[libfirm] / ir / opt / scalar_replace.c

/*
 * Copyright (C) 1995-2011 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 $Id$
 */
#include "config.h"

#include <string.h>
#include <stdbool.h>

#include "iroptimize.h"
#include "scalar_replace.h"
#include "opt_init.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 "irpass.h"
#include "irtools.h"
#include "xmalloc.h"
#include "debug.h"
#include "error.h"

static unsigned get_vnum(const ir_node *node)
{
        return (unsigned)PTR_TO_INT(get_irn_link(node));
}

static void set_vnum(ir_node *node, unsigned vnum)
{
        set_irn_link(node, INT_TO_PTR(vnum));
}

/**
 * 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;
        ir_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. */
        size_t      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. */
} 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 = (const path_t*)elt;
        const path_t *p2 = (const path_t*)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 = (const scalars_t*)elt;
        const scalars_t *c2 = (const scalars_t*)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 bool 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 false;
        }
        return true;
}

/**
 * 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 bool 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 false;
        }
        return true;
}

/*
 * Returns non-zero, if the address of an entity
 * represented by a Sel node (or its successor Sels) is taken.
 */
bool 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 true;

        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 true;
                        /* 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 true;
                        break;

                case iro_Store:
                        /* check that Sel is not the Store's value */
                        value = get_Store_value(succ);
                        if (value == sel)
                                return true;
                        /* do not remove volatile variables */
                        if (get_Store_volatility(succ) == volatility_is_volatile)
                                return true;
                        /* 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 true;
                        break;

                case iro_Sel: {
                        int       res;
                        ir_entity *entity = get_Sel_entity(succ);
                        /* we can't handle unions correctly yet -> address taken */
                        if (is_Union_type(get_entity_owner(entity)))
                                return true;

                        /* Check the Sel successor of Sel */
                        res = is_address_taken(succ);
                        if (res)
                                return true;
                        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 true;

                case iro_Id: {
                        int res = is_address_taken(succ);
                        if (res)
                                return true;
                        break;
                }

                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 true;
                                                }
                                        }
                                }
                        }
                        break;

                default:
                        /* another op, the address is taken */
                        return true;
                }
        }
        return false;
}

/**
 * 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
 */
static bool link_all_leave_sels(ir_entity *ent, ir_node *sel)
{
        int i;
        bool is_leave = true;

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

                if (is_Sel(succ)) {
                        /* the current leave has further Sel's, no leave */
                        is_leave = false;
                        link_all_leave_sels(ent, succ);
                } else if (is_Id(succ)) {
                        is_leave &= link_all_leave_sels(ent, succ);
                }
        }

        if (is_leave) {
                /* beware of Id's */
                sel = skip_Id(sel);

                /* we know we are at a leave, because this function is only
                 * called if the address is NOT taken, so sel's successor(s)
                 * must be Loads or Stores
                 */
                set_irn_link(sel, get_entity_link(ent));
                set_entity_link(ent, sel);
        }
        return is_leave;
}

/* 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, its 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;
        size_t  mem_idx;
        int     i;
        long    static_link_arg;
        int     res = 0;

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

        /* check for inner functions:
         * FIXME: need a way to get the argument position for the static link */
        static_link_arg = 0;
        for (mem_idx = get_class_n_members(frame_tp); mem_idx > 0;) {
                ir_entity *ent = get_class_member(frame_tp, --mem_idx);
                if (is_method_entity(ent)) {
                        ir_graph *inner_irg = get_entity_irg(ent);
                        ir_node  *args;
                        int      j;

                        assure_irg_outs(inner_irg);
                        args = get_irg_args(inner_irg);
                        for (j = get_irn_n_outs(args) - 1; j >= 0; --j) {
                                ir_node *arg = get_irn_out(args, j);

                                if (get_Proj_proj(arg) == static_link_arg) {
                                        int k;
                                        for (k = get_irn_n_outs(arg) - 1; k >= 0; --k) {
                                                ir_node *succ = get_irn_out(arg, k);

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

                                                        if (get_entity_owner(ent) == frame_tp) {
                                                                /* found an access to the outer frame */
                                                                set_entity_link(ent, ADDRESS_TAKEN);
                                                        }
                                                }
                                        }
                                }
                        }
                }
        }

        /*
         * 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;

