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, 51 Franklin Street, Fifth Floor,
  21 Boston, MA 02110-1301, 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 /* Validation of GIMPLE expressions.  */
  39
  40 /* Return true if T is a GIMPLE RHS for an assignment to a temporary.  */
  41
  42 bool
  43 is_gimple_formal_tmp_rhs (tree t)
  44 {
  45   enum tree_code code = TREE_CODE (t);
  46
  47   switch (TREE_CODE_CLASS (code))
  48     {
  49     case tcc_unary:
  50     case tcc_binary:
  51     case tcc_comparison:
  52       return true;
  53
  54     default:
  55       break;
  56     }
  57
  58   switch (code)
  59     {
  60     case TRUTH_NOT_EXPR:
  61     case TRUTH_AND_EXPR:
  62     case TRUTH_OR_EXPR:
  63     case TRUTH_XOR_EXPR:
  64     case ADDR_EXPR:
  65     case CALL_EXPR:
  66     case CONSTRUCTOR:
  67     case COMPLEX_EXPR:
  68     case INTEGER_CST:
  69     case REAL_CST:
  70     case STRING_CST:
  71     case COMPLEX_CST:
  72     case VECTOR_CST:
  73     case OBJ_TYPE_REF:
  74     case ASSERT_EXPR:
  75       return true;
  76
  77     default:
  78       break;
  79     }
  80
  81   return is_gimple_lvalue (t) || is_gimple_val (t);
  82 }
  83
  84 /* Returns true iff T is a valid RHS for an assignment to a renamed
  85    user -- or front-end generated artificial -- variable.  */
  86
  87 bool
  88 is_gimple_reg_rhs (tree t)
  89 {
  90   /* If the RHS of the MODIFY_EXPR may throw or make a nonlocal goto
  91      and the LHS is a user variable, then we need to introduce a formal
  92      temporary.  This way the optimizers can determine that the user
  93      variable is only modified if evaluation of the RHS does not throw.
  94
  95      Don't force a temp of a non-renamable type; the copy could be
  96      arbitrarily expensive.  Instead we will generate a V_MAY_DEF for
  97      the assignment.  */
  98
  99   if (is_gimple_reg_type (TREE_TYPE (t))
 100       && ((TREE_CODE (t) == CALL_EXPR && TREE_SIDE_EFFECTS (t))
 101           || tree_could_throw_p (t)))
 102     return false;
 103
 104   return is_gimple_formal_tmp_rhs (t);
 105 }
 106
 107 /* Returns true iff T is a valid RHS for an assignment to an un-renamed
 108    LHS, or for a call argument.  */
 109
 110 bool
 111 is_gimple_mem_rhs (tree t)
 112 {
 113   /* If we're dealing with a renamable type, either source or dest must be
 114      a renamed variable.  Also force a temporary if the type doesn't need
 115      to be stored in memory, since it's cheap and prevents erroneous
 116      tailcalls (PR 17526).  */
 117   if (is_gimple_reg_type (TREE_TYPE (t))
 118       || TYPE_MODE (TREE_TYPE (t)) != BLKmode)
 119     return is_gimple_val (t);
 120   else
 121     return is_gimple_formal_tmp_rhs (t);
 122 }
 123
 124 /* Returns the appropriate RHS predicate for this LHS.  */
 125
 126 gimple_predicate
 127 rhs_predicate_for (tree lhs)
 128 {
 129   if (is_gimple_formal_tmp_var (lhs))
 130     return is_gimple_formal_tmp_rhs;
 131   else if (is_gimple_reg (lhs))
 132     return is_gimple_reg_rhs;
 133   else
 134     return is_gimple_mem_rhs;
 135 }
 136
 137 /*  Return true if T is a valid LHS for a GIMPLE assignment expression.  */
 138
 139 bool
 140 is_gimple_lvalue (tree t)
 141 {
 142   return (is_gimple_addressable (t)
 143           || TREE_CODE (t) == WITH_SIZE_EXPR
 144           /* These are complex lvalues, but don't have addresses, so they
 145              go here.  */
 146           || TREE_CODE (t) == BIT_FIELD_REF);
 147 }
 148
 149 /*  Return true if T is a GIMPLE condition.  */
 150
 151 bool
 152 is_gimple_condexpr (tree t)
 153 {
 154   return (is_gimple_val (t) || COMPARISON_CLASS_P (t));
 155 }
 156
 157 /*  Return true if T is something whose address can be taken.  */
 158
 159 bool
 160 is_gimple_addressable (tree t)
 161 {
 162   return (is_gimple_id (t) || handled_component_p (t)
