[libfirm] / ir / be / bessaconstr.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       SSA construction for a set of nodes
 * @author      Sebastian Hack, Daniel Grund, Matthias Braun, Christian Wuerdig
 * @date        04.05.2005
 * @version     $Id$
 *
 * The problem: Given a value and a set of "copies" that are known to
 * represent the same abstract value, rewire all usages of the original value
 * to their closest copy while introducing phis as necessary.
 *
 * Algorithm: Mark all blocks in the iterated dominance frontiers of the value
 * and it's copies. Link the copies ordered by dominance to the blocks.  The
 * we search for each use all all definitions in the current block, if none is
 * found, then we search one in the immediate dominator. If we are in a block
 * of the dominance frontier, create a phi and search do the same search for
 * the phi arguments.
 *
 * A copy in this context means, that you want to introduce several new
 * abstract values (in Firm: nodes) for which you know, that they
 * represent the same concrete value. This is the case if you
 * - copy
 * - spill and reload
 * - re-materialize
 * a value.
 *
 * This function reroutes all uses of the original value to the copies in the
 * corresponding dominance subtrees and creates Phi functions where necessary.
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "bessaconstr.h"
#include "bemodule.h"
#include "besched_t.h"
#include "beintlive_t.h"
#include "beirg_t.h"
#include "be_t.h"

#include "debug.h"
#include "error.h"
#include "pdeq.h"
#include "array.h"
#include "irdom.h"

#include "ircons.h"
#include "iredges_t.h"

DEBUG_ONLY(static firm_dbg_module_t *dbg = NULL;)

static INLINE int is_inside(unsigned what, unsigned low, unsigned hi)
{
        return what - low < hi;
}

/**
 * Calculates the iterated dominance frontier of a set of blocks. Marks the
 * blocks as visited. Sets the link fields of the blocks in the dominance
 * frontier to the block itself.
 */
static
void mark_iterated_dominance_frontiers(const be_ssa_construction_env_t *env)
{
        stat_ev_cnt_decl(blocks);
        DBG((dbg, LEVEL_3, "Dominance Frontier:"));
        stat_ev_tim_push();
        while (!pdeq_empty(env->worklist)) {
                int i;
                ir_node *block = waitq_get(env->worklist);
                ir_node **domfront = be_get_dominance_frontier(env->domfronts, block);
                int domfront_len = ARR_LEN(domfront);

                for (i = 0; i < domfront_len; ++i) {
                        ir_node *y = domfront[i];
                        if (Block_block_visited(y))
                                continue;

                        /*
                         * It makes no sense to add phi-functions to blocks
                         * that are not dominated by any definition;
                         * all uses are dominated, hence the paths reaching the uses
                         * have to stay in the dominance subtrees of the given definitions.
                         */

                        if (!is_inside(get_Block_dom_tree_pre_num(y), env->min_dom, env->max_dom))
                                continue;

                        if (!irn_visited(y)) {
                                set_irn_link(y, NULL);
                                waitq_put(env->worklist, y);
                        }

                        DBG((dbg, LEVEL_3, " %+F", y));
                        mark_Block_block_visited(y);
                        stat_ev_cnt_inc(blocks);
                }
        }
        stat_ev_tim_pop("bessaconstr_idf_time");
        stat_ev_cnt_done(blocks, "bessaconstr_idf_blocks");
        DBG((dbg, LEVEL_3, "\n"));
}

static
ir_node *search_def_end_of_block(be_ssa_construction_env_t *env,
                                 ir_node *block);

static
ir_node *create_phi(be_ssa_construction_env_t *env, ir_node *block,
                    ir_node *link_with)
{
        int i, n_preds = get_Block_n_cfgpreds(block);
        ir_graph *irg = get_irn_irg(block);
        ir_node *phi;
        ir_node **ins = alloca(n_preds * sizeof(ins[0]));

        assert(n_preds > 1);

        for(i = 0; i < n_preds; ++i) {
                ins[i] = new_r_Unknown(irg, env->mode);
        }
        phi = new_r_Phi(irg, block, n_preds, ins, env->mode);
        if(env->new_phis != NULL) {
                ARR_APP1(ir_node*, env->new_phis, phi);
        }

        if(env->mode != mode_M) {
                sched_add_after(block, phi);
        }

        DBG((dbg, LEVEL_2, "\tcreating phi %+F in %+F\n", phi, block));
        set_irn_link(link_with, phi);
        mark_irn_visited(block);

        for(i = 0; i < n_preds; ++i) {
                ir_node *pred_block = get_Block_cfgpred_block(block, i);
                ir_node *pred_def   = search_def_end_of_block(env, pred_block);

