[libfirm] / ir / ana / irconsconfirm.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    Construction of Confirm nodes
 * @author   Michael Beck
 * @date     6.2005
 * @version  $Id$
 */
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include "irgraph_t.h"
#include "irnode_t.h"
#include "ircons_t.h"
#include "irgmod.h"
#include "iropt_dbg.h"
#include "iredges_t.h"
#include "irgwalk.h"
#include "irprintf.h"

/**
 * Walker environment.
 */
typedef struct _env_t {
  unsigned num_confirms;  /**< number of inserted Confirm nodes */
  unsigned num_consts;    /**< number of constants placed */
  unsigned num_eq;        /**< number of equalities placed */
} env_t;

/**
 * Return the effective use block of a node and it's predecessor on
 * position pos.
 *
 * @param node  the node
 * @param pos   the position of the used input
 *
 * This handles correctly Phi nodes.
 */
static ir_node *get_effective_use_block(ir_node *node, int pos) {
        /* the effective use of a Phi is in its predecessor block */
        if (is_Phi(node))
                return get_nodes_block(get_irn_n(node, pos));
        else
                return get_nodes_block(node);
}

/**
 * Handle a CASE-branch.
 *
 * @param block   the block which is entered by the branch
 * @param irn     the node expressing the switch value
 * @param nr      the branch label
 * @param env     statistical environment
 *
 * Branch labels are a simple case. We can replace the value
 * by a Const with the branch label.
 */
static void handle_case(ir_node *block, ir_node *irn, long nr, env_t *env) {
        const ir_edge_t *edge, *next;
        ir_node *c = NULL;

        if (is_Bad(irn))
                return;

        for (edge = get_irn_out_edge_first(irn); edge; edge = next) {
                ir_node *succ = get_edge_src_irn(edge);
                int     pos   = get_edge_src_pos(edge);
                ir_node *blk  = get_effective_use_block(succ, pos);

                next = get_irn_out_edge_next(irn, edge);

                if (block_dominates(block, blk)) {
                        /*
                         * Ok, we found a user of irn that is placed
                         * in a block dominated by the branch block.
                         * We can replace the input with the Constant
                         * branch label.
                         */

                        if (! c) {
                                ir_mode *mode = get_irn_mode(irn);
                                ir_type *tp   = get_irn_type(irn);
                                tarval *tv    = new_tarval_from_long(nr, mode);
                                c = new_r_Const_type(current_ir_graph, block, mode, tv, tp);
                        }

                        set_irn_n(succ, pos, c);
                        DBG_OPT_CONFIRM_C(irn, c);
//                      ir_printf("1 Replacing input %d of node %n with %n\n", pos, succ, c);

                        env->num_consts += 1;
                }
        }
}  /* handle_case */

/**
 * Handle an IF-branch.
 *
 * @param block   the block which is entered by the branch
 * @param cmp     the Cmp node expressing the branch condition
 * @param pnc     the Compare relation for taking this branch
 * @param env     statistical environment
 */
static void handle_if(ir_node *block, ir_node *cmp, pn_Cmp pnc, env_t *env) {
        ir_node *left  = get_Cmp_left(cmp);
        ir_node *right = get_Cmp_right(cmp);
        ir_node *cond_block;
        ir_op *op;
        const ir_edge_t *edge, *next;

        /* Beware of Bads */
        if (is_Bad(left) ||is_Bad(right))
                return;

        op = get_irn_op(left);

        /* Do not create Confirm nodes for Cmp(Const, Const) constructs.
           These are removed anyway */
        if (op == op_Const && is_Const(right))
                return;

        /* try to place the constant on the right side for a Confirm */
        if (op == op_Const || op == op_SymConst) {
                ir_node *t = left;

                left  = right;
                right = t;

                pnc = get_inversed_pnc(pnc);
        }

        /*
         * First case: both values are identical.
         * replace the left one by the right (potentially const) one.
         */
        if (pnc == pn_Cmp_Eq) {
                cond_block = get_Block_cfgpred_block(block, 0);
                for (edge = get_irn_out_edge_first(left); edge; edge = next) {
                        ir_node *user = get_edge_src_irn(edge);
                        int     pos   = get_edge_src_pos(edge);
                        ir_node *blk  = get_effective_use_block(user, pos);

                        next = get_irn_out_edge_next(left, edge);
                        if (block_dominates(block, blk)) {
                                /*
                                 * Ok, we found a usage of left in a block
                                 * dominated by the branch block.
                                 * We can replace the input with right.
                                 */
                                set_irn_n(user, pos, right);
                                DBG_OPT_CONFIRM(left, right);

//                              ir_printf("2 Replacing input %d of node %n with %n\n", pos, user, right);

                                env->num_eq += 1;
                        } else if (block_dominates(blk, cond_block)) {
                                if (is_Const(right) && get_irn_pinned(user) == op_pin_state_floats) {
                                        /*
                                         * left == Const and we found a movable user of left in a
                                         * dominator of the Cond block
                                         */
                                        const ir_edge_t *edge, *next;
                                        for (edge = get_irn_out_edge_first(user); edge; edge = next) {
                                                ir_node *usr_of_usr = get_edge_src_irn(edge);
                                                int      npos = get_edge_src_pos(edge);
                                                ir_node *blk  = get_effective_use_block(usr_of_usr, npos);

