| /* Control flow optimization code for GNU compiler. |
| Copyright (C) 1987-2017 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 "backend.h" |
| #include "target.h" |
| #include "rtl.h" |
| #include "tree.h" |
| #include "cfghooks.h" |
| #include "df.h" |
| #include "memmodel.h" |
| #include "tm_p.h" |
| #include "insn-config.h" |
| #include "emit-rtl.h" |
| #include "cselib.h" |
| #include "params.h" |
| #include "tree-pass.h" |
| #include "cfgloop.h" |
| #include "cfgrtl.h" |
| #include "cfganal.h" |
| #include "cfgbuild.h" |
| #include "cfgcleanup.h" |
| #include "dce.h" |
| #include "dbgcnt.h" |
| #include "rtl-iter.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 occurred in the latest run of try_optimize_cfg. */ |
| static bool crossjumps_occurred; |
| |
| /* 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_insn *, rtx_insn *); |
| |
| 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 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_insn *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_FOR_FN (cfun) |
| || !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_FOR_FN (cfun) |
| || jump_dest_block == EXIT_BLOCK_PTR_FOR_FN (cfun) |
| || !can_fallthru (jump_block, cbranch_dest_block)) |
| return false; |
| |
| /* Invert the conditional branch. */ |
| if (!invert_jump (as_a <rtx_jump_insn *> (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) |
| { |
| 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: |
| dest = XEXP (exp, 0); |
| if (REG_P (dest)) |
| bitmap_clear_range (nonequal, REGNO (dest), REG_NREGS (dest)); |
| 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; |
| bitmap_set_range (nonequal, REGNO (dest), REG_NREGS (dest)); |
| return false; |
| |
| default: |
| return false; |
| } |
| } |
| |
| /* Return true if X contains a register in NONEQUAL. */ |
| static bool |
| mentions_nonequal_regs (const_rtx x, regset nonequal) |
| { |
| subrtx_iterator::array_type array; |
| FOR_EACH_SUBRTX (iter, array, x, NONCONST) |
| { |
| const_rtx x = *iter; |
| if (REG_P (x)) |
| { |
| unsigned int end_regno = END_REGNO (x); |
| for (unsigned int regno = REGNO (x); regno < end_regno; ++regno) |
| if (REGNO_REG_SET_P (nonequal, regno)) |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /* 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; |
| rtx_insn *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 (mentions_nonequal_regs (cond2, 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 (JUMP_P (BB_END (b)) && CROSSING_JUMP_P (BB_END (b))) |
| return false; |
| |
| for (ei = ei_start (b->succs); (e = ei_safe_edge (ei)); ) |
| { |
| basic_block target, first; |
| location_t goto_locus; |
| int counter; |
| 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_FOR_FN (cfun) |
| && JUMP_P (BB_END (first)) |
| && CROSSING_JUMP_P (BB_END (first))) |
| return changed; |
| |
| while (counter < n_basic_blocks_for_fn (cfun)) |
| { |
| 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_FOR_FN (cfun)) |
| { |
| /* Bypass trivial infinite loops. */ |
| new_target = single_succ (target); |
| if (target == new_target) |
| counter = n_basic_blocks_for_fn (cfun); |
| else if (!optimize) |
| { |
| /* When not optimizing, ensure that edges or forwarder |
| blocks with different locus are not optimized out. */ |
| location_t new_locus = single_succ_edge (target)->goto_locus; |
| location_t locus = goto_locus; |
| |
| if (LOCATION_LOCUS (new_locus) != UNKNOWN_LOCATION |
| && LOCATION_LOCUS (locus) != UNKNOWN_LOCATION |
| && new_locus != locus) |
| new_target = NULL; |
| else |
| { |
| if (LOCATION_LOCUS (new_locus) != UNKNOWN_LOCATION) |
