gcc/java/java-gimplify.c

   1 /* Java(TM) language-specific gimplification routines.
   2    Copyright (C) 2003, 2004, 2006, 2007 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GCC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 51 Franklin Street, Fifth Floor,
  19 Boston, MA 02110-1301, USA.
  20
  21 Java and all Java-based marks are trademarks or registered trademarks
  22 of Sun Microsystems, Inc. in the United States and other countries.
  23 The Free Software Foundation is independent of Sun Microsystems, Inc.  */
  24
  25 #include "config.h"
  26 #include "system.h"
  27 #include "coretypes.h"
  28 #include "tm.h"
  29 #include "tree.h"
  30 #include "java-tree.h"
  31 #include "tree-dump.h"
  32 #include "tree-gimple.h"
  33 #include "toplev.h"
  34
  35 static tree java_gimplify_labeled_block_expr (tree);
  36 static tree java_gimplify_exit_block_expr (tree);
  37 static tree java_gimplify_block (tree);
  38 static tree java_gimplify_try_expr (tree);
  39 static enum gimplify_status java_gimplify_modify_expr (tree*, tree*, tree *);
  40 static enum gimplify_status java_gimplify_component_ref (tree*, tree*, tree *);
  41 static enum gimplify_status java_gimplify_self_mod_expr (tree*, tree*, tree *);
  42
  43 static void dump_java_tree (enum tree_dump_index, tree);
  44
  45 /* Convert a Java tree to GENERIC.  */
  46
  47 void
  48 java_genericize (tree fndecl)
  49 {
  50   dump_java_tree (TDI_original, fndecl);
  51
  52   /* Genericize with the gimplifier.  */
  53   gimplify_function_tree (fndecl);
  54
  55   dump_function (TDI_generic, fndecl);
  56 }
  57
  58 /* Gimplify a Java tree.  */
  59
  60 int
  61 java_gimplify_expr (tree *expr_p, tree *pre_p ATTRIBUTE_UNUSED,
  62                     tree *post_p ATTRIBUTE_UNUSED)
  63 {
  64   enum tree_code code = TREE_CODE (*expr_p);
  65
  66   switch (code)
  67     {
  68     case BLOCK:
  69       *expr_p = java_gimplify_block (*expr_p);
  70       break;
  71
  72     case LABELED_BLOCK_EXPR:
  73       *expr_p = java_gimplify_labeled_block_expr (*expr_p);
  74       break;
  75
  76     case EXIT_BLOCK_EXPR:
  77       *expr_p = java_gimplify_exit_block_expr (*expr_p);
  78       break;
  79
  80     case TRY_EXPR:
  81       *expr_p = java_gimplify_try_expr (*expr_p);
  82       break;
  83
  84     case VAR_DECL:
  85       *expr_p = java_replace_reference (*expr_p, /* want_lvalue */ false);
  86       return GS_UNHANDLED;
  87
  88       /* We don't handle GIMPLE_MODIFY_STMT, as MODIFY_EXPRs with java
  89          semantics should only be generated by the front-end, and never
  90          by anything after gimplification.  */
  91     case MODIFY_EXPR:
  92       return java_gimplify_modify_expr (expr_p, pre_p, post_p);
  93
  94     case SAVE_EXPR:
  95       /* Note that we can see <save_expr NULL> if the save_expr was
  96          already handled by gimplify_save_expr.  */
  97       if (TREE_OPERAND (*expr_p, 0) != NULL_TREE
  98           && TREE_CODE (TREE_OPERAND (*expr_p, 0)) == VAR_DECL)
  99         TREE_OPERAND (*expr_p, 0)
 100           = java_replace_reference (TREE_OPERAND (*expr_p, 0),
 101                                /* want_lvalue */ false);
 102       return GS_UNHANDLED;
 103
 104     case POSTINCREMENT_EXPR:
 105     case POSTDECREMENT_EXPR:
 106     case PREINCREMENT_EXPR:
 107     case PREDECREMENT_EXPR:
 108       return java_gimplify_self_mod_expr (expr_p, pre_p, post_p);
 109
 110     /* These should already be lowered before we get here.  */
 111     case URSHIFT_EXPR:
 112     case COMPARE_EXPR:
 113     case COMPARE_L_EXPR:
 114     case COMPARE_G_EXPR:
 115       gcc_unreachable ();
 116
 117     case COMPONENT_REF:
 118       return java_gimplify_component_ref (expr_p, pre_p, post_p);
 119
 120     default:
 121       /* Java insists on strict left-to-right evaluation of expressions.
