gcc/tree-gimple.c

   1 /* Functions to analyze and validate GIMPLE trees.
   2    Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007
   3    Free Software Foundation, Inc.
   4    Contributed by Diego Novillo <dnovillo@redhat.com>
   5    Rewritten by Jason Merrill <jason@redhat.com>
   6
   7 This file is part of GCC.
   8
   9 GCC is free software; you can redistribute it and/or modify
  10 it under the terms of the GNU General Public License as published by
  11 the Free Software Foundation; either version 3, or (at your option)
  12 any later version.
  13
  14 GCC is distributed in the hope that it will be useful,
  15 but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 GNU General Public License for more details.
  18
  19 You should have received a copy of the GNU General Public License
  20 along with GCC; see the file COPYING3.  If not see
  21 <http://www.gnu.org/licenses/>.  */
  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 COND_EXPR:
  65     case ADDR_EXPR:
  66     case CALL_EXPR:
  67     case CONSTRUCTOR:
  68     case COMPLEX_EXPR:
  69     case INTEGER_CST:
  70     case REAL_CST:
  71     case FIXED_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 GIMPLE_MODIFY_STMT 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 VDEF 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           && (TREE_CODE (t) != CALL_EXPR
 122               || ! aggregate_value_p (t, t))))
 123     return is_gimple_val (t);
 124   else
 125     return is_gimple_formal_tmp_rhs (t);
 126 }
 127
 128 /* Returns the appropriate RHS predicate for this LHS.  */
 129
 130 gimple_predicate
 131 rhs_predicate_for (tree lhs)
 132 {
 133   if (is_gimple_formal_tmp_var (lhs))
 134     return is_gimple_formal_tmp_rhs;
 135   else if (is_gimple_reg (lhs))
 136     return is_gimple_reg_rhs;
 137   else
 138     return is_gimple_mem_rhs;
 139 }
 140
 141 /*  Return true if T is a valid LHS for a GIMPLE assignment expression.  */
 142
 143 bool
 144 is_gimple_lvalue (tree t)
 145 {
 146   return (is_gimple_addressable (t)
 147           || TREE_CODE (t) == WITH_SIZE_EXPR
 148           /* These are complex lvalues, but don't have addresses, so they
 149              go here.  */
 150           || TREE_CODE (t) == BIT_FIELD_REF);
 151 }
 152
 153 /*  Return true if T is a GIMPLE condition.  */
 154
 155 bool
 156 is_gimple_condexpr (tree t)
 157 {
 158   return (is_gimple_val (t) || COMPARISON_CLASS_P (t));
 159 }
 160
 161 /*  Return true if T is something whose address can be taken.  */
 162
 163 bool
 164 is_gimple_addressable (tree t)
 165 {
 166   return (is_gimple_id (t) || handled_component_p (t)
 167           || INDIRECT_REF_P (t));
 168 }
 169
 170 /* Return true if T is a GIMPLE minimal invariant.  It's a restricted
 171    form of function invariant.  */
 172
 173 bool
 174 is_gimple_min_invariant (const_tree t)
 175 {
 176   switch (TREE_CODE (t))
 177     {
 178     case ADDR_EXPR:
 179       return TREE_INVARIANT (t);
 180
 181     case INTEGER_CST:
 182     case REAL_CST:
 183     case FIXED_CST:
 184     case STRING_CST:
 185     case COMPLEX_CST:
 186     case VECTOR_CST:
 187       return true;
 188
 189     /* Vector constant constructors are gimple invariant.  */
 190     case CONSTRUCTOR:
 191       if (TREE_TYPE (t) && TREE_CODE (TREE_TYPE (t)) == VECTOR_TYPE)
 192         return TREE_CONSTANT (t);
 193       else
 194         return false;
 195
 196     default:
 197       return false;
 198     }
 199 }
 200
 201 /* Return true if T looks like a valid GIMPLE statement.  */
 202
 203 bool
 204 is_gimple_stmt (tree t)
 205 {
 206   const enum tree_code code = TREE_CODE (t);
 207
 208   switch (code)
 209     {
 210     case NOP_EXPR:
 211       /* The only valid NOP_EXPR is the empty statement.  */
 212       return IS_EMPTY_STMT (t);
 213
 214     case BIND_EXPR:
 215     case COND_EXPR:
 216       /* These are only valid if they're void.  */
 217       return TREE_TYPE (t) == NULL || VOID_TYPE_P (TREE_TYPE (t));
 218
 219     case SWITCH_EXPR:
 220     case GOTO_EXPR:
 221     case RETURN_EXPR:
 222     case LABEL_EXPR:
 223     case CASE_LABEL_EXPR:
 224     case TRY_CATCH_EXPR:
 225     case TRY_FINALLY_EXPR:
 226     case EH_FILTER_EXPR:
 227     case CATCH_EXPR:
 228     case CHANGE_DYNAMIC_TYPE_EXPR:
 229     case ASM_EXPR:
 230     case RESX_EXPR:
 231     case PHI_NODE:
 232     case STATEMENT_LIST:
 233     case OMP_PARALLEL:
 234     case OMP_FOR:
 235     case OMP_SECTIONS:
 236     case OMP_SECTIONS_SWITCH:
 237     case OMP_SECTION:
 238     case OMP_SINGLE:
 239     case OMP_MASTER:
 240     case OMP_ORDERED:
 241     case OMP_CRITICAL:
 242     case OMP_RETURN:
 243     case OMP_CONTINUE:
 244     case OMP_ATOMIC_LOAD:
 245     case OMP_ATOMIC_STORE:
 246       /* These are always void.  */
 247       return true;
 248
 249     case CALL_EXPR:
 250     case GIMPLE_MODIFY_STMT:
 251       /* These are valid regardless of their type.  */
 252       return true;
 253
 254     default:
 255       return false;
 256     }
 257 }
 258
 259 /* Return true if T is a variable.  */
 260
 261 bool
 262 is_gimple_variable (tree t)
 263 {
 264   return (TREE_CODE (t) == VAR_DECL
 265           || TREE_CODE (t) == PARM_DECL
 266           || TREE_CODE (t) == RESULT_DECL
 267           || TREE_CODE (t) == SSA_NAME);
 268 }
 269
 270 /*  Return true if T is a GIMPLE identifier (something with an address).  */
 271
 272 bool
 273 is_gimple_id (tree t)
 274 {
 275   return (is_gimple_variable (t)
 276           || TREE_CODE (t) == FUNCTION_DECL
 277           || TREE_CODE (t) == LABEL_DECL
 278           || TREE_CODE (t) == CONST_DECL
 279           /* Allow string constants, since they are addressable.  */
 280           || TREE_CODE (t) == STRING_CST);
 281 }
 282
 283 /* Return true if TYPE is a suitable type for a scalar register variable.  */
 284
 285 bool
 286 is_gimple_reg_type (tree type)
 287 {
 288   return !AGGREGATE_TYPE_P (type);
 289 }
 290
 291 /* Return true if T is a non-aggregate register variable.  */
 292
 293 bool
 294 is_gimple_reg (tree t)
 295 {
 296   if (TREE_CODE (t) == SSA_NAME)
 297     t = SSA_NAME_VAR (t);
 298
 299   if (MTAG_P (t))
 300     return false;
 301
 302   if (!is_gimple_variable (t))
 303     return false;
 304
 305   if (!is_gimple_reg_type (TREE_TYPE (t)))
 306     return false;
 307
 308   /* A volatile decl is not acceptable because we can't reuse it as
 309      needed.  We need to copy it into a temp first.  */
 310   if (TREE_THIS_VOLATILE (t))
 311     return false;
 312
 313   /* We define "registers" as things that can be renamed as needed,
 314      which with our infrastructure does not apply to memory.  */
 315   if (needs_to_live_in_memory (t))
 316     return false;
 317
 318   /* Hard register variables are an interesting case.  For those that
 319      are call-clobbered, we don't know where all the calls are, since
 320      we don't (want to) take into account which operations will turn
 321      into libcalls at the rtl level.  For those that are call-saved,
 322      we don't currently model the fact that calls may in fact change
 323      global hard registers, nor do we examine ASM_CLOBBERS at the tree
 324      level, and so miss variable changes that might imply.  All around,
 325      it seems safest to not do too much optimization with these at the
 326      tree level at all.  We'll have to rely on the rtl optimizers to
 327      clean this up, as there we've got all the appropriate bits exposed.  */
 328   if (TREE_CODE (t) == VAR_DECL && DECL_HARD_REGISTER (t))
 329     return false;
 330
 331   /* Complex values must have been put into ssa form.  That is, no
 332      assignments to the individual components.  */
 333   if (TREE_CODE (TREE_TYPE (t)) == COMPLEX_TYPE
 334       || TREE_CODE (TREE_TYPE (t)) == VECTOR_TYPE)
 335     return DECL_GIMPLE_REG_P (t);
 336
 337   return true;
 338 }
 339
 340
 341 /* Returns true if T is a GIMPLE formal temporary variable.  */
 342
 343 bool
 344 is_gimple_formal_tmp_var (tree t)
 345 {
 346   if (TREE_CODE (t) == SSA_NAME)
 347     return true;
 348
 349   return TREE_CODE (t) == VAR_DECL && DECL_GIMPLE_FORMAL_TEMP_P (t);
 350 }
 351
 352 /* Returns true if T is a GIMPLE formal temporary register variable.  */
 353
 354 bool
 355 is_gimple_formal_tmp_reg (tree t)
 356 {
 357   /* The intent of this is to get hold of a value that won't change.