| locus = new_locus; |
| |
| rtx_insn *last = BB_END (target); |
| if (DEBUG_INSN_P (last)) |
| last = prev_nondebug_insn (last); |
| if (last && INSN_P (last)) |
| new_locus = INSN_LOCATION (last); |
| else |
| new_locus = UNKNOWN_LOCATION; |
| |
| if (LOCATION_LOCUS (new_locus) != UNKNOWN_LOCATION |
| && LOCATION_LOCUS (locus) != UNKNOWN_LOCATION |
| && new_locus != locus) |
| new_target = NULL; |
| else |
| { |
| if (LOCATION_LOCUS (new_locus) != UNKNOWN_LOCATION) |
| 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_for_fn (cfun)); |
| 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_for_fn (cfun); |
| break; |
| } |
| } |
| |
| /* Detect an infinite loop across the start block. */ |
| if (t->dest == b) |
| break; |
| |
| gcc_assert (nthreaded_edges |
| < (n_basic_blocks_for_fn (cfun) |
| - 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_for_fn (cfun)) |
| { |
| 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_FOR_FN (cfun)) |
| { |
| 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 = apply_probability (b->frequency, edge_probability); |
| |
| 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_insn *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_insn *barrier, *real_b_end; |
| rtx_insn *label; |
| rtx_jump_table_data *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; |
| |
| /* Protect the loop latches. */ |
| if (current_loops && c->loop_father->latch == c) |
| return NULL; |
| |
| 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_FOR_FN (cfun) ? 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_FOR_FN (cfun) ? 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_FOR_FN (cfun)) |
| 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_FOR_FN (cfun) ? next->next_bb : next; |
| } |
| |
| return NULL; |
| } |
| |
| |
| /* Removes the memory attributes of MEM expression |
| if they are not equal. */ |
| |
| static 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_eq_p (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)); |
| } |
| } |
| if (code == MEM) |
| { |
| if (MEM_READONLY_P (x) != MEM_READONLY_P (y)) |
| { |
| MEM_READONLY_P (x) = 0; |
| MEM_READONLY_P (y) = 0; |
| } |
| if (MEM_NOTRAP_P (x) != MEM_NOTRAP_P (y)) |
| { |
| MEM_NOTRAP_P (x) = 0; |
| MEM_NOTRAP_P (y) = 0; |
| } |
| if (MEM_VOLATILE_P (x) != MEM_VOLATILE_P (y)) |
| { |
| MEM_VOLATILE_P (x) = 1; |
| MEM_VOLATILE_P (y) = 1; |
| } |
| } |
| |
| 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; |
| } |
| |
| |
| /* NOTE1 is the REG_EQUAL note, if any, attached to an insn |
| that is a single_set with a SET_SRC of SRC1. Similarly |
| for NOTE2/SRC2. |
| |
| So effectively NOTE1/NOTE2 are an alternate form of |
| SRC1/SRC2 respectively. |
| |
| Return nonzero if SRC1 or NOTE1 has the same constant |
| integer value as SRC2 or NOTE2. Else return zero. */ |
| static int |
| values_equal_p (rtx note1, rtx note2, rtx src1, rtx src2) |
| { |
| if (note1 |
| && note2 |
| && CONST_INT_P (XEXP (note1, 0)) |
| && rtx_equal_p (XEXP (note1, 0), XEXP (note2, 0))) |
| return 1; |
| |
| if (!note1 |
| && !note2 |
| && CONST_INT_P (src1) |
| && CONST_INT_P (src2) |
| && rtx_equal_p (src1, src2)) |
| return 1; |
| |
| if (note1 |
| && CONST_INT_P (src2) |
| && rtx_equal_p (XEXP (note1, 0), src2)) |
| return 1; |
| |
| if (note2 |
| && CONST_INT_P (src1) |
| && rtx_equal_p (XEXP (note2, 0), src1)) |
| return 1; |
| |
| return 0; |
| } |
| |
| /* 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_insn *i1, rtx_insn *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); |
| |
| src1 = SET_SRC (s1); |
| src2 = SET_SRC (s2); |
| |
| if (!values_equal_p (note1, note2, src1, src2)) |