 122          A problem may arise if a variable used in the LHS of a binary
 123          operation is altered by an assignment to that value in the RHS
 124          before we've performed the operation.  So, we always copy every
 125          LHS to a temporary variable.
 126
 127          FIXME: Are there any other cases where we should do this?
 128          Parameter lists, maybe?  Or perhaps that's unnecessary because
 129          the front end already generates SAVE_EXPRs.  */
 130
 131       if (TREE_CODE_CLASS (code) == tcc_binary
 132           || TREE_CODE_CLASS (code) == tcc_comparison)
 133         {
 134           enum gimplify_status stat
 135             = gimplify_expr (&TREE_OPERAND (*expr_p, 0), pre_p, post_p,
 136                              is_gimple_formal_tmp_var, fb_rvalue);
 137           if (stat == GS_ERROR)
 138             return stat;
 139         }
 140
 141       return GS_UNHANDLED;
 142     }
 143
 144   return GS_OK;
 145 }
 146
 147 /* Gimplify a LABELED_BLOCK_EXPR into a LABEL_EXPR following
 148    a (possibly empty) body.  */
 149
 150 static tree
 151 java_gimplify_labeled_block_expr (tree expr)
 152 {
 153   tree body = LABELED_BLOCK_BODY (expr);
 154   tree label = LABELED_BLOCK_LABEL (expr);
 155   tree t;
 156
 157   DECL_CONTEXT (label) = current_function_decl;
 158   t = build1 (LABEL_EXPR, void_type_node, label);
 159   if (body != NULL_TREE)
 160     t = build2 (COMPOUND_EXPR, void_type_node, body, t);
 161   return t;
 162 }
 163
 164 /* Gimplify a EXIT_BLOCK_EXPR into a GOTO_EXPR.  */
 165
 166 static tree
 167 java_gimplify_exit_block_expr (tree expr)
 168 {
 169   tree labeled_block = EXIT_BLOCK_LABELED_BLOCK (expr);
 170   tree label;
 171
 172   /* First operand must be a LABELED_BLOCK_EXPR, which should
 173      already be lowered (or partially lowered) when we get here.  */
 174   gcc_assert (TREE_CODE (labeled_block) == LABELED_BLOCK_EXPR);
 175
 176   label = LABELED_BLOCK_LABEL (labeled_block);
 177   return build1 (GOTO_EXPR, void_type_node, label);
 178 }
 179
 180
 181
 182 static enum gimplify_status
 183 java_gimplify_component_ref (tree *expr_p, tree *pre_p, tree *post_p)
 184 {
 185   if (CLASS_FROM_SOURCE_P (output_class)
 186       && TREE_THIS_VOLATILE (TREE_OPERAND (*expr_p, 1))
 187       && ! TREE_THIS_VOLATILE (*expr_p))
 188   {
 189     enum gimplify_status stat;
 190     tree sync_expr;
 191
 192     /* Special handling for volatile fields.
 193
 194     A load has "acquire" semantics, implying that you can't move up
 195     later operations.  A store has "release" semantics meaning that
 196     earlier operations cannot be delayed past it.
 197
 198     This logic only handles loads: stores are handled in
 199     java_gimplify_modify_expr().
 200
 201     We gimplify this COMPONENT_REF, put the result in a tmp_var, and then
 202     return a COMPOUND_EXPR of the form {__sync_synchronize(); tmp_var}.
 203     This forces __sync_synchronize() to be placed immediately after
 204     loading from the volatile field.
