gcc/analyzer/region-model-reachability.cc

   1 /* Finding reachable regions and values.
   2    Copyright (C) 2020-2023 Free Software Foundation, Inc.
   3    Contributed by David Malcolm <dmalcolm@redhat.com>.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it
   8 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, but
  13 WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15 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 #include "config.h"
  22 #define INCLUDE_MEMORY
  23 #include "system.h"
  24 #include "coretypes.h"
  25 #include "tree.h"
  26 #include "function.h"
  27 #include "basic-block.h"
  28 #include "gimple.h"
  29 #include "gimple-iterator.h"
  30 #include "diagnostic-core.h"
  31 #include "graphviz.h"
  32 #include "options.h"
  33 #include "cgraph.h"
  34 #include "tree-dfa.h"
  35 #include "stringpool.h"
  36 #include "convert.h"
  37 #include "target.h"
  38 #include "fold-const.h"
  39 #include "tree-pretty-print.h"
  40 #include "bitmap.h"
  41 #include "analyzer/analyzer.h"
  42 #include "analyzer/analyzer-logging.h"
  43 #include "ordered-hash-map.h"
  44 #include "options.h"
  45 #include "analyzer/call-string.h"
  46 #include "analyzer/program-point.h"
  47 #include "analyzer/store.h"
  48 #include "analyzer/region-model.h"
  49 #include "analyzer/region-model-reachability.h"
  50 #include "diagnostic.h"
  51 #include "tree-diagnostic.h"
  52
  53 #if ENABLE_ANALYZER
  54
  55 namespace ana {
  56
  57 reachable_regions::reachable_regions (region_model *model)
  58 : m_model (model), m_store (model->get_store ()),
  59   m_reachable_base_regs (), m_mutable_base_regs ()
  60 {
  61 }
  62
  63 /* Callback called for each cluster when initializing this object.  */
  64
  65 void
  66 reachable_regions::init_cluster_cb (const region *base_reg,
  67                                     reachable_regions *this_ptr)
  68 {
  69   this_ptr->init_cluster (base_reg);
  70 }
  71
  72 /* Called for each cluster when initializing this object.  */
  73 void
  74 reachable_regions::init_cluster (const region *base_reg)
  75 {
  76   /* Mark any globals as mutable (and traverse what they point to).  */
  77   const region *parent = base_reg->get_parent_region ();
  78   gcc_assert (parent);
  79   if (parent->get_kind () == RK_GLOBALS)
  80     add (base_reg, true);
  81
  82   /* Mark any clusters that already escaped in previous unknown calls
  83      as mutable (and traverse what they currently point to).  */
  84   if (m_store->escaped_p (base_reg))
  85     add (base_reg, true);
  86
  87   if (const symbolic_region *sym_reg = base_reg->dyn_cast_symbolic_region ())
  88     {
  89       const svalue *ptr = sym_reg->get_pointer ();
  90       if (ptr->implicitly_live_p (NULL, m_model))
  91         add (base_reg, true);
  92       switch (ptr->get_kind ())
  93         {
  94         default:
  95           break;
  96         case SK_INITIAL:
  97           {
  98             /* If BASE_REG is *INIT_VAL(REG) for some other REG, see if REG is
  99                unbound and untouched.  If so, then add BASE_REG as a root.  */
 100             const initial_svalue *init_sval
 101               = as_a <const initial_svalue *> (ptr);
 102             const region *init_sval_reg = init_sval->get_region ();
 103             const region *other_base_reg = init_sval_reg->get_base_region ();
 104             const binding_cluster *other_cluster
 105               = m_store->get_cluster (other_base_reg);
 106             if (other_cluster == NULL
 107                 || !other_cluster->touched_p ())
 108               add (base_reg, true);
 109           }
 110           break;
 111
 112         case SK_UNKNOWN:
 113         case SK_CONJURED:
 114           {
 115             /* If this cluster is due to dereferencing an unknown/conjured
 116                pointer, any values written through the pointer could still
