[libfirm] / ir / be / bespill.c

/**
 * Author:      Daniel Grund, Sebastian Hack
 * Date:                29.09.2005
 * Copyright:   (c) Universitaet Karlsruhe
 * Licence:     This file protected by GPL -  GNU GENERAL PUBLIC LICENSE.
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdlib.h>

#include "pset.h"
#include "irnode_t.h"
#include "ircons_t.h"
#include "iredges_t.h"
#include "ident_t.h"
#include "type_t.h"
#include "entity_t.h"
#include "debug.h"
#include "irgwalk.h"
#include "array.h"

#include "belive_t.h"
#include "besched_t.h"
#include "bespill.h"
#include "benode_t.h"
#include "bechordal_t.h"

#undef REMAT
/* This enables re-computation of values. Current state: Unfinished and buggy. */
#undef BUGGY_REMAT

typedef struct _reloader_t reloader_t;
typedef struct _spill_info_t spill_info_t;

struct _reloader_t {
        reloader_t *next;
        ir_node *reloader;
};

struct _spill_info_t {
        ir_node *spilled_node;
        reloader_t *reloaders;
};

typedef struct _spill_ctx_t {
        ir_node *spilled;  /**< The spilled node. */
        ir_node *user;     /**< The node this spill is for. */
        ir_node *spill;    /**< The spill itself. */
} spill_ctx_t;

struct _spill_env_t {
        const arch_register_class_t *cls;
        const be_chordal_env_t *chordal_env;
        struct obstack obst;
        set *spill_ctxs;
        set *spills;                            /**< all spill_info_t's, which must be placed */
        pset *mem_phis;                         /**< set of all special spilled phis. allocated and freed separately */
        decide_irn_t is_mem_phi;        /**< callback func to decide if a phi needs special spilling */
        void *data;                                     /**< data passed to all callbacks */
        DEBUG_ONLY(firm_dbg_module_t *dbg;)
};

static int cmp_spillctx(const void *a, const void *b, size_t n) {
        const spill_ctx_t *p = a;
        const spill_ctx_t *q = b;
        return !(p->user == q->user && p->spilled == q->spilled);
}

static int cmp_spillinfo(const void *x, const void *y, size_t size) {
        const spill_info_t *xx = x;
        const spill_info_t *yy = y;
        return ! (xx->spilled_node == yy->spilled_node);
}

spill_env_t *be_new_spill_env(const be_chordal_env_t *chordal_env, decide_irn_t is_mem_phi, void *data) {
        spill_env_t *env = xmalloc(sizeof(env[0]));
        env->spill_ctxs  = new_set(cmp_spillctx, 1024);
        env->spills      = new_set(cmp_spillinfo, 1024);
        env->cls         = chordal_env->cls;
        env->is_mem_phi  = is_mem_phi;
        env->data        = data;
        env->chordal_env = chordal_env;
        obstack_init(&env->obst);
        return env;
}

void be_delete_spill_env(spill_env_t *senv) {
        del_set(senv->spill_ctxs);
        del_set(senv->spills);
        obstack_free(&senv->obst, NULL);
        free(senv);
}

static spill_ctx_t *be_get_spill_ctx(set *sc, ir_node *to_spill, ir_node *ctx_irn) {
        spill_ctx_t templ;

        templ.spilled = to_spill;
        templ.user    = ctx_irn;
        templ.spill   = NULL;

        return set_insert(sc, &templ, sizeof(templ), HASH_COMBINE(HASH_PTR(to_spill), HASH_PTR(ctx_irn)));
}

static ir_node *be_spill_irn(spill_env_t *senv, ir_node *irn, ir_node *ctx_irn) {
        spill_ctx_t *ctx;
        DBG((senv->dbg, LEVEL_1, "%+F in ctx %+F\n", irn, ctx_irn));

        ctx = be_get_spill_ctx(senv->spill_ctxs, irn, ctx_irn);
        if(!ctx->spill) {
                const be_main_env_t *env = senv->chordal_env->birg->main_env;
                ctx->spill = be_spill(env->arch_env, irn, ctx_irn);
        }

        return ctx->spill;
}

/**
 * If the first usage of a phi result would be out of memory
 * there is no sense in allocating a register for it.
 * Thus we spill it and all its operands to the same spill slot.
 * Therefore the phi/dataB becomes a phi/Memory
 */
static ir_node *be_spill_phi(spill_env_t *senv, ir_node *phi, ir_node *ctx_irn) {
        int i, n = get_irn_arity(phi);
        ir_node **ins, *bl = get_nodes_block(phi);
        ir_graph *irg = senv->chordal_env->irg;
        spill_ctx_t *ctx;

        assert(is_Phi(phi));
        DBG((senv->dbg, LEVEL_1, "%+F in ctx %+F\n", phi, ctx_irn));

