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   if (TREE_CODE (t) == SSA_NAME)
 270     t = SSA_NAME_VAR (t);
 271
 272   if (MTAG_P (t))
 273     return false;
 274
 275   if (!is_gimple_variable (t))
 276     return false;
 277
 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   /* Complex values must have been put into ssa form.  That is, no
 305      assignments to the individual components.  */
 306   if (TREE_CODE (TREE_TYPE (t)) == COMPLEX_TYPE)
 307     return DECL_COMPLEX_GIMPLE_REG_P (t);
 308
 309   return true;
 310 }
 311
 312
 313 /* Returns true if T is a GIMPLE formal temporary variable.  */
 314
 315 bool
 316 is_gimple_formal_tmp_var (tree t)
 317 {
 318   if (TREE_CODE (t) == SSA_NAME)
 319     return true;
 320
 321   return TREE_CODE (t) == VAR_DECL && DECL_GIMPLE_FORMAL_TEMP_P (t);
 322 }
 323
 324 /* Returns true if T is a GIMPLE formal temporary register variable.  */
 325
 326 bool
 327 is_gimple_formal_tmp_reg (tree t)
 328 {
 329   /* The intent of this is to get hold of a value that won't change.
 330      An SSA_NAME qualifies no matter if its of a user variable or not.  */
 331   if (TREE_CODE (t) == SSA_NAME)
 332     return true;
 333
 334   /* We don't know the lifetime characteristics of user variables.  */
 335   if (!is_gimple_formal_tmp_var (t))
 336     return false;
 337
 338   /* Finally, it must be capable of being placed in a register.  */
 339   return is_gimple_reg (t);
 340 }
 341
 342 /* Return true if T is a GIMPLE variable whose address is not needed.  */
 343
 344 bool
 345 is_gimple_non_addressable (tree t)
 346 {
 347   if (TREE_CODE (t) == SSA_NAME)
 348     t = SSA_NAME_VAR (t);
 349
 350   return (is_gimple_variable (t) && ! needs_to_live_in_memory (t));
 351 }
 352
 353 /* Return true if T is a GIMPLE rvalue, i.e. an identifier or a constant.  */
 354
 355 bool
 356 is_gimple_val (tree t)
 357 {
 358   /* Make loads from volatiles and memory vars explicit.  */
 359   if (is_gimple_variable (t)
 360       && is_gimple_reg_type (TREE_TYPE (t))
 361       && !is_gimple_reg (t))
 362     return false;
 363
 364   /* FIXME make these decls.  That can happen only when we expose the
 365      entire landing-pad construct at the tree level.  */
 366   if (TREE_CODE (t) == EXC_PTR_EXPR || TREE_CODE (t) == FILTER_EXPR)
 367     return 1;
 368
 369   return (is_gimple_variable (t) || is_gimple_min_invariant (t));
 370 }
 371
 372 /* Similarly, but accept hard registers as inputs to asm statements.  */
 373
 374 bool
 375 is_gimple_asm_val (tree t)
 376 {
 377   if (TREE_CODE (t) == VAR_DECL && DECL_HARD_REGISTER (t))
 378     return true;
 379
 380   return is_gimple_val (t);
 381 }
 382
 383 /* Return true if T is a GIMPLE minimal lvalue.  */
 384
 385 bool
 386 is_gimple_min_lval (tree t)
 387 {
 388   return (is_gimple_id (t)
 389           || TREE_CODE (t) == INDIRECT_REF);
 390 }
 391
 392 /* Return true if T is a typecast operation.  */
 393
 394 bool
 395 is_gimple_cast (tree t)
 396 {
 397   return (TREE_CODE (t) == NOP_EXPR
 398           || TREE_CODE (t) == CONVERT_EXPR
 399           || TREE_CODE (t) == FIX_TRUNC_EXPR
 400           || TREE_CODE (t) == FIX_CEIL_EXPR
 401           || TREE_CODE (t) == FIX_FLOOR_EXPR
 402           || TREE_CODE (t) == FIX_ROUND_EXPR);
 403 }
 404
 405 /* Return true if T is a valid op0 of a CALL_EXPR.  */
 406
 407 bool
 408 is_gimple_call_addr (tree t)
 409 {
 410   return (TREE_CODE (t) == OBJ_TYPE_REF
 411           || is_gimple_val (t));
 412 }
 413
 414 /* If T makes a function call, return the corresponding CALL_EXPR operand.
 415    Otherwise, return NULL_TREE.  */
 416
 417 tree
 418 get_call_expr_in (tree t)
 419 {
 420   if (TREE_CODE (t) == MODIFY_EXPR)
 421     t = TREE_OPERAND (t, 1);
 422   if (TREE_CODE (t) == WITH_SIZE_EXPR)
 423     t = TREE_OPERAND (t, 0);
 424   if (TREE_CODE (t) == CALL_EXPR)
 425     return t;
 426   return NULL_TREE;
 427 }
 428
 429 /* Given a memory reference expression T, return its base address.
 430    The base address of a memory reference expression is the main
 431    object being referenced.  For instance, the base address for
 432    'array[i].fld[j]' is 'array'.  You can think of this as stripping
 433    away the offset part from a memory address.
 434
 435    This function calls handled_component_p to strip away all the inner
 436    parts of the memory reference until it reaches the base object.  */
 437
 438 tree
 439 get_base_address (tree t)
 440 {
 441   while (handled_component_p (t))
 442     t = TREE_OPERAND (t, 0);
 443
 444   if (SSA_VAR_P (t)
 445       || TREE_CODE (t) == STRING_CST
 446       || TREE_CODE (t) == CONSTRUCTOR
 447       || INDIRECT_REF_P (t))
 448     return t;
 449   else
 450     return NULL_TREE;
 451 }
 452
 453 void
 454 recalculate_side_effects (tree t)
 455 {
 456   enum tree_code code = TREE_CODE (t);
 457   int len = TREE_CODE_LENGTH (code);
 458   int i;
 459
 460   switch (TREE_CODE_CLASS (code))
 461     {
 462     case tcc_expression:
 463       switch (code)
 464         {
 465         case INIT_EXPR:
 466         case MODIFY_EXPR:
 467         case VA_ARG_EXPR:
 468         case PREDECREMENT_EXPR:
 469         case PREINCREMENT_EXPR:
 470         case POSTDECREMENT_EXPR:
 471         case POSTINCREMENT_EXPR:
 472           /* All of these have side-effects, no matter what their
 473              operands are.  */
 474           return;
 475
 476         default:
 477           break;
 478         }
 479       /* Fall through.  */
 480
 481     case tcc_comparison:  /* a comparison expression */
 482     case tcc_unary:       /* a unary arithmetic expression */
 483     case tcc_binary:      /* a binary arithmetic expression */
 484     case tcc_reference:   /* a reference */
 485       TREE_SIDE_EFFECTS (t) = TREE_THIS_VOLATILE (t);
 486       for (i = 0; i < len; ++i)
 487         {
 488           tree op = TREE_OPERAND (t, i);
 489           if (op && TREE_SIDE_EFFECTS (op))
 490             TREE_SIDE_EFFECTS (t) = 1;
 491         }
 492       break;
 493
 494     default:
 495       /* Can never be used with non-expressions.  */
 496       gcc_unreachable ();
 497    }
 498 }