[libfirm] / ir / opt / scalar_replace.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   Scalar replacement of compounds.
 * @author  Beyhan Veliev, Michael Beck
 * @version $Id$
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <string.h>

#include "iroptimize.h"
#include "scalar_replace.h"
#include "irflag_t.h"
#include "irouts.h"
#include "set.h"
#include "pset.h"
#include "array.h"
#include "tv.h"
#include "ircons_t.h"
#include "hashptr.h"
#include "irgwalk.h"
#include "irgmod.h"
#include "irnode_t.h"
#include "irtools.h"
#include "xmalloc.h"
#include "debug.h"
#include "error.h"

#define SET_VNUM(node, vnum) set_irn_link(node, INT_TO_PTR(vnum))
#define GET_VNUM(node)       (unsigned)PTR_TO_INT(get_irn_link(node))

/**
 * A path element entry: it is either an entity
 * or a tarval, because we evaluate only constant array
 * accesses like a.b.c[8].d
 */
typedef union {
        ir_entity *ent;
        tarval *tv;
} path_elem_t;

/**
 * An access path, used to assign value numbers
 * to variables that will be scalar replaced.
 */
typedef struct _path_t {
        unsigned    vnum;      /**< The value number. */
        unsigned    path_len;  /**< The length of the access path. */
        path_elem_t path[1];   /**< The path. */
} path_t;

/** The size of a path in bytes. */
#define PATH_SIZE(p)  (sizeof(*(p)) + sizeof((p)->path[0]) * ((p)->path_len - 1))

typedef struct _scalars_t {
        ir_entity *ent;              /**< A entity for scalar replacement. */
        ir_type *ent_owner;          /**< The owner of this entity. */
} scalars_t;

DEBUG_ONLY(static firm_dbg_module_t *dbg;)

/**
 * Compare two pathes.
 *
 * @return 0 if they are identically
 */
static int path_cmp(const void *elt, const void *key, size_t size) {
        const path_t *p1 = elt;
        const path_t *p2 = key;
        (void) size;

        /* we can use memcmp here, because identical tarvals should have identical addresses */
        return memcmp(p1->path, p2->path, p1->path_len * sizeof(p1->path[0]));
}

/**
 * Compare two elements of the scalars_t set.
 *
 * @return 0 if they are identically
 */
static int ent_cmp(const void *elt, const void *key, size_t size) {
        const scalars_t *c1 = elt;
        const scalars_t *c2 = key;
        (void) size;

        return c1->ent != c2->ent;
}

/**
 * Calculate a hash value for a path.
 */
static unsigned path_hash(const path_t *path) {
        unsigned hash = 0;
        unsigned i;

        for (i = 0; i < path->path_len; ++i)
                hash ^= (unsigned)PTR_TO_INT(path->path[i].ent);

        return hash >> 4;
}

/**
 * Returns non-zero, if all indeces of a Sel node are constants.
 *
 * @param sel  the Sel node that will be checked
 */
static int is_const_sel(ir_node *sel) {
        int i, n = get_Sel_n_indexs(sel);

        for (i = 0; i < n; ++i) {
                ir_node *idx = get_Sel_index(sel, i);

                if (!is_Const(idx))
                        return 0;
        }
        return 1;
}

/**
 * Check the mode of a Load/Store with the mode of the entity
 * that is accessed.
 * If the mode of the entity and the Load/Store mode do not match, we
 * have the bad reinterpret case:
 *
 * int i;
 * char b = *(char *)&i;
 *
 * We do NOT count this as one value and return address_taken
 * in that case.
 * However, we support an often used case. If the mode is two-complement
 * we allow casts between signed/unsigned.
 *
 * @param mode     the mode of the Load/Store
 * @param ent_mode the mode of the accessed entity
 */
static int check_load_store_mode(ir_mode *mode, ir_mode *ent_mode) {
        if (ent_mode != mode) {
                if (ent_mode == NULL ||
                    get_mode_size_bits(ent_mode) != get_mode_size_bits(mode) ||
                    get_mode_sort(ent_mode) != get_mode_sort(mode) ||
                    get_mode_arithmetic(ent_mode) != irma_twos_complement ||
                    get_mode_arithmetic(mode) != irma_twos_complement)
                        return 0;
        }
        return 1;
}

