[libfirm] / ir / lower / lower_calls.c

/*
 * Copyright (C) 1995-2008 University of Karlsruhe.  All right reserved.
 *
 * This file is part of libFirm.
 *
 * This file may be distributed and/or modified under the terms of the
 * GNU General Public License version 2 as published by the Free Software
 * Foundation and appearing in the file LICENSE.GPL included in the
 * packaging of this file.
 *
 * Licensees holding valid libFirm Professional Edition licenses may use
 * this file in accordance with the libFirm Commercial License.
 * Agreement provided with the Software.
 *
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE.
 */

/**
 * @file
 * @brief   Lowering of Calls with compound parameters and return types.
 * @author  Michael Beck
 * @version $Id$
 */

#include "config.h"

#include "lowering.h"
#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"
#include "irmemory.h"
#include "irtools.h"
#include "iroptimize.h"
#include "array_t.h"
#include "pmap.h"
#include "error.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 && get_type_mode(e->value) == mode)
                res = e->value;
        else {
                res = new_type_pointer(e_type);
                set_type_mode(res, mode);
                set_type_alignment_bytes(res, alignment);
                pmap_insert(type_map, e_type, res);
        }
        return res;
}

/**
 * Creates a new lowered type for a method type with compound
 * arguments. The new type is associated to the old one and returned.
 *
 * @param lp   parameter struct
 * @param mtp  the method type to lower
 *
 * The current implementation expects that a lowered type already
 * includes the necessary changes ...
 */
static ir_type *create_modified_mtd_type(const lower_params_t *lp, ir_type *mtp)
{
        ir_type *lowered, *ptr_tp, *value_type;
        ir_type **params, **results, *res_tp;
        int     *param_map;
        ir_mode *modes[MAX_REGISTER_RET_VAL];
        int n_ress, n_params, nn_ress, nn_params, i, first_variadic;
        add_hidden hidden_params;
        int        changed = 0;
        ir_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 != NULL)
                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);

        NEW_ARR_A(int, param_map, 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)) {
                                int n_regs = 0;

                                if (lp->flags & LF_SMALL_CMP_IN_REGS)
                                        n_regs = lp->ret_compound_in_regs(res_tp, modes);

                                if (n_regs > 0) {
                                        /* this compound will be returned solely in registers */
                                        panic("Returning compounds in registers not yet implemented");
                                }
                                else {
                                        /* this compound will be allocated on callers stack and its
                                           address will be transmitted as a hidden parameter. */
                                        ptr_tp = lp->find_pointer_type(res_tp, get_modeP_data(), lp->def_ptr_alignment);
                                        params[nn_params]    = ptr_tp;
                                        param_map[nn_params] = -1 - i;
                                        ++nn_params;
                                        changed++;
                                        if (lp->flags & LF_RETURN_HIDDEN)
                                                results[nn_ress++] = ptr_tp;
                                }
                        } else {
                                /* scalar result */
                                results[nn_ress++] = res_tp;
                        }
                }

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

                for (i = 0; i < n_params; ++i, ++nn_params) {
                        params[nn_params]    = get_method_param_type(mtp, i);
                        param_map[nn_params] = 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);
                        param_map[nn_params] = 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);
                                param_map[nn_params] = -1 - i;
                                ++nn_params;
                        } else {
                                results[nn_ress++] = res_tp;
                        }
                }
        }

        /* create the new type */
        lowered = new_d_type_method(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 */
        if (changed) {
                set_method_calling_convention(lowered, get_method_calling_convention(mtp) | cc_compound_ret);
        }

        set_lowered_type(mtp, lowered);

        value_type = get_method_value_param_type(mtp);
        if (value_type != NULL) {
                /* set new param positions */
                for (i = 0; i < nn_params; ++i) {
                        ir_entity *ent = get_method_value_param_ent(lowered, i);
                        int       pos  = param_map[i];
                        ident     *id;

                        set_entity_link(ent, INT_TO_PTR(pos));
                        if (pos < 0) {
                                /* formally return value, ignore for now */
                                continue;
                        }

                        id = get_method_param_ident(mtp, pos);
                        if (id != NULL) {
                                set_method_param_ident(lowered, i, id);
                                set_entity_ident(ent, id);
                        }
                }

                set_lowered_type(value_type, get_method_value_param_type(lowered));
        }

        return lowered;
}

/**
 * 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().
 */
typedef struct _wlk_env_t {
        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. */
        const lower_params_t *params;          /**< Lowering parameters. */
        ir_type              *lowered_mtp;     /**< The lowered method type of the current irg if any. */
        ir_type              *value_params;    /**< The value params type if any. */
        unsigned             only_local_mem:1; /**< Set if only local memory access was found. */
        unsigned             changed:1;        /**< Set if the current graph was changed. */
} wlk_env;

/**
 * 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 = OALLOC(&env->obst, cl_entry);
                res->next  = env->cl_list;
                res->call  = call;
                res->copyb = NULL;
                set_irn_link(call, res);
                env->cl_list = res;
        }
        return res;
}

