initial work for phi-nodes (ifs should work, loops not yet)

[libfirm] / ir / be / benewalloc.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       New approach to allocation and copy coalescing
 * @author      Matthias Braun
 * @date        14.2.2009
 * @version     $Id$
 *
 * ... WE NEED A NAME FOR THIS ...
 *
 * Only a proof of concept at this moment...
 *
 * The idea is to allocate registers in 2 passes:
 * 1. A first pass to determine "preferred" registers for live-ranges. This
 *    calculates for each register and each live-range a value indicating
 *    the usefulness. (You can roughly think of the value as the negative
 *    costs needed for copies when the value is in the specific registers...)
 *
 * 2. Walk blocks and assigns registers in a greedy fashion. Preferring
 *    registers with high preferences. When register constraints are not met,
 *    add copies and split live-ranges.
 *
 * TODO:
 *  - output constraints are not ensured. The algorithm fails to copy values
 *    away, so the registers for constrained outputs are free.
 *  - must_be_different constraint is not respected
 *  - No parallel copies at basic block borders are created, no additional phis
 *    created after copies have been inserted.
 *  - Phi color assignment should give bonus points towards registers already
 *    assigned at predecessors.
 *  - think about a smarter sequence of visiting the blocks. Sorted by
 *    execfreq might be good, or looptree from inner to outermost loops going
 *    over blocks in a reverse postorder
 */
#include "config.h"

#include <float.h>

#include "obst.h"
#include "irnode_t.h"
#include "irgraph_t.h"
#include "iredges_t.h"
#include "ircons.h"
#include "irgwalk.h"
#include "execfreq.h"

#include "be.h"
#include "bera.h"
#include "belive_t.h"
#include "bemodule.h"
#include "bechordal_t.h"
#include "besched_t.h"
#include "beirg_t.h"
#include "benode_t.h"
#include "bespill.h"
#include "bespilloptions.h"
#include "beverify.h"

#include "bipartite.h"
#include "hungarian.h"

#define USE_FACTOR       1.0f
#define DEF_FACTOR       1.0f
#define NEIGHBOR_FACTOR  0.2f
#define SHOULD_BE_SAME   1.0f

DEBUG_ONLY(static firm_dbg_module_t *dbg = NULL;)

static struct obstack               obst;
static be_irg_t                    *birg;
static ir_graph                    *irg;
static const arch_register_class_t *cls;
static be_lv_t                     *lv;
static const ir_exec_freq          *execfreqs;
static unsigned                     n_regs;
static bitset_t                    *ignore_regs;

/** info about the current assignment for a register */
struct assignment_t {
        ir_node *value;            /**< currently assigned value */
};
typedef struct assignment_t assignment_t;

/** currently active assignments (while processing a basic block) */
static assignment_t *assignments;

/**
 * allocation information: last_uses, register preferences
 * the information is per firm-node.
 */
struct allocation_info_t {
        unsigned      last_uses;   /**< bitset indicating last uses (input pos) */
        assignment_t *current_assignment;
        float         prefs[0];    /**< register preferences */
};
typedef struct allocation_info_t allocation_info_t;

/** helper datastructure used when sorting register preferences */
struct reg_pref_t {
        unsigned num;
        float    pref;
};
typedef struct reg_pref_t reg_pref_t;

/** per basic-block information */
struct block_info_t {
        int          processed;       /**< indicate wether block is processed */
        assignment_t assignments[0];  /**< register assignments at end of block */
};
typedef struct block_info_t block_info_t;

/**
 * Get the allocation info for a node.
 * The info is allocated on the first visit of a node.
 */
static allocation_info_t *get_allocation_info(ir_node *node)
{
        allocation_info_t *info;
        if (!irn_visited(node)) {
                size_t size = sizeof(info[0]) + n_regs * sizeof(info->prefs[0]);
                info = obstack_alloc(&obst, size);
                memset(info, 0, size);
                set_irn_link(node, info);
                mark_irn_visited(node);
        } else {
                info = get_irn_link(node);
        }

        return info;
}

/**
 * Get allocation information for a basic block
 */
static block_info_t *get_block_info(ir_node *block)
{
        block_info_t *info;

        assert(is_Block(block));
        if (!irn_visited(block)) {
                size_t size = sizeof(info[0]) + n_regs * sizeof(info->assignments[0]);
                info = obstack_alloc(&obst, size);
                memset(info, 0, size);
                set_irn_link(block, info);
                mark_irn_visited(block);
        } else {
                info = get_irn_link(block);
        }

        return info;
}

/**
 * Link the allocation info of a node to a copy.
 * Afterwards, both nodes uses the same allocation info.
 * Copy must not have an allocation info assigned yet.
 *
 * @param copy   the node that gets the allocation info assigned
 * @param value  the original node
 */
static void link_to(ir_node *copy, ir_node *value)
{
        allocation_info_t *info = get_allocation_info(value);
        assert(!irn_visited(copy));
        set_irn_link(copy, info);
        mark_irn_visited(copy);
}

