contrib/gcc-4.1/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       /* These are always void.  */
 220       return true;
 221
 222     case CALL_EXPR:
 223     case MODIFY_EXPR:
 224       /* These are valid regardless of their type.  */
 225       return true;
 226
 227     default:
 228       return false;
 229     }
 230 }
 231
 232 /* Return true if T is a variable.  */
 233
 234 bool
 235 is_gimple_variable (tree t)
 236 {
 237   return (TREE_CODE (t) == VAR_DECL
 238           || TREE_CODE (t) == PARM_DECL
 239           || TREE_CODE (t) == RESULT_DECL
 240           || TREE_CODE (t) == SSA_NAME);
 241 }
 242
 243 /*  Return true if T is a GIMPLE identifier (something with an address).  */
 244
 245 bool
 246 is_gimple_id (tree t)
 247 {
 248   return (is_gimple_variable (t)
 249           || TREE_CODE (t) == FUNCTION_DECL
 250           || TREE_CODE (t) == LABEL_DECL
 251           || TREE_CODE (t) == CONST_DECL
 252           /* Allow string constants, since they are addressable.  */
 253           || TREE_CODE (t) == STRING_CST);
 254 }
 255
 256 /* Return true if TYPE is a suitable type for a scalar register variable.  */
 257
 258 bool
 259 is_gimple_reg_type (tree type)
 260 {
 261   return !AGGREGATE_TYPE_P (type);
 262 }
 263
 264 /* Return true if T is a non-aggregate register variable.  */
 265
 266 bool
 267 is_gimple_reg (tree t)
 268 {
 269   var_ann_t ann;
 270
 271   if (TREE_CODE (t) == SSA_NAME)
 272     t = SSA_NAME_VAR (t);
 273
 274   if (!is_gimple_variable (t))
 275     return false;
 276
 277   if (!is_gimple_reg_type (TREE_TYPE (t)))
 278     return false;
 279
 280   /* A volatile decl is not acceptable because we can't reuse it as
 281      needed.  We need to copy it into a temp first.  */
 282   if (TREE_THIS_VOLATILE (t))
 283     return false;
 284
 285   /* We define "registers" as things that can be renamed as needed,
 286      which with our infrastructure does not apply to memory.  */
 287   if (needs_to_live_in_memory (t))
 288     return false;
 289
 290   /* Hard register variables are an interesting case.  For those that
 291      are call-clobbered, we don't know where all the calls are, since
 292      we don't (want to) take into account which operations will turn
 293      into libcalls at the rtl level.  For those that are call-saved,
 294      we don't currently model the fact that calls may in fact change
 295      global hard registers, nor do we examine ASM_CLOBBERS at the tree
 296      level, and so miss variable changes that might imply.  All around,
 297      it seems safest to not do too much optimization with these at the
 298      tree level at all.  We'll have to rely on the rtl optimizers to
 299      clean this up, as there we've got all the appropriate bits exposed.  */
 300   if (TREE_CODE (t) == VAR_DECL && DECL_HARD_REGISTER (t))
 301     return false;
 302
 303   /* Complex values must have been put into ssa form.  That is, no
 304      assignments to the individual components.  */
 305   if (TREE_CODE (TREE_TYPE (t)) == COMPLEX_TYPE)
 306     return DECL_COMPLEX_GIMPLE_REG_P (t);
 307
 308   /* Some compiler temporaries are created to be used exclusively in
 309      virtual operands (currently memory tags and sub-variables).
 310      These variables should never be considered GIMPLE registers.  */
 311   if (DECL_ARTIFICIAL (t) && (ann = var_ann (t)) != NULL)
 312     return ann->mem_tag_kind == NOT_A_TAG;
 313
 314   return true;
 315 }
 316
 317
 318 /* Returns true if T is a GIMPLE formal temporary variable.  */
 319
 320 bool
 321 is_gimple_formal_tmp_var (tree t)
 322 {
 323   if (TREE_CODE (t) == SSA_NAME)
 324     return true;
 325
 326   return TREE_CODE (t) == VAR_DECL && DECL_GIMPLE_FORMAL_TEMP_P (t);
 327 }
 328
 329 /* Returns true if T is a GIMPLE formal temporary register variable.  */
 330
 331 bool
 332 is_gimple_formal_tmp_reg (tree t)
 333 {
 334   /* The intent of this is to get hold of a value that won't change.