/*
 * Returns non-zero, if the address of an entity
 * represented by a Sel node (or it's successor Sels) is taken.
 */
int is_address_taken(ir_node *sel)
{
        int       i, input_nr, k;
        ir_mode   *emode, *mode;
        ir_node   *value;
        ir_entity *ent;

        if (! is_const_sel(sel))
                return 1;

        for (i = get_irn_n_outs(sel) - 1; i >= 0; --i) {
                ir_node *succ = get_irn_out(sel, i);

                switch (get_irn_opcode(succ)) {
                case iro_Load:
                        /* do not remove volatile variables */
                        if (get_Load_volatility(succ) == volatility_is_volatile)
                                return 1;
                        /* check if this load is not a hidden conversion */
                        mode = get_Load_mode(succ);
                        ent = get_Sel_entity(sel);
                        emode = get_type_mode(get_entity_type(ent));
                        if (! check_load_store_mode(mode, emode))
                                return 1;
                        break;

                case iro_Store:
                        /* check that Sel is not the Store's value */
                        value = get_Store_value(succ);
                        if (value == sel)
                                return 1;
                        /* do not remove volatile variables */
                        if (get_Store_volatility(succ) == volatility_is_volatile)
                                return 1;
                        /* check if this Store is not a hidden conversion */
                        mode = get_irn_mode(value);
                        ent = get_Sel_entity(sel);
                        emode = get_type_mode(get_entity_type(ent));
                        if (! check_load_store_mode(mode, emode))
                                return 1;
                        break;

                case iro_Sel: {
                        /* Check the Sel successor of Sel */
                        int res = is_address_taken(succ);

                        if (res)
                                return 1;
                        break;
                }

                case iro_Call:
                        /* The address of an entity is given as a parameter.
                         * As long as we do not have analyses that can tell what
                         * is done with parameters, think is taken.
                         * One special case: If the Call type tells that it's a
                         * value parameter, the address is NOT taken.
                         */
                        return 1;

                case iro_Tuple:
                        /* Non-optimized Tuple, happens in inlining */
                        for (input_nr = get_Tuple_n_preds(succ) - 1; input_nr >= 0; --input_nr) {
                                ir_node *pred = get_Tuple_pred(succ, input_nr);

                                if (pred == sel) {
                                        /* we found one input */
                                        for (k = get_irn_n_outs(succ) - 1; k >= 0; --k) {
                                                ir_node *proj = get_irn_out(succ, k);

                                                if (is_Proj(proj) && get_Proj_proj(proj) == input_nr) {
                                                        int res = is_address_taken(proj);
                                                        if (res)
                                                                return 1;
                                                }
                                        }
                                }
                        }
                        break;

                default:
                        /* another op, the address is taken */
                        return 1;
                }
        }
        return 0;
}

/**
 * Link all leave Sels with the entity.
 *
 * @param ent  the entity that will be scalar replaced
 * @param sel  a Sel node that selects some fields of this entity
 *
 * Uses the visited flag to mark already linked Sel nodes.
 */
static void link_all_leave_sels(ir_entity *ent, ir_node *sel) {
        int i, flag = 1;

        for (i = get_irn_n_outs(sel) - 1; i >= 0; --i) {
                ir_node *succ = get_irn_out(sel, i);

                if (is_Sel(succ)) {
                        link_all_leave_sels(ent, succ);
                        flag = 0;
                }
        }

        if (flag) {
                /* if Sel nodes with memory inputs are used, a entity can be
                 * visited more than once causing a ring here, so we use the
                 * node flag to mark linked nodes
                 */
                if (irn_visited(sel))
                        return;

                /* we know we are at a leave, because this function is only
                 * called if the address is NOT taken, so succ must be a Load
                 * or a Store node
                 */
                set_irn_link(sel, get_entity_link(ent));
                set_entity_link(ent, sel);

                mark_irn_visited(sel);
        }
}

/* we need a special address that serves as an address taken marker */
static char _x;
static void *ADDRESS_TAKEN = &_x;

/**
 * Find possible scalar replacements.
 *
 * @param irg  an IR graph
 *
 * This function finds variables on the (members of the) frame type
 * that can be scalar replaced, because their address is never taken.
 * If such a variable is found, it's entity link will hold a list of all
 * Sel nodes, that selects the atomic fields of this entity.
 * Otherwise, the link will be ADDRESS_TAKEN or NULL.
 *
 * @return  non-zero if at least one entity could be replaced
 *          potentially
 */
static int find_possible_replacements(ir_graph *irg) {
        ir_node *irg_frame;
        ir_type *frame_tp;
        int     i;
        int     res = 0;

