gcc/gimple-range-infer.cc

   1 /* Gimple range inference implementation.
   2    Copyright (C) 2022 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
   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 #include "config.h"
  22 #include "system.h"
  23 #include "coretypes.h"
  24 #include "backend.h"
  25 #include "insn-codes.h"
  26 #include "tree.h"
  27 #include "gimple.h"
  28 #include "ssa.h"
  29 #include "gimple-pretty-print.h"
  30 #include "gimple-range.h"
  31 #include "value-range-storage.h"
  32 #include "tree-cfg.h"
  33 #include "target.h"
  34 #include "attribs.h"
  35 #include "gimple-iterator.h"
  36 #include "gimple-walk.h"
  37 #include "cfganal.h"
  38 #include "tree-dfa.h"
  39
  40 // Adapted from infer_nonnull_range_by_dereference and check_loadstore
  41 // to process nonnull ssa_name OP in S.  DATA contains a pointer to a
  42 // stmt range inference instance.
  43
  44 static bool
  45 non_null_loadstore (gimple *, tree op, tree, void *data)
  46 {
  47   if (TREE_CODE (op) == MEM_REF || TREE_CODE (op) == TARGET_MEM_REF)
  48     {
  49       /* Some address spaces may legitimately dereference zero.  */
  50       addr_space_t as = TYPE_ADDR_SPACE (TREE_TYPE (op));
  51       if (!targetm.addr_space.zero_address_valid (as))
  52         {
  53           tree ssa = TREE_OPERAND (op, 0);
  54           ((gimple_infer_range *)data)->add_nonzero (ssa);
  55         }
  56     }
  57   return false;
  58 }
  59
  60 // Process an ASSUME call to see if there are any inferred ranges available.
  61
  62 void
  63 gimple_infer_range::check_assume_func (gcall *call)
  64 {
  65   tree arg;
  66   unsigned i;
  67   tree assume_id = TREE_OPERAND (gimple_call_arg (call, 0), 0);
  68   if (!assume_id)
  69     return;
  70   struct function *fun = DECL_STRUCT_FUNCTION (assume_id);
  71   if (!fun)
  72     return;
  73   // Loop over arguments, matching them to the assume paramters.
  74   for (arg = DECL_ARGUMENTS (assume_id), i = 1;
  75        arg && i < gimple_call_num_args (call);
  76        i++, arg = DECL_CHAIN (arg))
  77     {
  78       tree op = gimple_call_arg (call, i);
  79       tree type = TREE_TYPE (op);
  80       if (gimple_range_ssa_p (op) && Value_Range::supports_type_p (type))
  81         {
  82           tree default_def = ssa_default_def (fun, arg);
  83           if (!default_def || type != TREE_TYPE (default_def))
  84             continue;
  85           // Query the global range of the default def in the assume function.
  86           Value_Range assume_range (type);
  87           global_ranges.range_of_expr (assume_range, default_def);
  88           // If there is a non-varying result, add it as an inferred range.
  89           if (!assume_range.varying_p ())
  90             {
  91               add_range (op, assume_range);
  92               if (dump_file)
  93                 {
  94                   print_generic_expr (dump_file, assume_id, TDF_SLIM);
  95                   fprintf (dump_file, " assume inferred range of ");
  96                   print_generic_expr (dump_file, op, TDF_SLIM);
  97                   fprintf (dump_file, " (param ");
  98                   print_generic_expr (dump_file, arg, TDF_SLIM);
  99                   fprintf (dump_file, ") = ");
 100                   assume_range.dump (dump_file);
 101                   fputc ('\n', dump_file);
 102                 }
 103             }
 104         }
 105     }
 106 }
 107
 108 // Add NAME and RANGE to the range inference summary.
 109
 110 void
 111 gimple_infer_range::add_range (tree name, vrange &range)
 112 {
 113   m_names[num_args] = name;
 114   m_ranges[num_args] = range;
 115   if (num_args < size_limit - 1)
 116     num_args++;
 117 }
 118
 119 // Add a nonzero range for NAME to the range inference summary.
 120
 121 void
 122 gimple_infer_range::add_nonzero (tree name)
 123 {
 124   if (!gimple_range_ssa_p (name))
 125     return;
 126   int_range<2> nz;
 127   nz.set_nonzero (TREE_TYPE (name));
 128   add_range (name, nz);
 129 }
 130
 131 // Process S for range inference and fill in the summary list.
 132 // This is the routine where new inferred ranges should be added.
