gcc/tree-gimple.c

   1 /* Functions to analyze and validate GIMPLE trees.
   2    Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
   3    Contributed by Diego Novillo <dnovillo@redhat.com>
   4    Rewritten by Jason Merrill <jason@redhat.com>
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 2, or (at your option)
  11 any later version.
  12
  13 GCC is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GCC; see the file COPYING.  If not, write to
  20 the Free Software Foundation, 59 Temple Place - Suite 330,
  21 Boston, MA 02111-1307, USA.  */
  22
  23 #include "config.h"
  24 #include "system.h"
  25 #include "coretypes.h"
  26 #include "ggc.h"
  27 #include "tm.h"
  28 #include "tree.h"
  29 #include "tree-gimple.h"
  30 #include "tree-flow.h"
  31 #include "output.h"
  32 #include "rtl.h"
  33 #include "expr.h"
  34 #include "bitmap.h"
  35
  36 /* For the definitive definition of GIMPLE, see doc/tree-ssa.texi.  */
  37
  38 static inline bool is_gimple_id (tree);
  39
  40 /* Validation of GIMPLE expressions.  */
  41
  42 /* Return true if T is a GIMPLE RHS for an assignment to a temporary.  */
  43
  44 bool
  45 is_gimple_formal_tmp_rhs (tree t)
  46 {
  47   enum tree_code code = TREE_CODE (t);
  48
  49   switch (TREE_CODE_CLASS (code))
  50     {
  51     case tcc_unary:
  52     case tcc_binary:
  53     case tcc_comparison:
  54       return true;
  55
  56     default:
  57       break;
  58     }
  59
  60   switch (code)
  61     {
  62     case TRUTH_NOT_EXPR:
  63     case TRUTH_AND_EXPR:
  64     case TRUTH_OR_EXPR:
  65     case TRUTH_XOR_EXPR:
  66     case ADDR_EXPR:
  67     case CALL_EXPR:
  68     case CONSTRUCTOR:
  69     case COMPLEX_EXPR:
  70     case INTEGER_CST:
  71     case REAL_CST:
  72     case STRING_CST:
  73     case COMPLEX_CST:
  74     case VECTOR_CST:
  75     case OBJ_TYPE_REF:
  76     case ASSERT_EXPR:
  77       return true;
  78
  79     default:
  80       break;
  81     }
  82
  83   return is_gimple_lvalue (t) || is_gimple_val (t);
  84 }
  85
  86 /* Returns true iff T is a valid RHS for an assignment to a renamed
  87    user -- or front-end generated artificial -- variable.  */
  88
  89 bool
  90 is_gimple_reg_rhs (tree t)
  91 {
  92   /* If the RHS of the MODIFY_EXPR may throw or make a nonlocal goto
  93      and the LHS is a user variable, then we need to introduce a formal
  94      temporary.  This way the optimizers can determine that the user
  95      variable is only modified if evaluation of the RHS does not throw.
  96
  97      Don't force a temp of a non-renamable type; the copy could be
  98      arbitrarily expensive.  Instead we will generate a V_MAY_DEF for
  99      the assignment.  */
 100
 101   if (is_gimple_reg_type (TREE_TYPE (t))
 102       && ((TREE_CODE (t) == CALL_EXPR && TREE_SIDE_EFFECTS (t))
 103           || tree_could_throw_p (t)))
 104     return false;
 105
 106   return is_gimple_formal_tmp_rhs (t);
 107 }
 108
 109 /* Returns true iff T is a valid RHS for an assignment to an un-renamed
 110    LHS, or for a call argument.  */
 111
 112 bool
 113 is_gimple_mem_rhs (tree t)
 114 {
 115   /* If we're dealing with a renamable type, either source or dest must be
 116      a renamed variable.  Also force a temporary if the type doesn't need
 117      to be stored in memory, since it's cheap and prevents erroneous
 118      tailcalls (PR 17526).  */
 119   if (is_gimple_reg_type (TREE_TYPE (t))
 120       || TYPE_MODE (TREE_TYPE (t)) != BLKmode)
 121     return is_gimple_val (t);
 122   else
 123     return is_gimple_formal_tmp_rhs (t);
 124 }
 125