 117                be live.  */
 118             add (base_reg, true);
 119           }
 120           break;
 121         }
 122     }
 123 }
 124
 125   /* Lazily mark the cluster containing REG as being reachable, recursively
 126      adding clusters reachable from REG's cluster.  */
 127 void
 128 reachable_regions::add (const region *reg, bool is_mutable)
 129 {
 130   gcc_assert (reg);
 131
 132   const region *base_reg = const_cast <region *> (reg->get_base_region ());
 133   gcc_assert (base_reg);
 134
 135   /* Bail out if this cluster is already in the sets at the IS_MUTABLE
 136      level of mutability.  */
 137   if (!is_mutable && m_reachable_base_regs.contains (base_reg))
 138     return;
 139   m_reachable_base_regs.add (base_reg);
 140
 141   if (is_mutable)
 142     {
 143       if (m_mutable_base_regs.contains (base_reg))
 144         return;
 145       else
 146         m_mutable_base_regs.add (base_reg);
 147     }
 148
 149   /* Add values within the cluster.  If any are pointers, add the pointee.  */
 150   if (binding_cluster *bind_cluster = m_store->get_cluster (base_reg))
 151     bind_cluster->for_each_value (handle_sval_cb, this);
 152   else
 153     handle_sval (m_model->get_store_value (reg, NULL));
 154 }
 155
 156 void
 157 reachable_regions::handle_sval_cb (const svalue *sval,
 158                                    reachable_regions *this_ptr)
 159 {
 160   this_ptr->handle_sval (sval);
 161 }
 162
 163 /* Add SVAL.  If it is a pointer, add the pointed-to region.  */
 164
 165 void
 166 reachable_regions::handle_sval (const svalue *sval)
 167 {
 168   m_reachable_svals.add (sval);
 169   m_mutable_svals.add (sval);
 170   if (const region_svalue *ptr = sval->dyn_cast_region_svalue ())
 171     {
 172       const region *pointee = ptr->get_pointee ();
 173       /* Use const-ness of pointer type to affect mutability.  */
 174       bool ptr_is_mutable = true;
 175       if (ptr->get_type ()
 176           && TREE_CODE (ptr->get_type ()) == POINTER_TYPE
 177           && TYPE_READONLY (TREE_TYPE (ptr->get_type ())))
 178         {
 179           ptr_is_mutable = false;
 180         }
 181       else
 182         {
 183           m_mutable_svals.add (sval);
 184         }
 185       add (pointee, ptr_is_mutable);
 186     }
 187   /* Treat all svalues within a compound_svalue as reachable.  */
 188   if (const compound_svalue *compound_sval
 189       = sval->dyn_cast_compound_svalue ())
 190     {
 191       for (compound_svalue::iterator_t iter = compound_sval->begin ();
 192            iter != compound_sval->end (); ++iter)
 193         {
 194           const svalue *iter_sval = (*iter).second;
 195           handle_sval (iter_sval);
 196         }
 197     }
 198   if (const svalue *cast = sval->maybe_undo_cast ())
 199     handle_sval (cast);
 200
 201   /* If SVAL is the result of a reversible operation, then the operands
 202      are reachable.  */
 203   switch (sval->get_kind ())
 204     {
 205     default:
 206       break;
 207     case SK_UNARYOP:
 208       {
 209         const unaryop_svalue *unaryop_sval = (const unaryop_svalue *)sval;
 210         switch (unaryop_sval->get_op ())
 211           {
 212           default:
 213             break;
 214           case NEGATE_EXPR:
 215             handle_sval (unaryop_sval->get_arg ());
 216             break;
 217           }
 218       }
 219       break;
 220     case SK_BINOP:
 221       {
 222         const binop_svalue *binop_sval = (const binop_svalue *)sval;
 223         switch (binop_sval->get_op ())
 224           {
 225           default:
 226             break;
 227           case POINTER_PLUS_EXPR:
 228             handle_sval (binop_sval->get_arg0 ());
 229             handle_sval (binop_sval->get_arg1 ());
 230             break;
 231           }
 232       }
 233     }
 234 }
 235
 236 /* Add SVAL.  If it is a pointer, add the pointed-to region.
