gcc/testsuite/g++.dg/plugin/selfassign.c

   1 /* This plugin contains an analysis pass that detects and warns about
   2    self-assignment statements.  */
   3 /* { dg-options "-O" } */
   4
   5 #include "gcc-plugin.h"
   6 #include "config.h"
   7 #include "system.h"
   8 #include "coretypes.h"
   9 #include "tm.h"
  10 #include "toplev.h"
  11 #include "basic-block.h"
  12 #include "gimple.h"
  13 #include "tree.h"
  14 #include "tree-pass.h"
  15 #include "intl.h"
  16 #include "plugin-version.h"
  17
  18 int plugin_is_GPL_compatible;
  19
  20 /* Indicate whether to check overloaded operator '=', which is performed by
  21    default. To disable it, use -fplugin-arg-NAME-no-check-operator-eq.  */
  22 bool check_operator_eq = true;
  23
  24 /* Given a rhs EXPR of a gimple assign statement, if it is
  25    - SSA_NAME : returns its var decl, or, if it is a temp variable,
  26                 returns the rhs of its SSA def statement.
  27    - VAR_DECL, PARM_DECL, FIELD_DECL, or a reference expression :
  28                 returns EXPR itself.
  29    - any other expression : returns NULL_TREE.  */
  30
  31 static tree
  32 get_real_ref_rhs (tree expr)
  33 {
  34   switch (TREE_CODE (expr))
  35     {
  36       case SSA_NAME:
  37         {
  38           /* Given a self-assign statement, say foo.x = foo.x,
  39              the IR (after SSA) looks like:
  40
  41              D.1797_14 = foo.x;
  42              foo.x ={v} D.1797_14;
  43
  44              So if the rhs EXPR is an SSA_NAME of a temp variable,
  45              e.g. D.1797_14, we need to grab the rhs of its SSA def
  46              statement (i.e. foo.x).  */
  47           tree vdecl = SSA_NAME_VAR (expr);
  48           if (DECL_ARTIFICIAL (vdecl)
  49               && !gimple_nop_p (SSA_NAME_DEF_STMT (expr)))
  50             {
  51               gimple def_stmt = SSA_NAME_DEF_STMT (expr);
  52               /* We are only interested in an assignment with a single
  53                  rhs operand because if it is not, the original assignment
  54                  will not possibly be a self-assignment.  */
  55               if (gimple_assign_single_p (def_stmt))
  56                 return get_real_ref_rhs (gimple_assign_rhs1 (def_stmt));
  57               else
  58                 return NULL_TREE;
  59             }
  60           else
  61             return vdecl;
  62         }
  63       case VAR_DECL:
  64       case PARM_DECL:
  65       case FIELD_DECL:
  66       case COMPONENT_REF:
  67       case MEM_REF:
  68       case ARRAY_REF:
  69         return expr;
  70       default:
  71         return NULL_TREE;
  72     }
  73 }
  74
  75 /* Given an expression tree, EXPR, that may contains SSA names, returns an
  76    equivalent tree with the SSA names converted to var/parm/field decls
  77    so that it can be used with '%E' format modifier when emitting warning
  78    messages.
  79
  80    This function currently only supports VAR/PARM/FIELD_DECL, reference
  81    expressions (COMPONENT_REF, INDIRECT_REF, ARRAY_REF), integer constant,
  82    and SSA_NAME. If EXPR contains any other tree nodes (e.g. an arithmetic
  83    expression appears in array index), NULL_TREE is returned.  */
  84
  85 static tree
  86 get_non_ssa_expr (tree expr)
  87 {
  88   switch (TREE_CODE (expr))
  89     {
  90       case VAR_DECL:
  91       case PARM_DECL:
  92       case FIELD_DECL:
  93         {
  94           if (DECL_NAME (expr))
  95             return expr;
  96           else
  97             return NULL_TREE;
  98         }
  99       case COMPONENT_REF:
 100         {
 101           tree base, orig_base = TREE_OPERAND (expr, 0);
 102           tree component, orig_component = TREE_OPERAND (expr, 1);
 103           base = get_non_ssa_expr (orig_base);
 104           if (!base)
 105             return NULL_TREE;
 106           component = get_non_ssa_expr (orig_component);
 107           if (!component)
 108             return NULL_TREE;
 109           /* If either BASE or COMPONENT is converted, build a new
 110              component reference tree.  */
 111           if (base != orig_base || component != orig_component)
 112             return build3 (COMPONENT_REF, TREE_TYPE (component),
 113                            base, component, NULL_TREE);
 114           else
 115             return expr;
 116         }
 117       case MEM_REF:
 118         {
 119           tree orig_base = TREE_OPERAND (expr, 0);
 120           if (TREE_CODE (orig_base) == SSA_NAME)
 121             {
 122               tree base = get_non_ssa_expr (orig_base);
