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/* This plugin contains an analysis pass that detects and warns about

   self-assignment statements.  */

/* { dg-options "-O" } */

#include "gcc-plugin.h"

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "toplev.h"

#include "basic-block.h"

#include "gimple.h"

#include "tree.h"

#include "tree-pass.h"

#include "intl.h"

#include "plugin-version.h"

int plugin_is_GPL_compatible;

/* Indicate whether to check overloaded operator '=', which is performed by

   default. To disable it, use -fplugin-arg-NAME-no-check-operator-eq.  */

bool check_operator_eq = true;

/* Given a rhs EXPR of a gimple assign statement, if it is

   - SSA_NAME : returns its var decl, or, if it is a temp variable,

                returns the rhs of its SSA def statement.

   - VAR_DECL, PARM_DECL, FIELD_DECL, or a reference expression :

                returns EXPR itself.

   - any other expression : returns NULL_TREE.  */

static tree

get_real_ref_rhs (tree expr)

{

  switch (TREE_CODE (expr))

    {

      case SSA_NAME:

        {

          /* Given a self-assign statement, say foo.x = foo.x,

             the IR (after SSA) looks like:

             D.1797_14 = foo.x;

             foo.x ={v} D.1797_14;

             So if the rhs EXPR is an SSA_NAME of a temp variable,

             e.g. D.1797_14, we need to grab the rhs of its SSA def

             statement (i.e. foo.x).  */

          tree vdecl = SSA_NAME_VAR (expr);

          if (DECL_ARTIFICIAL (vdecl)

              && !gimple_nop_p (SSA_NAME_DEF_STMT (expr)))

            {

              gimple def_stmt = SSA_NAME_DEF_STMT (expr);

              /* We are only interested in an assignment with a single

                 rhs operand because if it is not, the original assignment

                 will not possibly be a self-assignment.  */

              if (is_gimple_assign (def_stmt)

                  && (get_gimple_rhs_class (gimple_assign_rhs_code (def_stmt))

                      == GIMPLE_SINGLE_RHS))

                return get_real_ref_rhs (gimple_assign_rhs1 (def_stmt));

              else

                return NULL_TREE;

            }

          else

            return vdecl;

        }

      case VAR_DECL:

      case PARM_DECL:

      case FIELD_DECL:

      case COMPONENT_REF:

      case INDIRECT_REF:

      case ARRAY_REF:

        return expr;

      default:

        return NULL_TREE;

    }

}

/* Given an expression tree, EXPR, that may contains SSA names, returns an

   equivalent tree with the SSA names converted to var/parm/field decls

   so that it can be used with '%E' format modifier when emitting warning

   messages.

   This function currently only supports VAR/PARM/FIELD_DECL, reference

   expressions (COMPONENT_REF, INDIRECT_REF, ARRAY_REF), integer constant,

   and SSA_NAME. If EXPR contains any other tree nodes (e.g. an arithmetic

   expression appears in array index), NULL_TREE is returned.  */

static tree

get_non_ssa_expr (tree expr)

{

  switch (TREE_CODE (expr))

    {

      case VAR_DECL:

      case PARM_DECL:

      case FIELD_DECL:

        {

          if (DECL_NAME (expr))

            return expr;

          else

            return NULL_TREE;

        }

      case COMPONENT_REF:

        {

          tree base, orig_base = TREE_OPERAND (expr, 0);

          tree component, orig_component = TREE_OPERAND (expr, 1);

          base = get_non_ssa_expr (orig_base);

          if (!base)

            return NULL_TREE;

          component = get_non_ssa_expr (orig_component);

          if (!component)

            return NULL_TREE;

          /* If either BASE or COMPONENT is converted, build a new

             component reference tree.  */

          if (base != orig_base || component != orig_component)

            return build3 (COMPONENT_REF, TREE_TYPE (component),

                           base, component, NULL_TREE);

          else

            return expr;

        }

      case INDIRECT_REF:

        {

          tree orig_base = TREE_OPERAND (expr, 0);

          tree base = get_non_ssa_expr (orig_base);

          if (!base)

            return NULL_TREE;