 205
 206     */
 207
 208     TREE_THIS_VOLATILE (*expr_p) = 1;
 209     *expr_p = java_modify_addr_for_volatile (*expr_p);
 210     stat = gimplify_expr (expr_p, pre_p, post_p,
 211                           is_gimple_formal_tmp_var, fb_rvalue);
 212     if (stat == GS_ERROR)
 213       return stat;
 214
 215     sync_expr
 216       = build3 (CALL_EXPR, void_type_node,
 217                 build_address_of (built_in_decls[BUILT_IN_SYNCHRONIZE]),
 218                 NULL_TREE, NULL_TREE);
 219     TREE_SIDE_EFFECTS (sync_expr) = 1;
 220     *expr_p = build2 (COMPOUND_EXPR, TREE_TYPE (*expr_p),
 221                       sync_expr, *expr_p);
 222     TREE_SIDE_EFFECTS (*expr_p) = 1;
 223   }
 224
 225   return GS_UNHANDLED;
 226 }
 227
 228
 229 static enum gimplify_status
 230 java_gimplify_modify_expr (tree *modify_expr_p, tree *pre_p, tree *post_p)
 231 {
 232   tree modify_expr = *modify_expr_p;
 233   tree lhs = TREE_OPERAND (modify_expr, 0);
 234   tree rhs = TREE_OPERAND (modify_expr, 1);
 235   tree lhs_type = TREE_TYPE (lhs);
 236
 237   if (CLASS_FROM_SOURCE_P (output_class)
 238       && TREE_CODE (lhs) == COMPONENT_REF
 239       && TREE_THIS_VOLATILE (TREE_OPERAND (lhs, 1)))
 240     {
 241       /* Special handling for volatile fields.
 242
 243       A load has "acquire" semantics, implying that you can't move up
 244       later operations.  A store has "release" semantics meaning that
 245       earlier operations cannot be delayed past it.
 246
 247       This logic only handles stores; loads are handled in
 248       java_gimplify_component_ref().
 249
 250       We gimplify the rhs, put the result in a tmp_var, and then return
 251       a MODIFY_EXPR with an rhs of the form {__sync_synchronize(); tmp_var}.
 252       This forces __sync_synchronize() to be placed after evaluating
 253       the rhs and immediately before storing to the volatile field.
 254
 255       */
 256
 257       enum gimplify_status stat;
 258       tree sync_expr
 259         = build3 (CALL_EXPR, void_type_node,
 260                   build_address_of (built_in_decls[BUILT_IN_SYNCHRONIZE]),
 261                   NULL_TREE, NULL_TREE);
 262       TREE_SIDE_EFFECTS (sync_expr) = 1;
 263
 264       stat = gimplify_expr (&rhs, pre_p, post_p,
 265                             is_gimple_formal_tmp_var, fb_rvalue);
 266       if (stat == GS_ERROR)
 267         return stat;
 268
 269       rhs = build2 (COMPOUND_EXPR, TREE_TYPE (rhs),
 270                     sync_expr, rhs);
 271       TREE_SIDE_EFFECTS (rhs) = 1;
 272       TREE_THIS_VOLATILE (lhs) = 1;
 273       lhs = java_modify_addr_for_volatile (lhs);
 274       TREE_OPERAND (modify_expr, 0) = lhs;
 275       TREE_OPERAND (modify_expr, 1) = rhs;
 276     }
 277
 278   /* This is specific to the bytecode compiler.  If a variable has
 279      LOCAL_SLOT_P set, replace an assignment to it with an assignment
 280      to the corresponding variable that holds all its aliases.  */
 281   if (TREE_CODE (lhs) == VAR_DECL
 282       && DECL_LANG_SPECIFIC (lhs)
 283       && LOCAL_SLOT_P (lhs)
 284       && TREE_CODE (lhs_type) == POINTER_TYPE)
 285     {
 286       tree new_lhs = java_replace_reference (lhs, /* want_lvalue */ true);
 287       tree new_rhs = build1 (NOP_EXPR, TREE_TYPE (new_lhs), rhs);
 288       modify_expr = build2 (GIMPLE_MODIFY_STMT, TREE_TYPE (new_lhs),
 289                             new_lhs, new_rhs);
