gcc/c-gimplify.c

   1 /* Tree lowering pass.  This pass gimplifies the tree representation built
   2    by the C-based front ends.  The structure of gimplified, or
   3    language-independent, trees is dictated by the grammar described in this
   4    file.
   5    Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
   6    Lowering of expressions contributed by Sebastian Pop <s.pop@laposte.net>
   7    Re-written to support lowering of whole function trees, documentation
   8    and miscellaneous cleanups by Diego Novillo <dnovillo@redhat.com>
   9
  10 This file is part of GCC.
  11
  12 GCC is free software; you can redistribute it and/or modify it under
  13 the terms of the GNU General Public License as published by the Free
  14 Software Foundation; either version 2, or (at your option) any later
  15 version.
  16
  17 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  18 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  19 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  20 for more details.
  21
  22 You should have received a copy of the GNU General Public License
  23 along with GCC; see the file COPYING.  If not, write to the Free
  24 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  25 02110-1301, USA.  */
  26
  27 #include "config.h"
  28 #include "system.h"
  29 #include "coretypes.h"
  30 #include "tm.h"
  31 #include "tree.h"
  32 #include "varray.h"
  33 #include "c-tree.h"
  34 #include "c-common.h"
  35 #include "tree-gimple.h"
  36 #include "hard-reg-set.h"
  37 #include "basic-block.h"
  38 #include "tree-flow.h"
  39 #include "tree-inline.h"
  40 #include "diagnostic.h"
  41 #include "langhooks.h"
  42 #include "langhooks-def.h"
  43 #include "flags.h"
  44 #include "rtl.h"
  45 #include "toplev.h"
  46 #include "tree-dump.h"
  47 #include "c-pretty-print.h"
  48 #include "cgraph.h"
  49
  50
  51 /*  The gimplification pass converts the language-dependent trees
  52     (ld-trees) emitted by the parser into language-independent trees
  53     (li-trees) that are the target of SSA analysis and transformations.
  54
  55     Language-independent trees are based on the SIMPLE intermediate
  56     representation used in the McCAT compiler framework:
  57
  58     "Designing the McCAT Compiler Based on a Family of Structured
  59     Intermediate Representations,"
  60     L. Hendren, C. Donawa, M. Emami, G. Gao, Justiani, and B. Sridharan,
  61     Proceedings of the 5th International Workshop on Languages and
  62     Compilers for Parallel Computing, no. 757 in Lecture Notes in
  63     Computer Science, New Haven, Connecticut, pp. 406-420,
  64     Springer-Verlag, August 3-5, 1992.
  65
  66     http://www-acaps.cs.mcgill.ca/info/McCAT/McCAT.html
  67
  68     Basically, we walk down gimplifying the nodes that we encounter.  As we
  69     walk back up, we check that they fit our constraints, and copy them
  70     into temporaries if not.  */
  71
  72 /* Gimplification of statement trees.  */
  73
  74 /* Convert the tree representation of FNDECL from C frontend trees to
  75    GENERIC.  */
  76
  77 void
  78 c_genericize (tree fndecl)
  79 {
  80   FILE *dump_orig;
  81   int local_dump_flags;
  82   struct cgraph_node *cgn;
  83
  84   /* Dump the C-specific tree IR.  */
  85   dump_orig = dump_begin (TDI_original, &local_dump_flags);
  86   if (dump_orig)
  87     {
  88       fprintf (dump_orig, "\n;; Function %s",
  89                lang_hooks.decl_printable_name (fndecl, 2));
  90       fprintf (dump_orig, " (%s)\n",
  91                IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (fndecl)));
  92       fprintf (dump_orig, ";; enabled by -%s\n", dump_flag_name (TDI_original));
  93       fprintf (dump_orig, "\n");
  94
  95       if (local_dump_flags & TDF_RAW)
  96         dump_node (DECL_SAVED_TREE (fndecl),
  97                    TDF_SLIM | local_dump_flags, dump_orig);
  98       else
  99         print_c_tree (dump_orig, DECL_SAVED_TREE (fndecl));
 100       fprintf (dump_orig, "\n");
 101
 102       dump_end (TDI_original, dump_orig);
 103     }
 104
 105   /* Go ahead and gimplify for now.  */
 106   gimplify_function_tree (fndecl);
 107
 108   /* Dump the genericized tree IR.  */
 109   dump_function (TDI_generic, fndecl);
 110
 111   /* Genericize all nested functions now.  We do things in this order so
 112      that items like VLA sizes are expanded properly in the context of
 113      the correct function.  */
 114   cgn = cgraph_node (fndecl);
 115   for (cgn = cgn->nested; cgn ; cgn = cgn->next_nested)
 116     c_genericize (cgn->decl);
 117 }
 118
 119 static void
 120 add_block_to_enclosing (tree block)
 121 {
 122   tree enclosing;
 123
 124   for (enclosing = gimple_current_bind_expr ();
 125        enclosing; enclosing = TREE_CHAIN (enclosing))
 126     if (BIND_EXPR_BLOCK (enclosing))
 127       break;
 128
 129   enclosing = BIND_EXPR_BLOCK (enclosing);
 130   BLOCK_SUBBLOCKS (enclosing) = chainon (BLOCK_SUBBLOCKS (enclosing), block);
 131 }
 132
 133 /* Genericize a scope by creating a new BIND_EXPR.
