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) 2002-2017 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
10This file is part of GCC.
11
12GCC is free software; you can redistribute it and/or modify it under
13the terms of the GNU General Public License as published by the Free
14Software Foundation; either version 3, or (at your option) any later
15version.
16
17GCC is distributed in the hope that it will be useful, but WITHOUT ANY
18WARRANTY; without even the implied warranty of MERCHANTABILITY or
19FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
20for more details.
21
22You should have received a copy of the GNU General Public License
23along 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 "function.h"
31#include "basic-block.h"
32#include "tree.h"
33#include "gimple.h"
34#include "cgraph.h"
35#include "c-pretty-print.h"
36#include "gimplify.h"
37#include "langhooks.h"
38#include "dumpfile.h"
39#include "c-ubsan.h"
40
41/* The gimplification pass converts the language-dependent trees
42 (ld-trees) emitted by the parser into language-independent trees
43 (li-trees) that are the target of SSA analysis and transformations.
44
45 Language-independent trees are based on the SIMPLE intermediate
46 representation used in the McCAT compiler framework:
47
48 "Designing the McCAT Compiler Based on a Family of Structured
49 Intermediate Representations,"
50 L. Hendren, C. Donawa, M. Emami, G. Gao, Justiani, and B. Sridharan,
51 Proceedings of the 5th International Workshop on Languages and
52 Compilers for Parallel Computing, no. 757 in Lecture Notes in
53 Computer Science, New Haven, Connecticut, pp. 406-420,
54 Springer-Verlag, August 3-5, 1992.
55
56 http://www-acaps.cs.mcgill.ca/info/McCAT/McCAT.html
57
58 Basically, we walk down gimplifying the nodes that we encounter. As we
59 walk back up, we check that they fit our constraints, and copy them
60 into temporaries if not. */
61
62/* Callback for c_genericize. */
63
64static tree
65ubsan_walk_array_refs_r (tree *tp, int *walk_subtrees, void *data)
66{
67 hash_set<tree> *pset = (hash_set<tree> *) data;
68
69 if (TREE_CODE (*tp) == BIND_EXPR)
70 {
71 /* Since walk_tree doesn't call the callback function on the decls
72 in BIND_EXPR_VARS, we have to walk them manually, so we can avoid
73 instrumenting DECL_INITIAL of TREE_STATIC vars. */
74 *walk_subtrees = 0;
75 for (tree decl = BIND_EXPR_VARS (*tp); decl; decl = DECL_CHAIN (decl))
76 {
77 if (TREE_STATIC (decl))
78 continue;
79 walk_tree (&DECL_INITIAL (decl), ubsan_walk_array_refs_r, pset,
80 pset);
81 walk_tree (&DECL_SIZE (decl), ubsan_walk_array_refs_r, pset, pset);
82 walk_tree (&DECL_SIZE_UNIT (decl), ubsan_walk_array_refs_r, pset,
83 pset);
84 }
85 walk_tree (&BIND_EXPR_BODY (*tp), ubsan_walk_array_refs_r, pset, pset);
86 }
87 else if (TREE_CODE (*tp) == ADDR_EXPR
88 && TREE_CODE (TREE_OPERAND (*tp, 0)) == ARRAY_REF)
89 {
90 ubsan_maybe_instrument_array_ref (&TREE_OPERAND (*tp, 0), true);
91 /* Make sure ubsan_maybe_instrument_array_ref is not called again
92 on the ARRAY_REF, the above call might not instrument anything
93 as the index might be constant or masked, so ensure it is not
94 walked again and walk its subtrees manually. */
95 tree aref = TREE_OPERAND (*tp, 0);
96 pset->add (aref);
97 *walk_subtrees = 0;
98 walk_tree (&TREE_OPERAND (aref, 0), ubsan_walk_array_refs_r, pset, pset);
99 walk_tree (&TREE_OPERAND (aref, 1), ubsan_walk_array_refs_r, pset, pset);
100 walk_tree (&TREE_OPERAND (aref, 2), ubsan_walk_array_refs_r, pset, pset);
101 walk_tree (&TREE_OPERAND (aref, 3), ubsan_walk_array_refs_r, pset, pset);
102 }
103 else if (TREE_CODE (*tp) == ARRAY_REF)
104 ubsan_maybe_instrument_array_ref (tp, false);
105 return NULL_TREE;
106}
107
108/* Gimplification of statement trees. */
109
110/* Convert the tree representation of FNDECL from C frontend trees to
111 GENERIC. */
112
113void
114c_genericize (tree fndecl)
115{
116 FILE *dump_orig;
117 dump_flags_t local_dump_flags;
118 struct cgraph_node *cgn;
119
120 if (flag_sanitize & SANITIZE_BOUNDS)
121 {
122 hash_set<tree> pset;
123 walk_tree (&DECL_SAVED_TREE (fndecl), ubsan_walk_array_refs_r, &pset,
124 &pset);
125 }
126
127 if (warn_duplicated_branches)
128 walk_tree_without_duplicates (&DECL_SAVED_TREE (fndecl),
129 do_warn_duplicated_branches_r, NULL);
130
131 /* Dump the C-specific tree IR. */
132 dump_orig = get_dump_info (TDI_original, &local_dump_flags);
133 if (dump_orig)
134 {
135 fprintf (dump_orig, "\n;; Function %s",
136 lang_hooks.decl_printable_name (fndecl, 2));
137 fprintf (dump_orig, " (%s)\n",
138 (!DECL_ASSEMBLER_NAME_SET_P (fndecl) ? "null"
139 : IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (fndecl))));
140 fprintf (dump_orig, ";; enabled by -%s\n", dump_flag_name (TDI_original));
141 fprintf (dump_orig, "\n");
142
143 if (local_dump_flags & TDF_RAW)
144 dump_node (DECL_SAVED_TREE (fndecl),
145 TDF_SLIM | local_dump_flags, dump_orig);
146 else
147 print_c_tree (dump_orig, DECL_SAVED_TREE (fndecl));
148 fprintf (dump_orig, "\n");
149 }
150
151 /* Dump all nested functions now. */
152 cgn = cgraph_node::get_create (fndecl);
153 for (cgn = cgn->nested; cgn ; cgn = cgn->next_nested)
154 c_genericize (cgn->decl);
155}
156
157static void
158add_block_to_enclosing (tree block)
159{
160 unsigned i;
161 tree enclosing;
162 gbind *bind;
163 vec<gbind *> stack = gimple_bind_expr_stack ();
164
165 FOR_EACH_VEC_ELT (stack, i, bind)
166 if (gimple_bind_block (bind))
167 break;
168
169 enclosing = gimple_bind_block (bind);
170 BLOCK_SUBBLOCKS (enclosing) = chainon (BLOCK_SUBBLOCKS (enclosing), block);
171}
172
173/* Genericize a scope by creating a new BIND_EXPR.