 358      An SSA_NAME qualifies no matter if its of a user variable or not.  */
 359   if (TREE_CODE (t) == SSA_NAME)
 360     return true;
 361
 362   /* We don't know the lifetime characteristics of user variables.  */
 363   if (!is_gimple_formal_tmp_var (t))
 364     return false;
 365
 366   /* Finally, it must be capable of being placed in a register.  */
 367   return is_gimple_reg (t);
 368 }
 369
 370 /* Return true if T is a GIMPLE variable whose address is not needed.  */
 371
 372 bool
 373 is_gimple_non_addressable (tree t)
 374 {
 375   if (TREE_CODE (t) == SSA_NAME)
 376     t = SSA_NAME_VAR (t);
 377
 378   return (is_gimple_variable (t) && ! needs_to_live_in_memory (t));
 379 }
 380
 381 /* Return true if T is a GIMPLE rvalue, i.e. an identifier or a constant.  */
 382
 383 bool
 384 is_gimple_val (tree t)
 385 {
 386   /* Make loads from volatiles and memory vars explicit.  */
 387   if (is_gimple_variable (t)
 388       && is_gimple_reg_type (TREE_TYPE (t))
 389       && !is_gimple_reg (t))
 390     return false;
 391
 392   /* FIXME make these decls.  That can happen only when we expose the
 393      entire landing-pad construct at the tree level.  */
 394   if (TREE_CODE (t) == EXC_PTR_EXPR || TREE_CODE (t) == FILTER_EXPR)
 395     return true;
 396
 397   return (is_gimple_variable (t) || is_gimple_min_invariant (t));
 398 }
 399
 400 /* Similarly, but accept hard registers as inputs to asm statements.  */
 401
 402 bool
 403 is_gimple_asm_val (tree t)
 404 {
 405   if (TREE_CODE (t) == VAR_DECL && DECL_HARD_REGISTER (t))
 406     return true;
 407
 408   return is_gimple_val (t);
 409 }
 410
 411 /* Return true if T is a GIMPLE minimal lvalue.  */
 412
 413 bool
 414 is_gimple_min_lval (tree t)
 415 {
 416   return (is_gimple_id (t)
 417           || TREE_CODE (t) == INDIRECT_REF);
 418 }
 419
 420 /* Return true if T is a typecast operation.  */
 421
 422 bool
 423 is_gimple_cast (tree t)
 424 {
 425   return (TREE_CODE (t) == NOP_EXPR
 426           || TREE_CODE (t) == CONVERT_EXPR
 427           || TREE_CODE (t) == FIX_TRUNC_EXPR);
 428 }
 429
 430 /* Return true if T is a valid function operand of a CALL_EXPR.  */
 431
 432 bool
 433 is_gimple_call_addr (tree t)
 434 {
 435   return (TREE_CODE (t) == OBJ_TYPE_REF
 436           || is_gimple_val (t));
 437 }
 438
 439 /* If T makes a function call, return the corresponding CALL_EXPR operand.
 440    Otherwise, return NULL_TREE.  */
 441
 442 tree
 443 get_call_expr_in (tree t)
 444 {
 445   /* FIXME tuples: delete the assertion below when conversion complete.  */
 446   gcc_assert (TREE_CODE (t) != MODIFY_EXPR);
 447   if (TREE_CODE (t) == GIMPLE_MODIFY_STMT)
 448     t = GIMPLE_STMT_OPERAND (t, 1);
 449   if (TREE_CODE (t) == WITH_SIZE_EXPR)
 450     t = TREE_OPERAND (t, 0);
 451   if (TREE_CODE (t) == CALL_EXPR)
 452     return t;
 453   return NULL_TREE;
 454 }
 455
 456 /* Given a memory reference expression T, return its base address.