/**
 * Calculate the penalties for every register on a node and its live neighbors.
 *
 * @param live_nodes   the set of live nodes at the current position, may be NULL
 * @param penalty      the penalty to subtract from
 * @param limited      a raw bitset containing the limited set for the node
 * @param node         the node
 */
static void give_penalties_for_limits(const ir_nodeset_t *live_nodes,
                                      float penalty, const unsigned* limited,
                                                                          ir_node *node)
{
        ir_nodeset_iterator_t iter;
        unsigned              r;
        allocation_info_t     *info = get_allocation_info(node);
        ir_node               *neighbor;

        /* give penalty for all forbidden regs */
        for (r = 0; r < n_regs; ++r) {
                if (rbitset_is_set(limited, r))
                        continue;

                info->prefs[r] -= penalty;
        }

        /* all other live values should get a penalty for allowed regs */
        if (live_nodes == NULL)
                return;

        /* TODO: reduce penalty if there are multiple allowed registers... */
        penalty *= NEIGHBOR_FACTOR;
        foreach_ir_nodeset(live_nodes, neighbor, iter) {
                allocation_info_t *neighbor_info;

                /* TODO: if op is used on multiple inputs we might not do a
                 * continue here */
                if (neighbor == node)
                        continue;

                neighbor_info = get_allocation_info(neighbor);
                for (r = 0; r < n_regs; ++r) {
                        if (!rbitset_is_set(limited, r))
                                continue;

                        neighbor_info->prefs[r] -= penalty;
                }
        }
}

/**
 * Calculate the preferences of a definition for the current register class.
 * If the definition uses a limited set of registers, reduce the preferences
 * for the limited register on the node and its neighbors.
 *
 * @param live_nodes  the set of live nodes at the current node
 * @param weight      the weight
 * @param node        the current node
 */
static void check_defs(const ir_nodeset_t *live_nodes, float weight,
                       ir_node *node)
{
        const arch_register_req_t *req;

        if (get_irn_mode(node) == mode_T) {
                const ir_edge_t *edge;
                foreach_out_edge(node, edge) {
                        ir_node *proj = get_edge_src_irn(edge);
                        check_defs(live_nodes, weight, proj);
                }
                return;
        }

        if (!arch_irn_consider_in_reg_alloc(cls, node))
                return;

        req = arch_get_register_req_out(node);
        if (req->type & arch_register_req_type_limited) {
                const unsigned *limited = req->limited;
                float           penalty = weight * DEF_FACTOR;
                give_penalties_for_limits(live_nodes, penalty, limited, node);
        }

        if (req->type & arch_register_req_type_should_be_same) {
                ir_node           *insn  = skip_Proj(node);
                allocation_info_t *info  = get_allocation_info(node);
                int                arity = get_irn_arity(insn);
                int                i;

                float factor = 1.0f / rbitset_popcnt(&req->other_same, arity);
                for (i = 0; i < arity; ++i) {
                        ir_node           *op;
                        unsigned          r;
                        allocation_info_t *op_info;

                        if (!rbitset_is_set(&req->other_same, i))
                                continue;

                        op      = get_irn_n(insn, i);
                        op_info = get_allocation_info(op);
                        for (r = 0; r < n_regs; ++r) {
                                if (bitset_is_set(ignore_regs, r))
                                        continue;
                                op_info->prefs[r] += info->prefs[r] * factor;
                        }
                }
        }
}

/**
 * Walker: Runs an a block calculates the preferences for any
 * node and every register from the considered register class.
 */
static void analyze_block(ir_node *block, void *data)
{
        float         weight = get_block_execfreq(execfreqs, block);
        ir_nodeset_t  live_nodes;
        ir_node      *node;
        (void) data;

        ir_nodeset_init(&live_nodes);
        be_liveness_end_of_block(lv, cls, block, &live_nodes);

        sched_foreach_reverse(block, node) {
                allocation_info_t *info;
                int               i, arity;

                if (is_Phi(node)) {
                        /* TODO: handle constrained phi-nodes */
                        break;
                }

                /* TODO give/take penalties for should_be_same/different) */
                check_defs(&live_nodes, weight, node);

