[libfirm] / ir / be / becopyheur.c

/**
 * Heuristic for minimizing copies using a queue which holds 'qnodes' not yet
 * examined. A qnode has a 'target color', nodes out of the opt unit and
 * a 'conflict graph'. A 'max indep set' is determined form these. We try to
 * color this mis using a color-exchanging mechanism. Occuring conflicts are
 * modeled with 'conflict edges' and the qnode is reinserted in the queue. The
 * first qnode colored without conflicts is the best one.
 * @author Daniel Grund
 * @date 12.04.2005
 */

#include "becopyopt.h"
#include "becopystat.h"

#define DEBUG_LVL 0 //SET_LEVEL_1
static firm_dbg_module_t *dbg = NULL;

#define SLOTS_PINNED_GLOBAL 256
#define SLOTS_CONFLICTS 8
#define SLOTS_CHANGED_NODES 32

#define MIN(a,b) ((a<b)?a:b)
#define list_entry_queue(lh) list_entry(lh, qnode_t, queue)
#define HASH_CONFLICT(c) (HASH_PTR(c.n1) ^ HASH_PTR(c.n2))

/**
 * Modeling additional conflicts between nodes. NOT live range interference
 */
typedef struct _conflict_t {
        const ir_node *n1, *n2;
} conflict_t;

/**
 * If an irn is changed, the changes first get stored in a node_stat_t,
 * to allow undo of changes (=drop new data) in case of conflicts.
 */
typedef struct _node_stat_t {
        const ir_node *irn;
        int new_color;
        int pinned_local :1;
} node_stat_t;

/**
 * Represents a node in the optimization queue.
 */
typedef struct _qnode_t {
        struct list_head queue;         /**< chaining of unit_t->queue */
        const unit_t *ou;                       /**< the opt unit this qnode belongs to */
        int color;                                      /**< target color */
        set *conflicts;                         /**< contains conflict_t's. All internal conflicts */
        int mis_size;                           /**< number of nodes in the mis. */
        const ir_node **mis;            /**< the nodes of unit_t->nodes[] beeing part of the max idependent set */
        set *changed_nodes;                     /**< contains node_stat_t's. */
} qnode_t;

pset *pinned_global;                    /**< optimized nodes should not be altered any more */

static int set_cmp_conflict_t(const void *x, const void *y, size_t size) {
        const conflict_t *xx = x;
        const conflict_t *yy = y;
        return ! (xx->n1 == yy->n1 && xx->n2 == yy->n2);
}

/**
 * If a local pinned conflict occurs, a new edge in the conflict graph is added.
 * The next maximum independent set build, will regard it.
 */
static INLINE void qnode_add_conflict(const qnode_t *qn, const ir_node *n1, const ir_node *n2) {
        conflict_t c;
        DBG((dbg, LEVEL_4, "\t      %n -- %n\n", n1, n2));

        if ((int)n1 < (int)n2) {
                c.n1 = n1;
                c.n2 = n2;
        } else {
                c.n1 = n2;
                c.n2 = n1;
        }
        set_insert(qn->conflicts, &c, sizeof(c), HASH_CONFLICT(c));
}

/**
 * Checks if two nodes are in a conflict.
 */
static INLINE int qnode_are_conflicting(const qnode_t *qn, const ir_node *n1, const ir_node *n2) {
        conflict_t c;
        /* search for live range interference */
        if (n1!=n2 && values_interfere(n1, n2))
                return 1;
        /* search for recoloring conflicts */
        if ((int)n1 < (int)n2) {
                c.n1 = n1;
                c.n2 = n2;
        } else {
                c.n1 = n2;
                c.n2 = n1;
        }
        return (int) set_find(qn->conflicts, &c, sizeof(c), HASH_CONFLICT(c));
}

static int set_cmp_node_stat_t(const void *x, const void *y, size_t size) {
        return ((node_stat_t *)x)->irn != ((node_stat_t *)y)->irn;
}

/**
 * Finds a node status entry of a node if existent. Otherwise return NULL
 */
static INLINE node_stat_t *qnode_find_node(const qnode_t *qn, const ir_node *irn) {
        node_stat_t find;
        find.irn = irn;
        return set_find(qn->changed_nodes, &find, sizeof(find), HASH_PTR(irn));
}

