lower_calls.c 19.8 KB
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/*
 * Project:     libFIRM
 * File name:   ir/lower/lower_calls.c
 * Purpose:     lowering of Calls with compound parameters
 * Author:      Michael Beck
 * Created:
 * CVS-ID:      $Id$
 * Copyright:   (c) 1998-2005 Universitt Karlsruhe
 * Licence:     This file protected by GPL -  GNU GENERAL PUBLIC LICENSE.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef HAVE_ALLOCA_H
#include <alloca.h>
#endif
#ifdef HAVE_MALLOC_H
#include <malloc.h>
#endif

#include "irprog_t.h"
#include "irnode_t.h"
#include "type_t.h"
#include "irmode_t.h"
#include "ircons.h"
#include "irgmod.h"
#include "irgwalk.h"
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#include "typewalk.h"
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#include "lower_calls.h"
#include "return.h"
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#include "irtools.h"
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#include "array.h"
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#include "pmap.h"

/** A type map for def_find_pointer_type. */
static pmap *type_map;

/**
 * Default implementation for finding a pointer type for a given element type.
 * Simple create a new one.
 */
static ir_type *def_find_pointer_type(ir_type *e_type, ir_mode *mode, int alignment)
{
  ir_type *res;
  pmap_entry *e;

  /* Mode and alignment are always identical in all calls to def_find_pointer_type(), so
     we simply can use a map from the element type to the pointer type. */
  e = pmap_find(type_map, e_type);
  if (e)
    res = e->value;
  else {
    res = new_type_pointer(mangle_u(get_type_ident(e_type), new_id_from_chars("Ptr", 3)), e_type, mode);
    set_type_alignment_bytes(res, alignment);
    pmap_insert(type_map, e_type, res);
  }
  return res;
}
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/**
 * Creates a new lowered type for a method type with compound
 * arguments. The new type is associated to the old one and returned.
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 *
 * @param lp   parameter struct
 * @param mtp  the method type to lower
 *
 * The current implementation expects that a lowered type already
 * includes the necessery changes ...
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 */
static ir_type *create_modified_mtd_type(const lower_params_t *lp, ir_type *mtp)
{
  ir_type *lowered;
  ir_type **params, **results, *res_tp;
  int n_ress, n_params, nn_ress, nn_params, i, first_variadic;
  ident *id;
  add_hidden hidden_params;
  variadicity var;

  if (is_lowered_type(mtp)) {
    /* the type is already lowered. Not handled yet. */
    assert(0 && "lowered types NYI");
  }

  lowered = get_associated_type(mtp);
  if (lowered)
    return lowered;

  n_ress   = get_method_n_ress(mtp);
  NEW_ARR_A(ir_type *, results, n_ress);

  n_params = get_method_n_params(mtp);
  NEW_ARR_A(ir_type *, params, n_params + n_ress);

  first_variadic = get_method_first_variadic_param_index(mtp);

  hidden_params = lp->hidden_params;
  if (hidden_params == ADD_HIDDEN_SMART &&
    get_method_variadicity(mtp) == variadicity_variadic)
        hidden_params = ADD_HIDDEN_ALWAYS_IN_FRONT;

  if (hidden_params == ADD_HIDDEN_ALWAYS_IN_FRONT) {
    /* add hidden in front */
    for (nn_ress = nn_params = i = 0; i < n_ress; ++i) {
      res_tp = get_method_res_type(mtp, i);

      if (is_compound_type(res_tp))
        params[nn_params++] = lp->find_pointer_type(res_tp, get_modeP_data(), lp->def_ptr_alignment);
      else
        results[nn_ress++] = res_tp;
    }

