[libfirm] / ir / be / belower.c

/**
 * Author:      Christian Wuerdig
 * Date:        2005/12/14
 * Copyright:   (c) Universitaet Karlsruhe
 * Licence:     This file protected by GPL -  GNU GENERAL PUBLIC LICENSE.
 * CVS-Id:      $Id$
 *
 * Performs lowering of perm nodes and spill/reload optimization.
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdlib.h>

#include "ircons.h"

#include "bearch.h"
#include "belower.h"
#include "benode_t.h"
#include "bechordal_t.h"
#include "besched_t.h"

#include "irgmod.h"
#include "iredges_t.h"
#include "irgwalk.h"

#undef is_Perm
#define is_Perm(arch_env, irn) (arch_irn_classify(arch_env, irn) == arch_irn_class_perm)

#undef is_Call
#define is_Call(arch_env, irn) (arch_irn_classify(arch_env, irn) == arch_irn_class_call)

/* lowering walker environment */
typedef struct _lower_env_t {
        be_chordal_env_t  *chord_env;
        int                do_copy;
        firm_dbg_module_t *dbg_module;
} lower_env_t;

/* holds a perm register pair */
typedef struct _reg_pair_t {
        const arch_register_t *in_reg;    /**< a perm IN register */
        ir_node               *in_node;   /**< the in node to which the register belongs */

        const arch_register_t *out_reg;   /**< a perm OUT register */
        ir_node               *out_node;  /**< the out node to which the register belongs */

        int                    checked;   /**< indicates whether the pair was check for cycle or not */
} reg_pair_t;

typedef enum _perm_type_t {
        PERM_CYCLE,
        PERM_CHAIN,
        PERM_SWAP,
        PERM_COPY
} perm_type_t;

/* structure to represent cycles or chains in a perm */
typedef struct _perm_cycle_t {
        const arch_register_t **elems;       /**< the registers in the cycle */
        int                     n_elems;     /**< number of elements in the cycle */
        perm_type_t             type;        /**< type (CHAIN or CYCLE) */
} perm_cycle_t;

/* Compare the in registers of two register pairs */
static int compare_reg_pair(const void *a, const void *b) {
        const reg_pair_t *pair_a = a;
        const reg_pair_t *pair_b = b;

        if (pair_a->in_reg->index > pair_b->in_reg->index)
                return 1;
        else
                return -1;
}

/* returns the number register pairs marked as checked */
static int get_n_checked_pairs(reg_pair_t *pairs, int n) {
        int i, n_checked = 0;

        for (i = 0; i < n; i++) {
                if (pairs[i].checked)
                        n_checked++;
        }

        return n_checked;
}

/**
 * Gets the node corresponding to a register from an array of register pairs.
 * NOTE: The given registers pairs and the register to look for must belong
 *       to the same register class.
 *
 * @param pairs  The array of register pairs
 * @param n      The number of pairs
 * @param reg    The register to look for
 * @param in_out 0 == look for IN register, 1 == look for OUT register
 * @return The corresponding node or NULL if not found
 */
static ir_node *get_node_for_register(reg_pair_t *pairs, int n, const arch_register_t *reg, int in_out) {
        int i;

        if (in_out) {
                for (i = 0; i < n; i++) {
                        /* out register matches */
                        if (pairs[i].out_reg->index == reg->index)
                                return pairs[i].out_node;
                }
        }
        else {
                for (i = 0; i < n; i++) {
                        /* in register matches */
                        if (pairs[i].in_reg->index == reg->index)
                                return pairs[i].in_node;
                }
        }

        return NULL;
}

/**
 * Gets the index in the register pair array where the in/out register
 * corresponds to reg_idx.
 *
 * @param pairs  The array of register pairs
 * @param n      The number of pairs
 * @param reg    The register index to look for
 * @param in_out 0 == look for IN register, 1 == look for OUT register
 * @return The corresponding index in pairs or -1 if not found
 */
static int get_pairidx_for_regidx(reg_pair_t *pairs, int n, int reg_idx, int in_out) {
        int i;