 134    BLOCK is either a BLOCK representing the scope or a chain of _DECLs.
 135      In the latter case, we need to create a new BLOCK and add it to the
 136      BLOCK_SUBBLOCKS of the enclosing block.
 137    BODY is a chain of C _STMT nodes for the contents of the scope, to be
 138      genericized.  */
 139
 140 tree
 141 c_build_bind_expr (tree block, tree body)
 142 {
 143   tree decls, bind;
 144
 145   if (block == NULL_TREE)
 146     decls = NULL_TREE;
 147   else if (TREE_CODE (block) == BLOCK)
 148     decls = BLOCK_VARS (block);
 149   else
 150     {
 151       decls = block;
 152       if (DECL_ARTIFICIAL (decls))
 153         block = NULL_TREE;
 154       else
 155         {
 156           block = make_node (BLOCK);
 157           BLOCK_VARS (block) = decls;
 158           add_block_to_enclosing (block);
 159         }
 160     }
 161
 162   if (!body)
 163     body = build_empty_stmt ();
 164   if (decls || block)
 165     {
 166       bind = build3 (BIND_EXPR, void_type_node, decls, body, block);
 167       TREE_SIDE_EFFECTS (bind) = 1;
 168     }
 169   else
 170     bind = body;
 171
 172   return bind;
 173 }
 174
 175 /* Gimplification of expression trees.  */
 176
 177 /* Gimplify a C99 compound literal expression.  This just means adding
 178    the DECL_EXPR before the current statement and using its anonymous
 179    decl instead.  */
 180
 181 static enum gimplify_status
 182 gimplify_compound_literal_expr (tree *expr_p, tree *pre_p)
 183 {
 184   tree decl_s = COMPOUND_LITERAL_EXPR_DECL_STMT (*expr_p);
 185   tree decl = DECL_EXPR_DECL (decl_s);
 186
 187   /* This decl isn't mentioned in the enclosing block, so add it to the
 188      list of temps.  FIXME it seems a bit of a kludge to say that
 189      anonymous artificial vars aren't pushed, but everything else is.  */
 190   if (DECL_NAME (decl) == NULL_TREE && !DECL_SEEN_IN_BIND_EXPR_P (decl))
 191     gimple_add_tmp_var (decl);
 192
 193   gimplify_and_add (decl_s, pre_p);
 194   *expr_p = decl;
 195   return GS_OK;
 196 }
 197
 198 /* Do C-specific gimplification.  Args are as for gimplify_expr.  */
 199
 200 int
 201 c_gimplify_expr (tree *expr_p, tree *pre_p, tree *post_p ATTRIBUTE_UNUSED)
 202 {
 203   enum tree_code code = TREE_CODE (*expr_p);
 204
 205   switch (code)
 206     {
 207     case DECL_EXPR:
 208       /* This is handled mostly by gimplify.c, but we have to deal with
 209          not warning about int x = x; as it is a GCC extension to turn off
 210          this warning but only if warn_init_self is zero.  */
 211       if (TREE_CODE (DECL_EXPR_DECL (*expr_p)) == VAR_DECL
 212           && !DECL_EXTERNAL (DECL_EXPR_DECL (*expr_p))
 213           && !TREE_STATIC (DECL_EXPR_DECL (*expr_p))
 214           && (DECL_INITIAL (DECL_EXPR_DECL (*expr_p))
 215               == DECL_EXPR_DECL (*expr_p))
 216           && !warn_init_self)
 217         TREE_NO_WARNING (DECL_EXPR_DECL (*expr_p)) = 1;
 218       return GS_UNHANDLED;
 219
 220     case COMPOUND_LITERAL_EXPR:
 221       return gimplify_compound_literal_expr (expr_p, pre_p);
 222
 223     default:
 224       return GS_UNHANDLED;
 225     }
 226 }