    /* move the index of the first variadic parameter */
    first_variadic += nn_params;

    for (i = 0; i < n_params; ++i)
      params[nn_params++] = get_method_param_type(mtp, i);
  }
  else {
    /* add hidden parameters last */
    assert(get_method_variadicity(mtp) == variadicity_non_variadic &&
      "Cannot add hidden parameters at end of variadic function");

    for (nn_params = 0; nn_params < n_params; ++nn_params)
      params[nn_params] = get_method_param_type(mtp, nn_params);

    for (nn_ress = i = 0; i < n_ress; ++i) {
      res_tp = get_method_res_type(mtp, i);

      if (is_compound_type(res_tp))
        params[nn_params++] = lp->find_pointer_type(res_tp, get_modeP_data(), lp->def_ptr_alignment);
      else
        results[nn_ress++] = res_tp;
    }
  }

  /* create the new type */
  id = mangle_u(new_id_from_chars("L", 1), get_type_ident(mtp));
  lowered = new_d_type_method(id, nn_params, nn_ress, get_type_dbg_info(mtp));

  /* fill it */
  for (i = 0; i < nn_params; ++i)
    set_method_param_type(lowered, i, params[i]);
  for (i = 0; i < nn_ress; ++i)
    set_method_res_type(lowered, i, results[i]);

  var = get_method_variadicity(mtp);
  set_method_variadicity(lowered, var);
  if (var == variadicity_variadic)
    set_method_first_variadic_param_index(lowered, first_variadic);

  /* associate the lowered type with the original one for easier access */
  set_lowered_type(mtp, lowered);

  return lowered;
}

/**
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 * A call list entry.
 */
typedef struct cl_entry cl_entry;
struct cl_entry {
  cl_entry *next;   /**< Pointer to the next entry. */
  ir_node  *call;   /**< Pointer to the Call node. */
  ir_node  *copyb;  /**< List of all CopyB nodes. */
};

/**
 * Walker environment for fix_args_and_collect_calls().
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 */
typedef struct _wlk_env_t {
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  int            arg_shift;     /**< The Argument index shift for parameters. */
  int            first_hidden;  /**< The index of the first hidden argument. */
  struct obstack obst;          /**< An obstack to allocate the data on. */
  cl_entry       *cl_list;      /**< The call list. */
  pmap           *dummy_map;    /**< A map for finding the dummy arguments. */
  unsigned       dnr;           /**< The dummy index number. */
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} wlk_env;

/**
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 * Return the call list entry of a call node.
 * If no entry exists yet, allocate one and enter the node into
 * the call list of the environment.
 *
 * @param call   A Call node.
 * @param env    The environment.
 */
static cl_entry *get_Call_entry(ir_node *call, wlk_env *env) {
  cl_entry *res = get_irn_link(call);
  if (res == NULL) {
    cl_entry *res = obstack_alloc(&env->obst, sizeof(*res));
    res->next  = env->cl_list;
    res->call  = call;
    res->copyb = NULL;
    set_irn_link(call, res);
    env->cl_list = res;
  }
  return res;
}

/**
 * Post walker: shift all parameter indeces
 * and collect Calls with compound returns in the call list.
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 */
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static void fix_args_and_collect_calls(ir_node *n, void *ctx) {
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  wlk_env *env = ctx;
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  int i;
  ir_type *ctp;
  ir_op *op = get_irn_op(n);
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  if (env->arg_shift > 0 && op == op_Proj) {
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    ir_node *pred = get_Proj_pred(n);