 163           || INDIRECT_REF_P (t));
 164 }
 165
 166 /* Return true if T is function invariant.  Or rather a restricted
 167    form of function invariant.  */
 168
 169 bool
 170 is_gimple_min_invariant (tree t)
 171 {
 172   switch (TREE_CODE (t))
 173     {
 174     case ADDR_EXPR:
 175       return TREE_INVARIANT (t);
 176
 177     case INTEGER_CST:
 178     case REAL_CST:
 179     case STRING_CST:
 180     case COMPLEX_CST:
 181     case VECTOR_CST:
 182       return true;
 183
 184     default:
 185       return false;
 186     }
 187 }
 188
 189 /* Return true if T looks like a valid GIMPLE statement.  */
 190
 191 bool
 192 is_gimple_stmt (tree t)
 193 {
 194   enum tree_code code = TREE_CODE (t);
 195
 196   if (IS_EMPTY_STMT (t))
 197     return 1;
 198
 199   switch (code)
 200     {
 201     case BIND_EXPR:
 202     case COND_EXPR:
 203       /* These are only valid if they're void.  */
 204       return TREE_TYPE (t) == NULL || VOID_TYPE_P (TREE_TYPE (t));
 205
 206     case SWITCH_EXPR:
 207     case GOTO_EXPR:
 208     case RETURN_EXPR:
 209     case LABEL_EXPR:
 210     case CASE_LABEL_EXPR:
 211     case TRY_CATCH_EXPR:
 212     case TRY_FINALLY_EXPR:
 213     case EH_FILTER_EXPR:
 214     case CATCH_EXPR:
 215     case ASM_EXPR:
 216     case RESX_EXPR:
 217     case PHI_NODE:
 218     case STATEMENT_LIST:
 219     case OMP_PARALLEL:
 220     case OMP_FOR:
 221     case OMP_SECTIONS:
 222     case OMP_SECTION:
 223     case OMP_SINGLE:
 224     case OMP_MASTER:
 225     case OMP_ORDERED:
 226     case OMP_CRITICAL:
 227     case OMP_RETURN:
 228     case OMP_CONTINUE:
 229       /* These are always void.  */
 230       return true;
 231
 232     case CALL_EXPR:
 233     case MODIFY_EXPR:
 234       /* These are valid regardless of their type.  */
 235       return true;
 236
 237     default:
 238       return false;
 239     }
 240 }
 241
 242 /* Return true if T is a variable.  */
 243
 244 bool
 245 is_gimple_variable (tree t)
 246 {
 247   return (TREE_CODE (t) == VAR_DECL
 248           || TREE_CODE (t) == PARM_DECL
 249           || TREE_CODE (t) == RESULT_DECL
 250           || TREE_CODE (t) == SSA_NAME);
 251 }
 252
 253 /*  Return true if T is a GIMPLE identifier (something with an address).  */
 254
 255 bool
 256 is_gimple_id (tree t)
 257 {
 258   return (is_gimple_variable (t)
 259           || TREE_CODE (t) == FUNCTION_DECL
 260           || TREE_CODE (t) == LABEL_DECL
 261           || TREE_CODE (t) == CONST_DECL
 262           /* Allow string constants, since they are addressable.  */
 263           || TREE_CODE (t) == STRING_CST);
 264 }
 265
 266 /* Return true if TYPE is a suitable type for a scalar register variable.  */
 267
 268 bool
 269 is_gimple_reg_type (tree type)
 270 {
 271   return !AGGREGATE_TYPE_P (type);
 272 }
 273
 274 /* Return true if T is a non-aggregate register variable.  */
 275
 276 bool
 277 is_gimple_reg (tree t)
 278 {
 279   if (TREE_CODE (t) == SSA_NAME)
 280     t = SSA_NAME_VAR (t);
 281
 282   if (MTAG_P (t))
 283     return false;
 284
 285   if (!is_gimple_variable (t))
 286     return false;
 287
 288   if (!is_gimple_reg_type (TREE_TYPE (t)))
 289     return false;
 290
 291   /* A volatile decl is not acceptable because we can't reuse it as
 292      needed.  We need to copy it into a temp first.  */
 293   if (TREE_THIS_VOLATILE (t))
 294     return false;
 295
 296   /* We define "registers" as things that can be renamed as needed,
 297      which with our infrastructure does not apply to memory.  */
 298   if (needs_to_live_in_memory (t))
 299     return false;
 300
 301   /* Hard register variables are an interesting case.  For those that
 302      are call-clobbered, we don't know where all the calls are, since
 303      we don't (want to) take into account which operations will turn
 304      into libcalls at the rtl level.  For those that are call-saved,
