gcc/gimple-range-infer.cc

   1 /* Gimple range inference implementation.
   2    Copyright (C) 2022-2024 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 // Create the global oracle.
  41
  42 infer_range_oracle infer_oracle;
  43
  44 // This class is merely an accessor which is granted internals to
  45 // gimple_infer_range such that non_null_loadstore as a static callback can
  46 // call the protected add_nonzero ().
  47 // Static functions ccannot be friends, so we do it through a class wrapper.
  48
  49 class non_null_wrapper
  50 {
  51 public:
  52   inline non_null_wrapper (gimple_infer_range *infer) : m_infer (infer) { }
  53   inline void add_nonzero (tree name) { m_infer->add_nonzero (name); }
  54   inline void add_range (tree t, vrange &r) { m_infer->add_range (t, r); }
  55 private:
  56   gimple_infer_range *m_infer;
  57 };
  58
  59 // Adapted from infer_nonnull_range_by_dereference and check_loadstore
  60 // to process nonnull ssa_name OP in S.  DATA contains a pointer to a
  61 // stmt range inference instance.
  62
  63 static bool
  64 non_null_loadstore (gimple *, tree op, tree, void *data)
  65 {
  66   if (TREE_CODE (op) == MEM_REF || TREE_CODE (op) == TARGET_MEM_REF)
  67     {
  68       /* Some address spaces may legitimately dereference zero.  */
  69       addr_space_t as = TYPE_ADDR_SPACE (TREE_TYPE (op));
  70       if (!targetm.addr_space.zero_address_valid (as))
  71         {
  72           non_null_wrapper wrapper ((gimple_infer_range *)data);
  73           wrapper.add_nonzero (TREE_OPERAND (op, 0));
  74         }
  75     }
  76   return false;
  77 }
  78
  79 // Process an ASSUME call to see if there are any inferred ranges available.
  80
  81 void
  82 gimple_infer_range::check_assume_func (gcall *call)
  83 {
  84   tree arg;
  85   unsigned i;
  86   tree assume_id = TREE_OPERAND (gimple_call_arg (call, 0), 0);
  87   if (!assume_id)
  88     return;
  89   struct function *fun = DECL_STRUCT_FUNCTION (assume_id);
  90   if (!fun)
  91     return;
  92   // Loop over arguments, matching them to the assume parameters.
  93   for (arg = DECL_ARGUMENTS (assume_id), i = 1;
  94        arg && i < gimple_call_num_args (call);
  95        i++, arg = DECL_CHAIN (arg))
  96     {
  97       tree op = gimple_call_arg (call, i);
  98       tree type = TREE_TYPE (op);
  99       if (gimple_range_ssa_p (op) && value_range::supports_type_p (type))
 100         {
 101           tree default_def = ssa_default_def (fun, arg);
 102           if (!default_def || type != TREE_TYPE (default_def))
 103             continue;
 104           // Query the global range of the default def in the assume function.
 105           value_range assume_range (type);
 106           gimple_range_global (assume_range, default_def, fun);
 107           // If there is a non-varying result, add it as an inferred range.
 108           if (!assume_range.varying_p ())
 109             {
 110               add_range (op, assume_range);
 111               if (dump_file)
 112                 {
 113                   print_generic_expr (dump_file, assume_id, TDF_SLIM);
 114                   fprintf (dump_file, " assume inferred range of ");
 115                   print_generic_expr (dump_file, op, TDF_SLIM);
 116                   fprintf (dump_file, " (param ");
 117                   print_generic_expr (dump_file, arg, TDF_SLIM);
 118                   fprintf (dump_file, ") = ");
 119                   assume_range.dump (dump_file);
 120                   fputc ('\n', dump_file);
 121                 }
 122             }
 123         }
 124     }
 125 }
 126
 127 // Add NAME and RANGE to the range inference summary.
 128
 129 void
 130 gimple_infer_range::add_range (tree name, vrange &range)
 131 {
 132   // Do not add an inferred range if it is VARYING.
 133   if (range.varying_p ())
 134     return;
 135   m_names[num_args] = name;
 136   m_ranges[num_args] = range;
 137   if (num_args < size_limit - 1)
 138     num_args++;
 139 }
 140
 141 // Add a nonzero range for NAME to the range inference summary.