 133
 134 gimple_infer_range::gimple_infer_range (gimple *s)
 135 {
 136   num_args = 0;
 137
 138   if (is_a<gphi *> (s))
 139     return;
 140
 141   if (is_a<gcall *> (s) && flag_delete_null_pointer_checks)
 142     {
 143       tree fntype = gimple_call_fntype (s);
 144       bitmap nonnullargs = get_nonnull_args (fntype);
 145       // Process any non-null arguments
 146       if (nonnullargs)
 147         {
 148           for (unsigned i = 0; i < gimple_call_num_args (s); i++)
 149             {
 150               if (bitmap_empty_p (nonnullargs)
 151                   || bitmap_bit_p (nonnullargs, i))
 152                 {
 153                   tree op = gimple_call_arg (s, i);
 154                   if (POINTER_TYPE_P (TREE_TYPE (op)))
 155                     add_nonzero (op);
 156                 }
 157             }
 158           BITMAP_FREE (nonnullargs);
 159         }
 160       // Fallthru and walk load/store ops now.
 161     }
 162
 163   // Check for inferred ranges from ASSUME calls.
 164   if (is_a<gcall *> (s) && gimple_call_internal_p (s)
 165       && gimple_call_internal_fn (s) == IFN_ASSUME)
 166     check_assume_func (as_a<gcall *> (s));
 167
 168   // Look for possible non-null values.
 169   if (flag_delete_null_pointer_checks && gimple_code (s) != GIMPLE_ASM
 170       && !gimple_clobber_p (s))
 171     walk_stmt_load_store_ops (s, (void *)this, non_null_loadstore,
 172                               non_null_loadstore);
 173
 174 }
 175
 176 // -------------------------------------------------------------------------
 177
 178 // This class is an element in the list of infered ranges.
 179
 180 class exit_range
 181 {
 182 public:
 183   tree name;
 184   vrange *range;
 185   exit_range *next;
 186 };
 187
 188 // If there is an element which matches SSA, return a pointer to the element.
 189 // Otherwise return NULL.
 190
 191 exit_range *
 192 infer_range_manager::exit_range_head::find_ptr (tree ssa)
 193 {
 194   // Return NULL if SSA is not in this list.
 195   if (!m_names || !bitmap_bit_p (m_names, SSA_NAME_VERSION (ssa)))
 196     return NULL;
 197   for (exit_range *ptr = head; ptr != NULL; ptr = ptr->next)
 198     if (ptr->name == ssa)
 199       return ptr;
 200   // Should be unreachable.
 201   gcc_unreachable ();
 202   return NULL;
 203 }
 204
 205 // Construct a range infer manager.  DO_SEARCH indicates whether an immediate
 206 // use scan should be made the first time a name is processed.  This is for
 207 // on-demand clients who may not visit every statement and may miss uses.
 208
 209 infer_range_manager::infer_range_manager (bool do_search)
 210 {
 211   bitmap_obstack_initialize (&m_bitmaps);
 212   m_on_exit.create (0);
 213   m_on_exit.safe_grow_cleared (last_basic_block_for_fn (cfun) + 1);
 214   // m_seen == NULL indicates no scanning.  Otherwise the bit indicates a
 215   // scan has been performed on NAME.
 216   if (do_search)
 217     m_seen = BITMAP_ALLOC (&m_bitmaps);
 218   else
 219     m_seen = NULL;
 220   obstack_init (&m_list_obstack);
 221   // Non-zero elements are very common, so cache them for each ssa-name.
 222   m_nonzero.create (0);
 223   m_nonzero.safe_grow_cleared (num_ssa_names + 1);
 224   m_range_allocator = new obstack_vrange_allocator;
 225 }
 226
 227 // Destruct a range infer manager.
 228
 229 infer_range_manager::~infer_range_manager ()
 230 {
 231   m_nonzero.release ();
 232   obstack_free (&m_list_obstack, NULL);
 233   m_on_exit.release ();
 234   bitmap_obstack_release (&m_bitmaps);
 235   delete m_range_allocator;
 236 }
 237
 238 // Return a non-zero range value of the appropriate type for NAME from
 239 // the cache, creating it if necessary.
 240
 241 const vrange&
 242 infer_range_manager::get_nonzero (tree name)
 243 {
 244   unsigned v = SSA_NAME_VERSION (name);
 245   if (v >= m_nonzero.length ())
 246     m_nonzero.safe_grow_cleared (num_ssa_names + 20);
 247   if (!m_nonzero[v])
 248     {
 249       m_nonzero[v] = m_range_allocator->alloc_vrange (TREE_TYPE (name));
 250       m_nonzero[v]->set_nonzero (TREE_TYPE (name));
 251     }
 252   return *(m_nonzero[v]);
 253 }
 254
 255 // Return TRUE if NAME has a range inference in block BB.