/**
 * Finds a node status entry of a node if existent. Otherwise it will return
 * an initialized new entry for this node.
 */
static INLINE node_stat_t *qnode_find_or_insert_node(const qnode_t *qn, const ir_node *irn) {
        node_stat_t find;
        find.irn = irn;
        find.new_color = NO_COLOR;
        find.pinned_local = 0;
        return set_insert(qn->changed_nodes, &find, sizeof(find), HASH_PTR(irn));
}

/**
 * Returns the virtual color of a node if set before, else returns the real color.
 */
static INLINE int qnode_get_new_color(const qnode_t *qn, const ir_node *irn) {
        node_stat_t *found = qnode_find_node(qn, irn);
        if (found)
                return found->new_color;
        else
                return get_irn_color(irn);
}

/**
 * Sets the virtual color of a node.
 */
static INLINE void qnode_set_new_color(const qnode_t *qn, const ir_node *irn, int color) {
        node_stat_t *found = qnode_find_or_insert_node(qn, irn);
        found->new_color = color;
}

/**
 * Checks if a node is local pinned. A node is local pinned, iff it belongs
 * to the same optimization unit and has been optimized before the current
 * processed node.
 */
static INLINE int qnode_is_pinned_local(const qnode_t *qn, const ir_node *irn) {
        node_stat_t *found = qnode_find_node(qn, irn);
        if (found)
                return found->pinned_local;
        else
                return 0;
}

/**
 * Local-pins a node, so optimizations of further nodes of the same opt unit
 * can handle situations in which a color change would undo prior optimizations.
 */
static INLINE void qnode_pin_local(const qnode_t *qn, const ir_node *irn) {
        node_stat_t *found = qnode_find_or_insert_node(qn, irn);
        found->pinned_local = 1;
}

/**
 * Possible return values of qnode_color_irn()
 */
#define CHANGE_SAVE NULL
#define CHANGE_IMPOSSIBLE (ir_node *)1
#define is_conflicting_node(n) (((int)n) > 1)

/**
 * Performs virtual re-coloring of node @p n to color @p col. Virtual colors of
 * other nodes are changed too, as required to preserve correctness. Function is
 * aware of local and global pinning. Recursive.
 * @param  irn The node to set the color for
 * @param  col The color to set
 * @param  trigger The irn that caused the wish to change the color of the irn
 * @return CHANGE_SAVE iff setting the color is possible, with all transiteve effects.
 *         CHANGE_IMPOSSIBLE iff conflicts with reg-constraintsis occured.
 *         Else the first conflicting ir_node encountered is returned.
 *
 * ASSUMPTION: Assumes that a life range of a single value can't be spilt into
 *                         several smaller intervals where other values can live in between.
 *             This should be true in SSA.
 */
static const ir_node *qnode_color_irn(const qnode_t *qn, const ir_node *irn, int col, const ir_node *trigger) {
        const ir_node *res;
        struct obstack confl_ob;
        ir_node **confl, *cn;
        int i, irn_col;

        DBG((dbg, LEVEL_3, "\t      %n \tcaused col(%n) \t%2d --> %2d\n", trigger, irn, qnode_get_new_color(qn, irn), col));
        obstack_init(&confl_ob);
        irn_col = qnode_get_new_color(qn, irn);

        if (irn_col == col)
                goto ret_save;
        if (pset_find_ptr(pinned_global, irn) || qnode_is_pinned_local(qn, irn)) {
                res = irn;
                goto ret_confl;
        }
        if (!qn->ou->co->isa->is_reg_allocatable(irn, arch_register_for_index(qn->ou->co->cls, col)))
                goto ret_imposs;

        /* get all nodes which would conflict with this change */
        {
                struct obstack q;
                int in, out;
                ir_node *irn_bl;

                irn_bl = get_nodes_block(irn);