                /* mark last uses */
                arity = get_irn_arity(node);
                /* I was lazy, and only allocated 1 unsigned
                   => maximum of 32 uses per node (rewrite if necessary) */
                assert(arity <= (int) sizeof(unsigned) * 8);

                info = get_allocation_info(node);
                for (i = 0; i < arity; ++i) {
                        ir_node *op = get_irn_n(node, i);
                        if (!arch_irn_consider_in_reg_alloc(cls, op))
                                continue;

                        /* last usage of a value? */
                        if (!ir_nodeset_contains(&live_nodes, op)) {
                                rbitset_set(&info->last_uses, i);
                        }
                }

                be_liveness_transfer(cls, node, &live_nodes);

                /* update weights based on usage constraints */
                for (i = 0; i < arity; ++i) {
                        const arch_register_req_t *req;
                        const unsigned            *limited;
                        ir_node                   *op = get_irn_n(node, i);

                        if (!arch_irn_consider_in_reg_alloc(cls, op))
                                continue;

                        req = arch_get_register_req(node, i);
                        if ((req->type & arch_register_req_type_limited) == 0)
                                continue;

                        /* TODO: give penalties to neighbors for precolored nodes! */

                        limited = req->limited;
                        give_penalties_for_limits(&live_nodes, weight * USE_FACTOR, limited,
                                                  op);
                }
        }

        ir_nodeset_destroy(&live_nodes);
}

/**
 * Assign register reg to the given node.
 *
 * @param node  the node
 * @param reg   the register
 */
static void use_reg(ir_node *node, const arch_register_t *reg)
{
        unsigned           r          = arch_register_get_index(reg);
        assignment_t      *assignment = &assignments[r];
        allocation_info_t *info;

        assert(assignment->value == NULL);
        assignment->value = node;

        info = get_allocation_info(node);
        info->current_assignment = assignment;

        arch_set_irn_register(node, reg);
}

/**
 * Compare two register preferences in decreasing order.
 */
static int compare_reg_pref(const void *e1, const void *e2)
{
        const reg_pref_t *rp1 = (const reg_pref_t*) e1;
        const reg_pref_t *rp2 = (const reg_pref_t*) e2;
        if (rp1->pref < rp2->pref)
                return 1;
        if (rp1->pref > rp2->pref)
                return -1;
        return 0;
}

static void fill_sort_candidates(reg_pref_t *regprefs,
                                 const allocation_info_t *info)
{
        unsigned r;

        for (r = 0; r < n_regs; ++r) {
                float pref = info->prefs[r];
                if (bitset_is_set(ignore_regs, r)) {
                        pref = -10000;
                }
                regprefs[r].num  = r;
                regprefs[r].pref = pref;
        }
        /* TODO: use a stable sort here to avoid unnecessary register jumping */
        qsort(regprefs, n_regs, sizeof(regprefs[0]), compare_reg_pref);
}

/**
 * Determine and assign a register for node @p node
 */
static void assign_reg(const ir_node *block, ir_node *node)
{
        const arch_register_t     *reg;
        allocation_info_t         *info;
        const arch_register_req_t *req;
        reg_pref_t                *reg_prefs;
        ir_node                   *in_node;
        unsigned                  i;

        assert(arch_irn_consider_in_reg_alloc(cls, node));

        /* preassigned register? */
        reg = arch_get_irn_register(node);
        if (reg != NULL) {
                DB((dbg, LEVEL_2, "Preassignment %+F -> %s\n", node, reg->name));
                use_reg(node, reg);
                return;
        }

        /* give should_be_same boni */
        info = get_allocation_info(node);
        req  = arch_get_register_req_out(node);

        in_node = skip_Proj(node);
        if (req->type & arch_register_req_type_should_be_same) {
                float weight = get_block_execfreq(execfreqs, block);
                int   arity  = get_irn_arity(in_node);
                int   i;

                assert(arity <= (int) sizeof(req->other_same) * 8);
                for (i = 0; i < arity; ++i) {
                        ir_node               *in;
                        const arch_register_t *reg;
                        unsigned               r;
                        if (!rbitset_is_set(&req->other_same, i))
                                continue;

                        in  = get_irn_n(in_node, i);
                        reg = arch_get_irn_register(in);
                        assert(reg != NULL);
                        r = arch_register_get_index(reg);
                        if (bitset_is_set(ignore_regs, r))
                                continue;
                        info->prefs[r] += weight * SHOULD_BE_SAME;
                }
        }

