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, 2007 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 3, 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 COPYING3.  If not see
  24 <http://www.gnu.org/licenses/>.  */
  25
  26 #include "config.h"
  27 #include "system.h"
  28 #include "coretypes.h"
  29 #include "tm.h"
  30 #include "tree.h"
  31 #include "varray.h"
  32 #include "c-tree.h"
  33 #include "c-common.h"
  34 #include "tree-gimple.h"
  35 #include "hard-reg-set.h"
  36 #include "basic-block.h"
  37 #include "tree-flow.h"
  38 #include "tree-inline.h"
  39 #include "diagnostic.h"
  40 #include "langhooks.h"
  41 #include "langhooks-def.h"
  42 #include "flags.h"
  43 #include "rtl.h"
  44 #include "toplev.h"
  45 #include "tree-dump.h"
  46 #include "c-pretty-print.h"
  47 #include "cgraph.h"
  48
  49
  50 /*  The gimplification pass converts the language-dependent trees
  51     (ld-trees) emitted by the parser into language-independent trees
  52     (li-trees) that are the target of SSA analysis and transformations.
  53
  54     Language-independent trees are based on the SIMPLE intermediate
  55     representation used in the McCAT compiler framework:
  56
  57     "Designing the McCAT Compiler Based on a Family of Structured
  58     Intermediate Representations,"
  59     L. Hendren, C. Donawa, M. Emami, G. Gao, Justiani, and B. Sridharan,
  60     Proceedings of the 5th International Workshop on Languages and
  61     Compilers for Parallel Computing, no. 757 in Lecture Notes in
  62     Computer Science, New Haven, Connecticut, pp. 406-420,
  63     Springer-Verlag, August 3-5, 1992.
  64
  65     http://www-acaps.cs.mcgill.ca/info/McCAT/McCAT.html
  66
  67     Basically, we walk down gimplifying the nodes that we encounter.  As we
  68     walk back up, we check that they fit our constraints, and copy them
  69     into temporaries if not.  */
  70
  71 /* Gimplification of statement trees.  */
  72
  73 /* Convert the tree representation of FNDECL from C frontend trees to
  74    GENERIC.  */
  75
  76 void
  77 c_genericize (tree fndecl)
  78 {
  79   FILE *dump_orig;
  80   int local_dump_flags;
  81   struct cgraph_node *cgn;
  82
  83   /* Dump the C-specific tree IR.  */
  84   dump_orig = dump_begin (TDI_original, &local_dump_flags);
  85   if (dump_orig)
  86     {
  87       fprintf (dump_orig, "\n;; Function %s",
  88                lang_hooks.decl_printable_name (fndecl, 2));
  89       fprintf (dump_orig, " (%s)\n",
  90                IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (fndecl)));
  91       fprintf (dump_orig, ";; enabled by -%s\n", dump_flag_name (TDI_original));
  92       fprintf (dump_orig, "\n");
  93
  94       if (local_dump_flags & TDF_RAW)
  95         dump_node (DECL_SAVED_TREE (fndecl),
  96                    TDF_SLIM | local_dump_flags, dump_orig);
  97       else
  98         print_c_tree (dump_orig, DECL_SAVED_TREE (fndecl));
  99       fprintf (dump_orig, "\n");
 100
 101       dump_end (TDI_original, dump_orig);
 102     }
 103
 104   /* Go ahead and gimplify for now.  */
 105   gimplify_function_tree (fndecl);
 106
 107   /* Dump the genericized tree IR.  */
 108   dump_function (TDI_generic, fndecl);
 109
 110   /* Genericize all nested functions now.  We do things in this order so
 111      that items like VLA sizes are expanded properly in the context of
 112      the correct function.  */
 113   cgn = cgraph_node (fndecl);
 114   for (cgn = cgn->nested; cgn ; cgn = cgn->next_nested)
 115     c_genericize (cgn->decl);
 116 }
 117
 118 static void
 119 add_block_to_enclosing (tree block)
 120 {
 121   tree enclosing;
 122
 123   for (enclosing = gimple_current_bind_expr ();
 124        enclosing; enclosing = TREE_CHAIN (enclosing))
 125     if (BIND_EXPR_BLOCK (enclosing))
 126       break;
 127
 128   enclosing = BIND_EXPR_BLOCK (enclosing);
 129   BLOCK_SUBBLOCKS (enclosing) = chainon (BLOCK_SUBBLOCKS (enclosing), block);
 130 }
 131
 132 /* Genericize a scope by creating a new BIND_EXPR.