        /* search an existing spill for this context */
        ctx = be_get_spill_ctx(senv->spill_ctxs, phi, ctx_irn);

        /* if not found spill the phi */
        if(!ctx->spill) {
                /* build a new PhiM with dummy in-array */
    NEW_ARR_A(ir_node *, ins, n);
                for(i=0; i<n; ++i)
                        ins[i] = new_r_Unknown(irg, mode_M);
                ctx->spill = new_r_Phi(senv->chordal_env->irg, bl, n, ins, mode_M);

                /* re-wire the phiM */
                for(i=0; i<n; ++i) {
                        ir_node *arg = get_irn_n(phi, i);
                        ir_node *sub_res;

                        if(is_Phi(arg) && pset_find_ptr(senv->mem_phis, arg))
                                sub_res = be_spill_phi(senv, arg, ctx_irn);
                        else
                                sub_res = be_spill_irn(senv, arg, ctx_irn);

                        set_irn_n(ctx->spill, i, sub_res);
                }
        }
        return ctx->spill;
}

static ir_node *be_spill_node(spill_env_t *senv, ir_node *to_spill) {
        ir_node *res;
        if (pset_find_ptr(senv->mem_phis, to_spill))
                res = be_spill_phi(senv, to_spill, to_spill);
        else
                res = be_spill_irn(senv, to_spill, to_spill);

        return res;
}

static void phi_walker(ir_node *irn, void *env) {
        spill_env_t *senv = env;
        const arch_env_t *arch = senv->chordal_env->birg->main_env->arch_env;

        if (is_Phi(irn) && arch_irn_has_reg_class(arch, irn, 0, senv->cls)
                        && senv->is_mem_phi(irn, senv->data)) {
                DBG((senv->dbg, LEVEL_1, "  %+F\n", irn));
                pset_insert_ptr(senv->mem_phis, irn);
        }
}

#ifdef REMAT

#ifdef BUGGY_REMAT

static int check_remat_conditions(spill_env_t *senv, ir_node *spill, ir_node *spilled, ir_node *reloader) {
        int pos, max;

        /* check for 'normal' spill and general remat condition */
        if (!be_is_Spill(spill) || !arch_irn_is(senv->chordal_env->birg->main_env->arch_env, spilled, rematerializable))
                return 0;

        /* check availability of original arguments */
        if (is_Block(reloader)) {

                /* we want to remat at the end of a block.
                 * thus all arguments must be alive at the end of the block
                 */
                for (pos=0, max=get_irn_arity(spilled); pos<max; ++pos) {
                        ir_node *arg = get_irn_n(spilled, pos);
                        if (!is_live_end(reloader, arg))
                                return 0;
                }

        } else {

                /* we want to remat before the insn reloader
                 * thus an arguments is alive if
                 *   - it interferes with the reloaders result
                 * or
                 *   - or it is (last-) used by reloader itself
                 */
                for (pos=0, max=get_irn_arity(spilled); pos<max; ++pos) {
                        ir_node *arg = get_irn_n(spilled, pos);
                        int i, m;

                        if (values_interfere(reloader, arg))
                                goto is_alive;

                        for (i=0, m=get_irn_arity(reloader); i<m; ++i) {
                                ir_node *rel_arg = get_irn_n(reloader, i);
                                if (rel_arg == arg)
                                        goto is_alive;
                        }

                        /* arg is not alive before reloader */
                        return 0;

is_alive:       ;

                }

        }

        return 1;
}

#else /* BUGGY_REMAT */

static int check_remat_conditions(spill_env_t *senv, ir_node *spill, ir_node *spilled, ir_node *reloader) {
        const arch_env_t *aenv = senv->chordal_env->birg->main_env->arch_env;

        return get_irn_arity(spilled) == 0 &&
                   be_is_Spill(spill) &&
                   arch_irn_is(aenv, spilled, rematerializable);
}

#endif /* BUGGY_REMAT */

static ir_node *do_remat(spill_env_t *senv, ir_node *spilled, ir_node *reloader) {
        ir_node *res;
        ir_node *bl = (is_Block(reloader)) ? reloader : get_nodes_block(reloader);

        /* recompute the value */
        res = new_ir_node(get_irn_dbg_info(spilled), senv->chordal_env->irg, bl,
                get_irn_op(spilled),
                get_irn_mode(spilled),
                get_irn_arity(spilled),
                get_irn_in(spilled));
        copy_node_attr(spilled, res);