        /* TODO: handle must_be_different */

        /*  */
        DB((dbg, LEVEL_2, "Candidates for %+F:", node));
        reg_prefs = alloca(n_regs * sizeof(reg_prefs[0]));
        fill_sort_candidates(reg_prefs, info);
        for (i = 0; i < n_regs; ++i) {
                unsigned               num = reg_prefs[i].num;
                const arch_register_t *reg = arch_register_for_index(cls, num);
                DB((dbg, LEVEL_2, " %s(%f)", reg->name, reg_prefs[i].pref));
        }
        DB((dbg, LEVEL_2, "\n"));

        for (i = 0; i < n_regs; ++i) {
                unsigned r = reg_prefs[i].num;
                /* ignores should be last and we should have a non-ignore left */
                assert(!bitset_is_set(ignore_regs, r));
                /* already used? TODO: It might be better to copy the value occupying the register around here, find out when... */
                if (assignments[r].value != NULL)
                        continue;
                reg = arch_register_for_index(cls, r);
                DB((dbg, LEVEL_2, "Assign %+F -> %s\n", node, reg->name));
                use_reg(node, reg);
                break;
        }
}

static void free_reg_of_value(ir_node *node)
{
        allocation_info_t *info;
        assignment_t      *assignment;
        unsigned          r;

        if (!arch_irn_consider_in_reg_alloc(cls, node))
                return;

        info       = get_allocation_info(node);
        assignment = info->current_assignment;

        assert(assignment != NULL);

        r = assignment - assignments;
        DB((dbg, LEVEL_2, "Value %+F ended, freeing %s\n",
                node, arch_register_for_index(cls, r)->name));
        assignment->value        = NULL;
        info->current_assignment = NULL;
}

/**
 * Return the index of the currently assigned register of a node.
 */
static unsigned get_current_reg(ir_node *node)
{
        allocation_info_t *info       = get_allocation_info(node);
        assignment_t      *assignment = info->current_assignment;
        return assignment - assignments;
}

/**
 * Return the currently assigned assignment of a node.
 */
static assignment_t *get_current_assignment(ir_node *node)
{
        allocation_info_t *info = get_allocation_info(node);
        return info->current_assignment;
}

/**
 * Add an permutation in front of a node and change the assignments
 * due to this permutation.
 *
 * To understand this imagine a permutation like this:
 *
 * 1 -> 2
 * 2 -> 3
 * 3 -> 1, 5
 * 4 -> 6
 * 5
 * 6
 * 7 -> 7
 *
 * First we count how many destinations a single value has. At the same time
 * we can be sure that each destination register has at most 1 source register
 * (it can have 0 which means we don't care what value is in it).
 * We ignore all fullfilled permuations (like 7->7)
 * In a first pass we create as much copy instructions as possible as they
 * are generally cheaper than exchanges. We do this by counting into how many
 * destinations a register has to be copied (in the example it's 2 for register
 * 3, or 1 for the registers 1,2,4 and 7).
 * We can then create a copy into every destination register when the usecount
 * of that register is 0 (= noone else needs the value in the register).
 *
 * After this step we should have cycles left. We implement a cyclic permutation
 * of n registers with n-1 transpositions.
 *
 * @param live_nodes   the set of live nodes, updated due to live range split
 * @param before       the node before we add the permutation
 * @param permutation  the permutation array indices are the destination
 *                     registers, the values in the array are the source
 *                     registers.
 */
static void permutate_values(ir_nodeset_t *live_nodes, ir_node *before,
                             unsigned *permutation)
{
        ir_node   *block;
        ir_node  **ins    = ALLOCANZ(ir_node*, n_regs);
        unsigned  *n_used = ALLOCANZ(unsigned, n_regs);
        unsigned   r;

        /* create a list of permutations. Leave out fix points. */
        for (r = 0; r < n_regs; ++r) {
                unsigned      old_reg = permutation[r];
                assignment_t *assignment;
                ir_node      *value;

                /* no need to do anything for a fixpoint */
                if (old_reg == r)
                        continue;

                assignment = &assignments[old_reg];
                value      = assignment->value;
                if (value == NULL) {
                        /* nothing to do here, reg is not live. Mark it as fixpoint
                         * so we ignore it in the next steps */
                        permutation[r] = r;
                        continue;
                }

                ins[old_reg] = value;
                ++n_used[old_reg];

                /* free occupation infos, we'll add the values back later */
                if (live_nodes != NULL) {
                        free_reg_of_value(value);
                        ir_nodeset_remove(live_nodes, value);
                }
        }

        block = get_nodes_block(before);

        /* step1: create copies where immediately possible */
        for (r = 0; r < n_regs; /* empty */) {
                ir_node *copy;
                ir_node *src;
                const arch_register_t *reg;
                unsigned               old_r = permutation[r];

