source: trunk/third/gcc/cp/expr.c @ 8834

/* Convert language-specific tree expression to rtl instructions,
   for GNU compiler.
   Copyright (C) 1988, 1992, 1993, 1994, 1995 Free Software Foundation, Inc.

This file is part of GNU CC.

GNU CC 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.

GNU CC 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 GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */


#include "config.h"
#include "rtl.h"
#include "tree.h"
#include "flags.h"
#include "expr.h"
#include "cp-tree.h"

#undef NULL
#define NULL 0

/* Hook used by expand_expr to expand language-specific tree codes.  */

rtx
cplus_expand_expr (exp, target, tmode, modifier)
     tree exp;
     rtx target;
     enum machine_mode tmode;
     enum expand_modifier modifier;
{
  tree type = TREE_TYPE (exp);
  register enum machine_mode mode = TYPE_MODE (type);
  register enum tree_code code = TREE_CODE (exp);
  rtx original_target = target;
  int ignore = target == const0_rtx;

  if (ignore)
    target = 0, original_target = 0;

  /* No sense saving up arithmetic to be done
     if it's all in the wrong mode to form part of an address.
     And force_operand won't know whether to sign-extend or zero-extend.  */

  if (mode != Pmode && modifier == EXPAND_SUM)
    modifier = EXPAND_NORMAL;

  switch (code)
    {
    case NEW_EXPR:
      {
        /* Something needs to be initialized, but we didn't know
           where that thing was when building the tree.  For example,
           it could be the return value of a function, or a parameter
           to a function which lays down in the stack, or a temporary
           variable which must be passed by reference.

           Cleanups are handled in a language-specific way: they
           might be run by the called function (true in GNU C++
           for parameters with cleanups), or they might be
           run by the caller, after the call (true in GNU C++
           for other cleanup needs).  */

        tree func = TREE_OPERAND (exp, 0);
        tree args = TREE_OPERAND (exp, 1);
        tree type = TREE_TYPE (exp), slot;
        tree fn_type = TREE_TYPE (TREE_TYPE (func));
        tree return_type = TREE_TYPE (fn_type);
        tree call_exp;
        rtx call_target, return_target;
        int pcc_struct_return = 0;

        /* The expression `init' wants to initialize what
           `target' represents.  SLOT holds the slot for TARGET.  */
        slot = TREE_OPERAND (exp, 2);

        if (target == 0)
          {
            /* Should always be called with a target in BLKmode case.  */
            my_friendly_assert (mode != BLKmode, 205);
            my_friendly_assert (DECL_RTL (slot) != 0, 206);

            target = gen_reg_rtx (mode);
          }

        /* The target the initializer will initialize (CALL_TARGET)
           must now be directed to initialize the target we are
           supposed to initialize (TARGET).  The semantics for
           choosing what CALL_TARGET is is language-specific,
           as is building the call which will perform the
           initialization.  It is left here to show the choices that
           exist for C++.  */
           
        if (TREE_CODE (func) == ADDR_EXPR
            && TREE_CODE (TREE_OPERAND (func, 0)) == FUNCTION_DECL
            && DECL_CONSTRUCTOR_P (TREE_OPERAND (func, 0)))
          {
            type = build_pointer_type (type);
            /* Don't clobber a value that might be part of a default
               parameter value.  */
            mark_addressable (slot);
            if (TREE_PERMANENT (args))
              args = tree_cons (0, build1 (ADDR_EXPR, type, slot),
                                TREE_CHAIN (args));
            else
              TREE_VALUE (args) = build1 (ADDR_EXPR, type, slot);
            call_target = 0;
          }
        else if (TREE_CODE (return_type) == REFERENCE_TYPE)
          {
            type = return_type;
            call_target = 0;
          }
        else
          {
#ifdef PCC_STATIC_STRUCT_RETURN
            pcc_struct_return = 1;
            call_target = 0;
#else
            call_target = target;
#endif
          }
        if (call_target)
          {
            /* Make this a valid memory address now.  The code below assumes
               that it can compare rtx and make assumptions based on the
               result.  The assumptions are true only if the address was
               valid to begin with.  */
            call_target = validize_mem (call_target);
          }

        call_exp = build (CALL_EXPR, type, func, args, 0);
        TREE_SIDE_EFFECTS (call_exp) = 1;
        return_target = expand_call (call_exp, call_target, ignore);
        if (call_target == 0)
          {
            if (pcc_struct_return)
              {
                extern int flag_access_control;
                int old_ac = flag_access_control;

                tree init = build_decl (VAR_DECL, 0, type);
                TREE_ADDRESSABLE (init) = 1;
                DECL_RTL (init) = return_target;

                flag_access_control = 0;
                expand_aggr_init (slot, init, 0, LOOKUP_ONLYCONVERTING);
                flag_access_control = old_ac;

                if (TYPE_NEEDS_DESTRUCTOR (type))
                  {
                    init = build_decl (VAR_DECL, 0,
                                       build_reference_type (type));
                    DECL_RTL (init) = XEXP (return_target, 0);

                    init = maybe_build_cleanup (convert_from_reference (init));
                    if (init != NULL_TREE)
                      expand_expr (init, 0, 0, 0);
                  }
                call_target = return_target = DECL_RTL (slot);
              }
            else
              call_target = return_target;
          }

        if (call_target != return_target)
          {
            my_friendly_assert (TYPE_HAS_TRIVIAL_INIT_REF (type), 317);
            if (GET_MODE (return_target) == BLKmode)
              emit_block_move (call_target, return_target, expr_size (exp),
                               TYPE_ALIGN (type) / BITS_PER_UNIT);
            else
              emit_move_insn (call_target, return_target);
          }