| 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. */ |
| 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; |
| } |
| |
| /* Array of flags indexed by reg note kind, true if the given |
| reg note is CFA related. */ |
| static const bool reg_note_cfa_p[] = { |
| #undef REG_CFA_NOTE |
| #define DEF_REG_NOTE(NAME) false, |
| #define REG_CFA_NOTE(NAME) true, |
| #include "reg-notes.def" |
| #undef REG_CFA_NOTE |
| #undef DEF_REG_NOTE |
| false |
| }; |
| |
| /* Return true if I1 and I2 have identical CFA notes (the same order |
| and equivalent content). */ |
| |
| static bool |
| insns_have_identical_cfa_notes (rtx_insn *i1, rtx_insn *i2) |
| { |
| rtx n1, n2; |
| for (n1 = REG_NOTES (i1), n2 = REG_NOTES (i2); ; |
| n1 = XEXP (n1, 1), n2 = XEXP (n2, 1)) |
| { |
| /* Skip over reg notes not related to CFI information. */ |
| while (n1 && !reg_note_cfa_p[REG_NOTE_KIND (n1)]) |
| n1 = XEXP (n1, 1); |
| while (n2 && !reg_note_cfa_p[REG_NOTE_KIND (n2)]) |
| n2 = XEXP (n2, 1); |
| if (n1 == NULL_RTX && n2 == NULL_RTX) |
| return true; |
| if (n1 == NULL_RTX || n2 == NULL_RTX) |
| return false; |
| if (XEXP (n1, 0) == XEXP (n2, 0)) |
| ; |
| else if (XEXP (n1, 0) == NULL_RTX || XEXP (n2, 0) == NULL_RTX) |
| return false; |
| else if (!(reload_completed |
| ? rtx_renumbered_equal_p (XEXP (n1, 0), XEXP (n2, 0)) |
| : rtx_equal_p (XEXP (n1, 0), XEXP (n2, 0)))) |
| return false; |
| } |
| } |
| |
| /* 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_insn *i1, rtx_insn *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; |
| |
| /* Do not allow cross-jumping between frame related insns and other |
| insns. */ |
| if (RTX_FRAME_RELATED_P (i1) != RTX_FRAME_RELATED_P (i2)) |
| 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; |
| |
| /* For address sanitizer, never crossjump __asan_report_* builtins, |
| otherwise errors might be reported on incorrect lines. */ |
| if (flag_sanitize & SANITIZE_ADDRESS) |
| { |
| rtx call = get_call_rtx_from (i1); |
| if (call && GET_CODE (XEXP (XEXP (call, 0), 0)) == SYMBOL_REF) |
| { |
| rtx symbol = XEXP (XEXP (call, 0), 0); |
| if (SYMBOL_REF_DECL (symbol) |
| && TREE_CODE (SYMBOL_REF_DECL (symbol)) == FUNCTION_DECL) |
| { |
| if ((DECL_BUILT_IN_CLASS (SYMBOL_REF_DECL (symbol)) |
| == BUILT_IN_NORMAL) |
| && DECL_FUNCTION_CODE (SYMBOL_REF_DECL (symbol)) |
| >= BUILT_IN_ASAN_REPORT_LOAD1 |
| && DECL_FUNCTION_CODE (SYMBOL_REF_DECL (symbol)) |
| <= BUILT_IN_ASAN_STOREN) |
| return dir_none; |
| } |
| } |
| } |
| } |
| |
| /* If both i1 and i2 are frame related, verify all the CFA notes |
| in the same order and with the same content. */ |
| if (RTX_FRAME_RELATED_P (i1) && !insns_have_identical_cfa_notes (i1, 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_insn *i1, rtx_insn *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_insn **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_FN (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_insn **f1, |
| rtx_insn **f2, enum replace_direction *dir_p) |
| { |
| rtx_insn *i1, *i2, *last1, *last2, *afterlast1, *afterlast2; |
| int ninsns = 0; |
| 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; |
| 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. |
| Don't count any jumps if dir_p is NULL. */ |
| if (!simplejump_p (i2) && !returnjump_p (i2) && last1 && dir_p) |
| 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; |
| if (active_insn_p (i1)) |
| ninsns++; |
| } |
| |
| i1 = PREV_INSN (i1); |
| i2 = PREV_INSN (i2); |
| } |
| |
| /* Don't allow the insn after a compare to be shared by |
| cross-jumping unless the compare is also shared. */ |