        if (in_out) {
                for (i = 0; i < n; i++) {
                        /* out register matches */
                        if (pairs[i].out_reg->index == reg_idx)
                                return i;
                }
        }
        else {
                for (i = 0; i < n; i++) {
                        /* in register matches */
                        if (pairs[i].in_reg->index == reg_idx)
                                return i;
                }
        }

        return -1;
}

/**
 * Gets an array of register pairs and tries to identify a cycle or chain starting
 * at position start.
 *
 * @param cycle Variable to hold the cycle
 * @param pairs Array of register pairs
 * @param start Index to start
 * @return The cycle or chain
 */
static perm_cycle_t *get_perm_cycle(perm_cycle_t *cycle, reg_pair_t *pairs, int n, int start) {
        int head         = pairs[start].in_reg->index;
        int cur_idx      = pairs[start].out_reg->index;
        int cur_pair_idx = start;
        int n_pairs_done = get_n_checked_pairs(pairs, n) + 1;
        int idx;

        /* assume worst case: all remaining pairs build a cycle or chain */
        cycle->elems    = calloc(n - n_pairs_done, sizeof(cycle->elems[0]));
        cycle->n_elems  = 2;  /* initial number of elements is 2 */
        cycle->elems[0] = pairs[start].in_reg;
        cycle->elems[1] = pairs[start].out_reg;
        cycle->type     = PERM_CHAIN; /* default is CHAIN, only changed when we found a cycle */

        /* mark the first pair as checked */
        pairs[start].checked = 1;

        idx = 2;
        /* check for cycle or end of a chain */
        while (cur_idx != head && n_pairs_done < n) {
                /* goto next register in cycle or chain */
                cur_pair_idx = get_pairidx_for_regidx(pairs, n, cur_idx, 0);

                if (cur_pair_idx < 0)
                        break;

                cur_idx = pairs[cur_pair_idx].out_reg->index;

                /* it's not the first element: insert it */
                if (cur_idx != head) {
                        cycle->elems[idx++] = pairs[cur_pair_idx].out_reg;
                        cycle->n_elems++;

                        n_pairs_done++;
                }
                else {
                        /* we are there where we started -> CYCLE */
                        cycle->type = PERM_CYCLE;
                }

                /* mark the pair as checked */
                pairs[cur_pair_idx].checked = 1;
        }

        return cycle;
}

/**
 * Lowers a perm node.  Resolves cycles and creates a bunch of
 * copy and swap operations to permute registers.
 * Note: The caller of this function has to make sure, that irn
 *       is a Perm node.
 *
 * @param irn      The perm node
 * @param block    The block the perm node belongs to
 * @param walk_env The environment
 */
static void lower_perm_node(ir_node *irn, void *walk_env) {
        const arch_register_class_t *reg_class;
        const arch_env_t            *arch_env;
        firm_dbg_module_t           *mod;
        lower_env_t     *env = walk_env;
        reg_pair_t      *pairs;
        const ir_edge_t *edge;
        perm_cycle_t    *cycle;
        int              n, i, pn, do_copy;
        ir_node         *sched_point, *block, *in[2];
        ir_node         *arg1, *arg2, *res1, *res2;
        ir_node         *cpyxchg = NULL;

        arch_env = env->chord_env->main_env->arch_env;
        do_copy  = env->do_copy;
        mod      = env->dbg_module;
        block    = get_nodes_block(irn);

        /*
                Get the schedule predecessor node to the perm
                NOTE: This works with auto-magic. If we insert the
                        new copy/exchange nodes after this node, everything
                        should be ok.
        */
        sched_point = sched_prev(irn);
        DBG((mod, LEVEL_1, "sched point is %+F\n", sched_point));
        assert(sched_point && "Perm is not scheduled or has no predecessor");

        n = get_irn_arity(irn);
        assert(n == get_irn_n_edges(irn) && "perm's in and out numbers different");

        reg_class = arch_get_irn_register(arch_env, get_irn_n(irn, 0))->reg_class;
        pairs     = calloc(n, sizeof(pairs[0]));