 142
 143 void
 144 gimple_infer_range::add_nonzero (tree name)
 145 {
 146   if (!gimple_range_ssa_p (name))
 147     return;
 148   prange nz;
 149   nz.set_nonzero (TREE_TYPE (name));
 150   add_range (name, nz);
 151 }
 152
 153 // Process S for range inference and fill in the summary list.
 154 // This is the routine where new inferred ranges should be added.
 155 // If USE_RANGEOPS is true, invoke range-ops on stmts with a single
 156 // ssa-name aa constant to reflect an inferred range. ie
 157 // x_2 = y_3 + 1 will provide an inferred range for y_3 of [-INF, +INF - 1].
 158 // This defaults to FALSE as it can be expensive.,
 159
 160 gimple_infer_range::gimple_infer_range (gimple *s, bool use_rangeops)
 161 {
 162   num_args = 0;
 163
 164   if (is_a<gphi *> (s))
 165     return;
 166
 167   if (is_a<gcall *> (s) && flag_delete_null_pointer_checks)
 168     {
 169       tree fntype = gimple_call_fntype (s);
 170       bitmap nonnullargs = get_nonnull_args (fntype);
 171       // Process any non-null arguments
 172       if (nonnullargs)
 173         {
 174           for (unsigned i = 0; i < gimple_call_num_args (s); i++)
 175             {
 176               if (bitmap_empty_p (nonnullargs)
 177                   || bitmap_bit_p (nonnullargs, i))
 178                 {
 179                   tree op = gimple_call_arg (s, i);
 180                   if (POINTER_TYPE_P (TREE_TYPE (op)))
 181                     add_nonzero (op);
 182                 }
 183             }
 184           BITMAP_FREE (nonnullargs);
 185         }
 186       // Fallthru and walk load/store ops now.
 187     }
 188
 189   // Check for inferred ranges from ASSUME calls.
 190   if (is_a<gcall *> (s) && gimple_call_internal_p (s)
 191       && gimple_call_internal_fn (s) == IFN_ASSUME)
 192     check_assume_func (as_a<gcall *> (s));
 193
 194   // Look for possible non-null values.
 195   if (flag_delete_null_pointer_checks && gimple_code (s) != GIMPLE_ASM
 196       && !gimple_clobber_p (s))
 197     walk_stmt_load_store_ops (s, (void *)this, non_null_loadstore,
 198                               non_null_loadstore);
 199
 200   // Gated by flag.
 201   if (!use_rangeops)
 202     return;
 203
 204   // Check if there are any inferred ranges from range-ops.
 205   gimple_range_op_handler handler (s);
 206   if (!handler)
 207     return;
 208
 209   // Only proceed if ONE operand is an SSA_NAME,  This may provide an
 210   // inferred range for 'y + 3' , but will bypass expressions like
 211   // 'y + z' as it depends on symbolic values.
 212   tree ssa1 = gimple_range_ssa_p (handler.operand1 ());
 213   tree ssa2 = gimple_range_ssa_p (handler.operand2 ());
 214   if ((ssa1 != NULL) == (ssa2 != NULL))
 215     return;
 216
 217   // The other operand should be a constant, so just use the global range
 218   // query to pick up any other values.
 219   if (ssa1)
 220     {
 221       value_range op1 (TREE_TYPE (ssa1));
 222       if (op1_range (op1, s, get_global_range_query ()) && !op1.varying_p ())
 223         add_range (ssa1, op1);
 224     }
 225   else
 226     {
 227       gcc_checking_assert (ssa2);
 228       value_range op2 (TREE_TYPE (ssa2));
 229       if (op2_range (op2, s, get_global_range_query ()) && !op2.varying_p ())
 230         add_range (ssa2, op2);
 231     }
 232 }
 233
 234 // Create an single inferred range for NAMe using range R.
 235
 236 gimple_infer_range::gimple_infer_range (tree name, vrange &r)
 237 {
 238   num_args = 0;
 239   add_range (name, r);
 240 }
 241
 242 // -------------------------------------------------------------------------
 243
 244 // This class is an element in the list of inferred ranges.
