLOCK_P (src2)) + e2 = src2->pred, 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 (e1->dest->succ->dest)) + return false; + + if (FORWARDER_BLOCK_P (e2->dest) + && FORWARDER_BLOCK_P (e2->dest->succ->dest)) + return false; + + /* Likewise with dead code (possibly newly created by the other optimizations + of cfg_cleanup). */ + if (!src1->pred || !src2->pred) + 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 (mode, src1, src2, &newpos1, &newpos2); + if (!nmatch) + return false; + + /* Avoid splitting if possible. */ + if (newpos2 == src2->head) + redirect_to = src2; + else + { + if (rtl_dump_file) + fprintf (rtl_dump_file, "Splitting bb %i before %i insns\n", + src2->index, nmatch); + redirect_to = split_block (src2, PREV_INSN (newpos2))->dest; + } + + if (rtl_dump_file) + fprintf (rtl_dump_file, + "Cross jumping from bb %i to bb %i; %i common insns\n", + src1->index, src2->index, nmatch); + + redirect_to->count += src1->count; + redirect_to->frequency += src1->frequency; + + /* Recompute the frequencies and counts of outgoing edges. */ + for (s = redirect_to->succ; s; s = s->succ_next) + { + edge s2; + basic_block d = s->dest; + + if (FORWARDER_BLOCK_P (d)) + d = d->succ->dest; + + for (s2 = src1->succ; ; s2 = s2->succ_next) + { + basic_block d2 = s2->dest; + if (FORWARDER_BLOCK_P (d2)) + d2 = d2->succ->dest; + 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)) + { + s->dest->succ->count += s2->count; + s->dest->count += s2->count; + s->dest->frequency += EDGE_FREQUENCY (s); + } + + if (FORWARDER_BLOCK_P (s2->dest)) + { + s2->dest->succ->count -= s2->count; + if (s2->dest->succ->count < 0) + s2->dest->succ->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)); + } + + update_br_prob_note (redirect_to); + + /* Edit SRC1 to go to REDIRECT_TO at NEWPOS1. */ + + /* Skip possible basic block header. */ + if (GET_CODE (newpos1) == CODE_LABEL) + newpos1 = NEXT_INSN (newpos1); + + if (GET_CODE (newpos1) == NOTE) + newpos1 = NEXT_INSN (newpos1); + last = src1->end; + + /* Emit the jump insn. */ + label = block_label (redirect_to); + emit_jump_insn_after (gen_jump (label), src1->end); + JUMP_LABEL (src1->end) = label; + LABEL_NUSES (label)++; + + /* Delete the now unreachable instructions. */ + delete_insn_chain (newpos1, last); + + /* Make sure there is a barrier after the new jump. */ + last = next_nonnote_insn (src1->end); + if (!last || GET_CODE (last) != BARRIER) + emit_barrier_after (src1->end); + + /* Update CFG. */ + while (src1->succ) + remove_edge (src1->succ); + make_single_succ_edge (src1, redirect_to, 0); + + BB_SET_FLAG (src1, BB_UPDATE_LIFE); + update_forwarder_flag (src1); + + 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 (mode, bb) + int mode; + basic_block bb; +{ + edge e, e2, nexte2, nexte, fallthru; + bool changed; + + /* Nothing to do if there is not at least two incoming edges. */ + if (!bb->pred || !bb->pred->pred_next) + 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. */ + for (fallthru = bb->pred; fallthru; fallthru = fallthru->pred_next) + if (fallthru->flags & EDGE_FALLTHRU) + break; + + changed = false; + for (e = bb->pred; e; e = nexte) + { + nexte = e->pred_next; + + /* As noted above, first try with the fallthru predecessor. */ + 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 (try_crossjump_to_edge (mode, e, fallthru)) + { + changed = true; + nexte = bb->pred; + 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 (e->src->succ != e) + continue; + + for (e2 = bb->pred; e2; e2 = nexte2) + { + nexte2 = e2->pred_next; + + 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 (try_crossjump_to_edge (mode, e, e2)) + { + changed = true; + nexte = bb->pred; + break; + } + } + } + + return changed; +} + +/* Do simple CFG optimizations - basic block merging, simplifying of jump + instructions etc. Return nonzero if changes were made. */ + +static bool +try_optimize_cfg (mode) + int mode; +{ + int i; + bool changed_overall = false; + bool changed; + int iterations = 0; + sbitmap blocks; + + if (mode & CLEANUP_CROSSJUMP) + add_noreturn_fake_exit_edges (); + + for (i = 0; i < n_basic_blocks; i++) + update_forwarder_flag (BASIC_BLOCK (i)); + + /* 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 + { + changed = false; + iterations++; + + if (rtl_dump_file) + fprintf (rtl_dump_file, "\n\ntry_optimize_cfg iteration %i\n\n", + iterations); + + for (i = 0; i < n_basic_blocks;) + { + basic_block c, b = BASIC_BLOCK (i); + edge s; + bool changed_here = false; + + /* Delete trivially dead basic blocks. */ + while (b->pred == NULL) + { + c = BASIC_BLOCK (b->index - 1); + if (rtl_dump_file) + fprintf (rtl_dump_file, "Deleting block %i.