 305      we don't currently model the fact that calls may in fact change
 306      global hard registers, nor do we examine ASM_CLOBBERS at the tree
 307      level, and so miss variable changes that might imply.  All around,
 308      it seems safest to not do too much optimization with these at the
 309      tree level at all.  We'll have to rely on the rtl optimizers to
 310      clean this up, as there we've got all the appropriate bits exposed.  */
 311   if (TREE_CODE (t) == VAR_DECL && DECL_HARD_REGISTER (t))
 312     return false;
 313
 314   /* Complex values must have been put into ssa form.  That is, no
 315      assignments to the individual components.  */
 316   if (TREE_CODE (TREE_TYPE (t)) == COMPLEX_TYPE)
 317     return DECL_COMPLEX_GIMPLE_REG_P (t);
 318
 319   return true;
 320 }
 321
 322
 323 /* Returns true if T is a GIMPLE formal temporary variable.  */
 324
 325 bool
 326 is_gimple_formal_tmp_var (tree t)
 327 {
 328   if (TREE_CODE (t) == SSA_NAME)
 329     return true;
 330
 331   return TREE_CODE (t) == VAR_DECL && DECL_GIMPLE_FORMAL_TEMP_P (t);
 332 }
 333
 334 /* Returns true if T is a GIMPLE formal temporary register variable.  */
 335
 336 bool
 337 is_gimple_formal_tmp_reg (tree t)
 338 {
 339   /* The intent of this is to get hold of a value that won't change.
 340      An SSA_NAME qualifies no matter if its of a user variable or not.  */
 341   if (TREE_CODE (t) == SSA_NAME)
 342     return true;
 343
 344   /* We don't know the lifetime characteristics of user variables.  */
 345   if (!is_gimple_formal_tmp_var (t))
 346     return false;
 347
 348   /* Finally, it must be capable of being placed in a register.  */
 349   return is_gimple_reg (t);
 350 }
 351
 352 /* Return true if T is a GIMPLE variable whose address is not needed.  */
 353
 354 bool
 355 is_gimple_non_addressable (tree t)
 356 {
 357   if (TREE_CODE (t) == SSA_NAME)
 358     t = SSA_NAME_VAR (t);
 359
 360   return (is_gimple_variable (t) && ! needs_to_live_in_memory (t));
 361 }
 362
 363 /* Return true if T is a GIMPLE rvalue, i.e. an identifier or a constant.  */
 364
 365 bool
 366 is_gimple_val (tree t)
 367 {
 368   /* Make loads from volatiles and memory vars explicit.  */
 369   if (is_gimple_variable (t)
 370       && is_gimple_reg_type (TREE_TYPE (t))
 371       && !is_gimple_reg (t))
 372     return false;
 373
 374   /* FIXME make these decls.  That can happen only when we expose the
 375      entire landing-pad construct at the tree level.  */
 376   if (TREE_CODE (t) == EXC_PTR_EXPR || TREE_CODE (t) == FILTER_EXPR)
 377     return 1;
 378
 379   return (is_gimple_variable (t) || is_gimple_min_invariant (t));
 380 }
 381
 382 /* Similarly, but accept hard registers as inputs to asm statements.  */
 383
 384 bool
 385 is_gimple_asm_val (tree t)
 386 {
 387   if (TREE_CODE (t) == VAR_DECL && DECL_HARD_REGISTER (t))
 388     return true;
 389
 390   return is_gimple_val (t);
 391 }
 392
 393 /* Return true if T is a GIMPLE minimal lvalue.  */
 394
 395 bool
 396 is_gimple_min_lval (tree t)
 397 {
 398   return (is_gimple_id (t)
 399           || TREE_CODE (t) == INDIRECT_REF);
 400 }
 401
 402 /* Return true if T is a typecast operation.  */
 403
 404 bool
 405 is_gimple_cast (tree t)
 406 {
 407   return (TREE_CODE (t) == NOP_EXPR
 408           || TREE_CODE (t) == CONVERT_EXPR
 409           || TREE_CODE (t) == FIX_TRUNC_EXPR
 410           || TREE_CODE (t) == FIX_CEIL_EXPR
 411           || TREE_CODE (t) == FIX_FLOOR_EXPR
 412           || TREE_CODE (t) == FIX_ROUND_EXPR);
 413 }
 414
 415 /* Return true if T is a valid op0 of a CALL_EXPR.  */
 416
 417 bool
 418 is_gimple_call_addr (tree t)
 419 {
 420   return (TREE_CODE (t) == OBJ_TYPE_REF
 421           || is_gimple_val (t));
 422 }
 423
 424 /* If T makes a function call, return the corresponding CALL_EXPR operand.