| if (HAVE_cc0 && ninsns && reg_mentioned_p (cc0_rtx, last1) |
| && ! sets_cc0_p (last1)) |
| last1 = afterlast1, last2 = afterlast2, last_dir = afterlast_dir, ninsns--; |
| |
| /* 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. If STOP_AFTER is zero, count all INSN_P insns, if it is |
| non-zero, only count active insns. */ |
| |
| int |
| flow_find_head_matching_sequence (basic_block bb1, basic_block bb2, rtx_insn **f1, |
| rtx_insn **f2, int stop_after) |
| { |
| rtx_insn *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; |
| |
| 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; |
| if (!stop_after || active_insn_p (i1)) |
| 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); |
| } |
| |
| /* Don't allow a compare to be shared by cross-jumping unless the insn |
| after the compare is also shared. */ |
| if (HAVE_cc0 && ninsns && reg_mentioned_p (cc0_rtx, last1) |
| && sets_cc0_p (last1)) |
| last1 = beforelast1, last2 = beforelast2, ninsns--; |
| |
| 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 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_FOR_FN (cfun) |
| && (!JUMP_P (BB_END (bb1)) |
| /* Punt if the only successor is a fake edge to exit, the jump |
| must be some weird one. */ |
| || (single_succ_edge (bb1)->flags & EDGE_FAKE) != 0) |
| && !(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_insn *label1, *label2; |
| rtx_jump_table_data *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) |
| { |
| bool match; |
| |
| /* Temporarily replace references to LABEL1 with LABEL2 |
| in BB1->END so that we could compare the instructions. */ |
| replace_label_in_insn (BB_END (bb1), label1, label2, false); |
| |
| 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. */ |
| replace_label_in_insn (BB_END (bb1), label2, label1, false); |
| |
| return match; |
| } |
| } |
| return false; |
| } |
| } |
| |
| /* Find the last non-debug non-note instruction in each bb, except |
| stop when we see the NOTE_INSN_BASIC_BLOCK, as old_insns_match_p |
| handles that case specially. old_insns_match_p does not handle |
| other types of instruction notes. */ |
| rtx_insn *last1 = BB_END (bb1); |
| rtx_insn *last2 = BB_END (bb2); |
| while (!NOTE_INSN_BASIC_BLOCK_P (last1) && |
| (DEBUG_INSN_P (last1) || NOTE_P (last1))) |
| last1 = PREV_INSN (last1); |
| while (!NOTE_INSN_BASIC_BLOCK_P (last2) && |
| (DEBUG_INSN_P (last2) || NOTE_P (last2))) |
| last2 = PREV_INSN (last2); |
| gcc_assert (last1 && last2); |
| |
| /* First ensure that the instructions match. There may be many outgoing |
| edges so this test is generally cheaper. */ |
| if (old_insns_match_p (mode, last1, last2) != 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; |
| |
| bool nonfakeedges = false; |
| FOR_EACH_EDGE (e1, ei, bb1->succs) |
| { |
| e2 = EDGE_SUCC (bb2, ei.index); |
| |
| if ((e1->flags & EDGE_FAKE) == 0) |
| nonfakeedges = true; |
| |
| 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; |
| |
| /* If !ACCUMULATE_OUTGOING_ARGS, bb1 (and bb2) have no successors |
| and the last real insn doesn't have REG_ARGS_SIZE note, don't |
| attempt to optimize, as the two basic blocks might have different |
| REG_ARGS_SIZE depths. For noreturn calls and unconditional |
| traps there should be REG_ARG_SIZE notes, they could be missing |
| for __builtin_unreachable () uses though. */ |
| if (!nonfakeedges |
| && !ACCUMULATE_OUTGOING_ARGS |
| && (!INSN_P (last1) |
| || !find_reg_note (last1, REG_ARGS_SIZE, NULL))) |
| 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_insn *newpos1, *newpos2; |
| edge s; |
| edge_iterator ei; |
| |
| newpos1 = newpos2 = NULL; |
| |
