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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [gcc/] [cfgcleanup.c] - Rev 774
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/* 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, 2011 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, enum replace_direction); static bool try_crossjump_bb (int, basic_block); static bool outgoing_edges_match (int, basic_block, basic_block); static enum replace_direction 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); if (HARD_REGISTER_NUM_P (regno)) bitmap_clear_range (nonequal, regno, hard_regno_nregs[regno][GET_MODE (dest)]); else bitmap_clear_bit (nonequal, regno); } 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); if (HARD_REGISTER_NUM_P (regno)) bitmap_set_range (nonequal, regno, hard_regno_nregs[regno][GET_MODE (dest)]); else bitmap_set_bit (nonequal, regno); 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); 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); } 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 { HOST_WIDE_INT 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); clear_mem_offset (x); clear_mem_offset (y); } else if (MEM_OFFSET_KNOWN_P (x) != MEM_OFFSET_KNOWN_P (y) || (MEM_OFFSET_KNOWN_P (x) && MEM_OFFSET (x) != MEM_OFFSET (y))) { clear_mem_offset (x); clear_mem_offset (y); } if (MEM_SIZE_KNOWN_P (x) && MEM_SIZE_KNOWN_P (y)) { mem_size = MAX (MEM_SIZE (x), MEM_SIZE (y)); set_mem_size (x, mem_size); set_mem_size (y, mem_size); } else { clear_mem_size (x); clear_mem_size (y); } 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; } /* Checks if patterns P1 and P2 are equivalent, apart from the possibly different single sets S1 and S2. */ static bool equal_different_set_p (rtx p1, rtx s1, rtx p2, rtx s2) { int i; rtx e1, e2; if (p1 == s1 && p2 == s2) return true; if (GET_CODE (p1) != PARALLEL || GET_CODE (p2) != PARALLEL) return false; if (XVECLEN (p1, 0) != XVECLEN (p2, 0)) return false; for (i = 0; i < XVECLEN (p1, 0); i++) { e1 = XVECEXP (p1, 0, i); e2 = XVECEXP (p2, 0, i); if (e1 == s1 && e2 == s2) continue; if (reload_completed ? rtx_renumbered_equal_p (e1, e2) : rtx_equal_p (e1, e2)) continue; return false; } return true; } /* Examine register notes on I1 and I2 and return: - dir_forward if I1 can be replaced by I2, or - dir_backward if I2 can be replaced by I1, or - dir_both if both are the case. */ static enum replace_direction can_replace_by (rtx i1, rtx i2) { rtx s1, s2, d1, d2, src1, src2, note1, note2; bool c1, c2; /* Check for 2 sets. */ s1 = single_set (i1); s2 = single_set (i2); if (s1 == NULL_RTX || s2 == NULL_RTX) return dir_none; /* Check that the 2 sets set the same dest. */ d1 = SET_DEST (s1); d2 = SET_DEST (s2); if (!(reload_completed ? rtx_renumbered_equal_p (d1, d2) : rtx_equal_p (d1, d2))) return dir_none; /* Find identical req_equiv or reg_equal note, which implies that the 2 sets set dest to the same value. */ note1 = find_reg_equal_equiv_note (i1); note2 = find_reg_equal_equiv_note (i2); if (!note1 || !note2 || !rtx_equal_p (XEXP (note1, 0), XEXP (note2, 0)) || !CONST_INT_P (XEXP (note1, 0))) return dir_none; if (!equal_different_set_p (PATTERN (i1), s1, PATTERN (i2), s2)) return dir_none; /* Although the 2 sets set dest to the same value, we cannot replace (set (dest) (const_int)) by (set (dest) (reg)) because we don't know if the reg is live and has the same value at the location of replacement. */ src1 = SET_SRC (s1); src2 = SET_SRC (s2); c1 = CONST_INT_P (src1); c2 = CONST_INT_P (src2); if (c1 && c2) return dir_both; else if (c2) return dir_forward; else if (c1) return dir_backward; return dir_none; } /* Merges directions A and B. */ static enum replace_direction merge_dir (enum replace_direction a, enum replace_direction b) { /* Implements the following table: |bo fw bw no ---+----------- bo |bo fw bw no fw |-- fw no no bw |-- -- bw no no |-- -- -- no. */ if (a == b) return a; if (a == dir_both) return b; if (b == dir_both) return a; return dir_none; } /* Examine I1 and I2 and return: - dir_forward if I1 can be replaced by I2, or - dir_backward if I2 can be replaced by I1, or - dir_both if both are the case. */ static enum replace_direction 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 dir_none; /* __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 dir_both; /* ??? Do not allow cross-jumping between different stack levels. */ p1 = find_reg_note (i1, REG_ARGS_SIZE, NULL); p2 = find_reg_note (i2, REG_ARGS_SIZE, NULL); if (p1 && p2) { p1 = XEXP (p1, 0); p2 = XEXP (p2, 0); if (!rtx_equal_p (p1, p2)) return dir_none; /* ??? Worse, this adjustment had better be constant lest we have differing incoming stack levels. */ if (!frame_pointer_needed && find_args_size_adjust (i1) == HOST_WIDE_INT_MIN) return dir_none; } else if (p1 || p2) return dir_none; p1 = PATTERN (i1); p2 = PATTERN (i2); if (GET_CODE (p1) != GET_CODE (p2)) return dir_none; /* 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 dir_none; if (n1 && (!n2 || XEXP (n1, 0) != XEXP (n2, 0))) return dir_none; if (!rtx_equal_p (CALL_INSN_FUNCTION_USAGE (i1), CALL_INSN_FUNCTION_USAGE (i2)) || SIBLING_CALL_P (i1) != SIBLING_CALL_P (i2)) return dir_none; } #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 dir_none; } #endif if (reload_completed ? rtx_renumbered_equal_p (p1, p2) : rtx_equal_p (p1, p2)) return dir_both; return can_replace_by (i1, i2); } /* 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); } } /* Walks from I1 in BB1 backward till the next non-debug insn, and returns the resulting insn in I1, and the corresponding bb in BB1. At the head of a bb, if there is a predecessor bb that reaches this bb via fallthru, and FOLLOW_FALLTHRU, walks further in the predecessor bb and registers this in DID_FALLTHRU. Otherwise, stops at the head of the bb. */ static void walk_to_nondebug_insn (rtx *i1, basic_block *bb1, bool follow_fallthru, bool *did_fallthru) { edge fallthru; *did_fallthru = false; /* Ignore notes. */ while (!NONDEBUG_INSN_P (*i1)) { if (*i1 != BB_HEAD (*bb1)) { *i1 = PREV_INSN (*i1); continue; } if (!follow_fallthru) return; fallthru = find_fallthru_edge ((*bb1)->preds); if (!fallthru || fallthru->src == ENTRY_BLOCK_PTR_FOR_FUNCTION (cfun) || !single_succ_p (fallthru->src)) return; *bb1 = fallthru->src; *i1 = BB_END (*bb1); *did_fallthru = true; } } /* Look through the insns at the end of BB1 and BB2 and find the longest sequence that are either equivalent, or allow forward or backward replacement. Store the first insns for that sequence in *F1 and *F2 and return the sequence length. DIR_P indicates the allowed replacement direction on function entry, and the actual replacement direction on function exit. If NULL, only equivalent sequences are allowed. 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, enum replace_direction *dir_p) { rtx i1, i2, last1, last2, afterlast1, afterlast2; int ninsns = 0; rtx p1; enum replace_direction dir, last_dir, afterlast_dir; bool follow_fallthru, did_fallthru; if (dir_p) dir = *dir_p; else dir = dir_both; afterlast_dir = dir; last_dir = afterlast_dir; /* 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) { /* In the following example, we can replace all jumps to C by jumps to A. This removes 4 duplicate insns. [bb A] insn1 [bb C] insn1 insn2 insn2 [bb B] insn3 insn3 insn4 insn4 jump_insn jump_insn We could also replace all jumps to A by jumps to C, but that leaves B alive, and removes only 2 duplicate insns. In a subsequent crossjump step, all jumps to B would be replaced with jumps to the middle of C, achieving the same result with more effort. So we allow only the first possibility, which means that we don't allow fallthru in the block that's being replaced. */ follow_fallthru = dir_p && dir != dir_forward; walk_to_nondebug_insn (&i1, &bb1, follow_fallthru, &did_fallthru); if (did_fallthru) dir = dir_backward; follow_fallthru = dir_p && dir != dir_backward; walk_to_nondebug_insn (&i2, &bb2, follow_fallthru, &did_fallthru); if (did_fallthru) dir = dir_forward; if (i1 == BB_HEAD (bb1) || i2 == BB_HEAD (bb2)) break; dir = merge_dir (dir, old_insns_match_p (0, i1, i2)); if (dir == dir_none || (!dir_p && dir != dir_both)) 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; afterlast_dir = last_dir; last_dir = dir; p1 = PATTERN (i1); if (!