[libfirm] / ir / be / bephicoal.c

/**
 * @author Daniel Grund
 * @date 04.01.2005
 */

#include <stdlib.h>

#include "obst.h"
#include "pset.h"
#include "bitset.h"
#include "debug.h"

#include "bechordal.h"
#include "belive.h"
#include "bera_t.h"
#include "bephicongr_t.h"
#include "bephicoal_t.h"

#define DEBUG_LVL SET_LEVEL_2

#define MAX_PHI_CLS_SIZE (1<<(sizeof(unsigned char)*8)) /* possible colors added should fit into unsigned char */
#define MAX_COLORS 16
#define CHANGE_IMPOSSIBLE -1
#define CHANGE_SAVE 1

#define DRYRUN 1
#define PERFORM 0

typedef struct _phi_unit_t {
        unsigned char count;
        unsigned char phi_count;

        /* 1 phi */
        ir_node **members;                      /**< [0] is the phi node. [1..count-1] the arguments of the phi not interfering with it */
        char *is_live_in;                       /**< [i]==1 means members[i] is live-in in (all of) its cf-pred-blocks of the phi node */
        int *colors;                            /**< [i] is the color to set for members[i]. [i] == NO_COLOR means dont change anything for members[i]*/
        int size;                                       /**< size of the max independent set of members. The set is markes by colors[i] != NO_COLOR */
        int changes;                            /**< number of re-assigned nodes belonging to phi-classes */
} phi_unit_t;


static firm_dbg_module_t *dbgphi = NULL;

/**
 * Contains ir_nodes of phi-classes whose colors were reassigned during coalescing.
 * So one can check not to switch them twice or more.
 */
static pset *pinned_nodes = NULL;

/**
 * Contains ir_nodes of phi-classes whose colors may change unlimited times.
 * These nodes are not optimizable, so there is no need to pin their color.
 */
static pset *free_nodes = NULL;


/* TODO: ask/check if additional ir_node-space is initialized with 0000 */
#define belongs_to_a_phi_class(n) (get_irn_phi_info(n)->phi)

#define is_color_free(bl,col) (!bitset_is_set(get_ra_block_info(bl)->used_colors, col))

/**
 * Set the color of node @p n to @p col, but acts
 * pinning aware.
 */
static INLINE void set_color(ir_node *n, int col) {
        assert(!pset_find_ptr(pinned_nodes, n));
        set_irn_color(n, col);
        if (belongs_to_a_phi_class(n) && !pset_find_ptr(free_nodes, n))
                pset_insert_ptr(pinned_nodes, n);
}

/**
 * Tries to set the color of @p n to @p col.
 * @param  n The node to set the color for
 * @param  col The color to set.
 * @param  dryrun If true no colors are actually set, only testing is performed.
 *                If false colors get set and it must be sure that no conflicts will occur.
 * @return If setting the color is impossible CHANGE_IMPOSSIBLE is returned
 *         else the number of nodes that need a (cascading) change is returned.
 */
static int color_irn(ir_node *n, int col, int dryrun) {
        ir_node *bl;
        int res = 0;
        DBG((dbgphi, LEVEL_2, "\t\t\t%n --> %d\n", n, col));
        assert(is_color(col));

        if (get_irn_color(n) == col) {
                DBG((dbgphi, LEVEL_2, "\t\t\t  Same\n"));
                return 0;
        }

        if (pset_find_ptr(pinned_nodes, n)) {
                DBG((dbgphi, LEVEL_2, "\t\t\t  Pinned\n"));
                if (!dryrun)
                        assert(0 && "No prior check with dryrun=1 or buggy");
                return CHANGE_IMPOSSIBLE;
        }

        bl = get_nodes_block(n);
        if (is_color_free(bl, col) && !is_live_out(bl, n)) {
                DBG((dbgphi, LEVEL_2, "\t\t\t  Free\n"));
                if (!dryrun)
                        set_color(n, col);
                return 1;
        }

        /* for now, in the aldi-version return impossible */
        DBG((dbgphi, LEVEL_2, "\t\t\t  Impossible\n"));
        return CHANGE_IMPOSSIBLE;

        return res;
}


/**
 * Tries to set as much members of a phi unit as possible to color @p col.
 */
static void try_colors(phi_unit_t *pu, int col, int b_size, int b_changes) {
        struct obstack ob;
        struct obstack ob_changes;
        int i, o, cand_size, total_changes, *changes;
        ir_node **cand, **mis;

        cand_size = 0;
        obstack_init(&ob);
        obstack_init(&ob_changes);

        /* first init pessimistically, so we can just return
         * if we see there wont be a better result */
        for (i = 0; i < pu->count; ++i)
                pu->colors[i] = NO_COLOR;
        pu->size = 0;
        pu->changes = 0;