                /* first check for a conflicting node which is 'living in' the irns block */
                {
                        ir_node *n;
                        pset *live_ins = get_live_in(irn_bl);
                        for (n = pset_first(live_ins); n; n = pset_next(live_ins))
                                if (is_allocatable_irn(n) && n != trigger && qnode_get_new_color(qn, n) == col && values_interfere(irn, n)) {
                                        DBG((dbg, LEVEL_4, "\t        %n\ttroubles\n", n));
                                        obstack_ptr_grow(&confl_ob, n);
                                        pset_break(live_ins);
                                        break;
                                }
                }

                /* setup the queue of blocks. */
                obstack_init(&q);
                obstack_ptr_grow(&q, irn_bl);
                in = 1;
                out = 0;

                /* process the queue. The code below checks for every block dominated
                 * by the irns one, and in which the irn is live, if there are
                 * conflicting nodes */
                while (out < in) {
                        ir_node *curr_bl, *sub_bl;
                        int i, max;

                        curr_bl = ((ir_node **)obstack_base(&q))[out++];

                        /* Add to the result all nodes in the block, which have
                         * the target color and interfere with the irn */
                        for (i = 0, max = get_irn_n_outs(curr_bl); i < max; ++i) {
                                ir_node *n = get_irn_out(curr_bl, i);
                                if (is_allocatable_irn(n) && n != trigger && qnode_get_new_color(qn, n) == col && values_interfere(irn, n)) {
                                        DBG((dbg, LEVEL_4, "\t        %n\ttroubles\n", n));
                                        obstack_ptr_grow(&confl_ob, n);
                                }
                        }

                        /* If irn lives out check i-dominated blocks where the irn lives in */
                        /* Fill the queue */
                        if (is_live_out(curr_bl, irn)) {
                                dominates_for_each(curr_bl, sub_bl)
                                        if (is_live_in(sub_bl, irn)) {
                                                obstack_ptr_grow(&q, sub_bl);
                                                in++;
                                        }
                        }
                }
                obstack_free(&q, NULL);
                obstack_ptr_grow(&confl_ob, NULL);
                confl = (ir_node **) obstack_finish(&confl_ob);
        }

        /* process all nodes which would conflict with this change */
        for (i = 0, cn = confl[0]; cn; cn = confl[++i]) {
                const ir_node *sub_res;

                /* try to color the conflicting node cn with the color of the irn itself */
                sub_res = qnode_color_irn(qn, cn, irn_col, irn);
                if (sub_res != CHANGE_SAVE) {
                        res = sub_res;
                        goto ret_confl;
                }
        }
        /* if we arrive here all sub changes can be applied, so it's save to change this irn */

ret_save:
        DBG((dbg, LEVEL_3, "\t      %n save\n", irn));
        obstack_free(&confl_ob, NULL);
        qnode_set_new_color(qn, irn, col);
        return CHANGE_SAVE;

ret_imposs:
        DBG((dbg, LEVEL_3, "\t      %n impossible\n", irn));
        obstack_free(&confl_ob, NULL);
        return CHANGE_IMPOSSIBLE;

ret_confl:
        DBG((dbg, LEVEL_3, "\t      %n conflicting\n", irn));
        obstack_free(&confl_ob, NULL);
        return res;
}

/**
 * Tries to set the colors for all members of this queue node;
 * to the target color qn->color
 * @returns 1 iff all members colors could be set
 *          0 else
 */
static int qnode_try_color(const qnode_t *qn) {
        int i;
        for (i=0; i<qn->mis_size; ++i) {
                const ir_node *test_node, *confl_node;

                test_node = qn->mis[i];
                DBG((dbg, LEVEL_3, "\t    Testing %n\n", test_node));
                confl_node = qnode_color_irn(qn, test_node, qn->color, test_node);

                if (confl_node == CHANGE_SAVE) {
                        DBG((dbg, LEVEL_3, "\t    Save --> pin local\n"));
                        qnode_pin_local(qn, test_node);
                } else if (confl_node == CHANGE_IMPOSSIBLE) {
                        DBG((dbg, LEVEL_3, "\t    Impossible --> remove from qnode\n"));
                        qnode_add_conflict(qn, test_node, test_node);
                } else {
                        if (qnode_is_pinned_local(qn, confl_node)) {
                                /* changing test_node would change back a node of current ou */
                                DBG((dbg, LEVEL_3, "\t    Conflicting local --> add conflict\n"));
                                qnode_add_conflict(qn, confl_node, test_node);
                        }
                        if (pset_find_ptr(pinned_global, confl_node)) {
                                /* changing test_node would change back a node of a prior ou */
                                DBG((dbg, LEVEL_3, "\t    Conflicting global --> remove from qnode\n"));
                                qnode_add_conflict(qn, test_node, test_node);
                        }
                }

                if (confl_node != CHANGE_SAVE)
                        return 0;
        }
        return 1;
}

