[libfirm] / ir / be / bespillbelady.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       Beladys spillalgorithm.
 * @author      Daniel Grund, Matthias Braun
 * @date        20.09.2005
 * @version     $Id$
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdbool.h>

#include "obst.h"
#include "irprintf_t.h"
#include "irgraph.h"
#include "irnode.h"
#include "irmode.h"
#include "irgwalk.h"
#include "irloop.h"
#include "iredges_t.h"
#include "ircons_t.h"
#include "irprintf.h"
#include "irnodeset.h"
#include "xmalloc.h"
#include "pdeq.h"

#include "beutil.h"
#include "bearch_t.h"
#include "beuses.h"
#include "besched_t.h"
#include "beirgmod.h"
#include "belive_t.h"
#include "benode_t.h"
#include "bechordal_t.h"
#include "bespilloptions.h"
#include "beloopana.h"
#include "beirg_t.h"
#include "bespill.h"
#include "bemodule.h"

#define DBG_SPILL     1
#define DBG_WSETS     2
#define DBG_FIX       4
#define DBG_DECIDE    8
#define DBG_START    16
#define DBG_SLOTS    32
#define DBG_TRACE    64
#define DBG_WORKSET 128
DEBUG_ONLY(static firm_dbg_module_t *dbg = NULL;)

#define TIME_UNDEFINED 6666

//#define LOOK_AT_LOOPDEPTH

/**
 * An association between a node and a point in time.
 */
typedef struct loc_t {
        ir_node          *node;
        unsigned          time;     /**< A use time (see beuses.h). */
        bool              spilled;  /**< the value was already spilled on this path */
} loc_t;

typedef struct _workset_t {
        int   len;          /**< current length */
        loc_t vals[0];      /**< inlined array of the values/distances in this working set */
} workset_t;

static struct obstack               obst;
static const arch_env_t            *arch_env;
static const arch_register_class_t *cls;
static const be_lv_t               *lv;
static be_loopana_t                *loop_ana;
static int                          n_regs;
static workset_t                   *ws;     /**< the main workset used while
                                                     processing a block. */
static be_uses_t                   *uses;   /**< env for the next-use magic */
static ir_node                     *instr;  /**< current instruction */
static unsigned                     instr_nr; /**< current instruction number
                                                       (relative to block start) */
static spill_env_t                 *senv;   /**< see bespill.h */
static pdeq                        *worklist;

static bool                         move_spills      = true;
static bool                         respectloopdepth = true;
static bool                         improve_known_preds = true;
/* factor to weight the different costs of reloading/rematerializing a node
   (see bespill.h be_get_reload_costs_no_weight) */
static int                          remat_bonus      = 10;

static const lc_opt_table_entry_t options[] = {
        LC_OPT_ENT_BOOL   ("movespills", "try to move spills out of loops", &move_spills),
        LC_OPT_ENT_BOOL   ("respectloopdepth", "exprimental (outermost loop cutting)", &respectloopdepth),
        LC_OPT_ENT_BOOL   ("improveknownpreds", "experimental (known preds cutting)", &improve_known_preds),
        LC_OPT_ENT_INT    ("rematbonus", "give bonus to rematerialisable nodes", &remat_bonus),
        LC_OPT_LAST
};

static int loc_compare(const void *a, const void *b)
{
        const loc_t *p = a;
        const loc_t *q = b;
        return p->time - q->time;
}

void workset_print(const workset_t *w)
{
        int i;

        for(i = 0; i < w->len; ++i) {
                ir_fprintf(stderr, "%+F %d\n", w->vals[i].node, w->vals[i].time);
        }
}

/**
 * Alloc a new workset on obstack @p ob with maximum size @p max
 */
static workset_t *new_workset(void)
{
        workset_t *res;
        size_t     size = sizeof(*res) + n_regs * sizeof(res->vals[0]);

        res  = obstack_alloc(&obst, size);
        memset(res, 0, size);
        return res;
}

/**
 * Alloc a new instance on obstack and make it equal to @param workset
 */
static workset_t *workset_clone(workset_t *workset)
{
        workset_t *res;
        size_t size = sizeof(*res) + n_regs * sizeof(res->vals[0]);
        res = obstack_alloc(&obst, size);
        memcpy(res, workset, size);
        return res;
}