                /* - no need to do anything for fixed points.
                   - we can't copy if the value in the dest reg is still needed */
                if (old_r == r || n_used[r] > 0) {
                        ++r;
                        continue;
                }

                /* create a copy */
                src = ins[old_r];
                copy = be_new_Copy(cls, block, src);
                reg = arch_register_for_index(cls, r);
                DB((dbg, LEVEL_2, "Copy %+F (from %+F) -> %s\n", copy, src, reg->name));
                link_to(copy, src);
                use_reg(copy, reg);
                sched_add_before(before, copy);

                /* old register has 1 user less, permutation is resolved */
                assert(arch_register_get_index(arch_get_irn_register(src)) == old_r);
                assert(n_used[old_r] > 0);
                --n_used[old_r];
                permutation[r] = r;

                /* advance or jump back (this copy could have enabled another copy) */
                if (old_r < r && n_used[old_r] == 0) {
                        r = old_r;
                } else {
                        ++r;
                }
        }

        /* at this point we only have "cycles" left which we have to resolve with
         * perm instructions
         * TODO: if we have free registers left, then we should really use copy
         * instructions for any cycle longer than 2 registers...
         * (this is probably architecture dependent, there might be archs where
         *  copies are preferable even for 2 cycles)
         */

        /* create perms with the rest */
        for (r = 0; r < n_regs; /* empty */) {
                const arch_register_t *reg;
                unsigned  old_r = permutation[r];
                unsigned  r2;
                ir_node  *in[2];
                ir_node  *perm;
                ir_node  *proj0;
                ir_node  *proj1;

                if (old_r == r) {
                        ++r;
                        continue;
                }

                /* we shouldn't have copies from 1 value to multiple destinations left*/
                assert(n_used[old_r] == 1);

                /* exchange old_r and r2; after that old_r is a fixed point */
                r2 = permutation[old_r];

                in[0] = ins[r2];
                in[1] = ins[old_r];
                perm = be_new_Perm(cls, block, 2, in);

                proj0 = new_r_Proj(block, perm, get_irn_mode(in[0]), 0);
                link_to(proj0, in[0]);
                reg = arch_register_for_index(cls, old_r);
                use_reg(proj0, reg);

                proj1 = new_r_Proj(block, perm, get_irn_mode(in[1]), 1);

                /* 1 value is now in the correct register */
                permutation[old_r] = old_r;
                /* the source of r changed to r2 */
                permutation[r] = r2;
                ins[r2] = in[1];
                reg = arch_register_for_index(cls, r2);
                if (r == r2) {
                        /* if we have reached a fixpoint update data structures */
                        link_to(proj1, in[1]);
                        use_reg(proj1, reg);
                } else {
                        arch_set_irn_register(proj1, reg);
                }
        }

#ifdef DEBUG_libfirm
        /* now we should only have fixpoints left */
        for (r = 0; r < n_regs; ++r) {
                assert(permutation[r] == r);
        }
#endif
}

/**
 * Free regs for values last used.
 *
 * @param live_nodes   set of live nodes, will be updated
 * @param node         the node to consider
 */
static void free_last_uses(ir_nodeset_t *live_nodes, ir_node *node)
{
        allocation_info_t *info  = get_allocation_info(node);
        int                arity = get_irn_arity(node);
        int                i;
        for (i = 0; i < arity; ++i) {
                ir_node *op;

                /* check if one operand is the last use */
                if (!rbitset_is_set(&info->last_uses, i))
                        continue;

                op = get_irn_n(node, i);
                free_reg_of_value(op);
                ir_nodeset_remove(live_nodes, op);
        }
}

/**
 * Enforce constraints at a node by live range splits.
 *
 * @param live_nodes  the set of live nodes, might be changed
 * @param node        the current node
 */
static void enforce_constraints(ir_nodeset_t *live_nodes, ir_node *node)
{
        int arity = get_irn_arity(node);
        int i, dummy, res;
        hungarian_problem_t *bp;
        unsigned l, r, p;
        unsigned *assignment;

        /* see if any use constraints are not met */
        bool good = true;
        for (i = 0; i < arity; ++i) {
                ir_node                   *op = get_irn_n(node, i);
                const arch_register_req_t *req;
                const unsigned            *limited;
                unsigned                  r;

                if (!arch_irn_consider_in_reg_alloc(cls, op))
                        continue;