        /* For all members check if color would be possible.
         * Does not check if color is possible in combination with
         * other members colors being set */
        total_changes = 0;
        for (i = 0; i < pu->count; ++i) {
                DBG((dbgphi, 1, "\t\t    Testing %n\n", pu->members[i]));
                int curr_changes = color_irn(pu->members[i], col, DRYRUN);
                if (curr_changes != CHANGE_IMPOSSIBLE) {
                        DBG((dbgphi, 1, "\t\t\tAdding to cand\n"));
                        obstack_ptr_grow(&ob, pu->members[i]);
                        obstack_grow(&ob_changes, &curr_changes, sizeof(curr_changes));
                        cand_size++;
                        total_changes += curr_changes;
                } else {
                        DBG((dbgphi, 1, "\t\t\tImpossible\n"));
                }
                /* if color is not possible for the phi node then exit (phi comes first)*/
                if (cand_size == 0)
                        goto ret;
        }
        cand = obstack_finish(&ob);
        changes = obstack_finish(&ob_changes);

        /* shortcut: if cand is worse than best the mis wont be better. */
        if (cand_size < b_size || (cand_size == b_size && total_changes >= b_changes))
                goto ret;

        /* now take the candidates cand and determine a max independent set
         * with respect to edges representing live range interference */
        /* TODO: make this 'un-greedy' */
        DBG((dbgphi, 1, "\t\t    Max indep set\n"));
        for (i = 0; i < cand_size; ++i) {
                int intf_det = 0;
                for (o = 0; o < pu->size; ++o) {
                        mis = (ir_node**) obstack_base(&ob);
                        if (values_interfere(cand[i], mis[o])) {
                                intf_det = 1;
                                break;
                        }
                }

                if (!intf_det) {
                        DBG((dbgphi, 1, "\t\t\tAdding to mis %n\n", cand[i]));
                        obstack_ptr_grow(&ob, cand[i]);
                        pu->size++;
                        pu->changes += changes[i];
                }
        }
        mis = obstack_finish(&ob);

        /* Now set the colors of all nodes in the mis to col.
         * - Each change taken alone is conflict free.
         * - If all members are not live-in in their cf-pred-blocks there will be no
         *   conflict applying all changes
         * - If there is a member, which is live-in in its cf-pred-block of the phi
         *   node, it is possible that all changes together will conflict.
         */
        for (i = 0; i < pu->count; ++i)
                for (o = 0; o < pu->size; ++o)
                        if (pu->members[i] == mis[o] && get_irn_color(pu->members[i]) != col)
                                pu->colors[i] = col;

ret:
        obstack_free(&ob_changes, NULL);
        obstack_free(&ob, NULL);
}


/**
 * Sets the colors of members[i] to colors[i] as far as possible.
 * Each single change must be conflict free (checked by try_colors).
 * In some cases not all colors can be set.
 */
static void set_colors(phi_unit_t *pu) {
        int i;
        int change_is_save, live_in_occured = 0;

        for (i = 0; i < pu->count; ++i)
                if (pu->colors[i] != NO_COLOR) {
                        if (pu->is_live_in[i])
                                live_in_occured = 1;

                        change_is_save = CHANGE_SAVE;
                        if (live_in_occured)
                                change_is_save = color_irn(pu->members[i], pu->colors[i], DRYRUN);

                        /* HINT: Dont change to == CHANGE_SAVE */
                        if (change_is_save != CHANGE_IMPOSSIBLE) {
                                DBG((dbgphi, 1, "\t\tSetting %n to %d\n", pu->members[i], pu->colors[i]));
                                color_irn(pu->members[i], pu->colors[i], PERFORM);
                        } else {
                                DBG((dbgphi, 1, "\t\tConflict due to a live-in: %n\n", pu->members[i]));
                        }
                }
}


/**
 * Tries to re-allocate colors of this phi-class, to achieve a lower number of
 * copies placed during phi destruction. Optimized version. Works only for
 * phi-classes/phi-units with exactly 1 phi node, which is the case for approx.
 * 80%.
 */
static void coalesce_1_phi(phi_unit_t *pu) {
        int *b_colors, b_size, b_changes, b_color;
        int i, col;

        /* init best search result */
        b_colors = malloc(pu->count * sizeof(*b_colors));
        for (i = 0; i < pu->count; ++i)
                b_colors[i] = NO_COLOR;
        b_size = 0;
        b_changes = 0;
        b_color = NO_COLOR;

        /* find optimum of all colors */
        for (col = MAX_COLORS-1; col >= 0; --col) {
                DBG((dbgphi, 1, "\tTrying color %d\n", col));
                try_colors(pu, col, b_size, b_changes);

                /* did we find a better max ind. set? */
                if (pu->size > b_size || (pu->size == b_size && pu->changes < b_changes)) {
                        b_size = pu->size;
                        b_changes = pu->changes;
                        b_color = col;
                        memcpy(b_colors, pu->colors, pu->count * sizeof(*b_colors));
                        DBG((dbgphi, 1, "\t!! Better size: %d  Changes: %d\n", b_size, b_changes));
                }