        /* build the list of register pairs (in, out) */
        i = 0;
        foreach_out_edge(irn, edge) {
                pairs[i].out_node = get_edge_src_irn(edge);
                pn                = get_Proj_proj(pairs[i].out_node);
                pairs[i].in_node  = get_irn_n(irn, pn);

                pairs[i].in_reg  = arch_get_irn_register(arch_env, pairs[i].in_node);
                pairs[i].out_reg = arch_get_irn_register(arch_env, pairs[i].out_node);

                pairs[i].checked = 0;
                i++;
        }

        /* sort the register pairs by the indices of the in registers */
        qsort(pairs, n, sizeof(pairs[0]), compare_reg_pair);

        /* Mark all equal pairs as checked, and exchange the OUT proj with
                the IN node. */
        for (i = 0; i < n; i++) {
                if (pairs[i].in_reg->index == pairs[i].out_reg->index) {
                        DBG((mod, LEVEL_1, "%+F removing equal perm register pair (%+F, %+F, %s)\n",
                                irn, pairs[i].in_node, pairs[i].out_node, pairs[i].out_reg->name));

                        /* We have to check for a special case:
                                The in-node could be a Proj from a Perm. In this case,
                                we need to correct the projnum */
                        if (is_Perm(arch_env, pairs[i].in_node) && is_Proj(pairs[i].in_node)) {
                                set_Proj_proj(pairs[i].out_node, get_Proj_proj(pairs[i].in_node));
                        }

                        /* remove the proj from the schedule */
                        sched_remove(pairs[i].out_node);

                        /* reroute the edges from the proj to the argument */
                        edges_reroute(pairs[i].out_node, pairs[i].in_node, env->chord_env->irg);

                        pairs[i].checked = 1;
                }
        }

        /* Set do_copy to 0 if it's on but we have no free register */
        if (do_copy) {
                do_copy = 0;
        }

        /* check for cycles and chains */
        while (get_n_checked_pairs(pairs, n) < n) {
                i = 0;

                /* go to the first not-checked pair */
                while (pairs[i].checked) i++;
                cycle = calloc(1, sizeof(*cycle));
                cycle = get_perm_cycle(cycle, pairs, n, i);

                /* We don't need to do anything if we have a Perm with two
                        elements which represents a cycle, because those nodes
                        already represent exchange nodes */
                if (n == 2 && cycle->type == PERM_CYCLE) {
                        free(cycle);
                        continue;
                }

//TODO: - iff PERM_CYCLE && do_copy -> determine free temp reg and insert copy to/from it before/after
//        the copy cascade (this reduces the cycle into a chain)

                /* build copy/swap nodes from back to front */
                for (i = cycle->n_elems - 2; i >= 0; i--) {
                        arg1 = get_node_for_register(pairs, n, cycle->elems[i], 0);
                        arg2 = get_node_for_register(pairs, n, cycle->elems[i + 1], 0);

                        res1 = get_node_for_register(pairs, n, cycle->elems[i], 1);
                        res2 = get_node_for_register(pairs, n, cycle->elems[i + 1], 1);

                        /*
                                If we have a cycle and don't copy: we need to create exchange nodes
                                NOTE: An exchange node is a perm node with 2 INs and 2 OUTs
                                IN_1  = in node with register i
                                IN_2  = in node with register i + 1
                                OUT_1 = out node with register i + 1
                                OUT_2 = out node with register i
                        */
                        if (cycle->type == PERM_CYCLE && !do_copy) {
                                in[0] = arg1;
                                in[1] = arg2;

                                DBG((mod, LEVEL_1, "%+F creating exchange node (%+F, %s) and (%+F, %s) with\n",
                                        irn, arg1, cycle->elems[i]->name, arg2, cycle->elems[i + 1]->name));
                                DBG((mod, LEVEL_1, "%+F                        (%+F, %s) and (%+F, %s)\n",
                                        irn, res1, cycle->elems[i]->name, res2, cycle->elems[i + 1]->name));

