gcc/java/java-gimplify.c

   1 /* Java(TM) language-specific gimplification routines.
   2    Copyright (C) 2003, 2004, 2006, 2007, 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 3, 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 COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.
  19
  20 Java and all Java-based marks are trademarks or registered trademarks
  21 of Sun Microsystems, Inc. in the United States and other countries.
  22 The Free Software Foundation is independent of Sun Microsystems, Inc.  */
  23
  24 #include "config.h"
  25 #include "system.h"
  26 #include "coretypes.h"
  27 #include "tm.h"
  28 #include "tree.h"
  29 #include "java-tree.h"
  30 #include "tree-dump.h"
  31 #include "tree-gimple.h"
  32 #include "toplev.h"
  33
  34 static tree java_gimplify_block (tree);
  35 static enum gimplify_status java_gimplify_modify_expr (tree *);
  36 static enum gimplify_status java_gimplify_self_mod_expr (tree*, tree*, tree *);
  37
  38 static void dump_java_tree (enum tree_dump_index, tree);
  39
  40 /* Convert a Java tree to GENERIC.  */
  41
  42 void
  43 java_genericize (tree fndecl)
  44 {
  45   dump_java_tree (TDI_original, fndecl);
  46
  47   /* Genericize with the gimplifier.  */
  48   gimplify_function_tree (fndecl);
  49
  50   dump_function (TDI_generic, fndecl);
  51 }
  52
  53 /* Gimplify a Java tree.  */
  54
  55 int
  56 java_gimplify_expr (tree *expr_p, tree *pre_p ATTRIBUTE_UNUSED,
  57                     tree *post_p ATTRIBUTE_UNUSED)
  58 {
  59   enum tree_code code = TREE_CODE (*expr_p);
  60
  61   switch (code)
  62     {
  63     case BLOCK:
  64       *expr_p = java_gimplify_block (*expr_p);
  65       break;
  66
  67     case VAR_DECL:
  68       *expr_p = java_replace_reference (*expr_p, /* want_lvalue */ false);
  69       return GS_UNHANDLED;
  70
  71       /* We don't handle GIMPLE_MODIFY_STMT, as MODIFY_EXPRs with java
  72          semantics should only be generated by the front-end, and never
  73          by anything after gimplification.  */
  74     case MODIFY_EXPR:
  75       return java_gimplify_modify_expr (expr_p);
  76
  77     case SAVE_EXPR:
  78       /* Note that we can see <save_expr NULL> if the save_expr was
  79          already handled by gimplify_save_expr.  */
  80       if (TREE_OPERAND (*expr_p, 0) != NULL_TREE
  81           && TREE_CODE (TREE_OPERAND (*expr_p, 0)) == VAR_DECL)
  82         TREE_OPERAND (*expr_p, 0)
  83           = java_replace_reference (TREE_OPERAND (*expr_p, 0),
  84                                /* want_lvalue */ false);
  85       return GS_UNHANDLED;
  86
  87     case POSTINCREMENT_EXPR:
  88     case POSTDECREMENT_EXPR:
  89     case PREINCREMENT_EXPR:
  90     case PREDECREMENT_EXPR:
  91       return java_gimplify_self_mod_expr (expr_p, pre_p, post_p);
  92
  93     /* These should already be lowered before we get here.  */
  94     case URSHIFT_EXPR:
  95     case COMPARE_EXPR:
  96     case COMPARE_L_EXPR:
  97     case COMPARE_G_EXPR:
  98       gcc_unreachable ();
  99
 100     default:
 101       /* Java insists on strict left-to-right evaluation of expressions.
