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1 /* Generic dominator tree walker
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2 Copyright (C) 2003-2017 Free Software Foundation, Inc.
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3 Contributed by Diego Novillo <dnovillo@redhat.com>
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4
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5 This file is part of GCC.
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6
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7 GCC is free software; you can redistribute it and/or modify
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8 it under the terms of the GNU General Public License as published by
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9 the Free Software Foundation; either version 3, or (at your option)
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10 any later version.
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11
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12 GCC is distributed in the hope that it will be useful,
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13 but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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15 GNU General Public License for more details.
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16
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17 You should have received a copy of the GNU General Public License
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18 along with GCC; see the file COPYING3. If not see
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19 <http://www.gnu.org/licenses/>. */
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20
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21 #ifndef GCC_DOM_WALK_H
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22 #define GCC_DOM_WALK_H
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23
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24 /**
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25 * This is the main class for the dominator walker. It is expected that
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26 * consumers will have a custom class inheriting from it, which will over ride
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27 * at least one of before_dom_children and after_dom_children to implement the
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28 * custom behavior.
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29 */
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30 class dom_walker
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31 {
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32 public:
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33 static const edge STOP;
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34
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35 /* Use SKIP_UNREACHBLE_BLOCKS = true when your client can discover
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36 that some edges are not executable.
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37
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38 If a client can discover that a COND, SWITCH or GOTO has a static
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39 target in the before_dom_children callback, the taken edge should
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40 be returned. The generic walker will clear EDGE_EXECUTABLE on all
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41 edges it can determine are not executable.
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42
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43 You can provide a mapping of basic-block index to RPO if you
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44 have that readily available or you do multiple walks. */
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45 dom_walker (cdi_direction direction, bool skip_unreachable_blocks = false,
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46 int *bb_index_to_rpo = NULL);
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47
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48 ~dom_walker ();
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49
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50 /* Walk the dominator tree. */
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51 void walk (basic_block);
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52
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53 /* Function to call before the recursive walk of the dominator children.
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54
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55 Return value is the always taken edge if the block has multiple outgoing
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56 edges, NULL otherwise. When skipping unreachable blocks, the walker
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57 uses the taken edge information to clear EDGE_EXECUTABLE on the other
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58 edges, exposing unreachable blocks. A NULL return value means all
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59 outgoing edges should still be considered executable. A return value
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60 of STOP means to stop the domwalk from processing dominated blocks from
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61 here. This can be used to process a SEME region only (note domwalk
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62 will still do work linear in function size). */
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63 virtual edge before_dom_children (basic_block) { return NULL; }
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64
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65 /* Function to call after the recursive walk of the dominator children. */
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66 virtual void after_dom_children (basic_block) {}
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67
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68 private:
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69 /* This is the direction of the dominator tree we want to walk. i.e.,
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70 if it is set to CDI_DOMINATORS, then we walk the dominator tree,
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71 if it is set to CDI_POST_DOMINATORS, then we walk the post
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72 dominator tree. */
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73 const ENUM_BITFIELD (cdi_direction) m_dom_direction : 2;
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74 bool m_skip_unreachable_blocks;
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75 bool m_user_bb_to_rpo;
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76 basic_block m_unreachable_dom;
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77 int *m_bb_to_rpo;
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78
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79 /* Query whether or not the given block is reachable or not. */
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80 bool bb_reachable (struct function *, basic_block);
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81
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82 /* Given an unreachable block, propagate that property to outgoing
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83 and possibly incoming edges for the block. Typically called after
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84 determining a block is unreachable in the before_dom_children
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85 callback. */
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86 void propagate_unreachable_to_edges (basic_block, FILE *, dump_flags_t);
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87
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88 };
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89
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90 #endif
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