          /* If BASE is converted, build a new indirect reference tree.  */

          if (base != orig_base)

            return build1 (INDIRECT_REF, TREE_TYPE (TREE_TYPE (base)), base);

          else

            return expr;

        }

      case ARRAY_REF:

        {

          tree array, orig_array = TREE_OPERAND (expr, 0);

          tree index, orig_index = TREE_OPERAND (expr, 1);

          array = get_non_ssa_expr (orig_array);

          if (!array)

            return NULL_TREE;

          index = get_non_ssa_expr (orig_index);

          if (!index)

            return NULL_TREE;

          /* If either ARRAY or INDEX is converted, build a new array

             reference tree.  */

          if (array != orig_array || index != orig_index)

            return build4 (ARRAY_REF, TREE_TYPE (expr), array, index,

                           TREE_OPERAND (expr, 2), TREE_OPERAND (expr, 3));

          else

            return expr;

        }

      case SSA_NAME:

        {

          tree vdecl = SSA_NAME_VAR (expr);

          if (DECL_ARTIFICIAL (vdecl)

              && !gimple_nop_p (SSA_NAME_DEF_STMT (expr)))

            {

              gimple def_stmt = SSA_NAME_DEF_STMT (expr);

              if (is_gimple_assign (def_stmt)

                  && (get_gimple_rhs_class (gimple_assign_rhs_code (def_stmt))

                      == GIMPLE_SINGLE_RHS))

                vdecl = gimple_assign_rhs1 (def_stmt);

            }

          return get_non_ssa_expr (vdecl);

        }

      case INTEGER_CST:

        return expr;

      default:

        /* Return NULL_TREE for any other kind of tree nodes.  */

        return NULL_TREE;

    }

}

/* Given the LHS and (real) RHS of a gimple assign statement, STMT, check if

   they are the same. If so, print a warning message about self-assignment.  */

static void

compare_and_warn (gimple stmt, tree lhs, tree rhs)

{

  if (operand_equal_p (lhs, rhs, OEP_PURE_SAME))

    {

      location_t location;

      location = (gimple_has_location (stmt)

                  ? gimple_location (stmt)

                  : (DECL_P (lhs)

                     ? DECL_SOURCE_LOCATION (lhs)

                     : input_location));

      /* If LHS contains any tree node not currently supported by

         get_non_ssa_expr, simply emit a generic warning without

         specifying LHS in the message.  */

      lhs = get_non_ssa_expr (lhs);

      if (lhs)

        warning_at (location, 0, G_("%qE is assigned to itself"), lhs);

      else

        warning_at (location, 0, G_("self-assignment detected"));

    }

}

/* Check and warn if STMT is a self-assign statement.  */

static void

warn_self_assign (gimple stmt)

{

  tree rhs, lhs;

  /* Check assigment statement.  */

  if (is_gimple_assign (stmt)

      && (get_gimple_rhs_class (gimple_assign_rhs_code (stmt))

          == GIMPLE_SINGLE_RHS))

    {

      rhs = get_real_ref_rhs (gimple_assign_rhs1 (stmt));

      if (!rhs)

        return;

      lhs = gimple_assign_lhs (stmt);

      if (TREE_CODE (lhs) == SSA_NAME)

        {

          lhs = SSA_NAME_VAR (lhs);

          if (DECL_ARTIFICIAL (lhs))

            return;

        }

      compare_and_warn (stmt, lhs, rhs);

    }

  /* Check overloaded operator '=' (if enabled).  */

  else if (check_operator_eq && is_gimple_call (stmt))

    {

      tree fdecl = gimple_call_fndecl (stmt);

      if (fdecl && (DECL_NAME (fdecl) == maybe_get_identifier ("operator=")))

        {

          /* If 'operator=' takes reference operands, the arguments will be

             ADDR_EXPR trees. In this case, just remove the address-taken

             operator before we compare the lhs and rhs.  */

          lhs = gimple_call_arg (stmt, 0);

          if (TREE_CODE (lhs) == ADDR_EXPR)

            lhs = TREE_OPERAND (lhs, 0);

          rhs = gimple_call_arg (stmt, 1);

          if (TREE_CODE (rhs) == ADDR_EXPR)

            rhs = TREE_OPERAND (rhs, 0);

          compare_and_warn (stmt, lhs, rhs);