| /* 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 (crtl->has_bb_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_FOR_FN (cfun) || src2 |
| == ENTRY_BLOCK_PTR_FOR_FN (cfun)) |
| 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); |
| |
| /* Check that SRC1 and SRC2 have preds again. They may have changed |
| above due to the call to flow_find_cross_jump. */ |
| if (EDGE_COUNT (src1->preds) == 0 || EDGE_COUNT (src2->preds) == 0) |
| return false; |
| |
| 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_insn *, 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_insn *label1, *label2; |
| rtx_jump_table_data *table1, *table2; |
| |
| if (tablejump_p (BB_END (osrc1), &label1, &table1) |
| && tablejump_p (BB_END (osrc2), &label2, &table2) |
| && label1 != label2) |
| { |
| rtx_insn *insn; |
| |
| /* Replace references to LABEL1 with LABEL2. */ |
| 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)) |
| replace_label_in_insn (insn, label1, label2, true); |
| } |
| } |
| } |
| |
| /* 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_FOR_FN (cfun) |
| && 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_occurred = 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_insn **headptr, **currptr, **nextptr; |
| bool changed, moveall; |
| unsigned ix; |
| rtx_insn *e0_last_head; |
| rtx cond; |
| rtx_insn *move_before; |
| unsigned nedges = EDGE_COUNT (bb->succs); |
| rtx_insn *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_FOR_FN (cfun) |
| && computed_jump_p (BB_END (bb))) |
| return false; |
| |
| cond = get_condition (jump, &move_before, true, false); |
| if (cond == NULL_RTX) |
| { |
| if (HAVE_cc0 && reg_mentioned_p (cc0_rtx, jump)) |
| move_before = prev_nonnote_nondebug_insn (jump); |
| else |
| move_before = jump; |
| } |
| |
| for (ix = 0; ix < nedges; ix++) |
| if (EDGE_SUCC (bb, ix)->dest == EXIT_BLOCK_PTR_FOR_FN (cfun)) |
| 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; |
| changed = false; |
| |
| for (ix = 1; ix < nedges; ix++) |
| { |
| edge e = EDGE_SUCC (bb, ix); |
| rtx_insn *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_insn *, nedges); |
| headptr = XNEWVEC (rtx_insn *, nedges); |
| nextptr = XNEWVEC (rtx_insn *, nedges); |
| |
| for (ix = 0; ix < nedges; ix++) |
| { |
| int j; |
| basic_block merge_bb = EDGE_SUCC (bb, ix)->dest; |
| rtx_insn *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_insn *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) |
| { |
| if (HAVE_cc0 && reg_mentioned_p (cc0_rtx, jump)) |
| move_before = prev_nonnote_nondebug_insn (jump); |
| else |
| move_before = jump; |
| } |
| } |
| |
| do |
| { |
| rtx_insn *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; |
| |
| /* Don't try moving before a cc0 user, as that may invalidate |
| the cc0. */ |
| if (HAVE_cc0 && reg_mentioned_p (cc0_rtx, jump)) |
| break; |
| |
| 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_insn *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_insn *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; |
| |
| /* Don't try moving before a cc0 user, as that may invalidate |
| the cc0. */ |
| if (HAVE_cc0 && reg_mentioned_p (cc0_rtx, jump)) |
| break; |
| |
| for (ix = 0; ix < nedges; ix++) |
| currptr[ix] = headptr[ix] = nextptr[ix]; |
| } |
| } |
| while (!moveall); |
| |
| out: |
| free (currptr); |
| free (headptr); |
| free (nextptr); |
| |
| crossjumps_occurred |= 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 *insn = BB_END (bb); |
| |
| while (1) |
| { |
| if (insn == BB_HEAD (bb)) |
| return true; |
| if (!DEBUG_INSN_P (insn)) |
| return false; |
| insn = PREV_INSN (insn); |
| } |
| } |
| |
