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 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 }
 265
 266 /* Return true if T is a non-aggregate register variable.  */
 267
 268 bool
 269 is_gimple_reg (tree t)
 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   return true;
 309 }
 310
 311 /* Returns true if T is a GIMPLE formal temporary variable.  */
 312
 313 bool
 314 is_gimple_formal_tmp_var (tree t)
 315 {
 316   if (TREE_CODE (t) == SSA_NAME)
 317     return true;
 318
 319   return TREE_CODE (t) == VAR_DECL && DECL_GIMPLE_FORMAL_TEMP_P (t);
 320 }
 321
 322 /* Returns true if T is a GIMPLE formal temporary register variable.  */
 323
 324 bool
 325 is_gimple_formal_tmp_reg (tree t)
 326 {
 327   /* The intent of this is to get hold of a value that won't change.
 328      An SSA_NAME qualifies no matter if its of a user variable or not.  */
 329   if (TREE_CODE (t) == SSA_NAME)
 330     return true;
 331
 332   /* We don't know the lifetime characteristics of user variables.  */
 333   if (!is_gimple_formal_tmp_var (t))
 334     return false;
 335
 336   /* Finally, it must be capable of being placed in a register.  */
 337   return is_gimple_reg (t);
 338 }
 339
 340 /* Return true if T is a GIMPLE variable whose address is not needed.  */
 341
 342 bool
 343 is_gimple_non_addressable (tree t)
 344 {
 345   if (TREE_CODE (t) == SSA_NAME)
 346     t = SSA_NAME_VAR (t);
 347
 348   return (is_gimple_variable (t) && ! needs_to_live_in_memory (t));
 349 }
 350
 351 /* Return true if T is a GIMPLE rvalue, i.e. an identifier or a constant.  */
 352
 353 bool
 354 is_gimple_val (tree t)
 355 {
 356   /* Make loads from volatiles and memory vars explicit.  */
 357   if (is_gimple_variable (t)
 358       && is_gimple_reg_type (TREE_TYPE (t))
 359       && !is_gimple_reg (t))
 360     return false;
 361
 362   /* FIXME make these decls.  That can happen only when we expose the
 363      entire landing-pad construct at the tree level.  */
 364   if (TREE_CODE (t) == EXC_PTR_EXPR || TREE_CODE (t) == FILTER_EXPR)
 365     return 1;
 366
 367   return (is_gimple_variable (t) || is_gimple_min_invariant (t));
 368 }
 369
 370 /* Similarly, but accept hard registers as inputs to asm statements.  */
 371
 372 bool
 373 is_gimple_asm_val (tree t)
 374 {
 375   if (TREE_CODE (t) == VAR_DECL && DECL_HARD_REGISTER (t))
 376     return true;
 377
 378   return is_gimple_val (t);
 379 }
 380
 381 /* Return true if T is a GIMPLE minimal lvalue.  */
 382
 383 bool
 384 is_gimple_min_lval (tree t)
 385 {
 386   return (is_gimple_id (t)
 387           || TREE_CODE (t) == INDIRECT_REF);
 388 }
 389
 390 /* Return true if T is a typecast operation.  */
 391
 392 bool
 393 is_gimple_cast (tree t)
 394 {
 395   return (TREE_CODE (t) == NOP_EXPR
 396           || TREE_CODE (t) == CONVERT_EXPR
 397           || TREE_CODE (t) == FIX_TRUNC_EXPR
 398           || TREE_CODE (t) == FIX_CEIL_EXPR
 399           || TREE_CODE (t) == FIX_FLOOR_EXPR
 400           || TREE_CODE (t) == FIX_ROUND_EXPR);
 401 }
 402
 403 /* Return true if T is a valid op0 of a CALL_EXPR.  */
 404
 405 bool
 406 is_gimple_call_addr (tree t)
 407 {
 408   return (TREE_CODE (t) == OBJ_TYPE_REF
 409           || is_gimple_val (t));
 410 }
 411
 412 /* If T makes a function call, return the corresponding CALL_EXPR operand.
 413    Otherwise, return NULL_TREE.  */
 414
 415 tree
 416 get_call_expr_in (tree t)
 417 {
 418   if (TREE_CODE (t) == MODIFY_EXPR)
 419     t = TREE_OPERAND (t, 1);
 420   if (TREE_CODE (t) == WITH_SIZE_EXPR)
 421     t = TREE_OPERAND (t, 0);
 422   if (TREE_CODE (t) == CALL_EXPR)
 423     return t;
 424   return NULL_TREE;
 425 }
 426
 427 /* Given a memory reference expression T, return its base address.
 428    The base address of a memory reference expression is the main
 429    object being referenced.  For instance, the base address for
 430    'array[i].fld[j]' is 'array'.  You can think of this as stripping
 431    away the offset part from a memory address.
 432
 433    This function calls handled_component_p to strip away all the inner
 434    parts of the memory reference until it reaches the base object.  */
 435
 436 tree
 437 get_base_address (tree t)
 438 {
 439   while (handled_component_p (t))
 440     t = TREE_OPERAND (t, 0);
 441
 442   if (SSA_VAR_P (t)
 443       || TREE_CODE (t) == STRING_CST
 444       || TREE_CODE (t) == CONSTRUCTOR
 445       || INDIRECT_REF_P (t))
 446     return t;
 447   else
 448     return NULL_TREE;
 449 }
 450
 451 void
 452 recalculate_side_effects (tree t)
 453 {
 454   enum tree_code code = TREE_CODE (t);
 455   int len = TREE_CODE_LENGTH (code);
 456   int i;
 457
 458   switch (TREE_CODE_CLASS (code))
 459     {
 460     case tcc_expression:
 461       switch (code)
 462         {
 463         case INIT_EXPR:
 464         case MODIFY_EXPR:
 465         case VA_ARG_EXPR:
 466         case PREDECREMENT_EXPR:
 467         case PREINCREMENT_EXPR:
 468         case POSTDECREMENT_EXPR:
 469         case POSTINCREMENT_EXPR:
 470           /* All of these have side-effects, no matter what their
 471              operands are.  */
 472           return;
 473
 474         default:
 475           break;
 476         }
 477       /* Fall through.  */
 478
 479     case tcc_comparison:  /* a comparison expression */
 480     case tcc_unary:       /* a unary arithmetic expression */
 481     case tcc_binary:      /* a binary arithmetic expression */
 482     case tcc_reference:   /* a reference */
 483       TREE_SIDE_EFFECTS (t) = TREE_THIS_VOLATILE (t);
 484       for (i = 0; i < len; ++i)
 485         {
 486           tree op = TREE_OPERAND (t, i);
 487           if (op && TREE_SIDE_EFFECTS (op))
 488             TREE_SIDE_EFFECTS (t) = 1;
 489         }
 490       break;
 491
 492     default:
 493       /* Can never be used with non-expressions.  */
 494       gcc_unreachable ();
 495    }
 496 }