                /* are there any limitations for the i'th operand? */
                req = arch_get_register_req(node, i);
                if ((req->type & arch_register_req_type_limited) == 0)
                        continue;

                limited = req->limited;
                r       = get_current_reg(op);
                if (!rbitset_is_set(limited, r)) {
                        /* found an assignement outside the limited set */
                        good = false;
                        break;
                }
        }

        if (good)
                return;

        /* swap values around */
        bp = hungarian_new(n_regs, n_regs, HUNGARIAN_MATCH_PERFECT);

        /* add all combinations, then remove not allowed ones */
        for (l = 0; l < n_regs; ++l) {
                if (bitset_is_set(ignore_regs, l)) {
                        hungarian_add(bp, l, l, 90);
                        continue;
                }

                for (r = 0; r < n_regs; ++r) {
                        if (bitset_is_set(ignore_regs, r))
                                continue;

                        hungarian_add(bp, l, r, l == r ? 90 : 89);
                }
        }

        for (i = 0; i < arity; ++i) {
                ir_node                   *op = get_irn_n(node, i);
                const arch_register_req_t *req;
                const unsigned            *limited;
                unsigned                  current_reg;

                if (!arch_irn_consider_in_reg_alloc(cls, op))
                        continue;

                req = arch_get_register_req(node, i);
                if ((req->type & arch_register_req_type_limited) == 0)
                        continue;

                limited     = req->limited;
                current_reg = get_current_reg(op);
                for (r = 0; r < n_regs; ++r) {
                        if (rbitset_is_set(limited, r))
                                continue;
                        hungarian_remv(bp, current_reg, r);
                }
        }

        hungarian_print_costmatrix(bp, 1);
        hungarian_prepare_cost_matrix(bp, HUNGARIAN_MODE_MAXIMIZE_UTIL);

        assignment = ALLOCAN(unsigned, n_regs);
        res = hungarian_solve(bp, (int*) assignment, &dummy, 0);
        assert(res == 0);

        printf("Swap result:");
        for (p = 0; p < n_regs; ++p) {
                printf(" %d", assignment[p]);
        }
        printf("\n");

        hungarian_free(bp);

        permutate_values(live_nodes, node, assignment);
}

/** test wether a node @p n is a copy of the value of node @p of */
static int is_copy_of(ir_node *n, ir_node *of)
{
        allocation_info_t *of_info;

        if (n == NULL)
                return 0;

        if (n == of)
                return 1;

        of_info = get_allocation_info(of);
        if (!irn_visited(n))
                return 0;

        return of_info == get_irn_link(n);
}

/** find a value in the end-assignment of a basic block
 * @returns the index into the assignment array if found
 *          -1 if not found
 */
static int find_value_in_block_info(block_info_t *info, ir_node *value)
{
        unsigned      r;
        assignment_t *assignments = info->assignments;
        for (r = 0; r < n_regs; ++r) {
                const assignment_t *assignment = &assignments[r];
                if (is_copy_of(assignment->value, value))
                        return (int) r;
        }

        return -1;
}

/**
 * Create the necessary permutations at the end of a basic block to fullfill
 * the register assignment for phi-nodes in the next block
 */
static void add_phi_permutations(ir_node *block, int p)
{
        unsigned  r;
        unsigned *permutation;
        assignment_t *old_assignments;
        int       need_permutation;
        ir_node  *node;
        ir_node  *pred = get_Block_cfgpred_block(block, p);

        block_info_t *pred_info = get_block_info(pred);

        /* predecessor not processed yet? nothing to do */
        if (!pred_info->processed)
                return;

        permutation = ALLOCAN(unsigned, n_regs);
        for (r = 0; r < n_regs; ++r) {
                permutation[r] = r;
        }

        /* check phi nodes */
        need_permutation = 0;
        node = sched_first(block);
        for ( ; is_Phi(node); node = sched_next(node)) {
                const arch_register_t *reg;
                int                    regn;
                int                    a;
                ir_node               *op;

                if (!arch_irn_consider_in_reg_alloc(cls, node))
                        continue;

                op = get_Phi_pred(node, p);
                a = find_value_in_block_info(pred_info, op);
                assert(a >= 0);

                reg = arch_get_irn_register(node);
                regn = arch_register_get_index(reg);
                if (regn != a) {
                        permutation[regn] = a;
                        need_permutation = 1;
                }
        }

        old_assignments = assignments;
        assignments     = pred_info->assignments;
        permutate_values(NULL, be_get_end_of_block_insertion_point(pred),
                         permutation);
        assignments     = old_assignments;

        node = sched_first(block);
        for ( ; is_Phi(node); node = sched_next(node)) {
                int                    a;
                ir_node               *op;

                if (!arch_irn_consider_in_reg_alloc(cls, node))
                        continue;

                op = get_Phi_pred(node, p);
                /* TODO: optimize */
                a = find_value_in_block_info(pred_info, op);
                assert(a >= 0);

                op = pred_info->assignments[a].value;
                set_Phi_pred(node, p, op);
        }
}