/**
 * Finds the base address of an address by skipping Sel's and address
 * calculation.
 *
 * @param adr   the address
 * @param pEnt  points to the base entity if any
 */
static ir_node *find_base_adr(ir_node *ptr, ir_entity **pEnt) {
        ir_entity *ent = NULL;
        assert(mode_is_reference(get_irn_mode(ptr)));

        for (;;) {
                if (is_Sel(ptr)) {
                        ent = get_Sel_entity(ptr);
                        ptr = get_Sel_ptr(ptr);
                }
                else if (is_Add(ptr)) {
                        ir_node *left = get_Add_left(ptr);
                        if (mode_is_reference(get_irn_mode(left)))
                                ptr = left;
                        else
                                ptr = get_Add_right(ptr);
                        ent = NULL;
                } else if (is_Sub(ptr)) {
                        ptr = get_Sub_left(ptr);
                        ent = NULL;
                } else {
                        *pEnt = ent;
                        return ptr;
                }
        }
}

/**
 * Check if a given pointer represents non-local memory.
 */
static void check_ptr(ir_node *ptr, wlk_env *env) {
        ir_storage_class_class_t sc;
        ir_entity                *ent;

        /* still alias free */
        ptr = find_base_adr(ptr, &ent);
        sc  = GET_BASE_SC(classify_pointer(current_ir_graph, ptr, ent));
        if (sc != ir_sc_localvar && sc != ir_sc_malloced) {
                /* non-local memory access */
                env->only_local_mem = 0;
        }
}

/**
 * Post walker: shift all parameter indexes
 * and collect Calls with compound returns in the call list.
 * If a non-alias free memory access is found, reset the alias free
 * flag.
 */
static void fix_args_and_collect_calls(ir_node *n, void *ctx) {
        wlk_env *env = ctx;
        int      i;
        ir_type *ctp;
        ir_node *ptr;

        switch (get_irn_opcode(n)) {
        case iro_Sel:
                if (env->lowered_mtp != NULL && env->value_params != NULL) {
                        ir_entity *ent = get_Sel_entity(n);

                        if (get_entity_owner(ent) == env->value_params) {
                                int pos = get_struct_member_index(env->value_params, ent) + env->arg_shift;
                                ir_entity *new_ent;

                                new_ent = get_method_value_param_ent(env->lowered_mtp, pos);
                                set_entity_ident(new_ent, get_entity_ident(ent));
                                set_Sel_entity(n, new_ent);
                        }
                }
                break;
        case iro_Load:
        case iro_Store:
                if (env->only_local_mem) {
                        ptr = get_irn_n(n, 1);
                        check_ptr(ptr, env);
                }
                break;
        case iro_Proj:
                if (env->arg_shift > 0) {
                        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);
                                env->changed = 1;
                        }
                }
                break;
        case iro_Call:
                if (! is_self_recursive_Call(n)) {
                        /* any non self recursive call might access global memory */
                        env->only_local_mem = 0;
                }

                ctp = get_Call_type(n);
                if (env->params->flags & LF_COMPOUND_RETURN) {
                        /* check for compound returns */
                        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);
                                        break;
                                }
                        }
                }
                break;
        case iro_CopyB:
                if (env->only_local_mem) {
                        check_ptr(get_CopyB_src(n), env);
                        if (env->only_local_mem)
                                check_ptr(get_CopyB_dst(n), env);
                }
                if (env->params->flags & LF_COMPOUND_RETURN) {
                        /* check for compound returns */
                        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;
                                                        }
                                                }
                                        }
                                }
                        }
                }
                break;
        default:
                /* do nothing */
                break;
        }
}

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

/** A pair for the copy-return-optimization. */
typedef struct cr_pair {
        ir_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.
 *
 * 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.
 */
static void do_copy_return_opt(ir_node *n, void *ctx) {
        cr_pair *arr = ctx;
        int i;

        if (is_Sel(n)) {
                ir_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;
                        }
                }
        }
}

/**
 * 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_entity *ent;
        pmap_entry *e;

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

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

                if (get_type_state(ft) == layout_fixed) {
                        /* Fix the layout again */
                        assert(0 && "Fixed layout not implemented");
                }
        }
        return new_r_simpleSel(
                block,
                get_irg_no_mem(irg),
                get_irg_frame(irg),
                ent);
}

/**
 * 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, *blk;
        ir_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);
                blk      = get_nodes_block(p);

                /* get rid of the CopyB */
                turn_into_tuple(p, pn_CopyB_max);
                set_Tuple_pred(p, pn_CopyB_M,         mem);
                set_Tuple_pred(p, pn_CopyB_X_regular, new_r_Jmp(blk));
                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.
 *
 * @param irg  the graph
 * @param env  the environment
 */
static void fix_call_list(ir_graph *irg, wlk_env *env) {
        const lower_params_t *lp = env->params;
        cl_entry *p;
        ir_node *call, **new_in;
        ir_type *ctp, *lowered_mtp;
        add_hidden hidden_params;
        int i, n_params, n_com, pos;