 126 /* Returns the appropriate RHS predicate for this LHS.  */
 127
 128 gimple_predicate
 129 rhs_predicate_for (tree lhs)
 130 {
 131   if (is_gimple_formal_tmp_var (lhs))
 132     return is_gimple_formal_tmp_rhs;
 133   else if (is_gimple_reg (lhs))
 134     return is_gimple_reg_rhs;
 135   else
 136     return is_gimple_mem_rhs;
 137 }
 138
 139 /*  Return true if T is a valid LHS for a GIMPLE assignment expression.  */
 140
 141 bool
 142 is_gimple_lvalue (tree t)
 143 {
 144   return (is_gimple_addressable (t)
 145           || TREE_CODE (t) == WITH_SIZE_EXPR
 146           /* These are complex lvalues, but don't have addresses, so they
 147              go here.  */
 148           || TREE_CODE (t) == BIT_FIELD_REF);
 149 }
 150
 151 /*  Return true if T is a GIMPLE condition.  */
 152
 153 bool
 154 is_gimple_condexpr (tree t)
 155 {
 156   return (is_gimple_val (t) || COMPARISON_CLASS_P (t));
 157 }
 158
 159 /*  Return true if T is something whose address can be taken.  */
 160
 161 bool
 162 is_gimple_addressable (tree t)
 163 {
 164   return (is_gimple_id (t) || handled_component_p (t)
 165           || INDIRECT_REF_P (t));
 166 }
 167
 168 /* Return true if T is function invariant.  Or rather a restricted
 169    form of function invariant.  */
 170
 171 bool
 172 is_gimple_min_invariant (tree t)
 173 {
 174   switch (TREE_CODE (t))
 175     {
 176     case ADDR_EXPR:
 177       return TREE_INVARIANT (t);
 178
 179     case INTEGER_CST:
 180     case REAL_CST:
 181     case STRING_CST:
 182     case COMPLEX_CST:
 183     case VECTOR_CST:
 184       return true;
 185
 186     default:
 187       return false;
 188     }
 189 }
 190
 191 /* Return true if T looks like a valid GIMPLE statement.  */
 192
 193 bool
 194 is_gimple_stmt (tree t)
 195 {
 196   enum tree_code code = TREE_CODE (t);
 197
 198   if (IS_EMPTY_STMT (t))
 199     return 1;
 200
 201   switch (code)
 202     {
 203     case BIND_EXPR:
 204     case COND_EXPR:
 205       /* These are only valid if they're void.  */
 206       return TREE_TYPE (t) == NULL || VOID_TYPE_P (TREE_TYPE (t));
 207
 208     case SWITCH_EXPR:
 209     case GOTO_EXPR:
 210     case RETURN_EXPR:
 211     case LABEL_EXPR:
 212     case CASE_LABEL_EXPR:
 213     case TRY_CATCH_EXPR:
 214     case TRY_FINALLY_EXPR:
 215     case EH_FILTER_EXPR:
 216     case CATCH_EXPR:
 217     case ASM_EXPR:
 218     case RESX_EXPR:
 219     case PHI_NODE:
 220     case STATEMENT_LIST:
 221       /* These are always void.  */
 222       return true;
 223
 224     case CALL_EXPR:
 225     case MODIFY_EXPR:
 226       /* These are valid regardless of their type.  */
 227       return true;
 228
 229     default:
 230       return false;
 231     }
 232 }
 233
 234 /* Return true if T is a variable.  */
 235
 236 bool
 237 is_gimple_variable (tree t)
 238 {
 239   return (TREE_CODE (t) == VAR_DECL
 240           || TREE_CODE (t) == PARM_DECL
 241           || TREE_CODE (t) == RESULT_DECL
 242           || TREE_CODE (t) == SSA_NAME);
 243 }
 244
 245 /*  Return true if T is a GIMPLE identifier (something with an address).  */
 246
 247 static inline bool
 248 is_gimple_id (tree t)
 249 {
 250   return (is_gimple_variable (t)
 251           || TREE_CODE (t) == FUNCTION_DECL
 252           || TREE_CODE (t) == LABEL_DECL
 253           || TREE_CODE (t) == CONST_DECL
 254           /* Allow string constants, since they are addressable.  */
 255           || TREE_CODE (t) == STRING_CST);
 256 }
 257
 258 /* Return true if TYPE is a suitable type for a scalar register variable.  */
 259
 260 bool
 261 is_gimple_reg_type (tree type)
 262 {
 263   return (!AGGREGATE_TYPE_P (type)
