1/* -Wnonnull-compare warning support.
2   Copyright (C) 2016-2020 Free Software Foundation, Inc.
3   Contributed by Jakub Jelinek <jakub@redhat.com>
4
5This file is part of GCC.
6
7GCC is free software; you can redistribute it and/or modify
8it under the terms of the GNU General Public License as published by
9the Free Software Foundation; either version 3, or (at your option)
10any later version.
11
12GCC is distributed in the hope that it will be useful,
13but WITHOUT ANY WARRANTY; without even the implied warranty of
14MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15GNU General Public License for more details.
16
17You should have received a copy of the GNU General Public License
18along with GCC; see the file COPYING3.  If not see
19<http://www.gnu.org/licenses/>.  */
20
21#include "config.h"
22#include "system.h"
23#include "coretypes.h"
24#include "backend.h"
25#include "tree.h"
26#include "gimple.h"
27#include "tree-pass.h"
28#include "ssa.h"
29#include "diagnostic-core.h"
30#include "tree-dfa.h"
31
32/* Warn about comparison of nonnull_arg_p argument initial values
33   with NULL.  */
34
35static void
36do_warn_nonnull_compare (function *fun, tree arg)
37{
38  if (!POINTER_TYPE_P (TREE_TYPE (arg))
39      && TREE_CODE (TREE_TYPE (arg)) != OFFSET_TYPE)
40    return;
41
42  if (!nonnull_arg_p (arg))
43    return;
44
45  tree d = ssa_default_def (fun, arg);
46  if (d == NULL_TREE)
47    return;
48
49  use_operand_p use_p;
50  imm_use_iterator iter;
51
52  FOR_EACH_IMM_USE_FAST (use_p, iter, d)
53    {
54      gimple *stmt = USE_STMT (use_p);
55      tree op = NULL_TREE;
56      location_t loc = gimple_location (stmt);
57      if (gimple_code (stmt) == GIMPLE_COND)
58	switch (gimple_cond_code (stmt))
59	  {
60	  case EQ_EXPR:
61	  case NE_EXPR:
62	    if (gimple_cond_lhs (stmt) == d)
63	      op = gimple_cond_rhs (stmt);
64	    break;
65	  default:
66	    break;
67	  }
68      else if (is_gimple_assign (stmt))
69	switch (gimple_assign_rhs_code (stmt))
70	  {
71	  case EQ_EXPR:
72	  case NE_EXPR:
73	    if (gimple_assign_rhs1 (stmt) == d)
74	      op = gimple_assign_rhs2 (stmt);
75	    break;
76	  case COND_EXPR:
77	    switch (TREE_CODE (gimple_assign_rhs1 (stmt)))
78	      {
79	      case EQ_EXPR:
80	      case NE_EXPR:
81		op = gimple_assign_rhs1 (stmt);
82		if (TREE_OPERAND (op, 0) != d)
83		  {
84		    op = NULL_TREE;
85		    break;
86		  }
87		loc = EXPR_LOC_OR_LOC (op, loc);
88		op = TREE_OPERAND (op, 1);
89		break;
90	      default:
91		break;
92	      }
93	    break;
94	  default:
95	    break;
96	  }
97      if (op
98	  && (POINTER_TYPE_P (TREE_TYPE (arg))
99	      ? integer_zerop (op) : integer_minus_onep (op))
100	  && !gimple_no_warning_p (stmt))
101	warning_at (loc, OPT_Wnonnull_compare,
102		    "%<nonnull%> argument %qD compared to NULL", arg);
103    }
104}
105
106namespace {
107
108const pass_data pass_data_warn_nonnull_compare =
109{
110  GIMPLE_PASS, /* type */
111  "*nonnullcmp", /* name */
112  OPTGROUP_NONE, /* optinfo_flags */
113  TV_NONE, /* tv_id */
114  PROP_ssa, /* properties_required */
115  0, /* properties_provided */
116  0, /* properties_destroyed */
117  0, /* todo_flags_start */
118  0, /* todo_flags_finish */
119};
120
121class pass_warn_nonnull_compare : public gimple_opt_pass
122{
123public:
124  pass_warn_nonnull_compare (gcc::context *ctxt)
125    : gimple_opt_pass (pass_data_warn_nonnull_compare, ctxt)
126  {}
127
128  /* opt_pass methods: */
129  virtual bool gate (function *) { return warn_nonnull_compare; }
130
131  virtual unsigned int execute (function *);
132
133}; // class pass_warn_nonnull_compare
134
135unsigned int
136pass_warn_nonnull_compare::execute (function *fun)
137{
138  if (fun->static_chain_decl)
139    do_warn_nonnull_compare (fun, fun->static_chain_decl);
140
141  for (tree arg = DECL_ARGUMENTS (cfun->decl); arg; arg = DECL_CHAIN (arg))
142    do_warn_nonnull_compare (fun, arg);
143  return 0;
144}
145
146} // anon namespace
147
148gimple_opt_pass *
149make_pass_warn_nonnull_compare (gcc::context *ctxt)
150{
151  return new pass_warn_nonnull_compare (ctxt);
152}
153