        DBG((senv->dbg, LEVEL_1, "Insert remat %+F before reloader %+F\n", res, reloader));

        /* insert in schedule */
        if (is_Block(reloader)) {
                ir_node *insert = sched_skip(reloader, 0, sched_skip_cf_predicator, (void *) senv->chordal_env->birg->main_env->arch_env);
                sched_add_after(insert, res);
        } else {
                sched_add_before(reloader, res);
        }

        return res;
}

#endif

void be_insert_spills_reloads(spill_env_t *senv, pset *reload_set) {
        const arch_env_t *aenv = senv->chordal_env->birg->main_env->arch_env;
        ir_graph *irg          = senv->chordal_env->irg;
        ir_node *irn;
        spill_info_t *si;

        /* get all special spilled phis */
        DBG((senv->dbg, LEVEL_1, "Mem-phis:\n"));
        senv->mem_phis = pset_new_ptr_default();
        irg_walk_graph(senv->chordal_env->irg, phi_walker, NULL, senv);

        /* Add reloads for mem_phis */
        /* BETTER: These reloads (1) should only be inserted, if they are really needed */
        DBG((senv->dbg, LEVEL_1, "Reloads for mem-phis:\n"));
        for(irn = pset_first(senv->mem_phis); irn; irn = pset_next(senv->mem_phis)) {
                const ir_edge_t *e;
                DBG((senv->dbg, LEVEL_1, " Mem-phi %+F\n", irn));
                foreach_out_edge(irn, e) {
                        ir_node *user = e->src;
                        if (is_Phi(user) && !pset_find_ptr(senv->mem_phis, user)) {
                                        ir_node *use_bl = get_nodes_block(user);
                                        DBG((senv->dbg, LEVEL_1, " non-mem-phi user %+F\n", user));
                                        be_add_reload_on_edge(senv, irn, use_bl, e->pos); /* (1) */
                        }
                }
        }

        /* process each spilled node */
        DBG((senv->dbg, LEVEL_1, "Insert spills and reloads:\n"));
        for(si = set_first(senv->spills); si; si = set_next(senv->spills)) {
                reloader_t *rld;
                ir_mode *mode = get_irn_mode(si->spilled_node);
                pset *values = pset_new_ptr(16);

                /* go through all reloads for this spill */
                for(rld = si->reloaders; rld; rld = rld->next) {
                        ir_node *new_val;

                        /* the spill for this reloader */
                        ir_node *spill   = be_spill_node(senv, si->spilled_node);

#ifdef REMAT
                        if (check_remat_conditions(senv, spill, si->spilled_node, rld->reloader))
                                new_val = do_remat(senv, si->spilled_node, rld->reloader);
                        else
#endif
                                /* do a reload */
                                new_val = be_reload(aenv, senv->cls, rld->reloader, mode, spill);

                        DBG((senv->dbg, LEVEL_1, " %+F of %+F before %+F\n", new_val, si->spilled_node, rld->reloader));
                        pset_insert_ptr(values, new_val);
                        if(reload_set)
                                pset_insert_ptr(reload_set, new_val);
                }

                /* introduce copies, rewire the uses */
                assert(pset_count(values) > 0 && "???");
                pset_insert_ptr(values, si->spilled_node);
                be_ssa_constr_set_ignore(senv->chordal_env->dom_front, values, senv->mem_phis);

                del_pset(values);
        }

        for(irn = pset_first(senv->mem_phis); irn; irn = pset_next(senv->mem_phis)) {
                int i, n;
                for(i = 0, n = get_irn_arity(irn); i < n; ++i)
                        set_irn_n(irn, i, new_r_Bad(senv->chordal_env->irg));
                sched_remove(irn);
        }

        del_pset(senv->mem_phis);
}

void be_add_reload(spill_env_t *senv, ir_node *to_spill, ir_node *before) {
        spill_info_t templ, *res;
        reloader_t *rel;

        templ.spilled_node = to_spill;
        templ.reloaders    = NULL;
        res = set_insert(senv->spills, &templ, sizeof(templ), HASH_PTR(to_spill));

        rel           = obstack_alloc(&senv->obst, sizeof(rel[0]));
        rel->reloader = before;
        rel->next     = res->reloaders;
        res->reloaders = rel;
}

void be_add_reload_on_edge(spill_env_t *senv, ir_node *to_spill, ir_node *bl, int pos) {
        ir_node *insert_bl = get_irn_arity(bl) == 1 ? sched_first(bl) : get_Block_cfgpred_block(bl, pos);
        be_add_reload(senv, to_spill, insert_bl);
}