                set_irn_n(phi, i, pred_def);
        }

        return phi;
}

static
ir_node *get_def_at_idom(be_ssa_construction_env_t *env, ir_node *block)
{
        ir_node *dom = get_Block_idom(block);
        assert(dom != NULL);
        return search_def_end_of_block(env, dom);
}

static
ir_node *search_def_end_of_block(be_ssa_construction_env_t *env, ir_node *block)
{
        if(irn_visited(block)) {
                assert(get_irn_link(block) != NULL);
                return get_irn_link(block);
        } else if(Block_block_visited(block)) {
                return create_phi(env, block, block);
        } else {
                ir_node *def = get_def_at_idom(env, block);
                mark_irn_visited(block);
                set_irn_link(block, def);
                return def;
        }
}

static
ir_node *search_def(be_ssa_construction_env_t *env, ir_node *at)
{
        ir_node *block = get_nodes_block(at);
        ir_node *node;
        ir_node *def;

        DBG((dbg, LEVEL_3, "\t...searching def at %+F\n", at));

        /* no defs in the current block we can do the normal searching */
        if(!irn_visited(block) && !Block_block_visited(block)) {
                DBG((dbg, LEVEL_3, "\t...continue at idom\n"));
                return get_def_at_idom(env, block);
        }

        /* there are defs in the current block, walk the linked list to find
           the one immediately dominating us
         */
        node = block;
        def  = get_irn_link(node);
        while(def != NULL) {
                if(!value_dominates(at, def)) {
                        DBG((dbg, LEVEL_3, "\t...found dominating def %+F\n", def));
                        return def;
                }

                node = def;
                def  = get_irn_link(node);
        }

        /* block in dominance frontier? create a phi then */
        if(Block_block_visited(block)) {
                DBG((dbg, LEVEL_3, "\t...create phi at block %+F\n", block));
                assert(!is_Phi(node));
                return create_phi(env, block, node);
        }

        DBG((dbg, LEVEL_3, "\t...continue at idom (after checking block)\n"));
        return get_def_at_idom(env, block);
}

static
void update_domzone(be_ssa_construction_env_t *env, const ir_node *bl)
{
        int start = get_Block_dom_tree_pre_num(bl);
        int end   = get_Block_dom_max_subtree_pre_num(bl) + 1;

        env->min_dom = MIN(env->min_dom, start);
        env->max_dom = MAX(env->max_dom, end);
}

/**
 * Adds a definition into the link field of the block. The definitions are
 * sorted by dominance. A non-visited block means no definition has been
 * inserted yet.
 */
static
void introduce_def_at_block(ir_node *block, ir_node *def)
{
        if(irn_visited(block)) {
                ir_node *node = block;
                ir_node *current_def;

                while(1) {
                        current_def = get_irn_link(node);
                        if(current_def == def) {
                                /* already in block */
                                return;
                        }
                        if(current_def == NULL)
                                break;
                        if(value_dominates(current_def, def))
                                break;
                        node = current_def;
                }

                set_irn_link(node, def);
                set_irn_link(def, current_def);
        } else {
                set_irn_link(block, def);
                set_irn_link(def, NULL);
                mark_irn_visited(block);
        }
}

void be_ssa_construction_init(be_ssa_construction_env_t *env, be_irg_t *birg)
{
        ir_graph *irg = be_get_birg_irg(birg);
        ir_node *sb   = get_irg_start_block(irg);
        int n_blocks  = get_Block_dom_max_subtree_pre_num(sb);

        stat_ev_ctx_push_fobj("bessaconstr", irg);
        stat_ev_tim_push();

        (void) n_blocks;
        stat_ev_dbl("bessaconstr_n_blocks", n_blocks);

        memset(env, 0, sizeof(env[0]));
        be_assure_dom_front(birg);

        env->irg       = irg;
        env->domfronts = be_get_birg_dom_front(birg);
        env->new_phis  = NEW_ARR_F(ir_node*, 0);
        env->worklist  = new_waitq();
        env->min_dom   = INT_MAX;
        env->max_dom   = 0;

        set_using_visited(irg);
        set_using_block_visited(irg);
        set_using_irn_link(irg);

