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/* C++-specific tree lowering bits; see also c-gimplify.c and tree-gimple.c.

   Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.

   Contributed by Jason Merrill <jason@redhat.com>

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under

the terms of the GNU General Public License as published by the Free

Software Foundation; either version 2, or (at your option) any later

version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY

WARRANTY; without even the implied warranty of MERCHANTABILITY or

FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

for more details.

You should have received a copy of the GNU General Public License

along with GCC; see the file COPYING.  If not, write to the Free

Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "tree.h"

#include "cp-tree.h"

#include "c-common.h"

#include "toplev.h"

#include "tree-gimple.h"

#include "hashtab.h"

#include "pointer-set.h"

#include "flags.h"

/* Local declarations.  */

enum bc_t { bc_break = 0, bc_continue = 1 };

static struct cp_gimplify_ctx

{

  /* Stack of labels which are targets for "break" or "continue",

     linked through TREE_CHAIN.  */

  tree current_label[2];

} *ctxp;

static void

push_context (void)

{

  gcc_assert (!ctxp);

  ctxp = ((struct cp_gimplify_ctx *)

          xcalloc (1, sizeof (struct cp_gimplify_ctx)));

}

static void

pop_context (void)

{

  gcc_assert (ctxp

              && !ctxp->current_label[0]

              && !ctxp->current_label[1]);

  free (ctxp);

  ctxp = NULL;

}

/* Begin a scope which can be exited by a break or continue statement.  BC

   indicates which.

   Just creates a label and pushes it into the current context.  */

static tree

begin_bc_block (enum bc_t bc)

{

  tree label = create_artificial_label ();

  TREE_CHAIN (label) = ctxp->current_label[bc];

  ctxp->current_label[bc] = label;

  return label;

}

/* Finish a scope which can be exited by a break or continue statement.

   LABEL was returned from the most recent call to begin_bc_block.  BODY is

   an expression for the contents of the scope.

   If we saw a break (or continue) in the scope, append a LABEL_EXPR to

   body.  Otherwise, just forget the label.  */

static tree

finish_bc_block (enum bc_t bc, tree label, tree body)

{

  gcc_assert (label == ctxp->current_label[bc]);

  if (TREE_USED (label))

    {

      tree t, sl = NULL;

      t = build1 (LABEL_EXPR, void_type_node, label);

      append_to_statement_list (body, &sl);

      append_to_statement_list (t, &sl);

      body = sl;

    }

  ctxp->current_label[bc] = TREE_CHAIN (label);

  TREE_CHAIN (label) = NULL_TREE;

  return body;

}

/* Build a GOTO_EXPR to represent a break or continue statement.  BC

   indicates which.  */

static tree

build_bc_goto (enum bc_t bc)

{

  tree label = ctxp->current_label[bc];

  if (label == NULL_TREE)

    {

      if (bc == bc_break)

        error ("break statement not within loop or switch");

      else

        error ("continue statement not within loop or switch");

      return NULL_TREE;

    }

  /* Mark the label used for finish_bc_block.  */

  TREE_USED (label) = 1;

  return build1 (GOTO_EXPR, void_type_node, label);

}

/* Genericize a TRY_BLOCK.  */

static void

genericize_try_block (tree *stmt_p)

{

  tree body = TRY_STMTS (*stmt_p);

  tree cleanup = TRY_HANDLERS (*stmt_p);

  gimplify_stmt (&body);

  if (CLEANUP_P (*stmt_p))

    /* A cleanup is an expression, so it doesn't need to be genericized.  */;

  else

    gimplify_stmt (&cleanup);

  *stmt_p = build2 (TRY_CATCH_EXPR, void_type_node, body, cleanup);

}

/* Genericize a HANDLER by converting to a CATCH_EXPR.  */

static void

genericize_catch_block (tree *stmt_p)

{

  tree type = HANDLER_TYPE (*stmt_p);

  tree body = HANDLER_BODY (*stmt_p);

  gimplify_stmt (&body);

  /* FIXME should the caught type go in TREE_TYPE?  */

  *stmt_p = build2 (CATCH_EXPR, void_type_node, type, body);

}

/* Genericize an EH_SPEC_BLOCK by converting it to a

   TRY_CATCH_EXPR/EH_FILTER_EXPR pair.  */

static void

genericize_eh_spec_block (tree *stmt_p)