 264           && TREE_CODE (type) != COMPLEX_TYPE);
 265 }
 266
 267
 268 /* Return true if T is a scalar register variable.  */
 269
 270 bool
 271 is_gimple_reg (tree t)
 272 {
 273   if (TREE_CODE (t) == SSA_NAME)
 274     t = SSA_NAME_VAR (t);
 275
 276   if (!is_gimple_variable (t))
 277     return false;
 278   if (!is_gimple_reg_type (TREE_TYPE (t)))
 279     return false;
 280
 281   /* A volatile decl is not acceptable because we can't reuse it as
 282      needed.  We need to copy it into a temp first.  */
 283   if (TREE_THIS_VOLATILE (t))
 284     return false;
 285
 286   /* We define "registers" as things that can be renamed as needed,
 287      which with our infrastructure does not apply to memory.  */
 288   if (needs_to_live_in_memory (t))
 289     return false;
 290
 291   /* Hard register variables are an interesting case.  For those that
 292      are call-clobbered, we don't know where all the calls are, since
 293      we don't (want to) take into account which operations will turn
 294      into libcalls at the rtl level.  For those that are call-saved,
 295      we don't currently model the fact that calls may in fact change
 296      global hard registers, nor do we examine ASM_CLOBBERS at the tree
 297      level, and so miss variable changes that might imply.  All around,
 298      it seems safest to not do too much optimization with these at the
 299      tree level at all.  We'll have to rely on the rtl optimizers to
 300      clean this up, as there we've got all the appropriate bits exposed.  */
 301   if (TREE_CODE (t) == VAR_DECL && DECL_HARD_REGISTER (t))
 302     return false;
 303
 304   return true;
 305 }
 306
 307 /* Returns true if T is a GIMPLE formal temporary variable.  */
 308
 309 bool
 310 is_gimple_formal_tmp_var (tree t)
 311 {
 312   if (TREE_CODE (t) == SSA_NAME)
 313     return true;
 314
 315   return TREE_CODE (t) == VAR_DECL && DECL_GIMPLE_FORMAL_TEMP_P (t);
 316 }
 317
 318 /* Returns true if T is a GIMPLE formal temporary register variable.  */
 319
 320 bool
 321 is_gimple_formal_tmp_reg (tree t)
 322 {
 323   /* The intent of this is to get hold of a value that won't change.
 324      An SSA_NAME qualifies no matter if its of a user variable or not.  */
 325   if (TREE_CODE (t) == SSA_NAME)
 326     return true;
 327
 328   /* We don't know the lifetime characteristics of user variables.  */
 329   if (!is_gimple_formal_tmp_var (t))
 330     return false;
 331
 332   /* Finally, it must be capable of being placed in a register.  */
 333   return is_gimple_reg (t);
 334 }
 335
 336 /* Return true if T is a GIMPLE variable whose address is not needed.  */
 337
 338 bool
 339 is_gimple_non_addressable (tree t)
 340 {
 341   if (TREE_CODE (t) == SSA_NAME)
 342     t = SSA_NAME_VAR (t);
 343
 344   return (is_gimple_variable (t) && ! needs_to_live_in_memory (t));
 345 }
 346
 347 /* Return true if T is a GIMPLE rvalue, i.e. an identifier or a constant.  */
 348
 349 bool
 350 is_gimple_val (tree t)
 351 {
 352   /* Make loads from volatiles and memory vars explicit.  */
 353   if (is_gimple_variable (t)
 354       && is_gimple_reg_type (TREE_TYPE (t))
 355       && !is_gimple_reg (t))
 356     return false;
 357
 358   /* FIXME make these decls.  That can happen only when we expose the
 359      entire landing-pad construct at the tree level.  */
 360   if (TREE_CODE (t) == EXC_PTR_EXPR || TREE_CODE (t) == FILTER_EXPR)
 361     return 1;
 362
 363   return (is_gimple_variable (t) || is_gimple_min_invariant (t));
 364 }
 365
 366 /* Similarly, but accept hard registers as inputs to asm statements.  */
 367
 368 bool
 369 is_gimple_asm_val (tree t)