/**
 * Walker: assign registers to all nodes of a block that
 * needs registers from the currently considered register class.
 */
static void allocate_coalesce_block(ir_node *block, void *data)
{
        int                    i;
        unsigned               r;
        ir_nodeset_t           live_nodes;
        ir_nodeset_iterator_t  iter;
        ir_node               *node, *start;
        int                    n_preds;
        block_info_t          *block_info;
        block_info_t         **pred_block_infos;

        (void) data;
        DB((dbg, LEVEL_2, "Allocating in block %+F\n",
                block));

        /* clear assignments */
        block_info  = get_block_info(block);
        assignments = block_info->assignments;

        for (r = 0; r < n_regs; ++r) {
                assignment_t       *assignment = &assignments[r];
                ir_node            *value      = assignment->value;
                allocation_info_t  *info;

                if (value == NULL)
                        continue;

                info                     = get_allocation_info(value);
                info->current_assignment = assignment;
        }

        ir_nodeset_init(&live_nodes);

        /* gather regalloc infos of predecessor blocks */
        n_preds = get_Block_n_cfgpreds(block);
        pred_block_infos = ALLOCAN(block_info_t*, n_preds);
        for (i = 0; i < n_preds; ++i) {
                ir_node *pred = get_Block_cfgpred_block(block, i);
                pred_block_infos[i] = get_block_info(pred);
        }

        /* collect live-in nodes and preassigned values */
        be_lv_foreach(lv, block, be_lv_state_in, i) {
                const arch_register_t *reg;

                node = be_lv_get_irn(lv, block, i);
                if (!arch_irn_consider_in_reg_alloc(cls, node))
                        continue;

                /* remember that this node is live at the beginning of the block */
                ir_nodeset_insert(&live_nodes, node);

                /* if the node already has a register assigned use it */
                reg = arch_get_irn_register(node);
                if (reg != NULL) {
                        /* TODO: consult pred-block infos here. The value could be copied
                           away in some/all predecessor blocks. We need to construct
                           phi-nodes in this case.
                           We even need to construct some Phi_0 like constructs in cases
                           where the predecessor allocation is not determined yet. */
                        use_reg(node, reg);
                }
        }

        /* handle phis... */
        node = sched_first(block);
        for ( ; is_Phi(node); node = sched_next(node)) {
                const arch_register_t *reg;

                if (!arch_irn_consider_in_reg_alloc(cls, node))
                        continue;

                /* fill in regs already assigned */
                reg = arch_get_irn_register(node);
                if (reg != NULL) {
                        use_reg(node, reg);
                } else {
                        /* TODO: give boni for registers already assigned at the
                           predecessors */
                        assign_reg(block, node);
                }
        }
        start = node;

        /* assign regs for live-in values */
        foreach_ir_nodeset(&live_nodes, node, iter) {
                const arch_register_t *reg;
                reg = arch_get_irn_register(node);
                if (reg != NULL)
                        continue;

                assign_reg(block, node);
        }

        /* permutate values at end of predecessor blocks in case of phi-nodes */
        if (n_preds > 1) {
                int p;
                for (p = 0; p < n_preds; ++p) {
                        add_phi_permutations(block, p);
                }
        }

        /* assign instructions in the block */
        for (node = start; !sched_is_end(node); node = sched_next(node)) {
                int arity = get_irn_arity(node);
                int i;

                /* enforce use constraints */
                enforce_constraints(&live_nodes, node);

                /* exchange values to copied values where needed */
                for (i = 0; i < arity; ++i) {
                        ir_node      *op = get_irn_n(node, i);
                        assignment_t *assignment;

                        if (!arch_irn_consider_in_reg_alloc(cls, op))
                                continue;
                        assignment = get_current_assignment(op);
                        assert(assignment != NULL);
                        if (op != assignment->value) {
                                set_irn_n(node, i, assignment->value);
                        }
                }

                free_last_uses(&live_nodes, node);