| /* Return true if BB contains just a return and possibly a USE of the |
| return value. Fill in *RET and *USE with the return and use insns |
| if any found, otherwise NULL. */ |
| |
| static bool |
| bb_is_just_return (basic_block bb, rtx_insn **ret, rtx_insn **use) |
| { |
| *ret = *use = NULL; |
| rtx_insn *insn; |
| |
| if (bb == EXIT_BLOCK_PTR_FOR_FN (cfun)) |
| return false; |
| |
| FOR_BB_INSNS (bb, insn) |
| if (NONDEBUG_INSN_P (insn)) |
| { |
| if (!*ret && ANY_RETURN_P (PATTERN (insn))) |
| *ret = insn; |
| else if (!*ret && !*use && GET_CODE (PATTERN (insn)) == USE |
| && REG_P (XEXP (PATTERN (insn), 0)) |
| && REG_FUNCTION_VALUE_P (XEXP (PATTERN (insn), 0))) |
| *use = insn; |
| else |
| return false; |
| } |
| |
| return !!*ret; |
| } |
| |
| /* 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_occurred = false; |
| |
| FOR_EACH_BB_FN (bb, cfun) |
| 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_FOR_FN (cfun)->next_bb; b |
| != EXIT_BLOCK_PTR_FOR_FN (cfun);) |
| { |
| 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_FOR_FN (cfun))->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 (BB_FOOTER (b) |
| && BARRIER_P (BB_FOOTER (b))) |
| FOR_EACH_EDGE (e, ei, b->preds) |
| if ((e->flags & EDGE_FALLTHRU) |
| && BB_FOOTER (e->src) == NULL) |
| { |
| if (BB_FOOTER (b)) |
| { |
| BB_FOOTER (e->src) = BB_FOOTER (b); |
| BB_FOOTER (b) = NULL; |
| } |
| else |
| { |
| start_sequence (); |
| BB_FOOTER (e->src) = emit_barrier (); |
| end_sequence (); |
| } |
| } |
| } |
| else |
| { |
| rtx_insn *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 the exit block. */ |
| b = (c == ENTRY_BLOCK_PTR_FOR_FN (cfun) ? 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)) |
| && !LABEL_PRESERVE_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_FOR_FN (cfun) |
| || !JUMP_P (BB_END (single_pred (b))) |
| || ! label_is_jump_target_p (BB_HEAD (b), |
| BB_END (single_pred (b))))) |
| { |
| delete_insn (BB_HEAD (b)); |
| 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 | CLEANUP_NO_INSN_DEL)) |
| && 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_for_fn (cfun) > NUM_FIXED_BLOCKS + 1) |
| { |
| if (dump_file) |
| fprintf (dump_file, |
| "Deleting fallthru block %i.\n", |
| b->index); |
| |
| c = ((b->prev_bb == ENTRY_BLOCK_PTR_FOR_FN (cfun)) |
| ? 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_FOR_FN (cfun) |
| && 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; |
| } |
| } |
| |
| /* Try to change a branch to a return to just that return. */ |
| rtx_insn *ret, *use; |
| if (single_succ_p (b) |
| && onlyjump_p (BB_END (b)) |
| && bb_is_just_return (single_succ (b), &ret, &use)) |
| { |
| if (redirect_jump (as_a <rtx_jump_insn *> (BB_END (b)), |
| PATTERN (ret), 0)) |
| { |
| if (use) |
| emit_insn_before (copy_insn (PATTERN (use)), |
| BB_END (b)); |
| if (dump_file) |
| fprintf (dump_file, "Changed jump %d->%d to return.\n", |
| b->index, single_succ (b)->index); |
| redirect_edge_succ (single_succ_edge (b), |
| EXIT_BLOCK_PTR_FOR_FN (cfun)); |
| single_succ_edge (b)->flags &= ~EDGE_CROSSING; |
| changed_here = true; |
| } |
| } |
| |
| /* Try to change a conditional branch to a return to the |
| respective conditional return. */ |
| if (EDGE_COUNT (b->succs) == 2 |
| && any_condjump_p (BB_END (b)) |
| && bb_is_just_return (BRANCH_EDGE (b)->dest, &ret, &use)) |
| { |
| if (redirect_jump (as_a <rtx_jump_insn *> (BB_END (b)), |
| PATTERN (ret), 0)) |
| { |
| if (use) |
| emit_insn_before (copy_insn (PATTERN (use)), |
| BB_END (b)); |
| if (dump_file) |
| fprintf (dump_file, "Changed conditional jump %d->%d " |
| "to conditional return.\n", |