                                cpyxchg = be_new_Perm(reg_class, env->chord_env->irg, block, 2, in);

                                sched_remove(res1);
                                sched_remove(res2);

                                set_Proj_pred(res2, cpyxchg);
                                set_Proj_proj(res2, 0);
                                set_Proj_pred(res1, cpyxchg);
                                set_Proj_proj(res1, 1);

                                sched_add_after(sched_point, res1);
                                sched_add_after(sched_point, res2);

                                arch_set_irn_register(arch_env, res2, cycle->elems[i + 1]);
                                arch_set_irn_register(arch_env, res1, cycle->elems[i]);
                        }
                        else {
                                DBG((mod, LEVEL_1, "%+F creating copy node (%+F, %s) -> (%+F, %s)\n",
                                        irn, arg1, cycle->elems[i]->name, res2, cycle->elems[i + 1]->name));

                                cpyxchg = be_new_Copy(reg_class, env->chord_env->irg, block, arg1);
                                arch_set_irn_register(arch_env, cpyxchg, cycle->elems[i + 1]);

                                /* remove the proj from the schedule */
                                sched_remove(res2);

                                /* exchange copy node and proj */
                                exchange(res2, cpyxchg);
                        }

                        /* insert the copy/exchange node in schedule after the magic schedule node (see above) */
                        sched_add_after(sched_point, cpyxchg);

                        DBG((mod, LEVEL_1, "replacing %+F with %+F, placed new node after %+F\n", irn, cpyxchg, sched_point));
                }

//              free(cycle->elems);
                free(cycle);
        }

        /* remove the perm from schedule */
        sched_remove(irn);
}



/**
 * Adds Projs to keep nodes for each register class, which eats the
 * caller saved registers.
 * Note: The caller has to make sure, that call is a Call
 *
 * @param call     The Call node
 * @param walk_env The walker environment
 */
static void lower_call_node(ir_node *call, void *walk_env) {
        lower_env_t                 *env      = walk_env;
        const arch_env_t            *arch_env = env->chord_env->main_env->arch_env;
        firm_dbg_module_t           *mod      = env->dbg_module;
        const arch_register_class_t *reg_class;
        int                          i, j, set_size = 0, pn, keep_arity;
        arch_isa_t                  *isa      = arch_env_get_isa(arch_env);
        const ir_node               *proj_T   = NULL;
        ir_node                     **in_keep, *block = get_nodes_block(call);
        ir_node                     *last_proj = NULL;
        bitset_t                    *proj_set;
        const ir_edge_t             *edge;
        const arch_register_t       *reg;

        /* Prepare the bitset where we store the projnums which are already in use*/
        for (i = 0; i < arch_isa_get_n_reg_class(isa); i++) {
                reg_class  = arch_isa_get_reg_class(isa, i);
                set_size  += arch_register_class_n_regs(reg_class);
        }

        in_keep = malloc(set_size * sizeof(ir_node *));

        proj_set = bitset_malloc(set_size);
        bitset_clear_all(proj_set);

        /* check if there is a ProjT node and which arguments are used */
        foreach_out_edge(call, edge) {
                if (get_irn_mode(get_edge_src_irn(edge)) == mode_T)
                        proj_T = get_edge_src_irn(edge);
        }

        /* set all used arguments */
        if (proj_T) {


                foreach_out_edge(proj_T, edge) {
                        ir_node *proj       = get_edge_src_irn(edge);

                        assert(is_Proj(proj));
                        bitset_set(proj_set, get_Proj_proj(get_edge_src_irn(edge)));

                        /*
                         * Filter out the last proj in the schedule.
                         * After that one, we have to insert the Keep node.
                         */
                        if(!last_proj || sched_comes_after(last_proj, proj))
                                last_proj = proj;

                }
        }
        else {
                proj_T = new_r_Proj(current_ir_graph, block, call, mode_T, pn_Call_T_result);
        }

        /* Create for each caller save register a proj (keep node arguement) */
        /* if this proj is not already present */
        for (i = 0; i < arch_isa_get_n_reg_class(isa); i++) {