/**
 * Copy workset @param src to @param tgt
 */
static void workset_copy(workset_t *dest, const workset_t *src)
{
        size_t size = sizeof(*src) + n_regs * sizeof(src->vals[0]);
        memcpy(dest, src, size);
}

/**
 * Overwrites the current content array of @param ws with the
 * @param count locations given at memory @param locs.
 * Set the length of @param ws to count.
 */
static void workset_bulk_fill(workset_t *workset, int count, const loc_t *locs)
{
        workset->len = count;
        memcpy(&(workset->vals[0]), locs, count * sizeof(locs[0]));
}

/**
 * Inserts the value @p val into the workset, iff it is not
 * already contained. The workset must not be full.
 */
static void workset_insert(workset_t *workset, ir_node *val, bool spilled)
{
        loc_t *loc;
        int    i;
        /* check for current regclass */
        assert(arch_irn_consider_in_reg_alloc(arch_env, cls, val));

        /* check if val is already contained */
        for (i = 0; i < workset->len; ++i) {
                loc = &workset->vals[i];
                if (loc->node == val) {
                        if (spilled) {
                                loc->spilled = true;
                        }
                        return;
                }
        }

        /* insert val */
        assert(workset->len < n_regs && "Workset already full!");
        loc           = &workset->vals[workset->len];
        loc->node     = val;
        loc->spilled  = spilled;
        loc->time     = TIME_UNDEFINED;
        workset->len++;
}

/**
 * Removes all entries from this workset
 */
static void workset_clear(workset_t *workset)
{
        workset->len = 0;
}

/**
 * Removes the value @p val from the workset if present.
 */
static INLINE void workset_remove(workset_t *workset, ir_node *val)
{
        int i;
        for(i = 0; i < workset->len; ++i) {
                if (workset->vals[i].node == val) {
                        workset->vals[i] = workset->vals[--workset->len];
                        return;
                }
        }
}

static INLINE const loc_t *workset_contains(const workset_t *ws,
                                            const ir_node *val)
{
        int i;

        for (i = 0; i < ws->len; ++i) {
                if (ws->vals[i].node == val)
                        return &ws->vals[i];
        }

        return NULL;
}

/**
 * Iterates over all values in the working set.
 * @p ws The workset to iterate
 * @p v  A variable to put the current value in
 * @p i  An integer for internal use
 */
#define workset_foreach(ws, v, i)       for(i=0; \
                                                                                v=(i < ws->len) ? ws->vals[i].node : NULL, i < ws->len; \
                                                                                ++i)

#define workset_set_time(ws, i, t) (ws)->vals[i].time=t
#define workset_get_time(ws, i) (ws)->vals[i].time
#define workset_set_length(ws, length) (ws)->len = length
#define workset_get_length(ws) ((ws)->len)
#define workset_get_val(ws, i) ((ws)->vals[i].node)
#define workset_sort(ws) qsort((ws)->vals, (ws)->len, sizeof((ws)->vals[0]), loc_compare);

typedef struct _block_info_t
{
        workset_t *start_workset;
        workset_t *end_workset;
} block_info_t;


static void *new_block_info(void)
{
        block_info_t *res = obstack_alloc(&obst, sizeof(res[0]));
        memset(res, 0, sizeof(res[0]));

        return res;
}

#define get_block_info(block)        ((block_info_t *)get_irn_link(block))
#define set_block_info(block, info)  set_irn_link(block, info)

/**
 * @return The distance to the next use or 0 if irn has dont_spill flag set
 */
static INLINE unsigned get_distance(ir_node *from, unsigned from_step,
                                    const ir_node *def, int skip_from_uses)
{
        be_next_use_t use;
        int           flags = arch_irn_get_flags(arch_env, def);
        unsigned      costs;
        unsigned      time;

        assert(! (flags & arch_irn_flags_ignore));

        use  = be_get_next_use(uses, from, from_step, def, skip_from_uses);
        time = use.time;
        if (USES_IS_INFINITE(time))
                return USES_INFINITY;