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

        /*
         * First, clear the link field of all interesting entities.
         */
        frame_tp = get_irg_frame_type(irg);
        for (i = get_class_n_members(frame_tp) - 1; i >= 0; --i) {
                ir_entity *ent = get_class_member(frame_tp, i);
                set_entity_link(ent, NULL);
        }

        /*
         * Check the ir_graph for Sel nodes. If the entity of Sel
         * isn't a scalar replacement set the link of this entity
         * equal ADDRESS_TAKEN.
         */
        irg_frame = get_irg_frame(irg);
        for (i = get_irn_n_outs(irg_frame) - 1; i >= 0; --i) {
                ir_node *succ = get_irn_out(irg_frame, i);

                if (is_Sel(succ)) {
                        ir_entity *ent = get_Sel_entity(succ);
                        ir_type *ent_type;

                        if (get_entity_link(ent) == ADDRESS_TAKEN)
                                continue;

                        /*
                         * Beware: in rare cases even entities on the frame might be
                         * volatile. This might happen if the entity serves as a store
                         * to a value that must survive a exception. Do not optimize
                         * such entities away.
                         */
                        if (get_entity_volatility(ent) == volatility_is_volatile) {
                                set_entity_link(ent, ADDRESS_TAKEN);
                                continue;
                        }

                        ent_type = get_entity_type(ent);

                        /* we can handle arrays, structs and atomic types yet */
                        if (is_Array_type(ent_type) || is_Struct_type(ent_type) || is_atomic_type(ent_type)) {
                                if (is_address_taken(succ)) {
                                        if (get_entity_link(ent)) /* killing one */
                                                --res;
                                        set_entity_link(ent, ADDRESS_TAKEN);
                                } else {
                                        /* possible found one */
                                        if (get_entity_link(ent) == NULL)
                                                ++res;
                                        link_all_leave_sels(ent, succ);
                                }
                        }
                }
        }

        ir_free_resources(irg, IR_RESOURCE_IRN_VISITED);
        return res;
}

/**
 * Return a path from the Sel node sel to it's root.
 *
 * @param sel  the Sel node
 * @param len  the length of the path so far
 */
static path_t *find_path(ir_node *sel, unsigned len) {
        int pos, i, n;
        path_t *res;
        ir_node *pred = get_Sel_ptr(sel);

        /* the current Sel node will add some path elements */
        n    = get_Sel_n_indexs(sel);
        len += n + 1;

        if (! is_Sel(pred)) {
                /* we found the root */

                res = xmalloc(sizeof(*res) + (len - 1) * sizeof(res->path));
                res->path_len = len;
        } else
                res = find_path(pred, len);

        pos = res->path_len - len;

        res->path[pos++].ent = get_Sel_entity(sel);
        for (i = 0; i < n; ++i) {
                ir_node *index = get_Sel_index(sel, i);

                res->path[pos++].tv = get_Const_tarval(index);
        }
        return res;
}


/**
 * Allocate value numbers for the leaves
 * in our found entities.
 *
 * @param sels  a set that will contain all Sels that have a value number
 * @param ent   the entity that will be scalar replaced
 * @param vnum  the first value number we can assign
 * @param modes a flexible array, containing all the modes of
 *              the value numbers.
 *
 * @return the next free value number
 */
static unsigned allocate_value_numbers(pset *sels, ir_entity *ent, unsigned vnum, ir_mode ***modes)
{
        ir_node *sel, *next;
        path_t *key, *path;
        set *pathes = new_set(path_cmp, 8);

        DB((dbg, SET_LEVEL_3, "  Visiting Sel nodes of entity %+F\n", ent));
        /* visit all Sel nodes in the chain of the entity */
        for (sel = get_entity_link(ent); sel; sel = next) {
                next = get_irn_link(sel);

                /* we must mark this sel for later */
                pset_insert_ptr(sels, sel);

                key  = find_path(sel, 0);
                path = set_find(pathes, key, PATH_SIZE(key), path_hash(key));

                if (path) {
                        SET_VNUM(sel, path->vnum);
                        DB((dbg, SET_LEVEL_3, "  %+F represents value %u\n", sel, path->vnum));
                } else {
                        key->vnum = vnum++;

                        set_insert(pathes, key, PATH_SIZE(key), path_hash(key));

                        SET_VNUM(sel, key->vnum);
                        DB((dbg, SET_LEVEL_3, "  %+F represents value %u\n", sel, key->vnum));

                        ARR_EXTO(ir_mode *, *modes, (int)((key->vnum + 15) & ~15));

                        (*modes)[key->vnum] = get_type_mode(get_entity_type(get_Sel_entity(sel)));