 425    Otherwise, return NULL_TREE.  */
 426
 427 tree
 428 get_call_expr_in (tree t)
 429 {
 430   if (TREE_CODE (t) == MODIFY_EXPR)
 431     t = TREE_OPERAND (t, 1);
 432   if (TREE_CODE (t) == WITH_SIZE_EXPR)
 433     t = TREE_OPERAND (t, 0);
 434   if (TREE_CODE (t) == CALL_EXPR)
 435     return t;
 436   return NULL_TREE;
 437 }
 438
 439 /* Given a memory reference expression T, return its base address.
 440    The base address of a memory reference expression is the main
 441    object being referenced.  For instance, the base address for
 442    'array[i].fld[j]' is 'array'.  You can think of this as stripping
 443    away the offset part from a memory address.
 444
 445    This function calls handled_component_p to strip away all the inner
 446    parts of the memory reference until it reaches the base object.  */
 447
 448 tree
 449 get_base_address (tree t)
 450 {
 451   while (handled_component_p (t))
 452     t = TREE_OPERAND (t, 0);
 453
 454   if (SSA_VAR_P (t)
 455       || TREE_CODE (t) == STRING_CST
 456       || TREE_CODE (t) == CONSTRUCTOR
 457       || INDIRECT_REF_P (t))
 458     return t;
 459   else
 460     return NULL_TREE;
 461 }
 462
 463 void
 464 recalculate_side_effects (tree t)
 465 {
 466   enum tree_code code = TREE_CODE (t);
 467   int len = TREE_CODE_LENGTH (code);
 468   int i;
 469
 470   switch (TREE_CODE_CLASS (code))
 471     {
 472     case tcc_expression:
 473       switch (code)
 474         {
 475         case INIT_EXPR:
 476         case MODIFY_EXPR:
 477         case VA_ARG_EXPR:
 478         case PREDECREMENT_EXPR:
 479         case PREINCREMENT_EXPR:
 480         case POSTDECREMENT_EXPR:
 481         case POSTINCREMENT_EXPR:
 482           /* All of these have side-effects, no matter what their
 483              operands are.  */
 484           return;
 485
 486         default:
 487           break;
 488         }
 489       /* Fall through.  */
 490
 491     case tcc_comparison:  /* a comparison expression */
 492     case tcc_unary:       /* a unary arithmetic expression */
 493     case tcc_binary:      /* a binary arithmetic expression */
 494     case tcc_reference:   /* a reference */
 495       TREE_SIDE_EFFECTS (t) = TREE_THIS_VOLATILE (t);
 496       for (i = 0; i < len; ++i)
 497         {
 498           tree op = TREE_OPERAND (t, i);
 499           if (op && TREE_SIDE_EFFECTS (op))
 500             TREE_SIDE_EFFECTS (t) = 1;
 501         }
 502       break;
 503
 504     default:
 505       /* Can never be used with non-expressions.  */
 506       gcc_unreachable ();
 507    }
 508 }