/**
 * Determines a maximum independent set with respect to the interference and
 * conflict edges of all nodes in a qnode.
 */
static INLINE void qnode_max_ind_set(qnode_t *qn, const unit_t *ou) {
        int all_size, curr_size, i, o;
        int *which;
        const ir_node **curr, **all = alloca(ou->node_count * sizeof(*all));

        /* all contains all nodes not removed in this qn */
        all_size = 0;
        for (i=0; i<ou->node_count; ++i)
                if (!qnode_are_conflicting(qn, ou->nodes[i], ou->nodes[i]))
                        all[all_size++] = ou->nodes[i];

        /* which[i] says which element to take out of all[] and put into curr[i] */
        which = alloca(all_size*sizeof(*which));
        for (curr_size=0; curr_size<all_size; ++curr_size)
                which[curr_size] = curr_size;

        /* stores the currently examined set */
        curr = alloca(all_size*sizeof(*curr));

        while (1) { /* this loop will terminate because at least a single node'll be a max indep. set */
                /* build current set */
                for (i=0; i<curr_size; ++i)
                        curr[i] = all[which[all_size-curr_size+i]];

                /* check current set */
                for (i=0; i<curr_size; ++i)
                        for (o=i+1; o<curr_size; ++o)
                                if (qnode_are_conflicting(qn, curr[i], curr[o]))
                                        goto conflict_found;

                /* We had no conflict. This is the max indep. set */
                qn->mis_size = curr_size;
                for (i=0; i<curr_size; ++i)
                        qn->mis[i] = curr[i];
                return;

conflict_found:
                /* We had a conflict. Generate next set */
                if (which[all_size-curr_size+1] == all_size-curr_size+1) {
                        curr_size--;
                        for (i=0; i<curr_size; ++i)
                                which[all_size-curr_size+i] = i;
                } else {
                        int redo = 1;
                        while (redo) {
                                int pos = all_size;
                                do {
                                        pos--;
                                } while (!(which[pos] = (which[pos]+1) % all_size));

                                for (i=pos+1; i<all_size; ++i)
                                        which[i] = MIN(which[i-1]+1, all_size-1);

                                redo = 0;
                                for (i=all_size-curr_size; i<all_size-1; ++i)
                                        if (which[i]>=which[i+1]) {
                                                redo = 1;
                                                break;
                                        }
                        }
                }
        }
}

/**
 * Creates a new qnode
 */
static INLINE qnode_t *new_qnode(const unit_t *ou, int color) {
        qnode_t *qn = malloc(sizeof(*qn));
        qn->ou = ou;
        qn->color = color;
        qn->mis = malloc(ou->node_count * sizeof(*qn->mis));
        qn->conflicts = new_set(set_cmp_conflict_t, SLOTS_CONFLICTS);
        qn->changed_nodes = new_set(set_cmp_node_stat_t, SLOTS_CHANGED_NODES);
        return qn;
}

/**
 * Frees space used by a queue node
 */
static INLINE void free_qnode(qnode_t *qn) {
        del_set(qn->conflicts);
        del_set(qn->changed_nodes);
        free(qn->mis);
        free(qn);
}

/**
 * Inserts a qnode in the sorted queue of the outimization unit. Queue is
 * ordered by field 'size' (the size of the mis) in decreasing order.
 */
static INLINE void ou_insert_qnode(unit_t *ou, qnode_t *qn) {
        struct list_head *lh;

        if (qnode_are_conflicting(qn, ou->nodes[0], ou->nodes[0])) {
                /* root node is not in qnode */
                free_qnode(qn);
                return;
        }

        qnode_max_ind_set(qn, ou);