    /* Fix the argument numbers */
    if (pred == get_irg_args(current_ir_graph)) {
      long pnr = get_Proj_proj(n);
      set_Proj_proj(n, pnr + env->arg_shift);
    }
  }
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  else if (op == op_Call) {
    ctp = get_Call_type(n);
    for (i = get_method_n_ress(ctp) -1; i >= 0; --i) {
      if (is_compound_type(get_method_res_type(ctp, i))) {
        /*
         * This is a call with a compound return. As the result
         * might be ignored, we must put it in the list.
         */
        (void)get_Call_entry(n, env);
      }
    }
  }
  else if (op == op_CopyB) {
    ir_node *src = get_CopyB_src(n);
    /* older scheme using value_res_ent */
    if (is_Sel(src)) {
      ir_node *proj = get_Sel_ptr(src);
      if (is_Proj(proj) && get_Proj_proj(proj) == pn_Call_P_value_res_base) {
        ir_node *call = get_Proj_pred(proj);
        if (is_Call(call)) {
          /* found a CopyB from compound Call result */
          cl_entry *e = get_Call_entry(call, env);
          set_irn_link(n, e->copyb);
          e->copyb = n;
        }
      }
    } else
    /* new scheme: compound results are determined by the call type only */
    if (is_Proj(src)) {
      ir_node *proj = get_Proj_pred(src);
      if (is_Proj(proj) && get_Proj_proj(proj) == pn_Call_T_result) {
        ir_node *call = get_Proj_pred(proj);
        if (is_Call(call)) {
          ctp = get_Call_type(call);
          if (is_compound_type(get_method_res_type(ctp, get_Proj_proj(src)))) {
            /* found a CopyB from compound Call result */
            cl_entry *e = get_Call_entry(call, env);
            set_irn_link(n, e->copyb);
            e->copyb = n;
          }
        }
      }
    }
  }
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}

/**
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 * Returns non-zero if a node is a compound address
 * of a frame-type entity.
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 *
 * @param ft   the frame type
 * @param adr  the node
 */
static int is_compound_address(ir_type *ft, ir_node *adr)
{
  entity *ent;

  if (! is_Sel(adr))
    return 0;
  if (get_Sel_n_indexs(adr) != 0)
    return 0;
  ent = get_Sel_entity(adr);
  return get_entity_owner(ent) == ft;
}

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/** A pair for the copy-return-optimization. */
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typedef struct cr_pair {
  entity *ent;    /**< the entity than can be removed from the frame */
  ir_node *arg;   /**< the argument that replaces the entities address */
} cr_pair;

/**
 * Post walker: fixes all entities addresses for the copy-return
 * optimization.
 *
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 * Note: We expect the length of the cr_pair array (ie number of compound
 * return values) to be 1 (C, C++) in almost all cases, so ignore the
 * linear search complexity here.
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 */
static void do_copy_return_opt(ir_node *n, void *ctx) {
  cr_pair *arr = ctx;
  int i;

  if (is_Sel(n)) {
    entity *ent = get_Sel_entity(n);

    for (i = ARR_LEN(arr) - 1; i >= 0; --i) {
      if (ent == arr[i].ent) {
        exchange(n, arr[i].arg);
        break;
      }
    }
  }
}

/**
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 * Return a Sel node that selects a dummy argument of type tp.
 * Dummy arguments are only needed once and we use a map
 * to store them.
 * We could even assign all dummy arguments the same offset
 * in the frame type ...
 *
 * @param irg    the graph
 * @param block  the block where a newly create Sel should be placed
 * @param tp     the type of the dummy entity that should be create
 * @param env    the environment
 */
static ir_node *get_dummy_sel(ir_graph *irg, ir_node *block, ir_type *tp, wlk_env *env)
{
  ir_node *sel;
  pmap_entry *e;

  /* use a map the check if we already create such an entity */
  e = pmap_find(env->dummy_map, tp);
  if (e)
    sel = e->value;
  else {
    ir_type *ft = get_irg_frame_type(irg);
    entity *ent;
    char buf[16];

    snprintf(buf, sizeof(buf), "dummy.%u", env->dnr++);
    ent = new_entity(ft, new_id_from_str(buf), tp);
    sel = new_r_simpleSel(
      irg,
      block,
      get_irg_no_mem(irg),
      get_irg_frame(irg),
      ent);
    pmap_insert(env->dummy_map, tp, sel);

    if (get_type_state(ft) == layout_fixed) {
      /* Fix the layout again */
      assert(0 && "Fixed layout not implemented");
    }
  }
  return sel;
}