                /* reset the keep input, as we need one keep for each register class */
                memset(in_keep, 0, set_size * sizeof(ir_node *));
                keep_arity = 0;
                reg_class  = arch_isa_get_reg_class(isa, i);

                for (j = 0; j < arch_register_class_n_regs(reg_class); j++) {
                        reg = arch_register_for_index(reg_class, j);

                        /* only check caller save registers */
                        if (arch_register_type_is(reg, caller_saved)) {
                                pn = isa->impl->get_projnum_for_register(isa, reg);
                                if (!bitset_is_set(proj_set, pn)) {
                                        ir_node *proj = new_r_Proj(current_ir_graph, block, (ir_node *)proj_T, mode_Is, pn);

                                        in_keep[keep_arity++] = proj;
                                        sched_add_after(last_proj, proj);
                                        last_proj = proj;
                                }
                        }
                }

                /* ok, we found some caller save register which are not in use but must be saved */
                if (keep_arity) {
                        ir_node *keep;

                        keep = be_new_Keep(reg_class, current_ir_graph, block, keep_arity, in_keep);
                        sched_add_after(last_proj, keep);
                }
        }

        bitset_free(proj_set);
        return;
}



/**
 * Calls the backend code generator functions to lower Spill and
 * Reload nodes into Store and Load. The backend is fully responsible
 * for creating the new nodes and setting their input correct.
 * Note: The caller of this has to make sure that irn is a Spill
 *       or Reload!
 *
 * @param irn      The Spill/Reload node
 * @param walk_env The walker environment
 */
static void lower_spill_reload(ir_node *irn, void *walk_env) {
        lower_env_t           *env  = walk_env;
        arch_code_generator_t *cg   = env->chord_env->main_env->cg;
        const arch_env_t      *aenv = env->chord_env->main_env->arch_env;
        ir_node               *res  = NULL;
        ir_node               *sched_point;

        if (be_is_Spill(irn) && cg->impl->lower_spill) {
                res = cg->impl->lower_spill(cg, irn);
        }
        else if (be_is_Reload(irn) && cg->impl->lower_reload) {
                res = cg->impl->lower_reload(cg, irn);
                if (res && res != irn) {
                        /* copy the result register from the reload to the load */
                        arch_set_irn_register(aenv, res, arch_get_irn_register(aenv, irn));
                }
        }

        if (res && res != irn) {
                sched_point = sched_prev(irn);
                sched_remove(irn);
                exchange(irn, res);
                sched_add_after(sched_point, res);
        }
        else {
                DBG((env->dbg_module, LEVEL_1, "node %+F not lowered\n", irn));
        }

        return;
}



/**
 * Calls the corresponding lowering function for the node.
 *
 * @param irn      The node to be checked for lowering
 * @param walk_env The walker environment
 */
static void lower_nodes_walker(ir_node *irn, void *walk_env) {
        lower_env_t      *env      = walk_env;
        const arch_env_t *arch_env = env->chord_env->main_env->arch_env;

        if (!is_Block(irn) && !is_Proj(irn)) {
                if (is_Perm(arch_env, irn)) {
                        lower_perm_node(irn, walk_env);
                }
                else if (is_Call(arch_env, irn)) {
                        lower_call_node(irn, walk_env);
                }
                else if (be_is_Spill(irn) || be_is_Reload(irn)) {
                        lower_spill_reload(irn, walk_env);
                }
        }

        return;
}

/**
 * Walks over all blocks in an irg and performs some lowering.
 *
 * @param chord_env The chordal environment containing the irg
 * @param do_copy   1 == resolve cycles with a free reg if available
 */
void lower_nodes(be_chordal_env_t *chord_env, int do_copy) {
        lower_env_t env;

        env.chord_env  = chord_env;
        env.do_copy    = do_copy;
        env.dbg_module = firm_dbg_register("ir.be.lower");

        irg_walk_blkwise_graph(chord_env->irg, NULL, lower_nodes_walker, &env);
}

#undef is_Perm
#undef is_Call