{

  tree body = EH_SPEC_STMTS (*stmt_p);

  tree allowed = EH_SPEC_RAISES (*stmt_p);

  tree failure = build_call (call_unexpected_node,

                             tree_cons (NULL_TREE, build_exc_ptr (),

                                        NULL_TREE));

  gimplify_stmt (&body);

  *stmt_p = gimple_build_eh_filter (body, allowed, failure);

}

/* Genericize an IF_STMT by turning it into a COND_EXPR.  */

static void

gimplify_if_stmt (tree *stmt_p)

{

  tree stmt, cond, then_, else_;

  stmt = *stmt_p;

  cond = IF_COND (stmt);

  then_ = THEN_CLAUSE (stmt);

  else_ = ELSE_CLAUSE (stmt);

  if (!then_)

    then_ = build_empty_stmt ();

  if (!else_)

    else_ = build_empty_stmt ();

  if (integer_nonzerop (cond) && !TREE_SIDE_EFFECTS (else_))

    stmt = then_;

  else if (integer_zerop (cond) && !TREE_SIDE_EFFECTS (then_))

    stmt = else_;

  else

    stmt = build3 (COND_EXPR, void_type_node, cond, then_, else_);

  *stmt_p = stmt;

}

/* Build a generic representation of one of the C loop forms.  COND is the

   loop condition or NULL_TREE.  BODY is the (possibly compound) statement

   controlled by the loop.  INCR is the increment expression of a for-loop,

   or NULL_TREE.  COND_IS_FIRST indicates whether the condition is

   evaluated before the loop body as in while and for loops, or after the

   loop body as in do-while loops.  */

static tree

gimplify_cp_loop (tree cond, tree body, tree incr, bool cond_is_first)

{

  tree top, entry, exit, cont_block, break_block, stmt_list, t;

  location_t stmt_locus;

  stmt_locus = input_location;

  stmt_list = NULL_TREE;

  entry = NULL_TREE;

  break_block = begin_bc_block (bc_break);

  cont_block = begin_bc_block (bc_continue);

  /* If condition is zero don't generate a loop construct.  */

  if (cond && integer_zerop (cond))

    {

      top = NULL_TREE;

      exit = NULL_TREE;

      if (cond_is_first)

        {

          t = build_bc_goto (bc_break);

          append_to_statement_list (t, &stmt_list);

        }

    }

  else

    {

      /* If we use a LOOP_EXPR here, we have to feed the whole thing

         back through the main gimplifier to lower it.  Given that we

         have to gimplify the loop body NOW so that we can resolve

         break/continue stmts, seems easier to just expand to gotos.  */

      top = build1 (LABEL_EXPR, void_type_node, NULL_TREE);

      /* If we have an exit condition, then we build an IF with gotos either

         out of the loop, or to the top of it.  If there's no exit condition,

         then we just build a jump back to the top.  */

      exit = build_and_jump (&LABEL_EXPR_LABEL (top));

      if (cond && !integer_nonzerop (cond))

        {

          t = build_bc_goto (bc_break);

          exit = build3 (COND_EXPR, void_type_node, cond, exit, t);

          exit = fold (exit);

          gimplify_stmt (&exit);

          if (cond_is_first)

            {

              if (incr)

                {

                  entry = build1 (LABEL_EXPR, void_type_node, NULL_TREE);

                  t = build_and_jump (&LABEL_EXPR_LABEL (entry));

                }

              else

                t = build_bc_goto (bc_continue);

              append_to_statement_list (t, &stmt_list);

            }

        }

    }

  gimplify_stmt (&body);

  gimplify_stmt (&incr);

  body = finish_bc_block (bc_continue, cont_block, body);

  append_to_statement_list (top, &stmt_list);

  append_to_statement_list (body, &stmt_list);

  append_to_statement_list (incr, &stmt_list);

  append_to_statement_list (entry, &stmt_list);

  append_to_statement_list (exit, &stmt_list);

  annotate_all_with_locus (&stmt_list, stmt_locus);

  return finish_bc_block (bc_break, break_block, stmt_list);

}

/* Gimplify a FOR_STMT node.  Move the stuff in the for-init-stmt into the

   prequeue and hand off to gimplify_cp_loop.  */

static void

gimplify_for_stmt (tree *stmt_p, tree *pre_p)

{

  tree stmt = *stmt_p;

  if (FOR_INIT_STMT (stmt))

    gimplify_and_add (FOR_INIT_STMT (stmt), pre_p);

  *stmt_p = gimplify_cp_loop (FOR_COND (stmt), FOR_BODY (stmt),

                              FOR_EXPR (stmt), 1);