        }

    }

}

/* Entry point for the self-assignment detection pass.  */

static unsigned int

execute_warn_self_assign (void)

{

  gimple_stmt_iterator gsi;

  basic_block bb;

  FOR_EACH_BB (bb)

    {

      for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))

        warn_self_assign (gsi_stmt (gsi));

    }

  return 0;

}

/* Pass gate function. Currently always returns true.  */

static bool

gate_warn_self_assign (void)

{

  return true;

}

static struct gimple_opt_pass pass_warn_self_assign =

{

  {

    GIMPLE_PASS,

    "warn_self_assign",                   /* name */

    gate_warn_self_assign,                /* gate */

    execute_warn_self_assign,             /* execute */

    NULL,                                 /* sub */

    NULL,                                 /* next */

    0,                                    /* static_pass_number */

    0,                                    /* tv_id */

    PROP_ssa,                             /* properties_required */

    0,                                    /* properties_provided */

    0,                                    /* properties_destroyed */

    0,                                    /* todo_flags_start */

    TODO_dump_func                        /* todo_flags_finish */

  }

};

/* The initialization routine exposed to and called by GCC. The spec of this

   function is defined in gcc/gcc-plugin.h.

   PLUGIN_NAME - name of the plugin (useful for error reporting)

   ARGC        - the size of the ARGV array

   ARGV        - an array of key-value argument pair

   Returns 0 if initialization finishes successfully.

   Note that this function needs to be named exactly "plugin_init".  */

int

plugin_init (struct plugin_name_args *plugin_info,

             struct plugin_gcc_version *version)

{

  struct register_pass_info pass_info;

  const char *plugin_name = plugin_info->base_name;

  int argc = plugin_info->argc;

  struct plugin_argument *argv = plugin_info->argv;

  bool enabled = true;

  int i;

  if (!plugin_default_version_check (version, &gcc_version))

    return 1;

  /* Self-assign detection should happen after SSA is constructed.  */

  pass_info.pass = &pass_warn_self_assign.pass;

  pass_info.reference_pass_name = "ssa";

  pass_info.ref_pass_instance_number = 1;

  pass_info.pos_op = PASS_POS_INSERT_AFTER;

  /* Process the plugin arguments. This plugin takes the following arguments:

     check-operator-eq, no-check-operator-eq, enable, and disable.

     By default, the analysis is enabled with 'operator=' checked.  */

  for (i = 0; i < argc; ++i)

    {

      if (!strcmp (argv[i].key, "check-operator-eq"))

        {

          if (argv[i].value)

            warning (0, G_("option '-fplugin-arg-%s-check-operator-eq=%s'"

                           " ignored (superfluous '=%s')"),

                     plugin_name, argv[i].value, argv[i].value);

          else

            check_operator_eq = true;

        }

      else if (!strcmp (argv[i].key, "no-check-operator-eq"))

        {

          if (argv[i].value)

            warning (0, G_("option '-fplugin-arg-%s-no-check-operator-eq=%s'"

                           " ignored (superfluous '=%s')"),

                     plugin_name, argv[i].value, argv[i].value);

          else

            check_operator_eq = false;

        }

      else if (!strcmp (argv[i].key, "enable"))

        {

          if (argv[i].value)

            warning (0, G_("option '-fplugin-arg-%s-enable=%s' ignored"

                           " (superfluous '=%s')"),

                     plugin_name, argv[i].value, argv[i].value);

          else

            enabled = true;

        }

      else if (!strcmp (argv[i].key, "disable"))

        {

          if (argv[i].value)

            warning (0, G_("option '-fplugin-arg-%s-disable=%s' ignored"

                           " (superfluous '=%s')"),

                     plugin_name, argv[i].value, argv[i].value);

          else

            enabled = false;

        }

      else

        warning (0, G_("plugin %qs: unrecognized argument %qs ignored"),

                 plugin_name, argv[i].key);

    }

  /* Register this new pass with GCC if the analysis is enabled.  */

  if (enabled)

    register_callback (plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,

                       &pass_info);

  return 0;

}