/**
 * Add the hidden parameter from the CopyB node to the Call node.
 *
 * @param irg    the graph
 * @param n_com  number of compound results (will be number of hidden parameters)
 * @param ins    in array to store the hidden parameters into
 * @param entry  the call list
 * @param env    the environment
 */
static void add_hidden_param(ir_graph *irg, int n_com, ir_node **ins, cl_entry *entry, wlk_env *env)
{
  ir_node *p, *n, *src, *mem;
  entity *ent;
  ir_type *owner;
  int idx, n_args;

  n_args = 0;
  for (p = entry->copyb; p; p = n) {
    n   = get_irn_link(p);
    src = get_CopyB_src(p);

    /* old scheme using value_res_ent */
    if (is_Sel(src)) {
      ent = get_Sel_entity(src);
      owner = get_entity_owner(ent);

      /* find the hidden parameter index */
      for (idx = 0; idx < get_struct_n_members(owner); ++idx)
        if (get_struct_member(owner, idx) == ent)
          break;
      assert(idx < get_struct_n_members(owner));
    }
    else

    /* new scheme: compound returns are determined by the call type and are Proj's */
    idx = get_Proj_proj(src);

    ins[idx] = get_CopyB_dst(p);
    mem      = get_CopyB_mem(p);

    /* get rid of the CopyB */
    turn_into_tuple(p, pn_CopyB_max);
    set_Tuple_pred(p, pn_CopyB_M_regular, mem);
    set_Tuple_pred(p, pn_CopyB_M_except, get_irg_bad(irg));
    set_Tuple_pred(p, pn_CopyB_X_except, get_irg_bad(irg));
    ++n_args;
  }

  /* now create dummy entities for function with ignored return value */
  if (n_args < n_com) {
    ir_type *ctp = get_Call_type(entry->call);
    int i, j;

    if (is_lowered_type(ctp))
      ctp = get_associated_type(ctp);

    for (j = i = 0; i < get_method_n_ress(ctp); ++i) {
      ir_type *rtp = get_method_res_type(ctp, i);
      if (is_compound_type(rtp)) {
        if (ins[j] == NULL)
          ins[j] = get_dummy_sel(irg, get_nodes_block(entry->call), rtp, env);
        ++j;
      }
    }
  }
}

/**
 * Fix all calls on a call list by adding hidden parameters.
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 *
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 * @param lp   the parameter struct
 * @param irg  the graph
 * @param env  the environment
 */
static void fix_call_list(const lower_params_t *lp, ir_graph *irg, wlk_env *env) {
  cl_entry *p;
  ir_node *call, **new_in;
  ir_type *ctp, *lowered_mtp;
  add_hidden hidden_params;
  int i, n_params, n_com, pos;
  unsigned dnr = 0;

  new_in = NEW_ARR_F(ir_node *, 0);
  for (p = env->cl_list; p; p = p->next) {
    call = p->call;
    ctp = get_Call_type(call);
    lowered_mtp = create_modified_mtd_type(lp, ctp);
    set_Call_type(call, lowered_mtp);

    hidden_params = lp->hidden_params;
    if (hidden_params == ADD_HIDDEN_SMART &&
      get_method_variadicity(ctp) == variadicity_variadic)
      hidden_params = ADD_HIDDEN_ALWAYS_IN_FRONT;

    n_params = get_Call_n_params(call);

    n_com = 0;
    for (i = get_method_n_ress(ctp) - 1; i >= 0; --i) {
      if (is_compound_type(get_method_res_type(ctp, i)))
        ++n_com;
    }
    pos = 2;
    ARR_RESIZE(ir_node *, new_in, n_params + n_com + pos);
    memset(new_in, 0, sizeof(*new_in) * (n_params + n_com + pos));
    if (hidden_params == ADD_HIDDEN_ALWAYS_IN_FRONT) {
      add_hidden_param(irg, n_com, &new_in[pos], p, env);
      pos += n_com;
    }
    /* copy all other parameters */
    for (i = 0; i < n_params; ++i)
      new_in[pos++] = get_Call_param(call, i);
    if (hidden_params == ADD_HIDDEN_ALWAYS_LAST) {
      add_hidden_param(irg, n_com, &new_in[pos], p, env);
      pos += n_com;
    }
    new_in[0] = get_Call_mem(call);
    new_in[1] = get_Call_ptr(call);

