gcc/gimple-ssa-nonnull-compare.c

   1 /* -Wnonnull-compare warning support.
   2    Copyright (C) 2016-2017 Free Software Foundation, Inc.
   3    Contributed by Jakub Jelinek <jakub@redhat.com>
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 3, or (at your option)
  10 any later version.
  11
  12 GCC is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along 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
  35 static void
  36 do_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
 106 namespace {
 107
 108 const 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
 121 class pass_warn_nonnull_compare : public gimple_opt_pass
 122 {
 123 public:
 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
 135 unsigned int
 136 pass_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
 148 gimple_opt_pass *
 149 make_pass_warn_nonnull_compare (gcc::context *ctxt)
 150 {
 151   return new pass_warn_nonnull_compare (ctxt);
 152 }