        /* we use the visited flag to indicate blocks in the dominance frontier
         * and blocks that already have the relevant value at the end calculated */
        inc_irg_visited(irg);
        /* We use the block visited flag to indicate blocks in the dominance
         * frontier of some values (and this potentially needing phis) */
        inc_irg_block_visited(irg);
}

void be_ssa_construction_destroy(be_ssa_construction_env_t *env)
{
        stat_ev_int("bessaconstr_phis", ARR_LEN(env->new_phis));
        del_waitq(env->worklist);
        DEL_ARR_F(env->new_phis);

        clear_using_visited(env->irg);
        clear_using_block_visited(env->irg);
        clear_using_irn_link(env->irg);

        stat_ev_tim_pop("bessaconstr_total_time");
        stat_ev_ctx_pop("bessaconstr");
}

void be_ssa_construction_add_copy(be_ssa_construction_env_t *env,
                                  ir_node *copy)
{
        ir_node *block;

        assert(env->iterated_domfront_calculated == 0);

        if(env->mode == NULL) {
                env->mode = get_irn_mode(copy);
        } else {
                assert(env->mode == get_irn_mode(copy));
        }

        block = get_nodes_block(copy);

        if(!irn_visited(block)) {
                waitq_put(env->worklist, block);
        }
        introduce_def_at_block(block, copy);
        update_domzone(env, block);
}

void be_ssa_construction_add_copies(be_ssa_construction_env_t *env,
                                    ir_node **copies, size_t copies_len)
{
        size_t i;

        assert(env->iterated_domfront_calculated == 0);

        if(env->mode == NULL) {
                env->mode = get_irn_mode(copies[0]);
        }

        for(i = 0; i < copies_len; ++i) {
                ir_node *copy = copies[i];
                ir_node *block = get_nodes_block(copy);

                assert(env->mode == get_irn_mode(copy));
                if(!irn_visited(block)) {
                        waitq_put(env->worklist, block);
                }
                introduce_def_at_block(block, copy);
                update_domzone(env, block);
        }
}

void be_ssa_construction_set_ignore_uses(be_ssa_construction_env_t *env,
                                         const ir_nodeset_t *ignore_uses)
{
        env->ignore_uses = ignore_uses;
}

ir_node **be_ssa_construction_get_new_phis(be_ssa_construction_env_t *env)
{
        return env->new_phis;
}

void be_ssa_construction_fix_users_array(be_ssa_construction_env_t *env,
                                         ir_node **nodes, size_t nodes_len)
{
        stat_ev_cnt_decl(uses);
        const ir_edge_t *edge, *next;
        size_t i;

        BE_TIMER_PUSH(t_ssa_constr);

        if(!env->iterated_domfront_calculated) {
                mark_iterated_dominance_frontiers(env);
                env->iterated_domfront_calculated = 1;
        }

        stat_ev_int("bessaconstr_domzone", env->max_dom - env->min_dom);
        stat_ev_tim_push();
        for(i = 0; i < nodes_len; ++i) {
                ir_node *value = nodes[i];

                /*
                 * Search the valid def for each use and set it.
                 */
                foreach_out_edge_safe(value, edge, next) {
                        ir_node *use = get_edge_src_irn(edge);
                        ir_node *at  = use;
                        int pos      = get_edge_src_pos(edge);
                        ir_node *def;

                        if(env->ignore_uses != NULL     &&
                           ir_nodeset_contains(env->ignore_uses, use))
                                continue;
                        if(is_Anchor(use))
                                continue;

                        if(is_Phi(use)) {
                                ir_node *block = get_nodes_block(use);
                                ir_node *predblock = get_Block_cfgpred_block(block, pos);
                                at = sched_last(predblock);
                        }

                        def = search_def(env, at);

                        if(def == NULL) {
                                panic("no definition found for %+F at position %d\n", use, pos);
                        }

                        DBG((dbg, LEVEL_2, "\t%+F(%d) -> %+F\n", use, pos, def));
                        set_irn_n(use, pos, def);
                        stat_ev_cnt_inc(uses);
                }
        }
        BE_TIMER_POP(t_ssa_constr);

        stat_ev_tim_pop("bessaconstr_fix_time");
        stat_ev_cnt_done(uses, "bessaconstr_uses");
}

void be_ssa_construction_fix_users(be_ssa_construction_env_t *env, ir_node *value)
{
        be_ssa_construction_fix_users_array(env, &value, 1);
}


void be_ssa_construction_update_liveness_phis(be_ssa_construction_env_t *env,
                                              be_lv_t *lv)
{
        int i, n;

        BE_TIMER_PUSH(t_ssa_constr);

        n = ARR_LEN(env->new_phis);
        for(i = 0; i < n; ++i) {
                ir_node *phi = env->new_phis[i];
                be_liveness_introduce(lv, phi);
        }

        BE_TIMER_POP(t_ssa_constr);
}

void be_init_ssaconstr(void)
{
        FIRM_DBG_REGISTER(dbg, "firm.be.ssaconstr");
}

BE_REGISTER_MODULE_CONSTRUCTOR(be_init_ssaconstr);