    set_irn_in(call, n_params + n_com + 2, new_in);
  }
}

/**
 * Transform a graph. If it has compound parameter returns,
 * remove them and use the hidden parameter instead.
 * If it calls methods with compound parameter returns, add hidden
 * parameters.
 *
 * @param lp   parameter struct
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 * @param irg  the graph to transform
 */
static void transform_irg(const lower_params_t *lp, ir_graph *irg)
{
  entity *ent = get_irg_entity(irg);
  ir_type *mtp, *lowered_mtp, *res_tp, *ft;
  int i, j, k, n_ress, n_com, n_cr_opt;
  ir_node **new_in, *ret, *endbl, *bl, *mem, *copy;
  cr_pair *cr_opt;
  wlk_env env;
  add_hidden hidden_params;

  assert(ent && "Cannot tranform graph without an entity");
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  assert(get_irg_phase_state(irg) == phase_high && "call lowering must be done in phase high");
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  mtp    = get_entity_type(ent);
  n_ress = get_method_n_ress(mtp);
  for (n_com = i = 0; i < n_ress; ++i) {
    res_tp = get_method_res_type(mtp, i);

    if (is_compound_type(res_tp))
      ++n_com;
  }

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  if (n_com) {
    /* much easier if we have only one return */
    normalize_one_return(irg);
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    /* This graph has a compound argument. Create a new type */
    lowered_mtp = create_modified_mtd_type(lp, mtp);
    set_entity_type(ent, lowered_mtp);
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    hidden_params = lp->hidden_params;
    if (hidden_params == ADD_HIDDEN_SMART &&
      get_method_variadicity(mtp) == variadicity_variadic)
      hidden_params = ADD_HIDDEN_ALWAYS_IN_FRONT;
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    if (hidden_params == ADD_HIDDEN_ALWAYS_IN_FRONT) {
      /* hidden arguments are added first */
      env.arg_shift    = n_com;
      env.first_hidden = 0;
    }
    else {
      /* hidden arguments are added last */
      env.arg_shift    = 0;
      env.first_hidden = get_method_n_params(mtp);
    }
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  }
  else {
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    /* we must only search for calls */
    env.arg_shift = 0;
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  }
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  obstack_init(&env.obst);
  env.cl_list   = NULL;
  env.dummy_map = pmap_create_ex(8);
  env.dnr       = 0;

  /* scan the code, fix argument numbers and collect calls. */
  irg_walk_graph(irg, firm_clear_link, fix_args_and_collect_calls, &env);

  /* fix all calls */
  if (env.cl_list)
    fix_call_list(lp, irg, &env);

  if (n_com) {
    /*
     * Now fix the Return node of the current graph.
     */

    /* STEP 1: find the return. This is simple, we have normalized the graph. */
    endbl = get_irg_end_block(irg);
    ret = NULL;
    for (i = get_Block_n_cfgpreds(endbl) - 1; i >= 0; --i) {
      ir_node *pred = get_Block_cfgpred(endbl, i);

      if (is_Return(pred)) {
        ret = pred;
        break;
      }
    }
    /* there should always be a return */
    assert(ret);