174 BLOCK is either a BLOCK representing the scope or a chain of _DECLs.
175 In the latter case, we need to create a new BLOCK and add it to the
176 BLOCK_SUBBLOCKS of the enclosing block.
177 BODY is a chain of C _STMT nodes for the contents of the scope, to be
178 genericized. */
179
180tree
181c_build_bind_expr (location_t loc, tree block, tree body)
182{
183 tree decls, bind;
184
185 if (block == NULL_TREE)
186 decls = NULL_TREE;
187 else if (TREE_CODE (block) == BLOCK)
188 decls = BLOCK_VARS (block);
189 else
190 {
191 decls = block;
192 if (DECL_ARTIFICIAL (decls))
193 block = NULL_TREE;
194 else
195 {
196 block = make_node (BLOCK);
197 BLOCK_VARS (block) = decls;
198 add_block_to_enclosing (block);
199 }
200 }
201
202 if (!body)
203 body = build_empty_stmt (loc);
204 if (decls || block)
205 {
206 bind = build3 (BIND_EXPR, void_type_node, decls, body, block);
207 TREE_SIDE_EFFECTS (bind) = 1;
208 SET_EXPR_LOCATION (bind, loc);
209 }
210 else
211 bind = body;
212
213 return bind;
214}
215
216/* Gimplification of expression trees. */
217
218/* Do C-specific gimplification on *EXPR_P. PRE_P and POST_P are as in
219 gimplify_expr. */
220
221int
222c_gimplify_expr (tree *expr_p, gimple_seq *pre_p ATTRIBUTE_UNUSED,
223 gimple_seq *post_p ATTRIBUTE_UNUSED)
224{
225 enum tree_code code = TREE_CODE (*expr_p);
226
227 switch (code)
228 {
229 case LSHIFT_EXPR:
230 case RSHIFT_EXPR:
231 case LROTATE_EXPR:
232 case RROTATE_EXPR:
233 {
234 /* We used to convert the right operand of a shift-expression
235 to an integer_type_node in the FEs. But it is unnecessary
236 and not desirable for diagnostics and sanitizers. We keep
237 this here to not pessimize the code, but we convert to an
238 unsigned type, because negative shift counts are undefined
239 anyway.
240 We should get rid of this conversion when we have a proper
241 type demotion/promotion pass. */
242 tree *op1_p = &TREE_OPERAND (*expr_p, 1);
243 if (!VECTOR_TYPE_P (TREE_TYPE (*op1_p))
244 && !types_compatible_p (TYPE_MAIN_VARIANT (TREE_TYPE (*op1_p)),
245 unsigned_type_node)
246 && !types_compatible_p (TYPE_MAIN_VARIANT (TREE_TYPE (*op1_p)),
247 integer_type_node))
248 *op1_p = convert (unsigned_type_node, *op1_p);
249 break;
250 }
251
252 case DECL_EXPR:
253 /* This is handled mostly by gimplify.c, but we have to deal with
254 not warning about int x = x; as it is a GCC extension to turn off
255 this warning but only if warn_init_self is zero. */
256 if (VAR_P (DECL_EXPR_DECL (*expr_p))
257 && !DECL_EXTERNAL (DECL_EXPR_DECL (*expr_p))
258 && !TREE_STATIC (DECL_EXPR_DECL (*expr_p))
259 && (DECL_INITIAL (DECL_EXPR_DECL (*expr_p)) == DECL_EXPR_DECL (*expr_p))
260 && !warn_init_self)
261 TREE_NO_WARNING (DECL_EXPR_DECL (*expr_p)) = 1;
262 break;
263
264 case PREINCREMENT_EXPR:
265 case PREDECREMENT_EXPR:
266 case POSTINCREMENT_EXPR:
267 case POSTDECREMENT_EXPR:
268 {
269 tree type = TREE_TYPE (TREE_OPERAND (*expr_p, 0));
270 if (INTEGRAL_TYPE_P (type) && c_promoting_integer_type_p (type))
271 {
272 if (!TYPE_OVERFLOW_WRAPS (type))
273 type = unsigned_type_for (type);
274 return gimplify_self_mod_expr (expr_p, pre_p, post_p, 1, type);
275 }
276 break;
277 }
278
279 default:;
280 }
281
282 return GS_UNHANDLED;
283}
284