                        assert((*modes)[key->vnum] && "Value is not atomic");

#ifdef DEBUG_libfirm
                        /* Debug output */
                        {
                                unsigned i;
                                DB((dbg, SET_LEVEL_2, "  %s", get_entity_name(key->path[0].ent)));
                                for (i = 1; i < key->path_len; ++i) {
                                        if (is_entity(key->path[i].ent))
                                                DB((dbg, SET_LEVEL_2, ".%s", get_entity_name(key->path[i].ent)));
                                        else
                                                DB((dbg, SET_LEVEL_2, "[%ld]", get_tarval_long(key->path[i].tv)));
                                }
                                DB((dbg, SET_LEVEL_2, " = %u (%s)\n", PTR_TO_INT(get_irn_link(sel)), get_mode_name((*modes)[key->vnum])));
                        }
#endif /* DEBUG_libfirm */
                }
                free(key);
        }

        del_set(pathes);
        set_entity_link(ent, NULL);
        return vnum;
}

/**
 * A list entry for the fixing lists
 */
typedef struct _list_entry_t {
        ir_node  *node;   /**< the node that must be fixed */
        unsigned vnum;    /**< the value number of this node */
} list_entry_t;

/**
 * environment for memory walker
 */
typedef struct _env_t {
        int          nvals;       /**< number of values */
        ir_mode      **modes;     /**< the modes of the values */
        pset         *sels;       /**< A set of all Sel nodes that have a value number */
} env_t;

/**
 * topological post-walker.
 */
static void topologic_walker(ir_node *node, void *ctx) {
        env_t        *env = ctx;
        ir_node      *adr, *block, *mem, *val;
        ir_mode      *mode;
        unsigned     vnum;

        if (is_Load(node)) {
                /* a load, check if we can resolve it */
                adr = get_Load_ptr(node);

                DB((dbg, SET_LEVEL_3, "  checking %+F for replacement ", node));
                if (! is_Sel(adr)) {
                        DB((dbg, SET_LEVEL_3, "no Sel input (%+F)\n", adr));
                        return;
                }

                if (! pset_find_ptr(env->sels, adr)) {
                        DB((dbg, SET_LEVEL_3, "Sel %+F has no VNUM\n", adr));
                        return;
                }

                /* ok, we have a Load that will be replaced */
                vnum = GET_VNUM(adr);
                assert(vnum < (unsigned)env->nvals);

                DB((dbg, SET_LEVEL_3, "replacing by value %u\n", vnum));

                block = get_nodes_block(node);
                set_cur_block(block);

                /* check, if we can replace this Load */
                val = get_value(vnum, env->modes[vnum]);

                /* Beware: A Load can contain a hidden conversion in Firm.
                This happens for instance in the following code:

                 int i;
                 unsigned j = *(unsigned *)&i;

                Handle this here. */
                mode = get_Load_mode(node);
                if (mode != get_irn_mode(val))
                        val = new_d_Conv(get_irn_dbg_info(node), val, mode);

                mem = get_Load_mem(node);
                turn_into_tuple(node, pn_Load_max);
                set_Tuple_pred(node, pn_Load_M,         mem);
                set_Tuple_pred(node, pn_Load_res,       val);
                set_Tuple_pred(node, pn_Load_X_regular, new_Jmp());
                set_Tuple_pred(node, pn_Load_X_except,  new_Bad());
        } else if (is_Store(node)) {
                DB((dbg, SET_LEVEL_3, "  checking %+F for replacement ", node));

                /* a Store always can be replaced */
                adr = get_Store_ptr(node);

                if (! is_Sel(adr)) {
                        DB((dbg, SET_LEVEL_3, "no Sel input (%+F)\n", adr));
                        return;
                }

                if (! pset_find_ptr(env->sels, adr)) {
                        DB((dbg, SET_LEVEL_3, "Sel %+F has no VNUM\n", adr));
                        return;
                }

                vnum = GET_VNUM(adr);
                assert(vnum < (unsigned)env->nvals);

                DB((dbg, SET_LEVEL_3, "replacing by value %u\n", vnum));

                /* Beware: A Store can contain a hidden conversion in Firm. */
                val = get_Store_value(node);
                if (get_irn_mode(val) != env->modes[vnum])
                        val = new_d_Conv(get_irn_dbg_info(node), val, env->modes[vnum]);

                block = get_nodes_block(node);
                set_cur_block(block);
                set_value(vnum, val);

                mem = get_Store_mem(node);
                turn_into_tuple(node, pn_Store_max);
                set_Tuple_pred(node, pn_Store_M,         mem);
                set_Tuple_pred(node, pn_Store_X_regular, new_Jmp());
                set_Tuple_pred(node, pn_Store_X_except,  new_Bad());
        }
}