\n", b->index); + + flow_delete_block (b); + changed = true; + b = c; + } + + /* Remove code labels no longer used. Don't do this before + CALL_PLACEHOLDER is removed, as some branches may be hidden + within. */ + if (b->pred->pred_next == NULL + && (b->pred->flags & EDGE_FALLTHRU) + && !(b->pred->flags & EDGE_COMPLEX) + && GET_CODE (b->head) == CODE_LABEL + && (!(mode & CLEANUP_PRE_SIBCALL) + || !tail_recursion_label_p (b->head)) + /* 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). */ + && (b->pred->src == ENTRY_BLOCK_PTR + || GET_CODE (b->pred->src->end) != JUMP_INSN + || ! label_is_jump_target_p (b->head, b->pred->src->end))) + { + rtx label = b->head; + + b->head = NEXT_INSN (b->head); + delete_insn_chain (label, label); + if (rtl_dump_file) + fprintf (rtl_dump_file, "Deleted label in block %i.\n", + b->index); + } + + /* If we fall through an empty block, we can remove it. */ + if (b->pred->pred_next == NULL + && (b->pred->flags & EDGE_FALLTHRU) + && GET_CODE (b->head) != CODE_LABEL + && FORWARDER_BLOCK_P (b) + /* Note that forwarder_block_p true ensures that there + is a successor for this block. */ + && (b->succ->flags & EDGE_FALLTHRU) + && n_basic_blocks > 1) + { + if (rtl_dump_file) + fprintf (rtl_dump_file, "Deleting fallthru block %i.\n", + b->index); + + c = BASIC_BLOCK (b->index ? b->index - 1 : 1); + redirect_edge_succ_nodup (b->pred, b->succ->dest); + flow_delete_block (b); + changed = true; + b = c; + } + + /* Merge blocks. Loop because chains of blocks might be + combineable. */ + while ((s = b->succ) != NULL + && s->succ_next == NULL + && !(s->flags & EDGE_COMPLEX) + && (c = s->dest) != EXIT_BLOCK_PTR + && c->pred->pred_next == NULL + /* If the jump insn has side effects, + we can't kill the edge. */ + && (GET_CODE (b->end) != JUMP_INSN + || onlyjump_p (b->end)) + && merge_blocks (s, b, c, mode)) + changed_here = true; + + /* Simplify branch over branch. */ + if ((mode & CLEANUP_EXPENSIVE) && try_simplify_condjump (b)) + { + BB_SET_FLAG (b, BB_UPDATE_LIFE); + 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. + Use redirect_edge_and_branch to do the dirty work. */ + if (b->succ + && ! b->succ->succ_next + && b->succ->dest != EXIT_BLOCK_PTR + && onlyjump_p (b->end) + && redirect_edge_and_branch (b->succ, b->succ->dest)) + { + BB_SET_FLAG (b, BB_UPDATE_LIFE); + 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; + + /* Don't get confused by the index shift caused by deleting + blocks. */ + if (!changed_here) + i = b->index + 1; + else + changed = true; + } + + if ((mode & CLEANUP_CROSSJUMP) + && try_crossjump_bb (mode, EXIT_BLOCK_PTR)) + changed = true; + +#ifdef ENABLE_CHECKING + if (changed) + verify_flow_info (); +#endif + + changed_overall |= changed; + } + while (changed); + + if (mode & CLEANUP_CROSSJUMP) + remove_fake_edges (); + + if ((mode & CLEANUP_UPDATE_LIFE) && changed_overall) + { + bool found = 0; + + blocks = sbitmap_alloc (n_basic_blocks); + sbitmap_zero (blocks); + for (i = 0; i < n_basic_blocks; i++) + if (BB_FLAGS (BASIC_BLOCK (i)) & BB_UPDATE_LIFE) + { + found = 1; + SET_BIT (blocks, i); + } + + if (found) + update_life_info (blocks, UPDATE_LIFE_GLOBAL, + PROP_DEATH_NOTES | PROP_SCAN_DEAD_CODE + | PROP_KILL_DEAD_CODE); + sbitmap_free (blocks); + } + + for (i = 0; i < n_basic_blocks; i++) + BASIC_BLOCK (i)->aux = NULL; + + return changed_overall; +} + +/* Delete all unreachable basic blocks. */ + +static bool +delete_unreachable_blocks () +{ + int i; + bool changed = false; + + find_unreachable_blocks (); + + /* Delete all unreachable basic blocks. Count down so that we + don't interfere with the block renumbering that happens in + flow_delete_block. */ + + for (i = n_basic_blocks - 1; i >= 0; --i) + { + basic_block b = BASIC_BLOCK (i); + + if (!(b->flags & BB_REACHABLE)) + flow_delete_block (b), changed = true; + } + + if (changed) + tidy_fallthru_edges (); + return changed; +} + +/* Tidy the CFG by deleting unreachable code and whatnot. */ + +bool +cleanup_cfg (mode) + int mode; +{ + bool changed = false; + + timevar_push (TV_CLEANUP_CFG); + changed = delete_unreachable_blocks (); + if (try_optimize_cfg (mode)) + delete_unreachable_blocks (), changed = true; + + /* Kill the data we won't maintain. */ + free_EXPR_LIST_list (&label_value_list); + free_EXPR_LIST_list (&tail_recursion_label_list); + timevar_pop (TV_CLEANUP_CFG); + + return changed; +} |