 123               if (!base)
 124                 return NULL_TREE;
 125               return fold_build2 (MEM_REF, TREE_TYPE (expr),
 126                                   base, TREE_OPERAND (expr, 1));
 127             }
 128           return expr;
 129         }
 130       case ARRAY_REF:
 131         {
 132           tree array, orig_array = TREE_OPERAND (expr, 0);
 133           tree index, orig_index = TREE_OPERAND (expr, 1);
 134           array = get_non_ssa_expr (orig_array);
 135           if (!array)
 136             return NULL_TREE;
 137           index = get_non_ssa_expr (orig_index);
 138           if (!index)
 139             return NULL_TREE;
 140           /* If either ARRAY or INDEX is converted, build a new array
 141              reference tree.  */
 142           if (array != orig_array || index != orig_index)
 143             return build4 (ARRAY_REF, TREE_TYPE (expr), array, index,
 144                            TREE_OPERAND (expr, 2), TREE_OPERAND (expr, 3));
 145           else
 146             return expr;
 147         }
 148       case SSA_NAME:
 149         {
 150           tree vdecl = SSA_NAME_VAR (expr);
 151           if (DECL_ARTIFICIAL (vdecl)
 152               && !gimple_nop_p (SSA_NAME_DEF_STMT (expr)))
 153             {
 154               gimple def_stmt = SSA_NAME_DEF_STMT (expr);
 155               if (gimple_assign_single_p (def_stmt))
 156                 vdecl = gimple_assign_rhs1 (def_stmt);
 157             }
 158           return get_non_ssa_expr (vdecl);
 159         }
 160       case INTEGER_CST:
 161         return expr;
 162       default:
 163         /* Return NULL_TREE for any other kind of tree nodes.  */
 164         return NULL_TREE;
 165     }
 166 }
 167
 168 /* Given the LHS and (real) RHS of a gimple assign statement, STMT, check if
 169    they are the same. If so, print a warning message about self-assignment.  */
 170
 171 static void
 172 compare_and_warn (gimple stmt, tree lhs, tree rhs)
 173 {
 174   if (operand_equal_p (lhs, rhs, OEP_PURE_SAME))
 175     {
 176       location_t location;
 177       location = (gimple_has_location (stmt)
 178                   ? gimple_location (stmt)
 179                   : (DECL_P (lhs)
 180                      ? DECL_SOURCE_LOCATION (lhs)
 181                      : input_location));
 182       /* If LHS contains any tree node not currently supported by
 183          get_non_ssa_expr, simply emit a generic warning without
 184          specifying LHS in the message.  */
 185       lhs = get_non_ssa_expr (lhs);
 186       if (lhs)
 187         warning_at (location, 0, G_("%qE is assigned to itself"), lhs);
 188       else
 189         warning_at (location, 0, G_("self-assignment detected"));
 190     }
 191 }
 192
 193 /* Check and warn if STMT is a self-assign statement.  */
 194
 195 static void
 196 warn_self_assign (gimple stmt)
 197 {
 198   tree rhs, lhs;
 199
 200   /* Check assigment statement.  */
 201   if (gimple_assign_single_p (stmt))
 202     {
 203       rhs = get_real_ref_rhs (gimple_assign_rhs1 (stmt));
 204       if (!rhs)
 205         return;
 206
 207       lhs = gimple_assign_lhs (stmt);
 208       if (TREE_CODE (lhs) == SSA_NAME)
 209         {
 210           lhs = SSA_NAME_VAR (lhs);
 211           if (DECL_ARTIFICIAL (lhs))
 212             return;
 213         }
 214
 215       compare_and_warn (stmt, lhs, rhs);
 216     }
 217   /* Check overloaded operator '=' (if enabled).  */
 218   else if (check_operator_eq && is_gimple_call (stmt))
 219     {
 220       tree fdecl = gimple_call_fndecl (stmt);
 221       if (fdecl && (DECL_NAME (fdecl) == maybe_get_identifier ("operator=")))
 222         {
 223           /* If 'operator=' takes reference operands, the arguments will be
 224              ADDR_EXPR trees. In this case, just remove the address-taken
 225              operator before we compare the lhs and rhs.  */
 226           lhs = gimple_call_arg (stmt, 0);
 227           if (TREE_CODE (lhs) == ADDR_EXPR)
 228             lhs = TREE_OPERAND (lhs, 0);
 229           rhs = gimple_call_arg (stmt, 1);
 230           if (TREE_CODE (rhs) == ADDR_EXPR)
 231             rhs = TREE_OPERAND (rhs, 0);
 232
 233           compare_and_warn (stmt, lhs, rhs);
 234         }
 235     }
 236 }
 237
 238 /* Entry point for the self-assignment detection pass.  */
 239
 240 static unsigned int
 241 execute_warn_self_assign (void)
 242 {
 243   gimple_stmt_iterator gsi;
 244   basic_block bb;
 245
 246   FOR_EACH_BB (bb)
 247     {
 248       for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