 256
 257 bool
 258 infer_range_manager::has_range_p (tree name, basic_block bb)
 259 {
 260   // Check if this is an immediate use search model.
 261   if (m_seen && !bitmap_bit_p (m_seen, SSA_NAME_VERSION (name)))
 262     register_all_uses (name);
 263
 264   if (bb->index >= (int)m_on_exit.length ())
 265     return false;
 266   if (!m_on_exit[bb->index].m_names)
 267     return false;
 268   if (!bitmap_bit_p (m_on_exit[bb->index].m_names, SSA_NAME_VERSION (name)))
 269     return false;
 270   return true;
 271 }
 272
 273 // Return TRUE if NAME has a range inference in block BB, and adjust range R
 274 // to include it.
 275
 276 bool
 277 infer_range_manager::maybe_adjust_range (vrange &r, tree name, basic_block bb)
 278 {
 279   if (!has_range_p (name, bb))
 280     return false;
 281   exit_range *ptr = m_on_exit[bb->index].find_ptr (name);
 282   gcc_checking_assert (ptr);
 283   // Return true if this exit range changes R, otherwise false.
 284   return r.intersect (*(ptr->range));
 285 }
 286
 287 // Add range R as an inferred range for NAME in block BB.
 288
 289 void
 290 infer_range_manager::add_range (tree name, basic_block bb, const vrange &r)
 291 {
 292   if (bb->index >= (int)m_on_exit.length ())
 293     m_on_exit.safe_grow_cleared (last_basic_block_for_fn (cfun) + 1);
 294
 295   // Create the summary list bitmap if it doesn't exist.
 296   if (!m_on_exit[bb->index].m_names)
 297       m_on_exit[bb->index].m_names = BITMAP_ALLOC (&m_bitmaps);
 298
 299   if (dump_file && (dump_flags & TDF_DETAILS))
 300    {
 301      fprintf (dump_file, "   on-exit update ");
 302      print_generic_expr (dump_file, name, TDF_SLIM);
 303      fprintf (dump_file, " in BB%d : ",bb->index);
 304      r.dump (dump_file);
 305      fprintf (dump_file, "\n");
 306    }
 307
 308   // If NAME already has a range, intersect them and done.
 309   exit_range *ptr = m_on_exit[bb->index].find_ptr (name);
 310   if (ptr)
 311     {
 312       Value_Range cur (r);
 313       // If no new info is added, just return.
 314       if (!cur.intersect (*(ptr->range)))
 315         return;
 316       if (ptr->range->fits_p (cur))
 317         *(ptr->range) = cur;
 318       else
 319         {
 320           vrange &v = cur;
 321           ptr->range = m_range_allocator->clone (v);
 322         }
 323       return;
 324     }
 325
 326   // Otherwise create a record.
 327   bitmap_set_bit (m_on_exit[bb->index].m_names, SSA_NAME_VERSION (name));
 328   ptr = (exit_range *)obstack_alloc (&m_list_obstack, sizeof (exit_range));
 329   ptr->range = m_range_allocator->clone (r);
 330   ptr->name = name;
 331   ptr->next = m_on_exit[bb->index].head;
 332   m_on_exit[bb->index].head = ptr;
 333 }
 334
 335 // Add a non-zero inferred range for NAME in block BB.
 336
 337 void
 338 infer_range_manager::add_nonzero (tree name, basic_block bb)
 339 {
 340   add_range (name, bb, get_nonzero (name));
 341 }
 342
 343 // Follow immediate use chains and find all inferred ranges for NAME.
 344
 345 void
 346 infer_range_manager::register_all_uses (tree name)
 347 {
 348   gcc_checking_assert (m_seen);
 349
 350   // Check if we've already processed this name.
 351   unsigned v = SSA_NAME_VERSION (name);
 352   if (bitmap_bit_p (m_seen, v))
 353      return;
 354   bitmap_set_bit (m_seen, v);
 355
 356   use_operand_p use_p;
 357   imm_use_iterator iter;
 358
 359   // Loop over each immediate use and see if it has an inferred range.
 360   FOR_EACH_IMM_USE_FAST (use_p, iter, name)
 361     {
 362       gimple *s = USE_STMT (use_p);
 363       gimple_infer_range infer (s);
 364       for (unsigned x = 0; x < infer.num (); x++)
 365         {
 366           if (name == infer.name (x))
 367             add_range (name, gimple_bb (s), infer.range (x));
 368         }
 369     }
 370 }