}

/* Gimplify a WHILE_STMT node.  */

static void

gimplify_while_stmt (tree *stmt_p)

{

  tree stmt = *stmt_p;

  *stmt_p = gimplify_cp_loop (WHILE_COND (stmt), WHILE_BODY (stmt),

                              NULL_TREE, 1);

}

/* Gimplify a DO_STMT node.  */

static void

gimplify_do_stmt (tree *stmt_p)

{

  tree stmt = *stmt_p;

  *stmt_p = gimplify_cp_loop (DO_COND (stmt), DO_BODY (stmt),

                              NULL_TREE, 0);

}

/* Genericize a SWITCH_STMT by turning it into a SWITCH_EXPR.  */

static void

gimplify_switch_stmt (tree *stmt_p)

{

  tree stmt = *stmt_p;

  tree break_block, body;

  location_t stmt_locus = input_location;

  break_block = begin_bc_block (bc_break);

  body = SWITCH_STMT_BODY (stmt);

  if (!body)

    body = build_empty_stmt ();

  *stmt_p = build3 (SWITCH_EXPR, SWITCH_STMT_TYPE (stmt),

                    SWITCH_STMT_COND (stmt), body, NULL_TREE);

  SET_EXPR_LOCATION (*stmt_p, stmt_locus);

  gimplify_stmt (stmt_p);

  *stmt_p = finish_bc_block (bc_break, break_block, *stmt_p);

}

/*  Gimplify an EXPR_STMT node.  */

static void

gimplify_expr_stmt (tree *stmt_p)

{

  tree stmt = EXPR_STMT_EXPR (*stmt_p);

  if (stmt == error_mark_node)

    stmt = NULL;

  /* Gimplification of a statement expression will nullify the

     statement if all its side effects are moved to *PRE_P and *POST_P.

     In this case we will not want to emit the gimplified statement.

     However, we may still want to emit a warning, so we do that before

     gimplification.  */

  if (stmt && (extra_warnings || warn_unused_value))

    {

      if (!TREE_SIDE_EFFECTS (stmt))

        {

          if (!IS_EMPTY_STMT (stmt)

              && !VOID_TYPE_P (TREE_TYPE (stmt))

              && !TREE_NO_WARNING (stmt))

            warning (0, "statement with no effect");

        }

      else if (warn_unused_value)

        warn_if_unused_value (stmt, input_location);

    }

  if (stmt == NULL_TREE)

    stmt = alloc_stmt_list ();

  *stmt_p = stmt;

}

/* Gimplify initialization from an AGGR_INIT_EXPR.  */

static void

cp_gimplify_init_expr (tree *expr_p, tree *pre_p, tree *post_p)

{

  tree from = TREE_OPERAND (*expr_p, 1);

  tree to = TREE_OPERAND (*expr_p, 0);

  tree sub;

  /* If we are initializing something from a TARGET_EXPR, strip the

     TARGET_EXPR and initialize it directly.  */

  /* What about code that pulls out the temp and uses it elsewhere?  I

     think that such code never uses the TARGET_EXPR as an initializer.  If

     I'm wrong, we'll abort because the temp won't have any RTL.  In that

     case, I guess we'll need to replace references somehow.  */

  if (TREE_CODE (from) == TARGET_EXPR)

    from = TARGET_EXPR_INITIAL (from);

  if (TREE_CODE (from) == CLEANUP_POINT_EXPR)

    from = TREE_OPERAND (from, 0);

  /* Look through any COMPOUND_EXPRs.  */

  sub = expr_last (from);

  /* If we are initializing from an AGGR_INIT_EXPR, drop the INIT_EXPR and

     replace the slot operand with our target.

     Should we add a target parm to gimplify_expr instead?  No, as in this

     case we want to replace the INIT_EXPR.  */

  if (TREE_CODE (sub) == AGGR_INIT_EXPR)

    {

      gimplify_expr (&to, pre_p, post_p, is_gimple_lvalue, fb_lvalue);

      TREE_OPERAND (sub, 2) = to;

      *expr_p = from;

      /* The initialization is now a side-effect, so the container can

         become void.  */

      if (from != sub)

        TREE_TYPE (from) = void_type_node;

    }

}

/* Gimplify a MUST_NOT_THROW_EXPR.  */

static void

gimplify_must_not_throw_expr (tree *expr_p, tree *pre_p)