 370 {
 371   if (TREE_CODE (t) == VAR_DECL && DECL_HARD_REGISTER (t))
 372     return true;
 373
 374   return is_gimple_val (t);
 375 }
 376
 377 /* Return true if T is a GIMPLE minimal lvalue.  */
 378
 379 bool
 380 is_gimple_min_lval (tree t)
 381 {
 382   return (is_gimple_id (t)
 383           || TREE_CODE (t) == INDIRECT_REF);
 384 }
 385
 386 /* Return true if T is a typecast operation.  */
 387
 388 bool
 389 is_gimple_cast (tree t)
 390 {
 391   return (TREE_CODE (t) == NOP_EXPR
 392           || TREE_CODE (t) == CONVERT_EXPR
 393           || TREE_CODE (t) == FIX_TRUNC_EXPR
 394           || TREE_CODE (t) == FIX_CEIL_EXPR
 395           || TREE_CODE (t) == FIX_FLOOR_EXPR
 396           || TREE_CODE (t) == FIX_ROUND_EXPR);
 397 }
 398
 399 /* Return true if T is a valid op0 of a CALL_EXPR.  */
 400
 401 bool
 402 is_gimple_call_addr (tree t)
 403 {
 404   return (TREE_CODE (t) == OBJ_TYPE_REF
 405           || is_gimple_val (t));
 406 }
 407
 408 /* If T makes a function call, return the corresponding CALL_EXPR operand.
 409    Otherwise, return NULL_TREE.  */
 410
 411 tree
 412 get_call_expr_in (tree t)
 413 {
 414   if (TREE_CODE (t) == MODIFY_EXPR)
 415     t = TREE_OPERAND (t, 1);
 416   if (TREE_CODE (t) == WITH_SIZE_EXPR)
 417     t = TREE_OPERAND (t, 0);
 418   if (TREE_CODE (t) == CALL_EXPR)
 419     return t;
 420   return NULL_TREE;
 421 }
 422
 423 /* Given a memory reference expression T, return its base address.
 424    The base address of a memory reference expression is the main
 425    object being referenced.  For instance, the base address for
 426    'array[i].fld[j]' is 'array'.  You can think of this as stripping
 427    away the offset part from a memory address.
 428
 429    This function calls handled_component_p to strip away all the inner
 430    parts of the memory reference until it reaches the base object.  */
 431
 432 tree
 433 get_base_address (tree t)
 434 {
 435   while (handled_component_p (t))
 436     t = TREE_OPERAND (t, 0);
 437
 438   if (SSA_VAR_P (t)
 439       || TREE_CODE (t) == STRING_CST
 440       || TREE_CODE (t) == CONSTRUCTOR
 441       || INDIRECT_REF_P (t))
 442     return t;
 443   else
 444     return NULL_TREE;
 445 }
 446
 447 void
 448 recalculate_side_effects (tree t)
 449 {
 450   enum tree_code code = TREE_CODE (t);
 451   int len = TREE_CODE_LENGTH (code);
 452   int i;
 453
 454   switch (TREE_CODE_CLASS (code))
 455     {
 456     case tcc_expression:
 457       switch (code)
 458         {
 459         case INIT_EXPR:
 460         case MODIFY_EXPR:
 461         case VA_ARG_EXPR:
 462         case PREDECREMENT_EXPR:
 463         case PREINCREMENT_EXPR:
 464         case POSTDECREMENT_EXPR:
 465         case POSTINCREMENT_EXPR:
 466           /* All of these have side-effects, no matter what their
 467              operands are.  */
 468           return;
 469
 470         default:
 471           break;
 472         }
 473       /* Fall through.  */
 474
 475     case tcc_comparison:  /* a comparison expression */
 476     case tcc_unary:       /* a unary arithmetic expression */
 477     case tcc_binary:      /* a binary arithmetic expression */
 478     case tcc_reference:   /* a reference */
 479       TREE_SIDE_EFFECTS (t) = TREE_THIS_VOLATILE (t);
 480       for (i = 0; i < len; ++i)
 481         {
 482           tree op = TREE_OPERAND (t, i);
 483           if (op && TREE_SIDE_EFFECTS (op))
 484             TREE_SIDE_EFFECTS (t) = 1;
 485         }
 486       break;
 487
 488     default:
 489       /* Can never be used with non-expressions.  */
 490       gcc_unreachable ();
 491    }
 492 }