 290       modify_expr = build1 (NOP_EXPR, lhs_type, modify_expr);
 291     }
 292   else if (lhs_type != TREE_TYPE (rhs))
 293     /* Fix up type mismatches to make legal GIMPLE.  These are
 294        generated in several places, in particular null pointer
 295        assignment and subclass assignment.  */
 296     TREE_OPERAND (modify_expr, 1) = convert (lhs_type, rhs);
 297
 298   *modify_expr_p = modify_expr;
 299   return GS_UNHANDLED;
 300 }
 301
 302 /*  Special case handling for volatiles: we need to generate a barrier
 303     between the reading and the writing.  */
 304
 305 static enum gimplify_status
 306 java_gimplify_self_mod_expr (tree *expr_p, tree *pre_p ATTRIBUTE_UNUSED,
 307                              tree *post_p ATTRIBUTE_UNUSED)
 308 {
 309   tree lhs = TREE_OPERAND (*expr_p, 0);
 310
 311   if (TREE_CODE (lhs) == COMPONENT_REF
 312       && TREE_THIS_VOLATILE (TREE_OPERAND (lhs, 1)))
 313     TREE_THIS_VOLATILE (lhs) = 1;
 314
 315   return GS_UNHANDLED;
 316 }
 317
 318
 319 /* Gimplify BLOCK into a BIND_EXPR.  */
 320
 321 static tree
 322 java_gimplify_block (tree java_block)
 323 {
 324   tree decls = BLOCK_VARS (java_block);
 325   tree body = BLOCK_EXPR_BODY (java_block);
 326   tree outer = gimple_current_bind_expr ();
 327   tree block;
 328
 329   /* Don't bother with empty blocks.  */
 330   if (! body)
 331     return build_empty_stmt ();
 332
 333   if (IS_EMPTY_STMT (body))
 334     return body;
 335
 336   /* Make a proper block.  Java blocks are unsuitable for BIND_EXPR
 337      because they use BLOCK_SUBBLOCKS for another purpose.  */
 338   block = make_node (BLOCK);
 339   BLOCK_VARS (block) = decls;
 340
 341   /* The TREE_USED flag on a block determines whether the debug output
 342      routines generate info for the variables in that block.  */
 343   TREE_USED (block) = 1;
 344
 345   if (outer != NULL_TREE)
 346     {
 347       outer = BIND_EXPR_BLOCK (outer);
 348       BLOCK_SUBBLOCKS (outer) = chainon (BLOCK_SUBBLOCKS (outer), block);
 349     }
 350   BLOCK_EXPR_BODY (java_block) = NULL_TREE;
 351
 352   return build3 (BIND_EXPR, TREE_TYPE (java_block), decls, body, block);
 353 }
 354
 355 static tree
 356 java_gimplify_try_expr (tree try_expr)
 357 {
 358   tree body = TREE_OPERAND (try_expr, 0);
 359   tree handler = TREE_OPERAND (try_expr, 1);
 360   tree catch = NULL_TREE;
 361
 362   /* Build a CATCH_EXPR for each handler.  */
 363   while (handler)
 364     {
 365       tree java_catch = TREE_OPERAND (handler, 0);
 366       tree catch_type = TREE_TYPE (TREE_TYPE (BLOCK_EXPR_DECLS (java_catch)));
 367       tree expr = build2 (CATCH_EXPR, void_type_node,
 368                           prepare_eh_table_type (catch_type),
 369                           handler);
 370       if (catch)
 371         catch = build2 (COMPOUND_EXPR, void_type_node, catch, expr);
 372       else
 373         catch = expr;
 374       handler = TREE_CHAIN (handler);
 375     }
 376   return build2 (TRY_CATCH_EXPR, void_type_node, body, catch);
 377 }
 378
 379 /* Dump a tree of some kind.  This is a convenience wrapper for the
 380    dump_* functions in tree-dump.c.  */
 381 static void
 382 dump_java_tree (enum tree_dump_index phase, tree t)
 383 {
 384   FILE *stream;
 385   int flags;
 386
 387   stream = dump_begin (phase, &flags);
 388   flags |= TDF_SLIM;
 389   if (stream)
 390     {
 391       dump_node (t, flags, stream);
 392       dump_end (phase, stream);
 393     }
 394 }