        /* We have to keep nonspillable nodes in the workingset */
        if (flags & arch_irn_flags_dont_spill)
                return 0;

        /* give some bonus to rematerialisable nodes */
        if (remat_bonus > 0) {
                costs = be_get_reload_costs_no_weight(senv, def, use.before);
                assert(costs * remat_bonus < 1000);
                time  += 1000 - (costs * remat_bonus);
        }

        return time;
}

/**
 * Performs the actions necessary to grant the request that:
 * - new_vals can be held in registers
 * - as few as possible other values are disposed
 * - the worst values get disposed
 *
 * @p is_usage indicates that the values in new_vals are used (not defined)
 * In this case reloads must be performed
 */
static void displace(workset_t *new_vals, int is_usage)
{
        ir_node **to_insert = alloca(n_regs * sizeof(to_insert[0]));
        bool     *spilled   = alloca(n_regs * sizeof(spilled[0]));
        ir_node  *val;
        int       i;
        int       len;
        int       spills_needed;
        int       demand;
        int       iter;

        /* 1. Identify the number of needed slots and the values to reload */
        demand = 0;
        workset_foreach(new_vals, val, iter) {
                bool reloaded = false;

                if (! workset_contains(ws, val)) {
                        DB((dbg, DBG_DECIDE, "    insert %+F\n", val));
                        if (is_usage) {
                                DB((dbg, DBG_SPILL, "Reload %+F before %+F\n", val, instr));
                                be_add_reload(senv, val, instr, cls, 1);
                                reloaded = true;
                        }
                } else {
                        DB((dbg, DBG_DECIDE, "    %+F already in workset\n", val));
                        assert(is_usage);
                        /* remove the value from the current workset so it is not accidently
                         * spilled */
                        workset_remove(ws, val);
                }
                spilled[demand]   = reloaded;
                to_insert[demand] = val;
                ++demand;
        }

        /* 2. Make room for at least 'demand' slots */
        len           = workset_get_length(ws);
        spills_needed = len + demand - n_regs;
        assert(spills_needed <= len);

        /* Only make more free room if we do not have enough */
        if (spills_needed > 0) {
                ir_node   *curr_bb  = NULL;
                workset_t *ws_start = NULL;

                if (move_spills) {
                        curr_bb  = get_nodes_block(instr);
                        ws_start = get_block_info(curr_bb)->start_workset;
                }

                DB((dbg, DBG_DECIDE, "    disposing %d values\n", spills_needed));

                /* calculate current next-use distance for live values */
                for (i = 0; i < len; ++i) {
                        ir_node  *val  = workset_get_val(ws, i);
                        unsigned  dist = get_distance(instr, instr_nr, val, !is_usage);
                        workset_set_time(ws, i, dist);
                }

                /* sort entries by increasing nextuse-distance*/
                workset_sort(ws);

                for (i = len - spills_needed; i < len; ++i) {
                        ir_node *val = ws->vals[i].node;

                        DB((dbg, DBG_DECIDE, "    disposing node %+F (%u)\n", val,
                             workset_get_time(ws, i)));

                        if (move_spills) {
                                if (!USES_IS_INFINITE(ws->vals[i].time)
                                                && !ws->vals[i].spilled) {
                                        ir_node *after_pos = sched_prev(instr);
                                        DB((dbg, DBG_DECIDE, "Spill %+F after node %+F\n", val,
                                                after_pos));
                                        be_add_spill(senv, val, after_pos);
                                }
                        }
                }

                /* kill the last 'demand' entries in the array */
                workset_set_length(ws, len - spills_needed);
        }

        /* 3. Insert the new values into the workset */
        for (i = 0; i < demand; ++i) {
                ir_node *val = to_insert[i];

                workset_insert(ws, val, spilled[i]);
        }
}

enum {
        AVAILABLE_EVERYWHERE,
        AVAILABLE_NOWHERE,
        AVAILABLE_PARTLY,
        AVAILABLE_UNKNOWN
};

static unsigned available_in_all_preds(workset_t* const* pred_worksets,
                                       size_t n_pred_worksets,
                                       const ir_node *value, bool is_local_phi)
{
        size_t i;
        bool   avail_everywhere = true;
        bool   avail_nowhere    = true;

        assert(n_pred_worksets > 0);