                        /* we are only interested in entities on the frame, NOT
                           on the value type */
                        if (get_entity_owner(ent) != frame_tp)
                                continue;

                        if (get_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)) {
                                         /* killing one */
                                        if (get_entity_link(ent))
                                                --res;
                                        set_entity_link(ent, ADDRESS_TAKEN);
                                } else {
                                        /* possible found one */
                                        if (get_entity_link(ent) == NULL)
                                                ++res;
                                        link_all_leave_sels(ent, succ);
                                }
                        }
                }
        }

        return res;
}

/**
 * Return a path from the Sel node "sel" to its root.
 *
 * @param sel  the Sel node
 * @param len  the length of the path so far
 */
static path_t *find_path(ir_node *sel, size_t len)
{
        size_t pos;
        int 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 = XMALLOCF(path_t, path, len);
                res->path_len = len;
        } else
                res = find_path(pred, len);

        assert(len <= res->path_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 = (ir_node*)get_entity_link(ent); sel != NULL; sel = next) {
                next = (ir_node*)get_irn_link(sel);

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

                key  = find_path(sel, 0);
                path = (path_t*)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, (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;
}

/**
 * environment for memory walker
 */
typedef struct env_t {
        unsigned 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 walker(ir_node *node, void *ctx)
{
        env_t    *env = (env_t*)ctx;
        ir_graph *irg = get_irn_irg(node);
        ir_node  *addr, *block, *mem, *val;
        ir_mode  *mode;
        unsigned vnum;

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

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

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

                /* ok, we have a Load that will be replaced */
                vnum = get_vnum(addr);
                assert(vnum < 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_rd_Conv(get_irn_dbg_info(node), block, val, mode);

                mem = get_Load_mem(node);
                turn_into_tuple(node, pn_Load_max+1);
                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_r_Jmp(block));
                set_Tuple_pred(node, pn_Load_X_except,  new_r_Bad(irg, mode_X));
        } else if (is_Store(node)) {
                DB((dbg, SET_LEVEL_3, "  checking %+F for replacement ", node));

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

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

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

                vnum = get_vnum(addr);
                assert(vnum < env->nvals);

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

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

                /* 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_rd_Conv(get_irn_dbg_info(node), block, val, env->modes[vnum]);

                set_value(vnum, val);

                mem = get_Store_mem(node);
                turn_into_tuple(node, pn_Store_max+1);
                set_Tuple_pred(node, pn_Store_M,         mem);
                set_Tuple_pred(node, pn_Store_X_regular, new_r_Jmp(block));
                set_Tuple_pred(node, pn_Store_X_except,  new_r_Bad(irg, mode_X));
        }
}

/**
 * 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(ir_graph *irg, pset *sels, unsigned nvals,
                                   ir_mode **modes)
{
        env_t env;

        ssa_cons_start(irg, (int)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", irg));
        irg_walk_blkwise_graph(irg, NULL, walker, &env);

        ssa_cons_finish(irg);
}

/*
 * 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, *frame_tp;
        int       res = 0;

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

        /* we use the link field to store the VNUM */
        ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK);
        irp_reserve_resources(irp, IRP_RESOURCE_ENTITY_LINK);

        /* Find possible scalar replacements */
        if (find_possible_replacements(irg)) {
                DB((dbg, SET_LEVEL_1, "Scalar Replacement: %+F\n", 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);
                frame_tp  = get_irg_frame_type(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);

                                /* we are only interested in entities on the frame, NOT
                                   on the value type */
                                if (get_entity_owner(ent) != frame_tp)
                                        continue;

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

                                ent_type = get_entity_type(ent);

                                key.ent       = 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(irg, sels, nvals, modes);

                        foreach_set(set_ent, scalars_t*, value) {
                                free_entity(value->ent);
                        }

                        /*
                         * We changed the graph, but did NOT introduce new blocks
                         * neither changed control flow, cf-backedges should be still
                         * consistent.
                         */
                        res = 1;
                }
                del_pset(sels);
                del_set(set_ent);
                DEL_ARR_F(modes);
        }

        ir_free_resources(irg, IR_RESOURCE_IRN_LINK);
        irp_free_resources(irp, IRP_RESOURCE_ENTITY_LINK);

        return res;
}

ir_graph_pass_t *scalar_replacement_opt_pass(const char *name)
{
        return def_graph_pass_ret(name ? name : "scalar_rep",
                                  scalar_replacement_opt);
}

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