                /* shortcut: if all members can be colored we are content and doubt that
                 * reducing b_changes justifies all the further trying. */
                if (b_size == pu->count)
                        break;
        }

        /* now apply the found optimum */
        DBG((dbgphi, 1, "\tBest color: %d  Copies: %d/%d  Changes: %d\n", b_color, pu->count-b_size, pu->count, b_changes));
        pu->size = b_size;
        pu->changes = b_changes;
        memcpy(pu->colors, b_colors, pu->count * sizeof(*b_colors));
        set_colors(pu);

        free(b_colors);
}

/**
 * Tries to re-allocate colors of this phi-class, to achieve a lower number of
 * copies placed during phi destruction. General purpose version.
 */
static void coalesce_n_phi(phi_unit_t *pu) {
        DBG((dbgphi, 1, "\n"));
        /* TODO */
}

/**
 * Prepare a phi class for further processing as a phi unit.
 */
static phi_unit_t *new_phi_unit(pset *pc) {
        phi_unit_t *pu;
        ir_node *n, *phi = NULL;

        assert(pset_count(pc) <= MAX_PHI_CLS_SIZE && "Phi class too large!");

        pu = malloc(sizeof(*pu));
        pu->phi_count = 0;
        for (n = pset_first(pc); n; n = pset_next(pc))
                if (is_Phi(n)) {
                        phi = n;
                        pu->phi_count++;
                }

        if (pu->phi_count == 1) {
                ir_node **tmp, *phi_block;
                int i, max;
                struct obstack ob;

                obstack_init(&ob);

                /* build member set not containing phi interferers */
                DBG((dbgphi, 1, "Phi-1 class:\n"));
                pu->count = 1; /*for the phi*/
                for (n = pset_first(pc); n; n = pset_next(pc)) {
                        if (is_Phi(n))
                                continue;
                        if (!values_interfere(phi, n)) {
                                DBG((dbgphi, 1, "\tAdding to members: %n\n", n));
                                obstack_ptr_grow(&ob, n);
                                pu->count++;
                        } else {
                                DBG((dbgphi, 1, "\tPhi interferer: %n\n", n));
                                pset_insert_ptr(free_nodes, n);
                        }
                }
                tmp = obstack_finish(&ob);
                pu->members = malloc(pu->count * sizeof(*pu->members));
                pu->members[0] = phi;
                memcpy(&pu->members[1], tmp, (pu->count-1) * sizeof(*tmp));

                /* init of colors array */
                pu->colors = malloc(pu->count * sizeof(*pu->colors));

                /* live-in analysis */
                /* HINT: It is possible that a node occurs twice as arg of a phi,
                 * one time being live-in, and another time not being live-in.
                 */
                pu->is_live_in = calloc(pu->count, sizeof(*pu->is_live_in));
                phi_block = get_nodes_block(phi);
                for (i = 0, max = get_irn_arity(phi); i < max; ++i) {
                        int midx, o;
                ir_node *arg, *block_ith_pred;

                arg = get_irn_n(phi, i);
                        block_ith_pred = get_nodes_block(get_irn_n(phi_block, i));

                        /* find the arg in the members array */
                        midx = -1;
                        for (o = 0; o < pu->count; ++o)
                                if (pu->members[o] == arg) {
                                        midx = o;
                                        break;
                                }
                        if (midx == -1)
                                continue;

                        if (is_live_in(block_ith_pred, arg)) {
                                pu->is_live_in[midx] |= 1;
                                DBG((dbgphi, 1, "\t%n is live-in in %n\n", arg, block_ith_pred));
                        }
                }

                obstack_free(&ob, NULL);
        } else {
                DBG((dbgphi, 1, "Phi-n class:\n"));
                /* TODO */
        }

        DBG((dbgphi, 1, "\n"));
        return pu;
}

/**
 * Deletes a phi unit
 */
static void free_phi_unit(phi_unit_t *pu) {
        DBG((dbgphi, 1, "\n"));
        if (pu->phi_count == 1) {
                free(pu->members);
                free(pu->colors);
                free(pu->is_live_in);
        } else {
                /* TODO */
        }
        free(pu);
}


void be_phi_coalesce(pset *all_phi_classes) {
        pset *pc;

        pinned_nodes = pset_new_ptr(256);
        free_nodes = pset_new_ptr(64);

        for (pc = pset_first(all_phi_classes); pc; pc = pset_next(all_phi_classes)) {
                phi_unit_t *pu = new_phi_unit(pc);
                if (pu->phi_count == 1)
                        coalesce_1_phi(pu);
                else
                        coalesce_n_phi(pu);
                free_phi_unit(pu);
        }

        del_pset(free_nodes);
        del_pset(pinned_nodes);
}


void be_phi_coal_init(void) {
        dbgphi = firm_dbg_register("Phi coalescing");
        firm_dbg_set_mask(dbgphi, DEBUG_LVL);
}