        /* value available in all preds? */
        for (i = 0; i < n_pred_worksets; ++i) {
                bool             found     = false;
                const workset_t *p_workset = pred_worksets[i];
                int              p_len     = workset_get_length(p_workset);
                int              p_i;
                const ir_node   *l_value;

                if (is_local_phi) {
                        assert(is_Phi(value));
                        l_value = get_irn_n(value, i);
                } else {
                        l_value = value;
                }

                for (p_i = 0; p_i < p_len; ++p_i) {
                        const loc_t *p_l = &p_workset->vals[p_i];
                        if (p_l->node != l_value)
                                continue;

                        found = true;
                        break;
                }

                if (found) {
                        avail_nowhere = false;
                } else {
                        avail_everywhere = false;
                }
        }

        if (avail_everywhere) {
                assert(!avail_nowhere);
                return AVAILABLE_EVERYWHERE;
        } else if (avail_nowhere) {
                return AVAILABLE_NOWHERE;
        } else {
                return AVAILABLE_PARTLY;
        }
}

/** Decides whether a specific node should be in the start workset or not
 *
 * @param env      belady environment
 * @param first
 * @param node     the node to test
 * @param loop     the loop of the node
 */
static loc_t to_take_or_not_to_take(ir_node* first, ir_node *node,
                                    ir_loop *loop, unsigned available)
{
        be_next_use_t next_use;
        loc_t         loc;

        loc.time    = USES_INFINITY;
        loc.node    = node;
        loc.spilled = false;

        if (!arch_irn_consider_in_reg_alloc(arch_env, cls, node)) {
                loc.time = USES_INFINITY;
                return loc;
        }

        /* We have to keep nonspillable nodes in the workingset */
        if (arch_irn_get_flags(arch_env, node) & arch_irn_flags_dont_spill) {
                loc.time = 0;
                DB((dbg, DBG_START, "    %+F taken (dontspill node)\n", node, loc.time));
                return loc;
        }

        next_use = be_get_next_use(uses, first, 0, node, 0);
        if (USES_IS_INFINITE(next_use.time)) {
                // the nodes marked as live in shouldn't be dead, so it must be a phi
                assert(is_Phi(node));
                loc.time = USES_INFINITY;
                DB((dbg, DBG_START, "    %+F not taken (dead)\n", node));
                return loc;
        }

        loc.time = next_use.time;

        if (improve_known_preds) {
                if (available == AVAILABLE_EVERYWHERE) {
                        DB((dbg, DBG_START, "    %+F taken (%u, live in all preds)\n",
                            node, loc.time));
                        return loc;
                } else if(available == AVAILABLE_NOWHERE) {
                        DB((dbg, DBG_START, "    %+F not taken (%u, live in no pred)\n",
                            node, loc.time));
                        loc.time = USES_INFINITY;
                        return loc;
                }
        }

        if (!respectloopdepth || next_use.outermost_loop >= get_loop_depth(loop)) {
                DB((dbg, DBG_START, "    %+F taken (%u, loop %d)\n", node, loc.time,
                    next_use.outermost_loop));
        } else {
                loc.time = USES_PENDING;
                DB((dbg, DBG_START, "    %+F delayed (outerdepth %d < loopdepth %d)\n",
                    node, next_use.outermost_loop, get_loop_depth(loop)));
        }

        return loc;
}

/**
 * Computes the start-workset for a block with multiple predecessors. We assume
 * that at least 1 of the predeccesors is a back-edge which means we're at the
 * beginning of a loop. We try to reload as much values as possible now so they
 * don't get reloaded inside the loop.
 */
static void decide_start_workset(const ir_node *block)
{
        ir_loop    *loop = get_irn_loop(block);
        ir_node    *first;
        ir_node    *node;
        loc_t       loc;
        loc_t      *starters;
        loc_t      *delayed;
        int         i, len, ws_count;
        int             free_slots, free_pressure_slots;
        unsigned    pressure;
        int         arity;
        workset_t **pred_worksets;
        bool        all_preds_known;