/****************************************

        SPILL SLOT MANAGEMENT AND OPTS

****************************************/

typedef struct _spill_slot_t {
        unsigned size;
        unsigned align;
        pset *members;
        ir_mode *largest_mode;  /* the mode of all members with largest size */
} spill_slot_t;

typedef struct _ss_env_t {
        struct obstack ob;
        be_chordal_env_t *cenv;
        pmap *slots;            /* maps spill_contexts to spill_slots */
        pmap *types;    /* maps modes to types */
        DEBUG_ONLY(firm_dbg_module_t *dbg;)
} ss_env_t;

/**
 * Walker: compute the spill slots
 */
static void compute_spill_slots_walker(ir_node *spill, void *env) {
        ss_env_t *ssenv = env;
        ir_node *ctx;
        pmap_entry *entry;
        spill_slot_t *ss;

        if (!be_is_Spill(spill))
                return;

        /* check, if this spill is for a context already known */
        ctx = be_get_Spill_context(spill);
        entry = pmap_find(ssenv->slots, ctx);

        if (!entry) {
                struct _arch_env_t *arch_env     = ssenv->cenv->birg->main_env->arch_env;
                ir_node *spilled                 = get_irn_n(spill, be_pos_Spill_val);
                const arch_register_t *reg       = arch_get_irn_register(arch_env, spilled);
                const arch_register_class_t *cls = arch_register_get_class(reg);
                ir_mode *largest_mode            = arch_register_class_mode(cls);

                /* this is a new spill context */
                ss = obstack_alloc(&ssenv->ob, sizeof(*ss));
                ss->members      = pset_new_ptr(8);
                ss->largest_mode = largest_mode;
                ss->size         = get_mode_size_bytes(ss->largest_mode);
                ss->align        = arch_isa_get_reg_class_alignment(arch_env->isa, cls);
                pmap_insert(ssenv->slots, ctx, ss);
        } else {
                ir_node *irn;
                /* values with the same spill_ctx must go into the same spill slot */
                ss = entry->value;
                assert(ss->size == (unsigned)get_mode_size_bytes(get_irn_mode(get_irn_n(spill, be_pos_Spill_val))) && "Different sizes for the same spill slot are not allowed yet.");
                for (irn = pset_first(ss->members); irn; irn = pset_next(ss->members)) {
                        /* use values_interfere here, because it uses the dominance check,
                           which does work for values in memory */
                        assert(!values_interfere(spill, irn) && "Spills for the same spill slot must not interfere!");
                }
        }

        pset_insert_ptr(ss->members, spill);
}

static int ss_sorter(const void *v1, const void *v2) {
        const spill_slot_t *ss1 = v1;
        const spill_slot_t *ss2 = v2;
        return ((int) ss2->size) - ((int) ss1->size);
}


/**
 * This function should optimize the spill slots.
 *  - Coalescing of multiple slots
 *  - Ordering the slots
 *
 * Input slots are in @p ssenv->slots
 * @p size The count of initial spill slots in @p ssenv->slots
 *         This also is the size of the preallocated array @p ass
 *
 * @return An array of spill slots @p ass in specific order
 **/
static void optimize_slots(ss_env_t *ssenv, int size, spill_slot_t **ass) {
        int i, o, used_slots;
        pmap_entry *entr;

        i=0;
        pmap_foreach(ssenv->slots, entr)
                ass[i++] = entr->value;

        /* Sort the array to minimize fragmentation and cache footprint.
           Large slots come first */
        qsort(ass, size, sizeof(ass[0]), ss_sorter);

        /* For each spill slot:
                - assign a new offset to this slot
            - xor find another slot to coalesce with */
        used_slots = 0;
        for (i=0; i<size; ++i) { /* for each spill slot */
                ir_node *n1;
                int tgt_slot = -1;

                DBG((ssenv->dbg, LEVEL_1, "Spill slot %d members:\n", i));
                for(n1 = pset_first(ass[i]->members); n1; n1 = pset_next(ass[i]->members))
                        DBG((ssenv->dbg, LEVEL_1, "  %+F\n", n1));


                for (o=0; o < used_slots && tgt_slot == -1; ++o) { /* for each offset-assigned spill slot */
                        /* check inter-slot-pairs for interference */
                        ir_node *n2;
                        for(n1 = pset_first(ass[i]->members); n1; n1 = pset_next(ass[i]->members))
                                for(n2 = pset_first(ass[o]->members); n2; n2 = pset_next(ass[o]->members))
                                        if(values_interfere(n1, n2)) {
                                                pset_break(ass[i]->members);
                                                pset_break(ass[o]->members);
                                                DBG((ssenv->dbg, LEVEL_1, "    Interf %+F -- %+F\n", n1, n2));
                                                goto interf_detected;
                                        }