 133    BLOCK is either a BLOCK representing the scope or a chain of _DECLs.
 134      In the latter case, we need to create a new BLOCK and add it to the
 135      BLOCK_SUBBLOCKS of the enclosing block.
 136    BODY is a chain of C _STMT nodes for the contents of the scope, to be
 137      genericized.  */
 138
 139 tree
 140 c_build_bind_expr (tree block, tree body)
 141 {
 142   tree decls, bind;
 143
 144   if (block == NULL_TREE)
 145     decls = NULL_TREE;
 146   else if (TREE_CODE (block) == BLOCK)
 147     decls = BLOCK_VARS (block);
 148   else
 149     {
 150       decls = block;
 151       if (DECL_ARTIFICIAL (decls))
 152         block = NULL_TREE;
 153       else
 154         {
 155           block = make_node (BLOCK);
 156           BLOCK_VARS (block) = decls;
 157           add_block_to_enclosing (block);
 158         }
 159     }
 160
 161   if (!body)
 162     body = build_empty_stmt ();
 163   if (decls || block)
 164     {
 165       bind = build3 (BIND_EXPR, void_type_node, decls, body, block);
 166       TREE_SIDE_EFFECTS (bind) = 1;
 167     }
 168   else
 169     bind = body;
 170
 171   return bind;
 172 }
 173
 174 /* Gimplification of expression trees.  */
 175
 176 /* Gimplify a C99 compound literal expression.  This just means adding
 177    the DECL_EXPR before the current statement and using its anonymous
 178    decl instead.  */
 179
 180 static enum gimplify_status
 181 gimplify_compound_literal_expr (tree *expr_p, tree *pre_p)
 182 {
 183   tree decl_s = COMPOUND_LITERAL_EXPR_DECL_STMT (*expr_p);
 184   tree decl = DECL_EXPR_DECL (decl_s);
 185
 186   /* This decl isn't mentioned in the enclosing block, so add it to the
 187      list of temps.  FIXME it seems a bit of a kludge to say that
 188      anonymous artificial vars aren't pushed, but everything else is.  */
 189   if (DECL_NAME (decl) == NULL_TREE && !DECL_SEEN_IN_BIND_EXPR_P (decl))
 190     gimple_add_tmp_var (decl);
 191
 192   gimplify_and_add (decl_s, pre_p);
 193   *expr_p = decl;
 194   return GS_OK;
 195 }
 196
 197 /* Do C-specific gimplification.  Args are as for gimplify_expr.  */
 198
 199 int
 200 c_gimplify_expr (tree *expr_p, tree *pre_p, tree *post_p ATTRIBUTE_UNUSED)
 201 {
 202   enum tree_code code = TREE_CODE (*expr_p);
 203
 204   switch (code)
 205     {
 206     case DECL_EXPR:
 207       /* This is handled mostly by gimplify.c, but we have to deal with
 208          not warning about int x = x; as it is a GCC extension to turn off
 209          this warning but only if warn_init_self is zero.  */
 210       if (TREE_CODE (DECL_EXPR_DECL (*expr_p)) == VAR_DECL
 211           && !DECL_EXTERNAL (DECL_EXPR_DECL (*expr_p))
 212           && !TREE_STATIC (DECL_EXPR_DECL (*expr_p))
 213           && (DECL_INITIAL (DECL_EXPR_DECL (*expr_p))
 214               == DECL_EXPR_DECL (*expr_p))
 215           && !warn_init_self)
 216         TREE_NO_WARNING (DECL_EXPR_DECL (*expr_p)) = 1;
 217       return GS_UNHANDLED;
 218
 219     case COMPOUND_LITERAL_EXPR:
 220       return gimplify_compound_literal_expr (expr_p, pre_p);
 221
 222     default:
 223       return GS_UNHANDLED;
 224     }
 225 }