                                                next = get_irn_out_edge_next(user, edge);
                                                if (block_dominates(block, blk)) {
                                                        /*
                                                         * The user of the user is dominated by our true/false
                                                         * block. So, create a copy of user WITH the constant
                                                         * replacing it's pos'th input.
                                                         *
                                                         * This is always good for unop's and might be good
                                                         * for binops.
                                                         *
                                                         * If user has other user in the false/true block, code
                                                         * placement will move it down.
                                                         * If there are users in cond block or upper, we create
                                                         * "redundant ops", because one will have a const op,
                                                         * the other no const ...
                                                         */
                                                        ir_node *new_op = exact_copy(user);
                                                        set_nodes_block(new_op, block);
                                                        set_irn_n(new_op, pos, right);
                                                        set_irn_n(usr_of_usr, npos, new_op);
                                                }
                                        }
                                }
                        }
                }
        } else { /* not pn_Cmp_Eq cases */
                ir_node *c = NULL;

                for (edge = get_irn_out_edge_first(left); edge; edge = next) {
                        ir_node *succ = get_edge_src_irn(edge);
                        int     pos   = get_edge_src_pos(edge);
                        ir_node *blk  = get_effective_use_block(succ, pos);

                        next = get_irn_out_edge_next(left, edge);
                        if (block_dominates(block, blk)) {
                                /*
                                 * Ok, we found a usage of left in a block
                                 * dominated by the branch block.
                                 * We can replace the input with a Confirm(left, pnc, right).
                                 */
                                if (! c)
                                        c = new_r_Confirm(current_ir_graph, block, left, right, pnc);

                                pos = get_edge_src_pos(edge);
                                set_irn_n(succ, pos, c);
//                              ir_printf("3 Replacing input %d of node %n with %n\n", pos, user, c);

                                env->num_confirms += 1;
                        }
                }
        }
}  /* handle_if */

/**
 * Pre-walker: Called for every block to insert Confirm nodes
 */
static void insert_Confirm(ir_node *block, void *env) {
        ir_node *cond, *proj, *selector;
        ir_mode *mode;

        /*
         * we can only handle blocks with only ONE control flow
         * predecessor yet.
         */
        if (get_Block_n_cfgpreds(block) != 1)
                return;

        proj = get_Block_cfgpred(block, 0);
        if (get_irn_op(proj) != op_Proj)
                return;

        cond = get_Proj_pred(proj);
        if (get_irn_op(cond) != op_Cond)
                return;

        selector = get_Cond_selector(cond);
        mode = get_irn_mode(selector);

        if (mode == mode_b) {
                ir_node *cmp;
                pn_Cmp pnc;

                /* this should be an IF, check this */
                if (get_irn_op(selector) != op_Proj)
                        return;

                cmp = get_Proj_pred(selector);
                if (get_irn_op(cmp) != op_Cmp)
                        return;

                pnc = get_Proj_proj(selector);

                if (get_Proj_proj(proj) != pn_Cond_true) {
                        /* it's the false branch */
                        pnc = get_negated_pnc(pnc, mode);
                }
//              ir_printf("At %n using %n Confirm %=\n", block, cmp, pnc);

                handle_if(block, cmp, pnc, env);
        } else if (mode_is_int(mode)) {
                long proj_nr = get_Proj_proj(proj);

                /* this is a CASE, but we cannot handle the default case */
                if (proj_nr == get_Cond_defaultProj(cond))
                        return;

                handle_case(block, get_Cond_selector(cond), proj_nr, env);
        }
}  /* insert_Confirm */

/*
 * Construct Confirm nodes
 */
void construct_confirms(ir_graph *irg) {
        env_t env;
        int edges_active = edges_activated(irg);

        /* we need dominance info */
        assure_doms(irg);

        assert(get_irg_pinned(irg) == op_pin_state_pinned &&
               "Nodes must be placed to insert Confirms");

        if (! edges_active) {
                /* We need edges */
                edges_activate(irg);
        }

        env.num_confirms = 0;
        env.num_consts   = 0;
        env.num_eq       = 0;

        /* now, visit all blocks and add Confirms where possible */
        irg_block_walk_graph(irg, insert_Confirm, NULL, &env);

        if (env.num_confirms | env.num_consts | env.num_eq) {
                /* we have add nodes or changed DF edges */
                set_irg_outs_inconsistent(irg);

                /* the new nodes are not in the loop info */
                set_irg_loopinfo_inconsistent(irg);
        }

#if 0
        printf("# Confirms inserted : %u\n", env.num_confirms);
        printf("# Const replacements: %u\n", env.num_consts);
        printf("# node equalities   : %u\n", env.num_eq);
#endif

        /* deactivate edges if they where off */
        if (! edges_active)
                edges_deactivate(irg);
}  /* construct_confirms */

/**
 * Post-walker: Remove Confirm nodes
 */
static void rem_Confirm(ir_node *n, void *env) {
        (void) env;
        if (get_irn_op(n) == op_Confirm) {
                ir_node *value = get_Confirm_value(n);
                if (value != n)
                        exchange(n, value);
                else {
                        /*
                         * Strange: a Confirm is it's own bound. This can happen
                         * in dead blocks when Phi nodes are already removed.
                         */
                        exchange(n, new_Bad());
                }
        }
}  /* rem_Confirm */

/*
 * Remove all Confirm nodes from a graph.
 */
void remove_confirms(ir_graph *irg) {
        irg_walk_graph(irg, NULL, rem_Confirm, NULL);
}  /* remove_confirms */