        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
 * @param irg  the graph to transform
 */
static void transform_irg(const lower_params_t *lp, ir_graph *irg)
{
        ir_graph   * rem = current_ir_graph;
        ir_entity  *ent = get_irg_entity(irg);
        ir_type    *mtp, *lowered_mtp, *tp, *ft;
        int        i, j, k, n_ress = 0, n_ret_com = 0, n_cr_opt;
        ir_node    **new_in, *ret, *endbl, *bl, *mem, *copy;
        cr_pair    *cr_opt;
        wlk_env    env;
        add_hidden hidden_params;

        current_ir_graph = irg;

        assert(ent && "Cannot transform graph without an entity");
        assert(get_irg_phase_state(irg) == phase_high && "call lowering must be done in phase high");

        mtp = get_entity_type(ent);

        if (lp->flags & LF_COMPOUND_RETURN) {
                /* calculate the number of compound returns */
                n_ress = get_method_n_ress(mtp);
                for (n_ret_com = i = 0; i < n_ress; ++i) {
                        tp = get_method_res_type(mtp, i);

                        if (is_compound_type(tp))
                                ++n_ret_com;
                }
        }

        if (n_ret_com) {
                /* much easier if we have only one return */
                normalize_one_return(irg);

                /* This graph has a compound argument. Create a new type */
                lowered_mtp = create_modified_mtd_type(lp, mtp);
                set_entity_type(ent, lowered_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) {
                        /* hidden arguments are added first */
                        env.arg_shift    = n_ret_com;
                        env.first_hidden = 0;
                } else {
                        /* hidden arguments are added last */
                        env.arg_shift    = 0;
                        env.first_hidden = get_method_n_params(mtp);
                }
        } else {
                /* we must only search for calls */
                env.arg_shift = 0;
                lowered_mtp   = NULL;
        }
        obstack_init(&env.obst);
        env.cl_list        = NULL;
        env.dummy_map      = pmap_create_ex(8);
        env.dnr            = 0;
        env.params         = lp;
        env.lowered_mtp    = lowered_mtp;
        env.value_params   = get_method_value_param_type(mtp);
        env.only_local_mem = 1;
        env.changed        = 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(irg, &env);
                env.changed = 1;
        }

        if (n_ret_com) {
                /*
                 * Now fix the Return node of the current graph.
                 */
                env.changed = 1;

                /* 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 + 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_ret_com);
                n_cr_opt = 0;
                for (j = 1, i = k = 0; i < n_ress; ++i) {
                        ir_node *pred = get_Return_res(ret, i);
                        tp = get_method_res_type(mtp, i);

                        if (is_compound_type(tp)) {
                                ir_node *arg = get_irg_args(irg);
                                arg = new_r_Proj(get_nodes_block(arg), arg, mode_P_data, env.first_hidden + k);
                                ++k;

                                if (is_Unknown(pred)) {
                                        /* The Return(Unknown) is the Firm construct for a missing return.
                                           Do nothing. */
                                } else {
                                        /**
                                         * Sorrily detecting that copy-return is possible isn't that simple.
                                         * We must check, that the hidden address is alias free during the whole
                                         * function.
                                         * A simple heuristic: all Loads/Stores inside
                                         * the function access only local frame.
                                         */
                                        if (env.only_local_mem && 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(
                                                        bl,
                                                        mem,
                                                        arg,
                                                        pred,
                                                        tp
                                                        );
                                                mem = new_r_Proj(bl, copy, mode_M, pn_CopyB_M);
                                        }
                                }
                                if (lp->flags & LF_RETURN_HIDDEN) {
                                        new_in[j] = arg;
                                        ++j;
                                }
                        } else { /* scalar return value */
                                new_in[j] = pred;
                                ++j;
                        }
                }
                /* replace the in of the Return */
                new_in[0] = mem;
                set_irn_in(ret, j, new_in);

                if (n_cr_opt > 0) {
                        irg_walk_graph(irg, NULL, do_copy_return_opt, cr_opt);

                        for (i = ARR_LEN(cr_opt) - 1; i >= 0; --i) {
                                remove_class_member(ft, cr_opt[i].ent);
                        }
                }
        } /* if (n_ret_com) */

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

        if (env.changed) {
                /* invalidate the analysis info */
                set_irg_outs_inconsistent(irg);
                set_irg_loopinfo_state(irg, loopinfo_inconsistent);
        }
        current_ir_graph = rem;
}

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

  if (is_Method_type(tp)) {
    if (lp->flags & LF_COMPOUND_RETURN) {
      /* check for compound returns */
      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;
      }
    }
  }
  return 0;
}

/**
 * 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;

        /* fix method entities */
        if (is_entity(tore.ent)) {
                ir_entity *ent = tore.ent;
                tp = get_entity_type(ent);

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

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

/*
 * Lower calls with compound parameters and 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_calls_with_compounds(const lower_params_t *params)
{
        int i;
        ir_graph *irg;
        lower_params_t param = *params;

        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 */
        for (i = get_irp_n_irgs() - 1; i >= 0; --i) {
                irg = get_irp_irg(i);

                transform_irg(&param, irg);
        }

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

        if (type_map)
                pmap_destroy(type_map);
}