 237    Use PARAM_TYPE for determining mutability.  */
 238
 239 void
 240 reachable_regions::handle_parm (const svalue *sval, tree param_type)
 241 {
 242   bool is_mutable = true;
 243   if (param_type
 244       && TREE_CODE (param_type) == POINTER_TYPE
 245       &&  TYPE_READONLY (TREE_TYPE (param_type)))
 246     is_mutable = false;
 247   if (is_mutable)
 248     m_mutable_svals.add (sval);
 249   else
 250     m_reachable_svals.add (sval);
 251   if (const region *base_reg = sval->maybe_get_deref_base_region ())
 252     add (base_reg, is_mutable);
 253   /* Treat all svalues within a compound_svalue as reachable.  */
 254   if (const compound_svalue *compound_sval
 255       = sval->dyn_cast_compound_svalue ())
 256     {
 257       for (compound_svalue::iterator_t iter = compound_sval->begin ();
 258            iter != compound_sval->end (); ++iter)
 259         {
 260           const svalue *iter_sval = (*iter).second;
 261           handle_sval (iter_sval);
 262         }
 263     }
 264   if (const svalue *cast = sval->maybe_undo_cast ())
 265     handle_sval (cast);
 266 }
 267
 268 /* Update the store to mark the clusters that were found to be mutable
 269    as having escaped.
 270    Notify CTXT about escaping function_decls.  */
 271
 272 void
 273 reachable_regions::mark_escaped_clusters (region_model_context *ctxt)
 274 {
 275   auto_vec<const function_region *> escaped_fn_regs
 276     (m_mutable_base_regs.elements ());
 277   for (hash_set<const region *>::iterator iter = m_mutable_base_regs.begin ();
 278        iter != m_mutable_base_regs.end (); ++iter)
 279     {
 280       const region *base_reg = *iter;
 281       m_store->mark_as_escaped (base_reg);
 282
 283       /* If we have a function that's escaped, potentially add
 284          it to the worklist.  */
 285       if (const function_region *fn_reg = base_reg->dyn_cast_function_region ())
 286         escaped_fn_regs.quick_push (fn_reg);
 287     }
 288   if (ctxt)
 289     {
 290       /* Sort to ensure deterministic results.  */
 291       escaped_fn_regs.qsort (region::cmp_ptr_ptr);
 292       unsigned i;
 293       const function_region *fn_reg;
 294       FOR_EACH_VEC_ELT (escaped_fn_regs, i, fn_reg)
 295         ctxt->on_escaped_function (fn_reg->get_fndecl ());
 296     }
 297 }
 298
 299 /* Dump SET to PP, sorting it to avoid churn when comparing dumps.  */
 300
 301 template <typename T>
 302 static void
 303 dump_set (const hash_set<const T *> &set, pretty_printer *pp)
 304 {
 305   auto_vec<const T *> elements (set.elements ());
 306   for (typename hash_set<const T *>::iterator iter = set.begin ();
 307        iter != set.end (); ++iter)
 308     elements.quick_push (*iter);
 309
 310   elements.qsort (T::cmp_ptr_ptr);
 311
 312   unsigned i;
 313   const T *element;
 314   FOR_EACH_VEC_ELT (elements, i, element)
 315     {
 316       pp_string (pp, "  ");
 317       element->dump_to_pp (pp, true);
 318       pp_newline (pp);
 319     }
 320 }
 321
 322 /* Dump a multiline representation of this object to PP.  */
 323
 324 void
 325 reachable_regions::dump_to_pp (pretty_printer *pp) const
 326 {
 327   pp_string (pp, "reachable clusters: ");
 328   pp_newline (pp);
 329   dump_set (m_reachable_base_regs, pp);
 330
 331   pp_string (pp, "mutable clusters: ");
 332   pp_newline (pp);
 333   dump_set (m_mutable_base_regs, pp);
 334
 335   pp_string (pp, "reachable svals: ");
 336   pp_newline (pp);
 337   dump_set (m_reachable_svals, pp);
 338
 339   pp_string (pp, "mutable svals: ");
 340   pp_newline (pp);
 341   dump_set (m_mutable_svals, pp);
 342 }
 343
 344 /* Dump a multiline representation of this object to stderr.  */
 345
 346 DEBUG_FUNCTION void
 347 reachable_regions::dump () const
 348 {
 349   pretty_printer pp;
 350   pp_format_decoder (&pp) = default_tree_printer;
 351   pp_show_color (&pp) = pp_show_color (global_dc->printer);
 352   pp.buffer->stream = stderr;
 353   dump_to_pp (&pp);
 354   pp_flush (&pp);
 355 }
 356
 357 } // namespace ana
 358
 359 #endif /* #if ENABLE_ANALYZER */