 457    The base address of a memory reference expression is the main
 458    object being referenced.  For instance, the base address for
 459    'array[i].fld[j]' is 'array'.  You can think of this as stripping
 460    away the offset part from a memory address.
 461
 462    This function calls handled_component_p to strip away all the inner
 463    parts of the memory reference until it reaches the base object.  */
 464
 465 tree
 466 get_base_address (tree t)
 467 {
 468   while (handled_component_p (t))
 469     t = TREE_OPERAND (t, 0);
 470
 471   if (SSA_VAR_P (t)
 472       || TREE_CODE (t) == STRING_CST
 473       || TREE_CODE (t) == CONSTRUCTOR
 474       || INDIRECT_REF_P (t))
 475     return t;
 476   else
 477     return NULL_TREE;
 478 }
 479
 480 void
 481 recalculate_side_effects (tree t)
 482 {
 483   enum tree_code code = TREE_CODE (t);
 484   int len = TREE_OPERAND_LENGTH (t);
 485   int i;
 486
 487   switch (TREE_CODE_CLASS (code))
 488     {
 489     case tcc_expression:
 490       switch (code)
 491         {
 492         case INIT_EXPR:
 493         case GIMPLE_MODIFY_STMT:
 494         case VA_ARG_EXPR:
 495         case PREDECREMENT_EXPR:
 496         case PREINCREMENT_EXPR:
 497         case POSTDECREMENT_EXPR:
 498         case POSTINCREMENT_EXPR:
 499           /* All of these have side-effects, no matter what their
 500              operands are.  */
 501           return;
 502
 503         default:
 504           break;
 505         }
 506       /* Fall through.  */
 507
 508     case tcc_comparison:  /* a comparison expression */
 509     case tcc_unary:       /* a unary arithmetic expression */
 510     case tcc_binary:      /* a binary arithmetic expression */
 511     case tcc_reference:   /* a reference */
 512     case tcc_vl_exp:        /* a function call */
 513       TREE_SIDE_EFFECTS (t) = TREE_THIS_VOLATILE (t);
 514       for (i = 0; i < len; ++i)
 515         {
 516           tree op = TREE_OPERAND (t, i);
 517           if (op && TREE_SIDE_EFFECTS (op))
 518             TREE_SIDE_EFFECTS (t) = 1;
 519         }
 520       break;
 521
 522     default:
 523       /* Can never be used with non-expressions.  */
 524       gcc_unreachable ();
 525    }
 526 }
 527
 528 /* Canonicalize a tree T for use in a COND_EXPR as conditional.  Returns
 529    a canonicalized tree that is valid for a COND_EXPR or NULL_TREE, if
 530    we failed to create one.  */
 531
 532 tree
 533 canonicalize_cond_expr_cond (tree t)
 534 {
 535   /* For (bool)x use x != 0.  */
 536   if (TREE_CODE (t) == NOP_EXPR
 537       && TREE_TYPE (t) == boolean_type_node)
 538     {
 539       tree top0 = TREE_OPERAND (t, 0);
 540       t = build2 (NE_EXPR, TREE_TYPE (t),
 541                   top0, build_int_cst (TREE_TYPE (top0), 0));
 542     }
 543   /* For !x use x == 0.  */
 544   else if (TREE_CODE (t) == TRUTH_NOT_EXPR)
 545     {
 546       tree top0 = TREE_OPERAND (t, 0);
 547       t = build2 (EQ_EXPR, TREE_TYPE (t),
 548                   top0, build_int_cst (TREE_TYPE (top0), 0));
 549     }
 550   /* For cmp ? 1 : 0 use cmp.  */
 551   else if (TREE_CODE (t) == COND_EXPR
 552            && COMPARISON_CLASS_P (TREE_OPERAND (t, 0))
 553            && integer_onep (TREE_OPERAND (t, 1))
 554            && integer_zerop (TREE_OPERAND (t, 2)))
 555     {
 556       tree top0 = TREE_OPERAND (t, 0);
 557       t = build2 (TREE_CODE (top0), TREE_TYPE (t),
 558                   TREE_OPERAND (top0, 0), TREE_OPERAND (top0, 1));
 559     }
 560
 561   /* A valid conditional for a COND_EXPR is either a gimple value
 562      or a comparison with two gimple value operands.  */
 563   if (is_gimple_val (t)
 564       || (COMPARISON_CLASS_P (t)
 565           && is_gimple_val (TREE_OPERAND (t, 0))
 566           && is_gimple_val (TREE_OPERAND (t, 1))))
 567     return t;
 568
 569   return NULL_TREE;
 570 }