        /* check predecessors */
        arity           = get_irn_arity(block);
        pred_worksets   = alloca(sizeof(pred_worksets[0]) * arity);
        all_preds_known = true;
        for(i = 0; i < arity; ++i) {
                ir_node      *pred_block = get_Block_cfgpred_block(block, i);
                block_info_t *pred_info  = get_block_info(pred_block);

                if (pred_info == NULL) {
                        pred_worksets[i] = NULL;
                        all_preds_known  = false;
                } else {
                        pred_worksets[i] = pred_info->end_workset;
                }
        }

        /* Collect all values living at start of block */
        starters = NEW_ARR_F(loc_t, 0);
        delayed  = NEW_ARR_F(loc_t, 0);

        DB((dbg, DBG_START, "Living at start of %+F:\n", block));
        first = sched_first(block);

        /* check all Phis first */
        sched_foreach(block, node) {
                unsigned available;

                if (! is_Phi(node))
                        break;
                if (!arch_irn_consider_in_reg_alloc(arch_env, cls, node))
                        continue;

                if (all_preds_known) {
                        available = available_in_all_preds(pred_worksets, arity, node, true);
                } else {
                        available = AVAILABLE_UNKNOWN;
                }

                loc = to_take_or_not_to_take(first, node, loop, available);

                if (! USES_IS_INFINITE(loc.time)) {
                        if (USES_IS_PENDING(loc.time))
                                ARR_APP1(loc_t, delayed, loc);
                        else
                                ARR_APP1(loc_t, starters, loc);
                } else {
                        be_spill_phi(senv, node);
                }
        }

        /* check all Live-Ins */
        be_lv_foreach(lv, block, be_lv_state_in, i) {
                ir_node *node = be_lv_get_irn(lv, block, i);
                unsigned available;

                if (all_preds_known) {
                        available = available_in_all_preds(pred_worksets, arity, node, false);
                } else {
                        available = AVAILABLE_UNKNOWN;
                }

                loc = to_take_or_not_to_take(first, node, loop, available);

                if (! USES_IS_INFINITE(loc.time)) {
                        if (USES_IS_PENDING(loc.time))
                                ARR_APP1(loc_t, delayed, loc);
                        else
                                ARR_APP1(loc_t, starters, loc);
                }
        }

        pressure            = be_get_loop_pressure(loop_ana, cls, loop);
        assert(ARR_LEN(delayed) <= (signed)pressure);
        free_slots          = n_regs - ARR_LEN(starters);
        free_pressure_slots = n_regs - (pressure - ARR_LEN(delayed));
        free_slots          = MIN(free_slots, free_pressure_slots);

        /* so far we only put nodes into the starters list that are used inside
         * the loop. If register pressure in the loop is low then we can take some
         * values and let them live through the loop */
        DB((dbg, DBG_START, "Loop pressure %d, taking %d delayed vals\n",
            pressure, free_slots));
        if (free_slots > 0) {
                qsort(delayed, ARR_LEN(delayed), sizeof(delayed[0]), loc_compare);

                for (i = 0; i < ARR_LEN(delayed) && free_slots > 0; ++i) {
                        int    p, arity;
                        loc_t *loc = & delayed[i];

                        /* don't use values which are dead in a known predecessors
                         * to not induce unnecessary reloads */
                        arity = get_irn_arity(block);
                        for (p = 0; p < arity; ++p) {
                                ir_node      *pred_block = get_Block_cfgpred_block(block, p);
                                block_info_t *pred_info  = get_block_info(pred_block);

                                if (pred_info == NULL)
                                        continue;

                                if (!workset_contains(pred_info->end_workset, loc->node)) {
                                        DB((dbg, DBG_START,
                                            "    delayed %+F not live at pred %+F\n", loc->node,
                                            pred_block));
                                        goto skip_delayed;
                                }
                        }

                        DB((dbg, DBG_START, "    delayed %+F taken\n", loc->node));
                        ARR_APP1(loc_t, starters, *loc);
                        loc->node = NULL;
                        --free_slots;
                skip_delayed:
                        ;
                }
        }