 245
 246 class exit_range
 247 {
 248 public:
 249   tree name;
 250   gimple *stmt;
 251   vrange_storage *range;
 252   exit_range *next;
 253 };
 254
 255
 256 // If there is an element which matches SSA, return a pointer to the element.
 257 // Otherwise return NULL.
 258
 259 exit_range *
 260 infer_range_manager::exit_range_head::find_ptr (tree ssa)
 261 {
 262   // Return NULL if SSA is not in this list.
 263   if (!m_names || !bitmap_bit_p (m_names, SSA_NAME_VERSION (ssa)))
 264     return NULL;
 265   for (exit_range *ptr = head; ptr != NULL; ptr = ptr->next)
 266     if (ptr->name == ssa)
 267       return ptr;
 268   // Should be unreachable.
 269   gcc_unreachable ();
 270   return NULL;
 271 }
 272
 273 // Construct a range infer manager.  DO_SEARCH indicates whether an immediate
 274 // use scan should be made the first time a name is processed.  This is for
 275 // on-demand clients who may not visit every statement and may miss uses.
 276
 277 infer_range_manager::infer_range_manager (bool do_search)
 278 {
 279   bitmap_obstack_initialize (&m_bitmaps);
 280   m_on_exit.create (0);
 281   m_on_exit.safe_grow_cleared (last_basic_block_for_fn (cfun) + 1);
 282   // m_seen == NULL indicates no scanning.  Otherwise the bit indicates a
 283   // scan has been performed on NAME.
 284   if (do_search)
 285     m_seen = BITMAP_ALLOC (&m_bitmaps);
 286   else
 287     m_seen = NULL;
 288   obstack_init (&m_list_obstack);
 289   // Non-zero elements are very common, so cache them for each ssa-name.
 290   m_nonzero.create (0);
 291   m_nonzero.safe_grow_cleared (num_ssa_names + 1);
 292   m_range_allocator = new vrange_allocator;
 293 }
 294
 295 // Destruct a range infer manager.
 296
 297 infer_range_manager::~infer_range_manager ()
 298 {
 299   m_nonzero.release ();
 300   obstack_free (&m_list_obstack, NULL);
 301   m_on_exit.release ();
 302   bitmap_obstack_release (&m_bitmaps);
 303   delete m_range_allocator;
 304 }
 305
 306 // Return a non-zero range value of the appropriate type for NAME from
 307 // the cache, creating it if necessary.
 308
 309 const vrange&
 310 infer_range_manager::get_nonzero (tree name)
 311 {
 312   unsigned v = SSA_NAME_VERSION (name);
 313   if (v >= m_nonzero.length ())
 314     m_nonzero.safe_grow_cleared (num_ssa_names + 20);
 315   if (!m_nonzero[v])
 316     {
 317       m_nonzero[v]
 318         = (irange *) m_range_allocator->alloc (sizeof (int_range <2>));
 319       m_nonzero[v]->set_nonzero (TREE_TYPE (name));
 320     }
 321   return *(m_nonzero[v]);
 322 }
 323
 324 // Return TRUE if NAME has a range inference in block BB.  If NAME is NULL,
 325 // return TRUE if there are any name sin BB.
 326
 327 bool
 328 infer_range_manager::has_range_p (basic_block bb, tree name)
 329 {
 330   // Check if this is an immediate use search model.
 331   if (name && m_seen && !bitmap_bit_p (m_seen, SSA_NAME_VERSION (name)))
 332     register_all_uses (name);
 333
 334   if (bb->index >= (int)m_on_exit.length ())
 335     return false;
 336
 337   bitmap b = m_on_exit[bb->index].m_names;
 338   if (!b)
 339     return false;
 340
 341   if (name)
 342     return bitmap_bit_p (m_on_exit[bb->index].m_names, SSA_NAME_VERSION (name));
 343   return !bitmap_empty_p (b);
 344 }
 345
 346 // Return TRUE if NAME has a range inference in block BB, and adjust range R
 347 // to include it.