 102          A problem may arise if a variable used in the LHS of a binary
 103          operation is altered by an assignment to that value in the RHS
 104          before we've performed the operation.  So, we always copy every
 105          LHS to a temporary variable.
 106
 107          FIXME: Are there any other cases where we should do this?
 108          Parameter lists, maybe?  Or perhaps that's unnecessary because
 109          the front end already generates SAVE_EXPRs.  */
 110
 111       if (TREE_CODE_CLASS (code) == tcc_binary
 112           || TREE_CODE_CLASS (code) == tcc_comparison)
 113         {
 114           enum gimplify_status stat
 115             = gimplify_expr (&TREE_OPERAND (*expr_p, 0), pre_p, post_p,
 116                              is_gimple_formal_tmp_var, fb_rvalue);
 117           if (stat == GS_ERROR)
 118             return stat;
 119         }
 120
 121       return GS_UNHANDLED;
 122     }
 123
 124   return GS_OK;
 125 }
 126
 127 static enum gimplify_status
 128 java_gimplify_modify_expr (tree *modify_expr_p)
 129 {
 130   tree modify_expr = *modify_expr_p;
 131   tree lhs = TREE_OPERAND (modify_expr, 0);
 132   tree rhs = TREE_OPERAND (modify_expr, 1);
 133   tree lhs_type = TREE_TYPE (lhs);
 134
 135   /* This is specific to the bytecode compiler.  If a variable has
 136      LOCAL_SLOT_P set, replace an assignment to it with an assignment
 137      to the corresponding variable that holds all its aliases.  */
 138   if (TREE_CODE (lhs) == VAR_DECL
 139       && DECL_LANG_SPECIFIC (lhs)
 140       && LOCAL_SLOT_P (lhs)
 141       && TREE_CODE (lhs_type) == POINTER_TYPE)
 142     {
 143       tree new_lhs = java_replace_reference (lhs, /* want_lvalue */ true);
 144       tree new_rhs = build1 (NOP_EXPR, TREE_TYPE (new_lhs), rhs);
 145       modify_expr = build2 (GIMPLE_MODIFY_STMT, TREE_TYPE (new_lhs),
 146                             new_lhs, new_rhs);
 147       modify_expr = build1 (NOP_EXPR, lhs_type, modify_expr);
 148     }
 149   else if (lhs_type != TREE_TYPE (rhs))
 150     /* Fix up type mismatches to make legal GIMPLE.  These are
 151        generated in several places, in particular null pointer
 152        assignment and subclass assignment.  */
 153     TREE_OPERAND (modify_expr, 1) = convert (lhs_type, rhs);
 154
 155   *modify_expr_p = modify_expr;
 156   return GS_UNHANDLED;
 157 }
 158
 159 /*  Special case handling for volatiles: we need to generate a barrier
 160     between the reading and the writing.  */
 161
 162 static enum gimplify_status
 163 java_gimplify_self_mod_expr (tree *expr_p, tree *pre_p ATTRIBUTE_UNUSED,
 164                              tree *post_p ATTRIBUTE_UNUSED)
 165 {
 166   tree lhs = TREE_OPERAND (*expr_p, 0);
 167
 168   if (TREE_CODE (lhs) == COMPONENT_REF
 169       && TREE_THIS_VOLATILE (TREE_OPERAND (lhs, 1)))
 170     TREE_THIS_VOLATILE (lhs) = 1;
 171
 172   return GS_UNHANDLED;
 173 }
 174
 175
 176 /* Gimplify BLOCK into a BIND_EXPR.  */
 177
 178 static tree
 179 java_gimplify_block (tree java_block)
 180 {
 181   tree decls = BLOCK_VARS (java_block);
 182   tree body = BLOCK_EXPR_BODY (java_block);
 183   tree outer = gimple_current_bind_expr ();
 184   tree block;
 185
 186   /* Don't bother with empty blocks.  */
 187   if (! body)
 188     return build_empty_stmt ();
 189
 190   if (IS_EMPTY_STMT (body))
 191     return body;
 192
 193   /* Make a proper block.  Java blocks are unsuitable for BIND_EXPR
 194      because they use BLOCK_SUBBLOCKS for another purpose.  */
 195   block = make_node (BLOCK);
 196   BLOCK_VARS (block) = decls;
 197
 198   /* The TREE_USED flag on a block determines whether the debug output
 199      routines generate info for the variables in that block.  */
 200   TREE_USED (block) = 1;
 201
 202   if (outer != NULL_TREE)
 203     {
 204       outer = BIND_EXPR_BLOCK (outer);
 205       BLOCK_SUBBLOCKS (outer) = chainon (BLOCK_SUBBLOCKS (outer), block);
 206     }
 207   BLOCK_EXPR_BODY (java_block) = NULL_TREE;
 208
 209   return build3 (BIND_EXPR, TREE_TYPE (java_block), decls, body, block);
 210 }
 211
 212 /* Dump a tree of some kind.  This is a convenience wrapper for the
 213    dump_* functions in tree-dump.c.  */
 214 static void
 215 dump_java_tree (enum tree_dump_index phase, tree t)
 216 {
 217   FILE *stream;
 218   int flags;
 219
 220   stream = dump_begin (phase, &flags);
 221   flags |= TDF_SLIM;
 222   if (stream)
 223     {
 224       dump_node (t, flags, stream);
 225       dump_end (phase, stream);
 226     }
 227 }