| b->index, BRANCH_EDGE (b)->dest->index); |
| redirect_edge_succ (BRANCH_EDGE (b), |
| EXIT_BLOCK_PTR_FOR_FN (cfun)); |
| BRANCH_EDGE (b)->flags &= ~EDGE_CROSSING; |
| changed_here = true; |
| } |
| } |
| |
| /* Try to flip a conditional branch that falls through to |
| a return so that it becomes a conditional return and a |
| new jump to the original branch target. */ |
| if (EDGE_COUNT (b->succs) == 2 |
| && BRANCH_EDGE (b)->dest != EXIT_BLOCK_PTR_FOR_FN (cfun) |
| && any_condjump_p (BB_END (b)) |
| && bb_is_just_return (FALLTHRU_EDGE (b)->dest, &ret, &use)) |
| { |
| if (invert_jump (as_a <rtx_jump_insn *> (BB_END (b)), |
| JUMP_LABEL (BB_END (b)), 0)) |
| { |
| basic_block new_ft = BRANCH_EDGE (b)->dest; |
| if (redirect_jump (as_a <rtx_jump_insn *> (BB_END (b)), |
| PATTERN (ret), 0)) |
| { |
| if (use) |
| emit_insn_before (copy_insn (PATTERN (use)), |
| BB_END (b)); |
| if (dump_file) |
| fprintf (dump_file, "Changed conditional jump " |
| "%d->%d to conditional return, adding " |
| "fall-through jump.\n", |
| b->index, BRANCH_EDGE (b)->dest->index); |
| redirect_edge_succ (BRANCH_EDGE (b), |
| EXIT_BLOCK_PTR_FOR_FN (cfun)); |
| BRANCH_EDGE (b)->flags &= ~EDGE_CROSSING; |
| std::swap (BRANCH_EDGE (b)->probability, |
| FALLTHRU_EDGE (b)->probability); |
| update_br_prob_note (b); |
| basic_block jb = force_nonfallthru (FALLTHRU_EDGE (b)); |
| notice_new_block (jb); |
| if (!redirect_jump (as_a <rtx_jump_insn *> (BB_END (jb)), |
| block_label (new_ft), 0)) |
| gcc_unreachable (); |
| redirect_edge_succ (single_succ_edge (jb), new_ft); |
| changed_here = true; |
| } |
| else |
| { |
| /* Invert the jump back to what it was. This should |
| never fail. */ |
| if (!invert_jump (as_a <rtx_jump_insn *> (BB_END (b)), |
| JUMP_LABEL (BB_END (b)), 0)) |
| gcc_unreachable (); |
| } |
| } |
| } |
| |
| /* 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_FOR_FN (cfun) |
| && onlyjump_p (BB_END (b)) |
| && !CROSSING_JUMP_P (BB_END (b)) |
| && 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_FOR_FN (cfun))) |
| changed = true; |
| |
| if (block_was_dirty) |
| { |
| /* This should only be set by head-merging. */ |
| gcc_assert (mode & CLEANUP_CROSSJUMP); |
| df_analyze (); |
| } |
| |
| if (changed) |
| { |
| /* Edge forwarding in particular can cause hot blocks previously |
| reached by both hot and cold blocks to become dominated only |
| by cold blocks. This will cause the verification below to fail, |
| and lead to now cold code in the hot section. This is not easy |
| to detect and fix during edge forwarding, and in some cases |
| is only visible after newly unreachable blocks are deleted, |
| which will be done in fixup_partitions. */ |
| fixup_partitions (); |
| checking_verify_flow_info (); |
| } |
| |
| changed_overall |= changed; |
| first_pass = false; |
| } |
| while (changed); |
| } |
| |
| FOR_ALL_BB_FN (b, cfun) |
| 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_INSNS && current_ir_type () == IR_GIMPLE |
| && dom_info_available_p (CDI_DOMINATORS)) |
| { |
| for (b = EXIT_BLOCK_PTR_FOR_FN (cfun)->prev_bb; |
| b != ENTRY_BLOCK_PTR_FOR_FN (cfun); 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> h |
| = get_all_dominated_blocks (CDI_DOMINATORS, b); |
| |
| while (h.length ()) |
| { |
| b = h.pop (); |
| |
| prev_bb = b->prev_bb; |
| |
| gcc_assert (!(b->flags & BB_REACHABLE)); |
| |
| delete_basic_block (b); |
| } |
| |
| h.release (); |
| } |
| |
| changed = true; |
| } |
| } |
| } |
| else |
| { |
| for (b = EXIT_BLOCK_PTR_FOR_FN (cfun)->prev_bb; |
| b != ENTRY_BLOCK_PTR_FOR_FN (cfun); 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 |
|