/**
 * Make scalar replacement.
 *
 * @param sels    A set containing all Sel nodes that have a value number
 * @param nvals   The number of scalars.
 * @param modes   A flexible array, containing all the modes of
 *                the value numbers.
 */
static void do_scalar_replacements(pset *sels, int nvals, ir_mode **modes) {
        env_t env;

        ssa_cons_start(current_ir_graph, nvals);

        env.nvals     = nvals;
        env.modes     = modes;
        env.sels      = sels;

        /*
         * second step: walk over the graph blockwise in topological order
         * and fill the array as much as possible.
         */
        DB((dbg, SET_LEVEL_3, "Substituting Loads and Stores in %+F\n", current_ir_graph));
        irg_walk_blkwise_graph(current_ir_graph, NULL, topologic_walker, &env);

        ssa_cons_finish(current_ir_graph);
}

/*
 * Find possible scalar replacements
 *
 * @param irg  The current ir graph.
 */
int scalar_replacement_opt(ir_graph *irg) {
        unsigned  nvals;
        int       i;
        scalars_t key, *value;
        ir_node   *irg_frame;
        ir_mode   **modes;
        set       *set_ent;
        pset      *sels;
        ir_type   *ent_type;
        ir_graph  *rem;
        int       res = 0;

        if (! get_opt_scalar_replacement())
                return 0;

        rem = current_ir_graph;
        current_ir_graph = irg;

        /* Call algorithm that computes the out edges */
        assure_irg_outs(irg);

        /* Find possible scalar replacements */
        if (find_possible_replacements(irg)) {
                DB((dbg, SET_LEVEL_1, "Scalar Replacement: %s\n", get_entity_name(get_irg_entity(irg))));

                /* Insert in set the scalar replacements. */
                irg_frame = get_irg_frame(irg);
                nvals = 0;
                modes = NEW_ARR_F(ir_mode *, 16);
                set_ent = new_set(ent_cmp, 8);
                sels    = pset_new_ptr(8);

                for (i = get_irn_n_outs(irg_frame) - 1; i >= 0; --i) {
                        ir_node *succ = get_irn_out(irg_frame, i);

                        if (is_Sel(succ)) {
                                ir_entity *ent = get_Sel_entity(succ);

                                if (get_entity_link(ent) == NULL || get_entity_link(ent) == ADDRESS_TAKEN)
                                        continue;

                                ent_type = get_entity_type(ent);

                                key.ent       = ent;
                                key.ent_owner = get_entity_owner(ent);
                                set_insert(set_ent, &key, sizeof(key), HASH_PTR(key.ent));

#ifdef DEBUG_libfirm
                                if (is_Array_type(ent_type)) {
                                        DB((dbg, SET_LEVEL_1, "  found array %s\n", get_entity_name(ent)));
                                } else if (is_Struct_type(ent_type)) {
                                        DB((dbg, SET_LEVEL_1, "  found struct %s\n", get_entity_name(ent)));
                                } else if (is_atomic_type(ent_type))
                                        DB((dbg, SET_LEVEL_1, "  found atomic value %s\n", get_entity_name(ent)));
                                else {
                                        panic("Neither an array nor a struct or atomic value found in scalar replace");
                                }
#endif /* DEBUG_libfirm */

                                nvals = allocate_value_numbers(sels, ent, nvals, &modes);
                        }
                }

                DB((dbg, SET_LEVEL_1, "  %u values will be needed\n", nvals));

                /* If scalars were found. */
                if (nvals > 0) {
                        do_scalar_replacements(sels, nvals, modes);

                        foreach_set(set_ent, value) {
                                remove_class_member(value->ent_owner, value->ent);
                        }

                        /*
                         * We changed the graph, but did NOT introduce new blocks
                         * neither changed control flow, cf-backedges should be still
                         * consistent.
                         */
                        set_irg_outs_inconsistent(irg);
                        set_irg_loopinfo_inconsistent(irg);

                        res = 1;
                }
                del_pset(sels);
                del_set(set_ent);
                DEL_ARR_F(modes);
        }

        current_ir_graph = rem;
        return res;
}

void firm_init_scalar_replace(void) {
        FIRM_DBG_REGISTER(dbg, "firm.opt.scalar_replace");
}