        if (TREE_CODE (return_type) == REFERENCE_TYPE)
          {
            tree init;

            if (GET_CODE (call_target) == REG
                && REGNO (call_target) < FIRST_PSEUDO_REGISTER)
              my_friendly_abort (39);

            type = TREE_TYPE (exp);

            init = build (RTL_EXPR, return_type, 0, call_target);
            /* We got back a reference to the type we want.  Now initialize
               target with that.  */
            expand_aggr_init (slot, init, 0, LOOKUP_ONLYCONVERTING);
          }

        if (DECL_RTL (slot) != target)
          emit_move_insn (DECL_RTL (slot), target);
        return DECL_RTL (slot);
      }

    case OFFSET_REF:
      {
#if 1
        return expand_expr (default_conversion (resolve_offset_ref (exp)),
                            target, tmode, EXPAND_NORMAL);
#else
        /* This is old crusty code, and does not handle all that the
           resolve_offset_ref function does.  (mrs) */
        tree base = build_unary_op (ADDR_EXPR, TREE_OPERAND (exp, 0), 0);
        tree offset = build_unary_op (ADDR_EXPR, TREE_OPERAND (exp, 1), 0);
        return expand_expr (build (PLUS_EXPR, TREE_TYPE (exp), base, offset),
                            target, tmode, EXPAND_NORMAL);
#endif
      }

    case THUNK_DECL:
      return DECL_RTL (exp);

    case THROW_EXPR:
      expand_throw (TREE_OPERAND (exp, 0));
      return NULL;

    case UNSAVE_EXPR:
      {
        rtx temp;
        temp = expand_expr (TREE_OPERAND (exp, 0), target, tmode, modifier);
        TREE_OPERAND (exp, 0) = unsave_expr_now (TREE_OPERAND (exp, 0));
        return temp;
      }

    default:
      break;
    }
  my_friendly_abort (40);
  /* NOTREACHED */
  return NULL;
}

void
init_cplus_expand ()
{
  lang_expand_expr = cplus_expand_expr;
}

/* If DECL had its rtl moved from where callers expect it
   to be, fix it up.  RESULT is the nominal rtl for the RESULT_DECL,
   which may be a pseudo instead of a hard register.  */

void
fixup_result_decl (decl, result)
     tree decl;
     rtx result;
{
  if (REG_P (result))
    {
      if (REGNO (result) >= FIRST_PSEUDO_REGISTER)
        {
          rtx real_decl_result;

#ifdef FUNCTION_OUTGOING_VALUE
          real_decl_result
            = FUNCTION_OUTGOING_VALUE (TREE_TYPE (decl), current_function_decl);
#else
          real_decl_result
            = FUNCTION_VALUE (TREE_TYPE (decl), current_function_decl);
#endif
          REG_FUNCTION_VALUE_P (real_decl_result) = 1;
          result = real_decl_result;
        }
      store_expr (decl, result, 0);
      emit_insn (gen_rtx (USE, VOIDmode, result));
    }
}

/* Return nonzero iff DECL is memory-based.  The DECL_RTL of
   certain const variables might be a CONST_INT, or a REG
   in some cases.  We cannot use `memory_operand' as a test
   here because on most RISC machines, a variable's address
   is not, by itself, a legitimate address.  */

int
decl_in_memory_p (decl)
     tree decl;
{
  return DECL_RTL (decl) != 0 && GET_CODE (DECL_RTL (decl)) == MEM;
}

/* Expand this initialization inline and see if it's simple enough that
   it can be done at compile-time.  */

static tree
extract_aggr_init (decl, init)
     tree decl, init;
{
  return 0;
}

static tree
extract_scalar_init (decl, init)
     tree decl, init;
{
  rtx value, insns, insn;
  extern struct obstack temporary_obstack;
  tree t = NULL_TREE;

  push_obstacks (&temporary_obstack, &temporary_obstack);
  start_sequence ();
  value = expand_expr (init, NULL_RTX, VOIDmode, 0);
  insns = get_insns ();
  end_sequence ();
  reg_scan (insns, max_reg_num (), 0);
  jump_optimize (insns, 0, 0, 1);
  pop_obstacks ();

  for (insn = insns; insn; insn = NEXT_INSN (insn))
    {
      rtx r, to;

      if (GET_CODE (insn) == NOTE)
        continue;
      else if (GET_CODE (insn) != INSN)
        return 0;

      r = PATTERN (insn);
      if (GET_CODE (r) != SET)
        return 0;

      to = XEXP (r, 0);

      if (! (to == value ||
             (GET_CODE (to) == SUBREG && XEXP (to, 0) == value)))
        return 0;

      r = XEXP (r, 1);

      switch (GET_CODE (r))
        {
        case CONST_INT:
          t = build_int_2 (XEXP (r, 0), 0);
          break;
        default:
          return 0;
        }
    }

  return t; 
}

int
extract_init (decl, init)
     tree decl, init;
{
  return 0;

  if (IS_AGGR_TYPE (TREE_TYPE (decl))
      || TREE_CODE (TREE_TYPE (decl)) == ARRAY_TYPE)
    init = extract_aggr_init (decl, init);
  else
    init = extract_scalar_init (decl, init);

  if (init == NULL_TREE)
    return 0;

  DECL_INITIAL (decl) = init;
  return 1;
}