{

  tree stmt = *expr_p;

  tree temp = voidify_wrapper_expr (stmt, NULL);

  tree body = TREE_OPERAND (stmt, 0);

  gimplify_stmt (&body);

  stmt = gimple_build_eh_filter (body, NULL_TREE,

                                 build_call (terminate_node, NULL_TREE));

  if (temp)

    {

      append_to_statement_list (stmt, pre_p);

      *expr_p = temp;

    }

  else

    *expr_p = stmt;

}

/* Do C++-specific gimplification.  Args are as for gimplify_expr.  */

int

cp_gimplify_expr (tree *expr_p, tree *pre_p, tree *post_p)

{

  int saved_stmts_are_full_exprs_p = 0;

  enum tree_code code = TREE_CODE (*expr_p);

  enum gimplify_status ret;

  if (STATEMENT_CODE_P (code))

    {

      saved_stmts_are_full_exprs_p = stmts_are_full_exprs_p ();

      current_stmt_tree ()->stmts_are_full_exprs_p

        = STMT_IS_FULL_EXPR_P (*expr_p);

    }

  switch (code)

    {

    case PTRMEM_CST:

      *expr_p = cplus_expand_constant (*expr_p);

      ret = GS_OK;

      break;

    case AGGR_INIT_EXPR:

      simplify_aggr_init_expr (expr_p);

      ret = GS_OK;

      break;

    case THROW_EXPR:

      /* FIXME communicate throw type to backend, probably by moving

         THROW_EXPR into ../tree.def.  */

      *expr_p = TREE_OPERAND (*expr_p, 0);

      ret = GS_OK;

      break;

    case MUST_NOT_THROW_EXPR:

      gimplify_must_not_throw_expr (expr_p, pre_p);

      ret = GS_OK;

      break;

      /* We used to do this for MODIFY_EXPR as well, but that's unsafe; the

         LHS of an assignment might also be involved in the RHS, as in bug

         25979.  */

    case INIT_EXPR:

      cp_gimplify_init_expr (expr_p, pre_p, post_p);

      ret = GS_OK;

      break;

    case EMPTY_CLASS_EXPR:

      /* We create an empty CONSTRUCTOR with RECORD_TYPE.  */

      *expr_p = build_constructor (TREE_TYPE (*expr_p), NULL);

      ret = GS_OK;

      break;

    case BASELINK:

      *expr_p = BASELINK_FUNCTIONS (*expr_p);

      ret = GS_OK;

      break;

    case TRY_BLOCK:

      genericize_try_block (expr_p);

      ret = GS_OK;

      break;

    case HANDLER:

      genericize_catch_block (expr_p);

      ret = GS_OK;

      break;

    case EH_SPEC_BLOCK:

      genericize_eh_spec_block (expr_p);

      ret = GS_OK;

      break;

    case USING_STMT:

      /* Just ignore for now.  Eventually we will want to pass this on to

         the debugger.  */

      *expr_p = build_empty_stmt ();

      ret = GS_ALL_DONE;

      break;

    case IF_STMT:

      gimplify_if_stmt (expr_p);

      ret = GS_OK;

      break;

    case FOR_STMT:

      gimplify_for_stmt (expr_p, pre_p);

      ret = GS_ALL_DONE;

      break;

    case WHILE_STMT:

      gimplify_while_stmt (expr_p);

      ret = GS_ALL_DONE;

      break;

    case DO_STMT:

      gimplify_do_stmt (expr_p);

      ret = GS_ALL_DONE;

      break;

    case SWITCH_STMT:

      gimplify_switch_stmt (expr_p);

      ret = GS_ALL_DONE;

      break;

    case CONTINUE_STMT:

      *expr_p = build_bc_goto (bc_continue);

      ret = GS_ALL_DONE;

      break;

    case BREAK_STMT:

      *expr_p = build_bc_goto (bc_break);

      ret = GS_ALL_DONE;

      break;

    case EXPR_STMT:

      gimplify_expr_stmt (expr_p);

      ret = GS_OK;

      break;

    case UNARY_PLUS_EXPR:

      {

        tree arg = TREE_OPERAND (*expr_p, 0);

        tree type = TREE_TYPE (*expr_p);

        *expr_p = (TREE_TYPE (arg) != type) ? fold_convert (type, arg)

                                            : arg;

        ret = GS_OK;

      }

      break;

    default:

      ret = c_gimplify_expr (expr_p, pre_p, post_p);

      break;

