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, 2008
   6    Free Software Foundation, Inc.
   7    Lowering of expressions contributed by Sebastian Pop <s.pop@laposte.net>
   8    Re-written to support lowering of whole function trees, documentation
   9    and miscellaneous cleanups by Diego Novillo <dnovillo@redhat.com>
  10
  11 This file is part of GCC.
  12
  13 GCC is free software; you can redistribute it and/or modify it under
  14 the terms of the GNU General Public License as published by the Free
  15 Software Foundation; either version 3, or (at your option) any later
  16 version.
  17
  18 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  19 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  20 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  21 for more details.
  22
  23 You should have received a copy of the GNU General Public License
  24 along with GCC; see the file COPYING3.  If not see
  25 <http://www.gnu.org/licenses/>.  */
  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 "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                (!DECL_ASSEMBLER_NAME_SET_P (fndecl) ? "null"
  92                 : IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (fndecl))));
  93       fprintf (dump_orig, ";; enabled by -%s\n", dump_flag_name (TDI_original));
  94       fprintf (dump_orig, "\n");
  95
  96       if (local_dump_flags & TDF_RAW)
  97         dump_node (DECL_SAVED_TREE (fndecl),
  98                    TDF_SLIM | local_dump_flags, dump_orig);
  99       else
 100         print_c_tree (dump_orig, DECL_SAVED_TREE (fndecl));
 101       fprintf (dump_orig, "\n");
 102
 103       dump_end (TDI_original, dump_orig);
 104     }
 105
 106   /* Go ahead and gimplify for now.  */
 107   gimplify_function_tree (fndecl);
 108
 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   unsigned i;
 123   tree enclosing;
 124   gimple bind;
 125   VEC(gimple, heap) *stack = gimple_bind_expr_stack ();
 126
 127   for (i = 0; VEC_iterate (gimple, stack, i, bind); i++)
 128     if (gimple_bind_block (bind))
 129       break;
 130
 131   enclosing = gimple_bind_block (bind);
 132   BLOCK_SUBBLOCKS (enclosing) = chainon (BLOCK_SUBBLOCKS (enclosing), block);
 133 }
 134
 135 /* Genericize a scope by creating a new BIND_EXPR.
 136    BLOCK is either a BLOCK representing the scope or a chain of _DECLs.
 137      In the latter case, we need to create a new BLOCK and add it to the
 138      BLOCK_SUBBLOCKS of the enclosing block.
 139    BODY is a chain of C _STMT nodes for the contents of the scope, to be
 140      genericized.  */
 141
 142 tree
 143 c_build_bind_expr (location_t loc, tree block, tree body)
 144 {
 145   tree decls, bind;
 146
 147   if (block == NULL_TREE)
 148     decls = NULL_TREE;
 149   else if (TREE_CODE (block) == BLOCK)
 150     decls = BLOCK_VARS (block);
 151   else
 152     {
 153       decls = block;
 154       if (DECL_ARTIFICIAL (decls))
 155         block = NULL_TREE;
 156       else
 157         {
 158           block = make_node (BLOCK);
 159           BLOCK_VARS (block) = decls;
 160           add_block_to_enclosing (block);
 161         }
 162     }
 163
 164   if (!body)
 165     body = build_empty_stmt (loc);
 166   if (decls || block)
 167     {
 168       bind = build3 (BIND_EXPR, void_type_node, decls, body, block);
 169       TREE_SIDE_EFFECTS (bind) = 1;
 170       SET_EXPR_LOCATION (bind, loc);
 171     }
 172   else
 173     bind = body;
 174
 175   return bind;
 176 }
 177
 178 /* Gimplification of expression trees.  */
 179
 180 /* Do C-specific gimplification on *EXPR_P.  PRE_P and POST_P are as in
 181    gimplify_expr.  */
 182
 183 int
 184 c_gimplify_expr (tree *expr_p, gimple_seq *pre_p ATTRIBUTE_UNUSED,
 185                  gimple_seq *post_p ATTRIBUTE_UNUSED)
 186 {
 187   enum tree_code code = TREE_CODE (*expr_p);
 188
 189   /* This is handled mostly by gimplify.c, but we have to deal with
 190      not warning about int x = x; as it is a GCC extension to turn off
 191      this warning but only if warn_init_self is zero.  */
 192   if (code == DECL_EXPR
 193       && TREE_CODE (DECL_EXPR_DECL (*expr_p)) == VAR_DECL
 194       && !DECL_EXTERNAL (DECL_EXPR_DECL (*expr_p))
 195       && !TREE_STATIC (DECL_EXPR_DECL (*expr_p))
 196       && (DECL_INITIAL (DECL_EXPR_DECL (*expr_p)) == DECL_EXPR_DECL (*expr_p))
 197       && !warn_init_self)
 198     TREE_NO_WARNING (DECL_EXPR_DECL (*expr_p)) = 1;
 199
 200   return GS_UNHANDLED;
 201 }