        /* spill phis (the actual phis not just their values) that are in this block
         * but not in the start workset */
        for (i = ARR_LEN(delayed) - 1; i >= 0; --i) {
                ir_node *node = delayed[i].node;
                if (node == NULL || !is_Phi(node) || get_nodes_block(node) != block)
                        continue;

                DB((dbg, DBG_START, "    spilling delayed phi %+F\n", node));
                be_spill_phi(senv, node);
        }
        DEL_ARR_F(delayed);

        /* Sort start values by first use */
        qsort(starters, ARR_LEN(starters), sizeof(starters[0]), loc_compare);

        /* Copy the best ones from starters to start workset */
        ws_count = MIN(ARR_LEN(starters), n_regs);
        workset_clear(ws);
        workset_bulk_fill(ws, ws_count, starters);

        /* spill phis (the actual phis not just their values) that are in this block
         * but not in the start workset */
        len = ARR_LEN(starters);
        for (i = ws_count; i < len; ++i) {
                ir_node *node = starters[i].node;
                if (! is_Phi(node) || get_nodes_block(node) != block)
                        continue;

                DB((dbg, DBG_START, "    spilling phi %+F\n", node));
                be_spill_phi(senv, node);
        }

        DEL_ARR_F(starters);

        /* determine spill status of the values: If there's 1 pred block (which
         * is no backedge) where the value is spilled then we must set it to
         * spilled here. */
        for(i = 0; i < ws_count; ++i) {
                loc_t   *loc     = &ws->vals[i];
                ir_node *value   = loc->node;
                bool     spilled;
                int      n;

                /* phis from this block aren't spilled */
                if (get_nodes_block(value) == block) {
                        assert(is_Phi(value));
                        loc->spilled = false;
                        continue;
                }

                /* determine if value was spilled on any predecessor */
                spilled = false;
                for(n = 0; n < arity; ++n) {
                        workset_t *pred_workset = pred_worksets[n];
                        int        p_len;
                        int        p;

                        if (pred_workset == NULL)
                                continue;

                        p_len = workset_get_length(pred_workset);
                        for(p = 0; p < p_len; ++p) {
                                loc_t *l = &pred_workset->vals[p];

                                if (l->node != value)
                                        continue;

                                if (l->spilled) {
                                        spilled = true;
                                }
                                break;
                        }
                }

                loc->spilled = spilled;
        }
}

/**
 * For the given block @p block, decide for each values
 * whether it is used from a register or is reloaded
 * before the use.
 */
static void belady(ir_node *block)
{
        workset_t       *new_vals;
        ir_node         *irn;
        int              iter;
        block_info_t    *block_info;
        int              i, arity;
        int              has_backedges = 0;
        //int              first         = 0;
        const ir_edge_t *edge;

        /* no need to process a block twice */
        if (get_block_info(block) != NULL) {
                return;
        }

        /* check if all predecessor blocks are processed yet (though for backedges
         * we have to make an exception as we can't process them first) */
        arity = get_Block_n_cfgpreds(block);
        for(i = 0; i < arity; ++i) {
                ir_node      *pred_block = get_Block_cfgpred_block(block, i);
                block_info_t *pred_info  = get_block_info(pred_block);

                if (pred_info == NULL) {
                        /* process predecessor first (it will be in the queue already) */
                        if (!is_backedge(block, i)) {
                                return;
                        }
                        has_backedges = 1;
                }
        }
        (void) has_backedges;
        if (arity == 0) {
                workset_clear(ws);
        } else if (arity == 1) {
                ir_node      *pred_block = get_Block_cfgpred_block(block, 0);
                block_info_t *pred_info  = get_block_info(pred_block);

                assert(pred_info != NULL);
                workset_copy(ws, pred_info->end_workset);
        } else {
                /* we need 2 heuristics here, for the case when all predecessor blocks
                 * are known and when some are backedges (and therefore can't be known
                 * yet) */
                decide_start_workset(block);
        }

        DB((dbg, DBG_DECIDE, "\n"));
        DB((dbg, DBG_DECIDE, "Decide for %+F\n", block));

        block_info = new_block_info();
        set_block_info(block, block_info);