                /* assign output registers */
                /* TODO: 2 phases: first: pre-assigned ones, 2nd real regs */
                if (get_irn_mode(node) == mode_T) {
                        const ir_edge_t *edge;
                        foreach_out_edge(node, edge) {
                                ir_node *proj = get_edge_src_irn(edge);
                                if (!arch_irn_consider_in_reg_alloc(cls, proj))
                                        continue;
                                assign_reg(block, proj);
                        }
                } else if (arch_irn_consider_in_reg_alloc(cls, node)) {
                        assign_reg(block, node);
                }
        }

        ir_nodeset_destroy(&live_nodes);
        assignments = NULL;

        block_info->processed = 1;

        /* if we have exactly 1 successor then we might be able to produce phi
           copies now */
        if (get_irn_n_edges_kind(block, EDGE_KIND_BLOCK) == 1) {
                const ir_edge_t *edge
                        = get_irn_out_edge_first_kind(block, EDGE_KIND_BLOCK);
                ir_node      *succ      = get_edge_src_irn(edge);
                int           p         = get_edge_src_pos(edge);
                block_info_t *succ_info = get_block_info(succ);

                if (succ_info->processed) {
                        add_phi_permutations(succ, p);
                }
        }
}

/**
 * Run the register allocator for the current register class.
 */
static void be_straight_alloc_cls(void)
{
        n_regs         = arch_register_class_n_regs(cls);
        lv             = be_assure_liveness(birg);
        be_liveness_assure_sets(lv);
        be_liveness_assure_chk(lv);

        assignments = NULL;

        ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_IRN_VISITED);
        inc_irg_visited(irg);

        DB((dbg, LEVEL_2, "=== Allocating registers of %s ===\n", cls->name));

        irg_block_walk_graph(irg, NULL, analyze_block, NULL);
        irg_block_walk_graph(irg, NULL, allocate_coalesce_block, NULL);

        ir_free_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_IRN_VISITED);
}

/**
 * Run the spiller on the current graph.
 */
static void spill(void)
{
        /* make sure all nodes show their real register pressure */
        BE_TIMER_PUSH(t_ra_constr);
        be_pre_spill_prepare_constr(birg, cls);
        BE_TIMER_POP(t_ra_constr);

        /* spill */
        BE_TIMER_PUSH(t_ra_spill);
        be_do_spill(birg, cls);
        BE_TIMER_POP(t_ra_spill);

        BE_TIMER_PUSH(t_ra_spill_apply);
        check_for_memory_operands(irg);
        BE_TIMER_POP(t_ra_spill_apply);
}

/**
 * The straight register allocator for a whole procedure.
 */
static void be_straight_alloc(be_irg_t *new_birg)
{
        const arch_env_t *arch_env = new_birg->main_env->arch_env;
        int   n_cls                = arch_env_get_n_reg_class(arch_env);
        int   c;

        obstack_init(&obst);

        birg      = new_birg;
        irg       = be_get_birg_irg(birg);
        execfreqs = birg->exec_freq;

        /* TODO: extract some of the stuff from bechordal allocator, like
         * statistics, time measurements, etc. and use them here too */

        for (c = 0; c < n_cls; ++c) {
                cls = arch_env_get_reg_class(arch_env, c);
                if (arch_register_class_flags(cls) & arch_register_class_flag_manual_ra)
                        continue;

                stat_ev_ctx_push_str("bestraight_cls", cls->name);

                n_regs      = cls->n_regs;
                ignore_regs = bitset_malloc(n_regs);
                be_put_ignore_regs(birg, cls, ignore_regs);

                spill();

                /* verify schedule and register pressure */
                BE_TIMER_PUSH(t_verify);
                if (birg->main_env->options->vrfy_option == BE_CH_VRFY_WARN) {
                        be_verify_schedule(birg);
                        be_verify_register_pressure(birg, cls, irg);
                } else if (birg->main_env->options->vrfy_option == BE_CH_VRFY_ASSERT) {
                        assert(be_verify_schedule(birg) && "Schedule verification failed");
                        assert(be_verify_register_pressure(birg, cls, irg)
                                && "Register pressure verification failed");
                }
                BE_TIMER_POP(t_verify);

                BE_TIMER_PUSH(t_ra_color);
                be_straight_alloc_cls();
                BE_TIMER_POP(t_ra_color);

                bitset_free(ignore_regs);

                /* TODO: dump intermediate results */

                stat_ev_ctx_pop("bestraight_cls");
        }

        obstack_free(&obst, NULL);
}

/**
 * Initializes this module.
 */
void be_init_straight_alloc(void)
{
        static be_ra_t be_ra_straight = {
                be_straight_alloc,
        };

        FIRM_DBG_REGISTER(dbg, "firm.be.straightalloc");

        be_register_allocator("straight", &be_ra_straight);
}

BE_REGISTER_MODULE_CONSTRUCTOR(be_init_straight_alloc);