 249         warn_self_assign (gsi_stmt (gsi));
 250     }
 251
 252   return 0;
 253 }
 254
 255 /* Pass gate function. Currently always returns true.  */
 256
 257 static bool
 258 gate_warn_self_assign (void)
 259 {
 260   return true;
 261 }
 262
 263 static struct gimple_opt_pass pass_warn_self_assign =
 264 {
 265   {
 266     GIMPLE_PASS,
 267     "warn_self_assign",                   /* name */
 268     gate_warn_self_assign,                /* gate */
 269     execute_warn_self_assign,             /* execute */
 270     NULL,                                 /* sub */
 271     NULL,                                 /* next */
 272     0,                                    /* static_pass_number */
 273     TV_NONE,                              /* tv_id */
 274     PROP_ssa,                             /* properties_required */
 275     0,                                    /* properties_provided */
 276     0,                                    /* properties_destroyed */
 277     0,                                    /* todo_flags_start */
 278     TODO_dump_func                        /* todo_flags_finish */
 279   }
 280 };
 281
 282 /* The initialization routine exposed to and called by GCC. The spec of this
 283    function is defined in gcc/gcc-plugin.h.
 284
 285    PLUGIN_NAME - name of the plugin (useful for error reporting)
 286    ARGC        - the size of the ARGV array
 287    ARGV        - an array of key-value argument pair
 288
 289    Returns 0 if initialization finishes successfully.
 290
 291    Note that this function needs to be named exactly "plugin_init".  */
 292
 293 int
 294 plugin_init (struct plugin_name_args *plugin_info,
 295              struct plugin_gcc_version *version)
 296 {
 297   struct register_pass_info pass_info;
 298   const char *plugin_name = plugin_info->base_name;
 299   int argc = plugin_info->argc;
 300   struct plugin_argument *argv = plugin_info->argv;
 301   bool enabled = true;
 302   int i;
 303
 304   if (!plugin_default_version_check (version, &gcc_version))
 305     return 1;
 306
 307   /* Self-assign detection should happen after SSA is constructed.  */
 308   pass_info.pass = &pass_warn_self_assign.pass;
 309   pass_info.reference_pass_name = "ssa";
 310   pass_info.ref_pass_instance_number = 1;
 311   pass_info.pos_op = PASS_POS_INSERT_AFTER;
 312
 313   /* Process the plugin arguments. This plugin takes the following arguments:
 314      check-operator-eq, no-check-operator-eq, enable, and disable.
 315      By default, the analysis is enabled with 'operator=' checked.  */
 316   for (i = 0; i < argc; ++i)
 317     {
 318       if (!strcmp (argv[i].key, "check-operator-eq"))
 319         {
 320           if (argv[i].value)
 321             warning (0, G_("option '-fplugin-arg-%s-check-operator-eq=%s'"
 322                            " ignored (superfluous '=%s')"),
 323                      plugin_name, argv[i].value, argv[i].value);
 324           else
 325             check_operator_eq = true;
 326         }
 327       else if (!strcmp (argv[i].key, "no-check-operator-eq"))
 328         {
 329           if (argv[i].value)
 330             warning (0, G_("option '-fplugin-arg-%s-no-check-operator-eq=%s'"
 331                            " ignored (superfluous '=%s')"),
 332                      plugin_name, argv[i].value, argv[i].value);
 333           else
 334             check_operator_eq = false;
 335         }
 336       else if (!strcmp (argv[i].key, "enable"))
 337         {
 338           if (argv[i].value)
 339             warning (0, G_("option '-fplugin-arg-%s-enable=%s' ignored"
 340                            " (superfluous '=%s')"),
 341                      plugin_name, argv[i].value, argv[i].value);
 342           else
 343             enabled = true;
 344         }
 345       else if (!strcmp (argv[i].key, "disable"))
 346         {
 347           if (argv[i].value)
 348             warning (0, G_("option '-fplugin-arg-%s-disable=%s' ignored"
 349                            " (superfluous '=%s')"),
 350                      plugin_name, argv[i].value, argv[i].value);
 351           else
 352             enabled = false;
 353         }
 354       else
 355         warning (0, G_("plugin %qs: unrecognized argument %qs ignored"),
 356                  plugin_name, argv[i].key);
 357     }
 358
 359   /* Register this new pass with GCC if the analysis is enabled.  */
 360   if (enabled)
 361     register_callback (plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
 362                        &pass_info);
 363
 364   return 0;
 365 }