    }

  /* Restore saved state.  */

  if (STATEMENT_CODE_P (code))

    current_stmt_tree ()->stmts_are_full_exprs_p

      = saved_stmts_are_full_exprs_p;

  return ret;

}

static inline bool

is_invisiref_parm (tree t)

{

  return ((TREE_CODE (t) == PARM_DECL || TREE_CODE (t) == RESULT_DECL)

          && DECL_BY_REFERENCE (t));

}

/* Perform any pre-gimplification lowering of C++ front end trees to

   GENERIC.  */

static tree

cp_genericize_r (tree *stmt_p, int *walk_subtrees, void *data)

{

  tree stmt = *stmt_p;

  struct pointer_set_t *p_set = (struct pointer_set_t*) data;

  if (is_invisiref_parm (stmt)

      /* Don't dereference parms in a thunk, pass the references through. */

      && !(DECL_THUNK_P (current_function_decl)

           && TREE_CODE (stmt) == PARM_DECL))

    {

      *stmt_p = convert_from_reference (stmt);

      *walk_subtrees = 0;

      return NULL;

    }

  /* Other than invisiref parms, don't walk the same tree twice.  */

  if (pointer_set_contains (p_set, stmt))

    {

      *walk_subtrees = 0;

      return NULL_TREE;

    }

  if (TREE_CODE (stmt) == ADDR_EXPR

      && is_invisiref_parm (TREE_OPERAND (stmt, 0)))

    {

      *stmt_p = convert (TREE_TYPE (stmt), TREE_OPERAND (stmt, 0));

      *walk_subtrees = 0;

    }

  else if (TREE_CODE (stmt) == RETURN_EXPR

           && TREE_OPERAND (stmt, 0)

           && is_invisiref_parm (TREE_OPERAND (stmt, 0)))

    /* Don't dereference an invisiref RESULT_DECL inside a RETURN_EXPR.  */

    *walk_subtrees = 0;

  else if (IS_TYPE_OR_DECL_P (stmt))

    *walk_subtrees = 0;

  /* Due to the way voidify_wrapper_expr is written, we don't get a chance

     to lower this construct before scanning it, so we need to lower these

     before doing anything else.  */

  else if (TREE_CODE (stmt) == CLEANUP_STMT)

    *stmt_p = build2 (CLEANUP_EH_ONLY (stmt) ? TRY_CATCH_EXPR

                                             : TRY_FINALLY_EXPR,

                      void_type_node,

                      CLEANUP_BODY (stmt),

                      CLEANUP_EXPR (stmt));

  pointer_set_insert (p_set, *stmt_p);

  return NULL;

}

void

cp_genericize (tree fndecl)

{

  tree t;

  struct pointer_set_t *p_set;

  /* Fix up the types of parms passed by invisible reference.  */

  for (t = DECL_ARGUMENTS (fndecl); t; t = TREE_CHAIN (t))

    if (TREE_ADDRESSABLE (TREE_TYPE (t)))

      {

        /* If a function's arguments are copied to create a thunk,

           then DECL_BY_REFERENCE will be set -- but the type of the

           argument will be a pointer type, so we will never get

           here.  */

        gcc_assert (!DECL_BY_REFERENCE (t));

        gcc_assert (DECL_ARG_TYPE (t) != TREE_TYPE (t));

        TREE_TYPE (t) = DECL_ARG_TYPE (t);

        DECL_BY_REFERENCE (t) = 1;

        TREE_ADDRESSABLE (t) = 0;

        relayout_decl (t);

      }

  /* Do the same for the return value.  */

  if (TREE_ADDRESSABLE (TREE_TYPE (DECL_RESULT (fndecl))))

    {

      t = DECL_RESULT (fndecl);

      TREE_TYPE (t) = build_reference_type (TREE_TYPE (t));

      DECL_BY_REFERENCE (t) = 1;

      TREE_ADDRESSABLE (t) = 0;

      relayout_decl (t);

    }

  /* If we're a clone, the body is already GIMPLE.  */

  if (DECL_CLONED_FUNCTION_P (fndecl))

    return;

  /* We do want to see every occurrence of the parms, so we can't just use

     walk_tree's hash functionality.  */

  p_set = pointer_set_create ();

  walk_tree (&DECL_SAVED_TREE (fndecl), cp_genericize_r, p_set, NULL);

  pointer_set_destroy (p_set);

  /* Do everything else.  */

  push_context ();

  c_genericize (fndecl);

  pop_context ();

}