(GET_CODE (p1) == USE || GET_CODE (p1) == CLOBBER)) 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, last_dir = afterlast_dir, 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) { bb1 = BLOCK_FOR_INSN (last1); 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); bb2 = BLOCK_FOR_INSN (last2); 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; } if (dir_p) *dir_p = last_dir; 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) != dir_both) 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 we performed shrink-wrapping, edges to the EXIT_BLOCK_PTR can only be distinguished for JUMP_INSNs. The two paths may differ in whether they went through the prologue. Sibcalls are fine, we know that we either didn't need or inserted an epilogue before them. */ if (crtl->shrink_wrapped && single_succ_p (bb1) && single_succ (bb1) == EXIT_BLOCK_PTR && !JUMP_P (BB_END (bb1)) && !(CALL_P (BB_END (bb1)) && SIBLING_CALL_P (BB_END (bb1)))) return false; /* 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)) == dir_both); 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)) != dir_both) 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 (dir_forward), or the other way around (dir_backward). DIR specifies the allowed replacement direction. */ static bool try_crossjump_to_edge (int mode, edge e1, edge e2, enum replace_direction dir) { int nmatch; basic_block src1 = e1->src, src2 = e2->src; basic_block redirect_to, redirect_from, to_remove; basic_block osrc1, osrc2, redirect_edges_to, tmp; 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, &dir); osrc1 = src1; osrc2 = src2; if (newpos1 != NULL_RTX) src1 = BLOCK_FOR_INSN (newpos1); if (newpos2 != NULL_RTX) src2 = BLOCK_FOR_INSN (newpos2); if (dir == dir_backward) { #define SWAP(T, X, Y) do { T tmp = (X); (X) = (Y); (Y) = tmp; } while (0) SWAP (basic_block, osrc1, osrc2); SWAP (basic_block, src1, src2); SWAP (edge, e1, e2); SWAP (rtx, newpos1, newpos2); #undef SWAP } /* 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 (osrc1), &label1, &table1) && tablejump_p (BB_END (osrc2), &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 (osrc1)) 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); if (osrc2 == src2) redirect_edges_to = redirect_to; else redirect_edges_to = osrc2; /* Recompute the frequencies and counts of outgoing edges. */ FOR_EACH_EDGE (s, ei, redirect_edges_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_edges_to->frequency && !src1->frequency) s->probability = (s->probability + s2->probability) / 2; else s->probability = ((s->probability * redirect_edges_to->frequency + s2->probability * src1->frequency) / (redirect_edges_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. */ tmp = redirect_to; do { tmp->count += src1->count; tmp->frequency += src1->frequency; if (tmp->frequency > BB_FREQ_MAX) tmp->frequency = BB_FREQ_MAX; if (tmp == redirect_edges_to) break; tmp = find_fallthru_edge (tmp->succs)->dest; } while (true); update_br_prob_note (redirect_edges_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; /* 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; ix < EDGE_COUNT (bb->preds);) { e = EDGE_PRED (bb, 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, dir_forward)) { changed = true; ix = 0; 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; ix2 < EDGE_COUNT (bb->preds); ix2++) { e2 = EDGE_PRED (bb, 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; /* Both e and e2 are not fallthru edges, so we can crossjump in either direction. */ if (try_crossjump_to_edge (mode, e, e2, dir_both)) { changed = true; 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)) { update_forwarder_flag (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_verify_rtl_sharing, /* todo_flags_finish */ } };
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