    /*
     * STEP 2: fix it. For all compound return values add a CopyB,
     * all others are copied.
     */
    NEW_ARR_A(ir_node *, new_in, n_ress - n_com + 1);

    bl  = get_nodes_block(ret);
    mem = get_Return_mem(ret);

    ft = get_irg_frame_type(irg);
    NEW_ARR_A(cr_pair, cr_opt, n_com);
    n_cr_opt = 0;
    for (j = 1, i = k = 0; i < n_ress; ++i) {
      ir_node *pred = get_Return_res(ret, i);
      res_tp = get_method_res_type(mtp, i);
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      if (is_compound_type(res_tp)) {
        ir_node *arg = get_irg_args(irg);
        arg = new_r_Proj(irg, get_nodes_block(arg), arg, mode_P_data, env.first_hidden + k);
        ++k;

        if (is_compound_address(ft, pred)) {
          /* we can do the copy-return optimization here */
          cr_opt[n_cr_opt].ent = get_Sel_entity(pred);
          cr_opt[n_cr_opt].arg = arg;
          ++n_cr_opt;
        }
        else { /* copy-return optimization is impossible, do the copy. */
          copy = new_r_CopyB(
                  irg, bl,
                  mem,
                  arg,
                  pred,
                  res_tp
                 );
          mem = new_r_Proj(irg, bl, copy, mode_M, pn_CopyB_M_regular);
        }
      }
      else { /* skalar return value */
        new_in[j] = pred;
        ++j;
      }
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    }
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    new_in[0] = mem;
    set_irn_in(ret, j, new_in);
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    if (n_cr_opt > 0) {
      irg_walk_graph(irg, NULL, do_copy_return_opt, cr_opt);
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      for (i = ARR_LEN(cr_opt) - 1; i >= 0; --i) {
        remove_class_member(ft, cr_opt[i].ent);
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      }
    }
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  } /* n_com */

  pmap_destroy(env.dummy_map);
  obstack_free(&env.obst, NULL);
}

/**
 * Returns non-zero if the given type is a method
 * type that must be lowered.
 *
 * @param tp  The type.
 */
static int must_be_lowered(ir_type *tp) {
  int i, n_ress;
  ir_type *res_tp;

  if (is_Method_type(tp)) {
    n_ress = get_method_n_ress(tp);
    for (i = 0; i < n_ress; ++i) {
      res_tp = get_method_res_type(tp, i);

      if (is_compound_type(res_tp))
        return 1;
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    }
  }
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  return 0;
}
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/**
 * type-walker: lower all method types of entities
 * and points-to types.
 */
static void lower_method_types(type_or_ent *tore, void *env)
{
  const lower_params_t *lp = env;
  ir_type *tp;
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  /* fix method entities */
  if (is_entity(tore)) {
    entity *ent = (entity *)tore;
    tp = get_entity_type(ent);

    if (must_be_lowered(tp)) {
      tp = create_modified_mtd_type(lp, tp);
      set_entity_type(ent, tp);
    }
  }
  else {
    tp = (ir_type *)tore;

    /* fix pointer to methods */
    if (is_Pointer_type(tp)) {
      ir_type *etp = get_pointer_points_to_type(tp);
      if (must_be_lowered(etp)) {
        etp = create_modified_mtd_type(lp, etp);
        set_pointer_points_to_type(tp, etp);
      }
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    }
  }
}

/*
 * Lower calls with compound return types.
 * This function does the following transformations:
 *
 * - Adds a new (hidden) pointer parameter for
 *   any return compound type.
 *
 * - Use of the hidden parameters in the function code.
 *
 * - Change all calls to functions with compound return
 *   by providing space for the hidden parameter on the callers
 *   stack.
 *
 * - Replace a possible block copy after the function call.
 */
void lower_compound_ret_calls(const lower_params_t *params)
{
  int i;
  ir_graph *irg;
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  lower_params_t param = *params;
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  if (param.find_pointer_type == NULL) {
    param.find_pointer_type = def_find_pointer_type;
    type_map = pmap_create_ex(8);
  }
  else
    type_map = NULL;

  /* first step: Transform all graphs */
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  for (i = get_irp_n_irgs() - 1; i >= 0; --i) {
    irg = get_irp_irg(i);

    if (irg == get_const_code_irg())
      continue;

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    transform_irg(&param, irg);
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  }

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  /* second step: Lower all method types of visible entities */
  type_walk(NULL, lower_method_types, &param);

  if (type_map)
    pmap_destroy(type_map);
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}