gcc/c-family/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, 2009, 2010
   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 "c-common.h"
  33 #include "gimple.h"
  34 #include "basic-block.h"
  35 #include "tree-inline.h"
  36 #include "diagnostic-core.h"
  37 #include "langhooks.h"
  38 #include "langhooks-def.h"
  39 #include "flags.h"
  40 #include "tree-dump.h"
  41 #include "c-pretty-print.h"
  42 #include "cgraph.h"
  43
  44
  45 /*  The gimplification pass converts the language-dependent trees
  46     (ld-trees) emitted by the parser into language-independent trees
  47     (li-trees) that are the target of SSA analysis and transformations.
  48
  49     Language-independent trees are based on the SIMPLE intermediate
  50     representation used in the McCAT compiler framework:
  51
  52     "Designing the McCAT Compiler Based on a Family of Structured
  53     Intermediate Representations,"
  54     L. Hendren, C. Donawa, M. Emami, G. Gao, Justiani, and B. Sridharan,
  55     Proceedings of the 5th International Workshop on Languages and
  56     Compilers for Parallel Computing, no. 757 in Lecture Notes in
  57     Computer Science, New Haven, Connecticut, pp. 406-420,
  58     Springer-Verlag, August 3-5, 1992.
  59
  60     http://www-acaps.cs.mcgill.ca/info/McCAT/McCAT.html
  61
  62     Basically, we walk down gimplifying the nodes that we encounter.  As we
  63     walk back up, we check that they fit our constraints, and copy them
  64     into temporaries if not.  */
  65
  66 /* Gimplification of statement trees.  */
  67
  68 /* Convert the tree representation of FNDECL from C frontend trees to
  69    GENERIC.  */
  70
  71 void
  72 c_genericize (tree fndecl)
  73 {
  74   FILE *dump_orig;
  75   int local_dump_flags;
  76   struct cgraph_node *cgn;
  77
  78   /* Dump the C-specific tree IR.  */
  79   dump_orig = dump_begin (TDI_original, &local_dump_flags);
  80   if (dump_orig)
  81     {
  82       fprintf (dump_orig, "\n;; Function %s",
  83                lang_hooks.decl_printable_name (fndecl, 2));
  84       fprintf (dump_orig, " (%s)\n",
  85                (!DECL_ASSEMBLER_NAME_SET_P (fndecl) ? "null"
  86                 : IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (fndecl))));
  87       fprintf (dump_orig, ";; enabled by -%s\n", dump_flag_name (TDI_original));
  88       fprintf (dump_orig, "\n");
  89
  90       if (local_dump_flags & TDF_RAW)
  91         dump_node (DECL_SAVED_TREE (fndecl),
  92                    TDF_SLIM | local_dump_flags, dump_orig);
  93       else
  94         print_c_tree (dump_orig, DECL_SAVED_TREE (fndecl));
  95       fprintf (dump_orig, "\n");
  96
  97       dump_end (TDI_original, dump_orig);
  98     }
  99
 100   /* Dump all nested functions now.  */
 101   cgn = cgraph_get_create_node (fndecl);
 102   for (cgn = cgn->nested; cgn ; cgn = cgn->next_nested)
 103     c_genericize (cgn->decl);
 104 }
 105
 106 static void
 107 add_block_to_enclosing (tree block)
 108 {
 109   unsigned i;
 110   tree enclosing;
 111   gimple bind;
 112   VEC(gimple, heap) *stack = gimple_bind_expr_stack ();
 113
 114   FOR_EACH_VEC_ELT (gimple, stack, i, bind)
 115     if (gimple_bind_block (bind))
 116       break;
 117
 118   enclosing = gimple_bind_block (bind);
 119   BLOCK_SUBBLOCKS (enclosing) = chainon (BLOCK_SUBBLOCKS (enclosing), block);
 120 }
 121
 122 /* Genericize a scope by creating a new BIND_EXPR.
 123    BLOCK is either a BLOCK representing the scope or a chain of _DECLs.
 124      In the latter case, we need to create a new BLOCK and add it to the
 125      BLOCK_SUBBLOCKS of the enclosing block.
 126    BODY is a chain of C _STMT nodes for the contents of the scope, to be
 127      genericized.  */
 128
 129 tree
 130 c_build_bind_expr (location_t loc, tree block, tree body)
 131 {
 132   tree decls, bind;
 133
 134   if (block == NULL_TREE)
 135     decls = NULL_TREE;
 136   else if (TREE_CODE (block) == BLOCK)
 137     decls = BLOCK_VARS (block);
 138   else
 139     {
 140       decls = block;
 141       if (DECL_ARTIFICIAL (decls))
 142         block = NULL_TREE;
 143       else
 144         {
 145           block = make_node (BLOCK);
 146           BLOCK_VARS (block) = decls;
 147           add_block_to_enclosing (block);
 148         }
 149     }
 150
 151   if (!body)
 152     body = build_empty_stmt (loc);
 153   if (decls || block)
 154     {
 155       bind = build3 (BIND_EXPR, void_type_node, decls, body, block);
 156       TREE_SIDE_EFFECTS (bind) = 1;
 157       SET_EXPR_LOCATION (bind, loc);
 158     }
 159   else
 160     bind = body;
 161
 162   return bind;
 163 }
 164
 165 /* Gimplification of expression trees.  */
 166
 167 /* Do C-specific gimplification on *EXPR_P.  PRE_P and POST_P are as in
 168    gimplify_expr.  */
 169
 170 int
 171 c_gimplify_expr (tree *expr_p, gimple_seq *pre_p ATTRIBUTE_UNUSED,
 172                  gimple_seq *post_p ATTRIBUTE_UNUSED)
 173 {
 174   enum tree_code code = TREE_CODE (*expr_p);
 175
 176   /* This is handled mostly by gimplify.c, but we have to deal with
 177      not warning about int x = x; as it is a GCC extension to turn off
 178      this warning but only if warn_init_self is zero.  */
 179   if (code == DECL_EXPR
 180       && TREE_CODE (DECL_EXPR_DECL (*expr_p)) == VAR_DECL
 181       && !DECL_EXTERNAL (DECL_EXPR_DECL (*expr_p))
 182       && !TREE_STATIC (DECL_EXPR_DECL (*expr_p))
 183       && (DECL_INITIAL (DECL_EXPR_DECL (*expr_p)) == DECL_EXPR_DECL (*expr_p))
 184       && !warn_init_self)
 185     TREE_NO_WARNING (DECL_EXPR_DECL (*expr_p)) = 1;
 186
 187   return GS_UNHANDLED;
 188 }