        /* set ou->mis_size for lower bound compution */
        if (ou->mis_size < qn->mis_size)
                ou->mis_size = qn->mis_size;

        /* do the insertion */
        DBG((dbg, LEVEL_4, "\t  Insert qnode color %d with size %d\n", qn->color, qn->mis_size));
        lh = &ou->queue;
        while (lh->next != &ou->queue) {
                qnode_t *curr = list_entry_queue(lh->next);
                if (curr->mis_size <= qn->mis_size)
                        break;
                lh = lh->next;
        }
        list_add(&qn->queue, lh);
}

/**
 * Tries to re-allocate colors of nodes in this opt unit, to achieve a lower
 * number of copy instructions placed during SSA-destruction and lowering.
 * Works only for opt units with exactly 1 root node, which is the
 * case for approximately 80% of all phi classes and all register constrained
 * nodes. (All other phi classes are reduced to this case.)
 */
static void ou_optimize(unit_t *ou) {
        int i;
        qnode_t *curr, *tmp;
        bitset_t *pos_regs = bitset_alloca(ou->co->cls->n_regs);

        DBG((dbg, LEVEL_1, "\tOptimizing unit:\n"));
        for (i=0; i<ou->node_count; ++i)
                DBG((dbg, LEVEL_1, "\t %n\n", ou->nodes[i]));

        /* init queue */
        INIT_LIST_HEAD(&ou->queue);
        ou->co->isa->get_allocatable_regs(ou->nodes[0], ou->co->cls, pos_regs);
        bitset_foreach(pos_regs, i)
                ou_insert_qnode(ou, new_qnode(ou, i));

        /* search best */
        while (!list_empty(&ou->queue)) {
                /* get head of queue */
                curr = list_entry_queue(ou->queue.next);
                list_del(&curr->queue);
                DBG((dbg, LEVEL_2, "\t  Examine qnode color %d with size %d\n", curr->color, curr->mis_size));

                /* try */
                if (qnode_try_color(curr))
                        break;
                /* no success, so re-insert */
                del_set(curr->changed_nodes);
                curr->changed_nodes = new_set(set_cmp_node_stat_t, SLOTS_CHANGED_NODES);
                ou_insert_qnode(ou, curr);
        }

        /* apply the best found qnode */
        if (curr->mis_size >= 2) {
                DBG((dbg, LEVEL_1, "\t  Best color: %d  Copies: %d/%d\n", curr->color, ou->interf+ou->node_count-curr->mis_size, ou->interf+ou->node_count-1));
                /* globally pin root and eventually others */
                pset_insert_ptr(pinned_global, ou->nodes[0]);
                for (i=1; i<ou->node_count; ++i) {
                        const ir_node *irn = ou->nodes[i];
                        int nc = qnode_get_new_color(curr, irn);
                        if (nc != NO_COLOR && nc == qnode_get_new_color(curr, ou->nodes[0]))
                                pset_insert_ptr(pinned_global, irn);
                }

                /* set color of all changed nodes */
                node_stat_t *ns;
                for (ns = set_first(curr->changed_nodes); ns; ns = set_next(curr->changed_nodes)) {
                        /* NO_COLOR is possible, if we had an undo */
                        if (ns->new_color != NO_COLOR) {
                                DBG((dbg, LEVEL_2, "\t    color(%n) := %d\n", ns->irn, ns->new_color));
                                set_irn_color(ns->irn, ns->new_color);
                        }
                }
        }

        /* free best qnode (curr) and queue */
        free_qnode(curr);
        list_for_each_entry_safe(qnode_t, curr, tmp, &ou->queue, queue)
                free_qnode(curr);
}

void co_heur_opt(copy_opt_t *co) {
        unit_t *curr;
        dbg = firm_dbg_register("ir.be.copyoptheur");
        firm_dbg_set_mask(dbg, DEBUG_LVL);
        if (!strcmp(co->name, DEBUG_IRG))
                firm_dbg_set_mask(dbg, -1);

        pinned_global = pset_new_ptr(SLOTS_PINNED_GLOBAL);
        list_for_each_entry(unit_t, curr, &co->units, units)
                if (curr->node_count > 1)
                        ou_optimize(curr);

        del_pset(pinned_global);
}