                        /* if we are here, there is no interference between ass[i] and ass[o] */
                        tgt_slot = o;

interf_detected: /*nothing*/ ;
                }

                /* now the members of ass[i] join the members of ass[tgt_slot] */

                /* do we need a new slot? */
                if (tgt_slot == -1) {
                        tgt_slot = used_slots;
                        used_slots++;

                        /* init slot */
                        if (tgt_slot != i) {
                                ass[tgt_slot]->size = ass[i]->size;
                                del_pset(ass[tgt_slot]->members);
                                ass[tgt_slot]->members = pset_new_ptr(8);
                        }
                }

                /* copy the members to the target pset */
                /* NOTE: If src and tgt pset are the same, inserting while iterating is not allowed */
                if (tgt_slot != i)
                        for(n1 = pset_first(ass[i]->members); n1; n1 = pset_next(ass[i]->members))
                                        pset_insert_ptr(ass[tgt_slot]->members, n1);
        }
}

#define ALIGN_SPILL_AREA 16
#define pset_foreach(pset, elm)  for(elm=pset_first(pset); elm; elm=pset_next(pset))

/**
 * Returns a spill type for a mode. Keep them in a map to reduce
 * the number of types.
 */
static ir_type *get_spill_type(pmap *types, ir_mode *mode) {
  pmap_entry *e = pmap_find(types, mode);
  ir_type *res;

  if (! e) {
                char buf[64];
    snprintf(buf, sizeof(buf), "spill_slot_type_%s", get_mode_name(mode));
    res = new_type_primitive(new_id_from_str(buf), mode);
    pmap_insert(types, mode, res);
  }
  else
    res = e->value;
  return res;
}

static void assign_entities(ss_env_t *ssenv, int n, spill_slot_t **ss) {
        int i, offset;
        ir_type *frame = get_irg_frame_type(ssenv->cenv->irg);

        /* aligning by increasing frame size */
        offset = get_type_size_bits(frame) / 8;
        offset = round_up2(offset, ALIGN_SPILL_AREA);
        set_type_size_bytes(frame, -1);

        /* create entities and assign offsets according to size and alignment*/
        for (i=0; i<n; ++i) {
                char buf[64];
                ident *name;
                entity *spill_ent;
                ir_node *irn;

                /* build entity */
                snprintf(buf, sizeof(buf), "spill_slot_%d", i);
                name = new_id_from_str(buf);

                spill_ent = new_entity(frame, name, get_spill_type(ssenv->types, ss[i]->largest_mode));

                /* align */
                offset = round_up2(offset, ss[i]->align);
                /* set */
                set_entity_offset_bytes(spill_ent, offset);
                /* next possible offset */
                offset += ss[i]->size;

                pset_foreach(ss[i]->members, irn)
                        be_set_Spill_entity(irn, spill_ent);
        }

        /* set final size of stack frame */
        set_type_size_bytes(frame, offset);
}

void be_compute_spill_offsets(be_chordal_env_t *cenv) {
        ss_env_t ssenv;
        spill_slot_t **ss;
        int ss_size;
        pmap_entry *pme;

        obstack_init(&ssenv.ob);
        ssenv.cenv  = cenv;
        ssenv.slots = pmap_create();
        ssenv.types = pmap_create();
        FIRM_DBG_REGISTER(ssenv.dbg, "ir.be.spillslots");

        /* Get initial spill slots */
        irg_walk_graph(cenv->irg, NULL, compute_spill_slots_walker, &ssenv);

        /* Build an empty array for optimized spill slots */
        ss_size = pmap_count(ssenv.slots);
        ss = obstack_alloc(&ssenv.ob, ss_size * sizeof(*ss));
        optimize_slots(&ssenv, ss_size, ss);

        /* Integrate slots into the stack frame entity */
        assign_entities(&ssenv, ss_size, ss);

        /* Clean up */
        pmap_foreach(ssenv.slots, pme)
        del_pset(((spill_slot_t *)pme->value)->members);
        pmap_destroy(ssenv.slots);
        pmap_destroy(ssenv.types);
        obstack_free(&ssenv.ob, NULL);

        be_copy_entities_to_reloads(cenv->irg);
}