gcc/value-relation.h

   1 /* Header file for the value range relational processing.
   2    Copyright (C) 2020-2021 Free Software Foundation, Inc.
   3    Contributed by Andrew MacLeod <amacleod@redhat.com>
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 3, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15  for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING3.  If not see
  19 <http://www.gnu.org/licenses/>.  */
  20
  21 #ifndef GCC_VALUE_RELATION_H
  22 #define GCC_VALUE_RELATION_H
  23
  24
  25 // This file provides access to a relation oracle which can be used to
  26 // maintain and query relations and equivalences between SSA_NAMES.
  27 //
  28 // The general range_query object provided in value-query.h provides
  29 // access to an oracle, if one is available, via the oracle() method.
  30 // Thre are also a couple of access routines provided, which even if there is
  31 // no oracle, will return the default VREL_NONE no relation.
  32 //
  33 // Typically, when a ranger object is active, there will be an oracle, and
  34 // any information available can be directly queried.  Ranger also sets and
  35 // utilizes the relation information to enhance it's range calculations, this
  36 // is totally transparent to the client, and they are free to make queries.
  37 //
  38 //
  39 // relation_kind is a typedef of enum tree_code, but has restricted range
  40 // and a couple of extra values.
  41 //
  42 // A query is made requesting the relation between SSA1 and SSA@ in a basic
  43 // block, or on an edge, the possible return values are:
  44 //
  45 //  EQ_EXPR, NE_EXPR, LT_EXPR, LE_EXPR, GT_EXPR, and GE_EXPR mean the same.
  46 //  VREL_NONE : No relation between the 2 names.
  47 //  VREL_EMPTY : Impossible relation (ie, A < B && A > B produces VREL_EMPTY.
  48 //
  49 // The oracle maintains EQ_EXPR relations with equivalency sets, so if a
  50 // relation comes back EQ_EXPR, it is also possible to query the set of
  51 // equivlaencies.  These are basically bitmaps over ssa_names.
  52 //
  53 // relations are maintained via the dominace trees, are are optimized assuming
  54 // they are registered in dominance order.   When a new relation is added, it
  55 // is intersected with whatever existing relation exists in the dominance tree
  56 // and registered at the specified block.
  57
  58
  59 // Rather than introduce a new enumerated type for relations, we can use the
  60 // existing tree_codes for relations, plus add a couple of #defines for
  61 // the other cases.  These codes are arranged such that VREL_NONE is the first
  62 // code, and all the rest are contiguous.
  63
  64 typedef enum tree_code relation_kind;
  65
  66 #define VREL_NONE               TRUTH_NOT_EXPR
  67 #define VREL_EMPTY              LTGT_EXPR
  68
  69 // General relation kind transformations.
  70 relation_kind relation_union (relation_kind r1, relation_kind r2);
  71 relation_kind relation_intersect (relation_kind r1, relation_kind r2);
  72 relation_kind relation_negate (relation_kind r);
  73 relation_kind relation_swap (relation_kind r);
  74 void print_relation (FILE *f, relation_kind rel);
  75
  76
  77 class relation_oracle
  78 {
  79 public:
  80   virtual ~relation_oracle () { }
  81   // register a relation between 2 ssa names at a stmt.
  82   void register_stmt (gimple *, relation_kind, tree, tree);
  83   // register a relation between 2 ssa names on an edge.
  84   void register_edge (edge, relation_kind, tree, tree);
  85
  86   // Return equivalency set for an SSA name in a basic block.
  87   virtual const_bitmap equiv_set (tree, basic_block) = 0;
  88   // register a relation between 2 ssa names in a basic block.
  89   virtual void register_relation (basic_block, relation_kind, tree, tree) = 0;
  90   // Query for a relation between two ssa names in a basic block.
  91   virtual relation_kind query_relation (basic_block, tree, tree) = 0;
  92   // Query for a relation between two equivalency stes in a basic block.
  93   virtual relation_kind query_relation (basic_block, const_bitmap,
  94                                         const_bitmap) = 0;
  95
  96   virtual void dump (FILE *, basic_block) const = 0;
  97   virtual void dump (FILE *) const = 0;
  98   void debug () const;
  99 };
 100
 101 // This class represents an equivalency set, and contains a link to the next
 102 // one in the list to be searched.
 103
 104 class equiv_chain
 105 {
 106 public:
 107   bitmap m_names;               // ssa-names in equiv set.
 108   basic_block m_bb;             // Block this belongs to
 109   equiv_chain *m_next;          // Next in block list.
 110   void dump (FILE *f) const;    // Show names in this list.
 111   equiv_chain *find (unsigned ssa);
 112 };
 113
 114 // The equivalency oracle maintains equivalencies using the dominator tree.
 115 // Equivalencies apply to an entire basic block.  Equivalencies on edges
 116 // can be represented only on edges whose destination is a single-pred block,
 117 // and the equivalence is simply applied to that succesor block.
