gcc/tree-ssa-threadupdate.h

   1 /* Communication between registering jump thread requests and
   2    updating the SSA/CFG for jump threading.
   3    Copyright (C) 2013-2023 Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 3, or (at your option)
  10 any later version.
  11
  12 GCC is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License 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 _TREE_SSA_THREADUPDATE_H
  22 #define _TREE_SSA_THREADUPDATE_H 1
  23
  24 enum jump_thread_edge_type
  25 {
  26   EDGE_START_JUMP_THREAD,
  27   EDGE_COPY_SRC_BLOCK,
  28   EDGE_COPY_SRC_JOINER_BLOCK,
  29   EDGE_NO_COPY_SRC_BLOCK
  30 };
  31
  32 // We keep the registered jump threading opportunities in this
  33 // vector as edge pairs (original_edge, target_edge).
  34
  35 class jump_thread_edge
  36 {
  37 public:
  38   jump_thread_edge (edge e, jump_thread_edge_type t) : e (e), type (t) {}
  39
  40   edge e;
  41   jump_thread_edge_type type;
  42 };
  43
  44 class jump_thread_path_allocator
  45 {
  46 public:
  47   jump_thread_path_allocator ();
  48   ~jump_thread_path_allocator ();
  49   jump_thread_edge *allocate_thread_edge (edge, jump_thread_edge_type);
  50   vec<jump_thread_edge *> *allocate_thread_path ();
  51 private:
  52   DISABLE_COPY_AND_ASSIGN (jump_thread_path_allocator);
  53   obstack m_obstack;
  54 };
  55
  56 // Abstract class for the jump thread registry.
  57 //
  58 // When all candidates have been registered with
  59 // register_jump_thread(), thread_through_all_blocks() is called to
  60 // update the CFG.
  61
  62 class jt_path_registry
  63 {
  64 public:
  65   jt_path_registry (bool backedge_threads);
  66   virtual ~jt_path_registry ();
  67   bool register_jump_thread (vec<jump_thread_edge *> *);
  68   bool thread_through_all_blocks (bool peel_loop_headers);
  69   void push_edge (vec<jump_thread_edge *> *path, edge, jump_thread_edge_type);
  70   vec<jump_thread_edge *> *allocate_thread_path ();
  71   void debug ();
  72 protected:
  73   void debug_path (FILE *, int pathno);
  74   vec<vec<jump_thread_edge *> *> m_paths;
  75   unsigned long m_num_threaded_edges;
  76 private:
  77   virtual bool update_cfg (bool peel_loop_headers) = 0;
  78   bool cancel_invalid_paths (vec<jump_thread_edge *> &path);
  79   jump_thread_path_allocator m_allocator;
  80   // True if threading through back edges is allowed.  This is only
  81   // allowed in the generic copier in the backward threader.
  82   bool m_backedge_threads;
  83   DISABLE_COPY_AND_ASSIGN (jt_path_registry);
  84 };
  85
  86 // Forward threader path registry using a custom BB copier.
  87
  88 class fwd_jt_path_registry : public jt_path_registry
  89 {
  90 public:
  91   fwd_jt_path_registry ();
  92   ~fwd_jt_path_registry ();
  93   void remove_jump_threads_including (edge);
  94 private:
  95   bool update_cfg (bool peel_loop_headers) override;
  96   void mark_threaded_blocks (bitmap threaded_blocks);
  97   bool thread_block_1 (basic_block, bool noloop_only, bool joiners);
  98   bool thread_block (basic_block, bool noloop_only);
  99   bool thread_through_loop_header (class loop *loop,
 100                                    bool may_peel_loop_headers);
 101   class redirection_data *lookup_redirection_data (edge e, enum insert_option);
 102
 103   hash_table<struct removed_edges> *m_removed_edges;
 104
 105   // Main data structure to hold information for duplicates of BB.
 106   hash_table<redirection_data> *m_redirection_data;
 107 };
 108
 109 // Backward threader path registry using a generic BB copier.
 110
 111 class back_jt_path_registry : public jt_path_registry
 112 {
 113 public:
 114   back_jt_path_registry ();
 115 private:
 116   bool update_cfg (bool peel_loop_headers) override;
 117   void adjust_paths_after_duplication (unsigned curr_path_num);
 118   bool duplicate_thread_path (edge entry, edge exit, basic_block *region,
 119                               unsigned n_region, unsigned current_path_no);
 120   bool rewire_first_differing_edge (unsigned path_num, unsigned edge_num);
 121 };
 122
 123 // Rather than search all the edges in jump thread paths each time DOM
 124 // is able to simply if control statement, we build a hash table with
 125 // the deleted edges.  We only care about the address of the edge, not
 126 // its contents.
 127 struct removed_edges : nofree_ptr_hash<edge_def>
 128 {
 129   static hashval_t hash (edge e) { return htab_hash_pointer (e); }
 130   static bool equal (edge e1, edge e2) { return e1 == e2; }
 131 };
 132
 133 extern unsigned int estimate_threading_killed_stmts (basic_block);
 134
 135 enum bb_dom_status
 136 {
 137   /* BB does not dominate latch of the LOOP.  */
 138   DOMST_NONDOMINATING,
 139   /* The LOOP is broken (there is no path from the header to its latch.  */
 140   DOMST_LOOP_BROKEN,
 141   /* BB dominates the latch of the LOOP.  */
 142   DOMST_DOMINATING
 143 };
 144
 145 enum bb_dom_status determine_bb_domination_status (class loop *, basic_block);
 146
 147 // In tree-ssa-dom.cc.
 148 extern void free_dom_edge_info (edge);
 149
 150 #endif