 335      An SSA_NAME qualifies no matter if its of a user variable or not.  */
 336   if (TREE_CODE (t) == SSA_NAME)
 337     return true;
 338
 339   /* We don't know the lifetime characteristics of user variables.  */
 340   if (!is_gimple_formal_tmp_var (t))
 341     return false;
 342
 343   /* Finally, it must be capable of being placed in a register.  */
 344   return is_gimple_reg (t);
 345 }
 346
 347 /* Return true if T is a GIMPLE variable whose address is not needed.  */
 348
 349 bool
 350 is_gimple_non_addressable (tree t)
 351 {
 352   if (TREE_CODE (t) == SSA_NAME)
 353     t = SSA_NAME_VAR (t);
 354
 355   return (is_gimple_variable (t) && ! needs_to_live_in_memory (t));
 356 }
 357
 358 /* Return true if T is a GIMPLE rvalue, i.e. an identifier or a constant.  */
 359
 360 bool
 361 is_gimple_val (tree t)
 362 {
 363   /* Make loads from volatiles and memory vars explicit.  */
 364   if (is_gimple_variable (t)
 365       && is_gimple_reg_type (TREE_TYPE (t))
 366       && !is_gimple_reg (t))
 367     return false;
 368
 369   /* FIXME make these decls.  That can happen only when we expose the
 370      entire landing-pad construct at the tree level.  */
 371   if (TREE_CODE (t) == EXC_PTR_EXPR || TREE_CODE (t) == FILTER_EXPR)
 372     return 1;
 373
 374   return (is_gimple_variable (t) || is_gimple_min_invariant (t));
 375 }
 376
 377 /* Similarly, but accept hard registers as inputs to asm statements.  */
 378
 379 bool
 380 is_gimple_asm_val (tree t)
 381 {
 382   if (TREE_CODE (t) == VAR_DECL && DECL_HARD_REGISTER (t))
 383     return true;
 384
 385   return is_gimple_val (t);
 386 }
 387
 388 /* Return true if T is a GIMPLE minimal lvalue.  */
 389
 390 bool
 391 is_gimple_min_lval (tree t)
 392 {
 393   return (is_gimple_id (t)
 394           || TREE_CODE (t) == INDIRECT_REF);
 395 }
 396
 397 /* Return true if T is a typecast operation.  */
 398
 399 bool
 400 is_gimple_cast (tree t)
 401 {
 402   return (TREE_CODE (t) == NOP_EXPR
 403           || TREE_CODE (t) == CONVERT_EXPR
 404           || TREE_CODE (t) == FIX_TRUNC_EXPR
 405           || TREE_CODE (t) == FIX_CEIL_EXPR
 406           || TREE_CODE (t) == FIX_FLOOR_EXPR
 407           || TREE_CODE (t) == FIX_ROUND_EXPR);
 408 }
 409
 410 /* Return true if T is a valid op0 of a CALL_EXPR.  */
 411
 412 bool
 413 is_gimple_call_addr (tree t)
 414 {
 415   return (TREE_CODE (t) == OBJ_TYPE_REF
 416           || is_gimple_val (t));
 417 }
 418
 419 /* If T makes a function call, return the corresponding CALL_EXPR operand.
 420    Otherwise, return NULL_TREE.  */
 421
 422 tree
 423 get_call_expr_in (tree t)
 424 {
 425   if (TREE_CODE (t) == MODIFY_EXPR)
 426     t = TREE_OPERAND (t, 1);
 427   if (TREE_CODE (t) == WITH_SIZE_EXPR)
 428     t = TREE_OPERAND (t, 0);
 429   if (TREE_CODE (t) == CALL_EXPR)
 430     return t;
 431   return NULL_TREE;
 432 }
 433
 434 /* Given a memory reference expression T, return its base address.
 435    The base address of a memory reference expression is the main
 436    object being referenced.  For instance, the base address for
 437    'array[i].fld[j]' is 'array'.  You can think of this as stripping
 438    away the offset part from a memory address.
 439
 440    This function calls handled_component_p to strip away all the inner
 441    parts of the memory reference until it reaches the base object.  */
 442
 443 tree
 444 get_base_address (tree t)
 445 {
 446   while (handled_component_p (t))
 447     t = TREE_OPERAND (t, 0);
 448
 449   if (SSA_VAR_P (t)
 450       || TREE_CODE (t) == STRING_CST
 451       || TREE_CODE (t) == CONSTRUCTOR
 452       || INDIRECT_REF_P (t))
 453     return t;
 454   else
 455     return NULL_TREE;
 456 }
 457
 458 void
 459 recalculate_side_effects (tree t)
 460 {
 461   enum tree_code code = TREE_CODE (t);
 462   int len = TREE_CODE_LENGTH (code);
 463   int i;
 464
 465   switch (TREE_CODE_CLASS (code))
 466     {
 467     case tcc_expression:
 468       switch (code)
 469         {
 470         case INIT_EXPR:
 471         case MODIFY_EXPR:
 472         case VA_ARG_EXPR:
 473         case PREDECREMENT_EXPR:
 474         case PREINCREMENT_EXPR:
 475         case POSTDECREMENT_EXPR:
 476         case POSTINCREMENT_EXPR:
 477           /* All of these have side-effects, no matter what their
 478              operands are.  */
 479           return;
 480
 481         default:
 482           break;
 483         }
 484       /* Fall through.  */
 485
 486     case tcc_comparison:  /* a comparison expression */
 487     case tcc_unary:       /* a unary arithmetic expression */
 488     case tcc_binary:      /* a binary arithmetic expression */
 489     case tcc_reference:   /* a reference */
 490       TREE_SIDE_EFFECTS (t) = TREE_THIS_VOLATILE (t);
 491       for (i = 0; i < len; ++i)
 492         {
 493           tree op = TREE_OPERAND (t, i);
 494           if (op && TREE_SIDE_EFFECTS (op))
 495             TREE_SIDE_EFFECTS (t) = 1;
 496         }
 497       break;
 498
 499     default:
 500       /* Can never be used with non-expressions.  */
 501       gcc_unreachable ();
 502    }
 503 }