 118
 119 class equiv_oracle : public relation_oracle
 120 {
 121 public:
 122   equiv_oracle ();
 123   ~equiv_oracle ();
 124
 125   const_bitmap equiv_set (tree ssa, basic_block bb);
 126   void register_relation (basic_block bb, relation_kind k, tree ssa1,
 127                           tree ssa2);
 128
 129   relation_kind query_relation (basic_block, tree, tree);
 130   relation_kind query_relation (basic_block, const_bitmap, const_bitmap);
 131   void dump (FILE *f, basic_block bb) const;
 132   void dump (FILE *f) const;
 133
 134 protected:
 135   bitmap_obstack m_bitmaps;
 136   struct obstack m_chain_obstack;
 137 private:
 138   bitmap m_equiv_set;   // Index by ssa-name. true if an equivalence exists.
 139   vec <equiv_chain *> m_equiv;  // Index by BB.  list of equivalences.
 140   vec <bitmap> m_self_equiv;  // Index by ssa-name, self equivalency set.
 141
 142   void limit_check (basic_block bb = NULL);
 143   equiv_chain *find_equiv_block (unsigned ssa, int bb) const;
 144   equiv_chain *find_equiv_dom (tree name, basic_block bb) const;
 145
 146   bitmap register_equiv (basic_block bb, unsigned v, equiv_chain *equiv_1);
 147   bitmap register_equiv (basic_block bb, equiv_chain *equiv_1,
 148                          equiv_chain *equiv_2);
 149   void register_initial_def (tree ssa);
 150   void add_equiv_to_block (basic_block bb, bitmap equiv);
 151 };
 152
 153 // Summary block header for relations.
 154
 155 class relation_chain_head
 156 {
 157 public:
 158   bitmap m_names;               // ssa_names with relations in this block.
 159   class relation_chain *m_head; // List of relations in block.
 160   relation_kind find_relation (const_bitmap b1, const_bitmap b2) const;
 161 };
 162
 163 // A relation oracle maintains a set of relations between ssa_names using the
 164 // dominator tree structures.  Equivalencies are considered a subset of
 165 // a general relation and maintained by an equivalence oracle by transparently
 166 // passing any EQ_EXPR relations to it.
 167 // Relations are handled at the basic block level.  All relations apply to
 168 // an entire block, and are thus kept in a summary index by block.
 169 // Similar to the equivalence oracle, edges are handled by applying the
 170 // relation to the destination block of the edge, but ONLY if that block
 171 // has a single successor.  For now.
 172
 173 class dom_oracle : public equiv_oracle
 174 {
 175 public:
 176   dom_oracle ();
 177   ~dom_oracle ();
 178
 179   void register_relation (basic_block bb, relation_kind k, tree op1, tree op2);
 180
 181   relation_kind query_relation (basic_block bb, tree ssa1, tree ssa2);
 182   relation_kind query_relation (basic_block bb, const_bitmap b1,
 183                                    const_bitmap b2);
 184
 185   void dump (FILE *f, basic_block bb) const;
 186   void dump (FILE *f) const;
 187 private:
 188   bitmap m_tmp, m_tmp2;
 189   bitmap m_relation_set;  // Index by ssa-name. True if a relation exists
 190   vec <relation_chain_head> m_relations;  // Index by BB, list of relations.
 191   relation_kind find_relation_block (unsigned bb, const_bitmap b1,
 192                                      const_bitmap b2) const;
 193   relation_kind find_relation_block (int bb, unsigned v1, unsigned v2,
 194                                      relation_chain **obj = NULL) const;
 195   relation_kind find_relation_dom (basic_block bb, unsigned v1, unsigned v2) const;
 196   relation_chain *set_one_relation (basic_block bb, relation_kind k, tree op1,
 197                                     tree op2);
 198   void register_transitives (basic_block, const class value_relation &);
 199
 200 };
 201
 202 // A path_oracle implements relations in a list.  The only sense of ordering
 203 // is the latest registered relation is the first found during a search.
 204 // It can be constructed with an optional "root" oracle which will be used
 205 // to look up any relations not found in the list.
 206 // This allows the client to walk paths starting at some block and register
 207 // and query relations along that path, ignoring other edges.
 208 //
 209 // For registering a relation, a query if made of the root oracle if there is
 210 // any known relationship at block BB, and it is combined with this new
 211 // relation and entered in the list.
 212 //
 213 // Queries are resolved by looking first in the list, and only if nothing is
 214 // found is the root oracle queried at block BB.
 215 //
 216 // reset_path is used to clear all locally registered paths to initial state.
 217
 218 class path_oracle : public relation_oracle
 219 {
 220 public:
 221   path_oracle (relation_oracle *oracle = NULL);
 222   ~path_oracle ();
 223   const_bitmap equiv_set (tree, basic_block);
 224   void register_relation (basic_block, relation_kind, tree, tree);
 225   void killing_def (tree);
 226   relation_kind query_relation (basic_block, tree, tree);
 227   relation_kind query_relation (basic_block, const_bitmap, const_bitmap);
 228   void reset_path ();
 229   void dump (FILE *, basic_block) const;
 230   void dump (FILE *) const;
 231 private:
 232   void register_equiv (basic_block bb, tree ssa1, tree ssa2);
 233   equiv_chain m_equiv;
 234   relation_chain_head m_relations;
 235   relation_oracle *m_root;
 236   bitmap m_killed_defs;
 237
 238   bitmap_obstack m_bitmaps;
 239   struct obstack m_chain_obstack;
 240 };
 241 #endif  /* GCC_VALUE_RELATION_H */