        DB((dbg, DBG_WSETS, "Start workset for %+F:\n", block));
        workset_foreach(ws, irn, iter) {
                DB((dbg, DBG_WSETS, "  %+F (%u)\n", irn,
                     workset_get_time(ws, iter)));
        }

        block_info->start_workset = workset_clone(ws);

        /* process the block from start to end */
        DB((dbg, DBG_WSETS, "Processing...\n"));
        instr_nr = 0;
        /* TODO: this leaks (into the obstack)... */
        new_vals = new_workset();

        sched_foreach(block, irn) {
                int i, arity;
                assert(workset_get_length(ws) <= n_regs);

                /* Phis are no real instr (see insert_starters()) */
                if (is_Phi(irn)) {
                        continue;
                }
                DB((dbg, DBG_DECIDE, "  ...%+F\n", irn));

                /* set instruction in the workset */
                instr = irn;

                /* allocate all values _used_ by this instruction */
                workset_clear(new_vals);
                for(i = 0, arity = get_irn_arity(irn); i < arity; ++i) {
                        ir_node *in = get_irn_n(irn, i);
                        if (!arch_irn_consider_in_reg_alloc(arch_env, cls, in))
                                continue;

                        /* (note that "spilled" is irrelevant here) */
                        workset_insert(new_vals, in, false);
                }
                displace(new_vals, 1);

                /* allocate all values _defined_ by this instruction */
                workset_clear(new_vals);
                if (get_irn_mode(irn) == mode_T) {
                        const ir_edge_t *edge;

                        foreach_out_edge(irn, edge) {
                                ir_node *proj = get_edge_src_irn(edge);
                                if (!arch_irn_consider_in_reg_alloc(arch_env, cls, proj))
                                        continue;
                                workset_insert(new_vals, proj, false);
                        }
                } else {
                        if (!arch_irn_consider_in_reg_alloc(arch_env, cls, irn))
                                continue;
                        workset_insert(new_vals, irn, false);
                }
                displace(new_vals, 0);

                instr_nr++;
        }

        /* Remember end-workset for this block */
        block_info->end_workset = workset_clone(ws);
        DB((dbg, DBG_WSETS, "End workset for %+F:\n", block));
        workset_foreach(ws, irn, iter)
                DB((dbg, DBG_WSETS, "  %+F (%u)\n", irn,
                     workset_get_time(ws, iter)));

        /* add successor blocks into worklist */
        foreach_block_succ(block, edge) {
                ir_node *succ = get_edge_src_irn(edge);
                pdeq_putr(worklist, succ);
        }
}

/**
 * 'decide' is block-local and makes assumptions
 * about the set of live-ins. Thus we must adapt the
 * live-outs to the live-ins at each block-border.
 */
static void fix_block_borders(ir_node *block, void *data)
{
        workset_t    *start_workset;
        int           arity;
        int           i;
        int           iter;
        (void) data;

        DB((dbg, DBG_FIX, "\n"));
        DB((dbg, DBG_FIX, "Fixing %+F\n", block));

        start_workset = get_block_info(block)->start_workset;

        /* process all pred blocks */
        arity = get_irn_arity(block);
        for (i = 0; i < arity; ++i) {
                ir_node   *pred = get_Block_cfgpred_block(block, i);
                workset_t *pred_end_workset = get_block_info(pred)->end_workset;
                ir_node   *node;

                DB((dbg, DBG_FIX, "  Pred %+F\n", pred));

                /* spill all values not used anymore */
                workset_foreach(pred_end_workset, node, iter) {
                        ir_node *n2;
                        int      iter2;
                        bool     found = false;
                        workset_foreach(start_workset, n2, iter2) {
                                if (n2 == node) {
                                        found = true;
                                        break;
                                }
                                /* note that we do not look at phi inputs, becuase the values
                                 * will be either live-end and need no spill or
                                 * they have other users in which must be somewhere else in the
                                 * workset */
                        }

                        if (found)
                                continue;