 348
 349 bool
 350 infer_range_manager::maybe_adjust_range (vrange &r, tree name, basic_block bb)
 351 {
 352   if (!has_range_p (bb, name))
 353     return false;
 354   exit_range *ptr = m_on_exit[bb->index].find_ptr (name);
 355   gcc_checking_assert (ptr);
 356   // Return true if this exit range changes R, otherwise false.
 357   tree type = TREE_TYPE (name);
 358   value_range tmp (type);
 359   ptr->range->get_vrange (tmp, type);
 360   return r.intersect (tmp);
 361 }
 362
 363 // Add all inferred ranges in INFER at stmt S.
 364
 365 void
 366 infer_range_manager::add_ranges (gimple *s, gimple_infer_range &infer)
 367 {
 368   for (unsigned x = 0; x < infer.num (); x++)
 369     add_range (infer.name (x), s, infer.range (x));
 370 }
 371
 372 // Add range R as an inferred range for NAME on stmt S.
 373
 374 void
 375 infer_range_manager::add_range (tree name, gimple *s, const vrange &r)
 376 {
 377   basic_block bb = gimple_bb (s);
 378   if (!bb)
 379     return;
 380   if (bb->index >= (int)m_on_exit.length ())
 381     m_on_exit.safe_grow_cleared (last_basic_block_for_fn (cfun) + 1);
 382
 383   // Create the summary list bitmap if it doesn't exist.
 384   if (!m_on_exit[bb->index].m_names)
 385       m_on_exit[bb->index].m_names = BITMAP_ALLOC (&m_bitmaps);
 386
 387   if (dump_file && (dump_flags & TDF_DETAILS))
 388    {
 389      fprintf (dump_file, "   on-exit update ");
 390      print_generic_expr (dump_file, name, TDF_SLIM);
 391      fprintf (dump_file, " in BB%d : ",bb->index);
 392      r.dump (dump_file);
 393      fprintf (dump_file, "\n");
 394    }
 395
 396   // If NAME already has a range, intersect them and done.
 397   exit_range *ptr = m_on_exit[bb->index].find_ptr (name);
 398   if (ptr)
 399     {
 400       tree type = TREE_TYPE (name);
 401       value_range cur (r), name_range (type);
 402       ptr->range->get_vrange (name_range, type);
 403       // If no new info is added, just return.
 404       if (!cur.intersect (name_range))
 405         return;
 406       if (ptr->range->fits_p (cur))
 407         ptr->range->set_vrange (cur);
 408       else
 409         ptr->range = m_range_allocator->clone (cur);
 410       ptr->stmt = s;
 411       return;
 412     }
 413
 414   // Otherwise create a record.
 415   bitmap_set_bit (m_on_exit[bb->index].m_names, SSA_NAME_VERSION (name));
 416   ptr = (exit_range *)obstack_alloc (&m_list_obstack, sizeof (exit_range));
 417   ptr->range = m_range_allocator->clone (r);
 418   ptr->name = name;
 419   ptr->stmt = s;
 420   ptr->next = m_on_exit[bb->index].head;
 421   m_on_exit[bb->index].head = ptr;
 422 }
 423
 424 // Add a non-zero inferred range for NAME at stmt S.
 425
 426 void
 427 infer_range_manager::add_nonzero (tree name, gimple *s)
 428 {
 429   add_range (name, s, get_nonzero (name));
 430 }
 431
 432 // Follow immediate use chains and find all inferred ranges for NAME.
 433
 434 void
 435 infer_range_manager::register_all_uses (tree name)
 436 {
 437   gcc_checking_assert (m_seen);
 438
 439   // Check if we've already processed this name.
 440   unsigned v = SSA_NAME_VERSION (name);
 441   if (bitmap_bit_p (m_seen, v))
 442      return;
 443   bitmap_set_bit (m_seen, v);
 444
 445   use_operand_p use_p;
 446   imm_use_iterator iter;
 447
 448   // Loop over each immediate use and see if it has an inferred range.
 449   FOR_EACH_IMM_USE_FAST (use_p, iter, name)
 450     {
 451       gimple *s = USE_STMT (use_p);
 452       gimple_infer_range infer (s);
 453       for (unsigned x = 0; x < infer.num (); x++)
 454         {
 455           if (name == infer.name (x))
 456             add_range (name, s, infer.range (x));
 457         }
 458     }
 459 }