                        if (move_spills && be_is_live_in(lv, block, node)
                                        && !pred_end_workset->vals[iter].spilled) {
                                ir_node *insert_point;
                                if (arity > 1) {
                                        insert_point = be_get_end_of_block_insertion_point(pred);
                                        insert_point = sched_prev(insert_point);
                                } else {
                                        insert_point = block;
                                }
                                DB((dbg, DBG_SPILL, "Spill %+F after %+F\n", node,
                                     insert_point));
                                be_add_spill(senv, node, insert_point);
                        }
                }

                /* reload missing values in predecessors, add missing spills */
                workset_foreach(start_workset, node, iter) {
                        const loc_t *l    = &start_workset->vals[iter];
                        const loc_t *pred_loc;

                        /* if node is a phi of the current block we reload
                         * the corresponding argument, else node itself */
                        if (is_Phi(node) && get_nodes_block(node) == block) {
                                node = get_irn_n(node, i);
                                assert(!l->spilled);

                                /* we might have unknowns as argument for the phi */
                                if (!arch_irn_consider_in_reg_alloc(arch_env, cls, node))
                                        continue;
                        }

                        /* check if node is in a register at end of pred */
                        pred_loc = workset_contains(pred_end_workset, node);
                        if (pred_loc != NULL) {
                                /* we might have to spill value on this path */
                                if (move_spills && !pred_loc->spilled && l->spilled) {
                                        ir_node *insert_point
                                                = be_get_end_of_block_insertion_point(pred);
                                        insert_point = sched_prev(insert_point);
                                        DB((dbg, DBG_SPILL, "Spill %+F after %+F\n", node,
                                            insert_point));
                                        be_add_spill(senv, node, insert_point);
                                }
                        } else {
                                /* node is not in register at the end of pred -> reload it */
                                DB((dbg, DBG_FIX, "    reload %+F\n", node));
                                DB((dbg, DBG_SPILL, "Reload %+F before %+F,%d\n", node, block, i));
                                be_add_reload_on_edge(senv, node, block, i, cls, 1);
                        }
                }
        }
}

static void be_spill_belady(be_irg_t *birg, const arch_register_class_t *rcls)
{
        ir_graph *irg = be_get_birg_irg(birg);

        be_liveness_assure_sets(be_assure_liveness(birg));

        /* construct control flow loop tree */
        if (! (get_irg_loopinfo_state(irg) & loopinfo_cf_consistent)) {
                construct_cf_backedges(irg);
        }

        be_clear_links(irg);

        /* init belady env */
        obstack_init(&obst);
        arch_env = birg->main_env->arch_env;
        cls      = rcls;
        lv       = be_get_birg_liveness(birg);
        n_regs   = cls->n_regs - be_put_ignore_regs(birg, cls, NULL);
        ws       = new_workset();
        uses     = be_begin_uses(irg, lv);
        loop_ana = be_new_loop_pressure(birg);
        senv     = be_new_spill_env(birg);
        worklist = new_pdeq();

        pdeq_putr(worklist, get_irg_start_block(irg));

        while(!pdeq_empty(worklist)) {
                ir_node *block = pdeq_getl(worklist);
                belady(block);
        }
        /* end block might not be reachable in endless loops */
        belady(get_irg_end_block(irg));

        del_pdeq(worklist);

        /* belady was block-local, fix the global flow by adding reloads on the
         * edges */
        irg_block_walk_graph(irg, fix_block_borders, NULL, NULL);

        /* Insert spill/reload nodes into the graph and fix usages */
        be_insert_spills_reloads(senv);

        /* clean up */
        be_delete_spill_env(senv);
        be_end_uses(uses);
        be_free_loop_pressure(loop_ana);
        obstack_free(&obst, NULL);
}

void be_init_spillbelady(void)
{
        static be_spiller_t belady_spiller = {
                be_spill_belady
        };
        lc_opt_entry_t *be_grp       = lc_opt_get_grp(firm_opt_get_root(), "be");
        lc_opt_entry_t *belady_group = lc_opt_get_grp(be_grp, "belady");
        lc_opt_add_table(belady_group, options);

        be_register_spiller("belady", &belady_spiller);
        FIRM_DBG_REGISTER(dbg, "firm.be.spill.belady");
}

BE_REGISTER_MODULE_CONSTRUCTOR(be_init_spillbelady);