[libfirm] / ir / be / bespillbelady.c

/**
 * Author:      Daniel Grund
 * Date:                20.09.2005
 * Copyright:   (c) Universitaet Karlsruhe
 * Licence:     This file protected by GPL -  GNU GENERAL PUBLIC LICENSE.
 */

#include <alloca.h>
#include "obst.h"
#include "set.h"
#include "pset.h"
#include "irgraph.h"
#include "irnode.h"
#include "irmode.h"
#include "ircons.h"
#include "irgwalk.h"
#include "iredges_t.h"

#include "beutil.h"
#include "bearch.h"
#include "bespillbelady.h"
#include "beuses_t.h"
#include "besched_t.h"
#include "beirgmod.h"
#include "belive_t.h"
#include "benode_t.h"

#define MIN(a,b) (((a)<(b))?(a):(b))

#define DBG_DECIDE 1
#define DBG_WSETS 2
#define DBG_FIX 4
#define DBG_SPILL 8
#define DBG_TRACE 32
#define DEBUG_LVL (DBG_DECIDE | DBG_WSETS | DBG_FIX | DBG_SPILL)
static firm_dbg_module_t *dbg = NULL;


typedef struct _workset_t workset_t;
typedef struct _block_info_t block_info_t;
typedef struct _reloader_t reloader_t;
typedef struct _spill_info_t spill_info_t;
typedef struct _spill_ctx_t spill_ctx_t;
typedef struct _belady_env_t belady_env_t;

struct _workset_t {
        belady_env_t *bel;
        int i;                          /**< used for iteration */
        int len;                        /**< current length */
        loc_t vals[1];          /**< inlined array of the values/distances in this working set */
};

struct _block_info_t {
        workset_t *ws_start, *ws_end;
};

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

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

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. */
};

struct _belady_env_t {
        struct obstack ob;
        const be_main_session_env_t *session;
        const be_node_factory_t *factory;
        const arch_env_t *arch;
        const arch_register_class_t *cls;
        int n_regs;                     /** number of regs in this reg-class */

        workset_t *ws;          /**< the main workset used while processing a block. ob-allocated */
        be_uses_t *uses;        /**< env for the next-use magic */
        ir_node *instr;         /**< current instruction */
        unsigned instr_nr;      /**< current instruction number (relative to block start) */
        pset *used;                     /**< holds the values used (so far) in the current BB */
        set *spills;            /**< all spill_info_t's, which must be placed */

        set *spill_ctxs;        /**< all spill contexts (multiple spilling and stop recursion) */
        pset *mem_phis;         /**< all phis which must be converted to memory phis */
        pset *reloads;          /**< all reload nodes placed */
};

static int set_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);
}

static int set_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);
}

/**
 * Alloc a new workset on obstack @p ob with maximum size @p max
 */
static INLINE workset_t *new_workset(struct obstack *ob, belady_env_t *bel) {
        workset_t *res;
        size_t size = sizeof(*res) + (bel->n_regs-1)*sizeof(res->vals[0]);
        res = obstack_alloc(ob, size);
        memset(res, 0, size);
        res->bel = bel;
        return res;
}

static INLINE workset_t *workset_clone(struct obstack *ob, workset_t *ws) {
        workset_t *res;
        size_t size = sizeof(*res) + (ws->bel->n_regs-1)*sizeof(res->vals[0]);
        res = obstack_alloc(ob, size);
        memcpy(res, ws, size);
        return res;
}

/**
 * Inserts the value @p val into the workset, iff it is not
 * already contained. The workset must not be full.
 */
static INLINE void workset_insert(workset_t *ws, ir_node *val) {
        int i;
        assert(ws->len < ws->bel->n_regs && "Workset already full!");
        /* check for current regclass */
        if (arch_get_irn_reg_class(ws->bel->arch, val, 0) != ws->bel->cls) {
                DBG((dbg, 0, "Dropped %+F\n", val));
                return;
        }

        /* check if val is already contained */
        for(i=0; i<ws->len; ++i)
                if (ws->vals[i].irn == val)
                        return;

        /* insert val */
        ws->vals[ws->len++].irn = val;
}

/**
 * Inserts all values in array @p vals of length @p cnt
 * into the workset. There must be enough space for the
 * entries.
 */
static INLINE void workset_bulk_insert(workset_t *ws, int cnt, ir_node **vals) {
        int i, o;
        assert(ws->len + cnt <= ws->bel->n_regs && "Workset does not have enough room!");

        for(o=0; o<cnt; ++o) {
                ir_node *val = vals[o];
                DBG((dbg, DBG_TRACE, "Bulk insert %+F\n", val));
                /* check for current regclass */
                if (arch_get_irn_reg_class(ws->bel->arch, val, 0) != ws->bel->cls) {
                        DBG((dbg, DBG_TRACE, "Wrong reg class\n"));
                        goto no_insert;
                }

                /* check if val is already contained */
                for(i=0; i<ws->len; ++i)
                        if (ws->vals[i].irn == val) {
                                DBG((dbg, DBG_TRACE, "Already contained\n"));
                                goto no_insert;
                        }

                /* insert val */
                ws->vals[ws->len++].irn = val;
                DBG((dbg, DBG_TRACE, "Inserted\n"));

no_insert:
                /*epsilon statement :)*/;
        }
}

/**
 * Overwrites the current contents of @p ws with the
 * locations given in @p locs
 */
#define workset_bulk_fill(ws, count, locs) memcpy(&(ws)->vals[0], locs, ((ws)->len=count)*sizeof(locs[0]));

/**
 * Removes all entries from this workset
 */
#define workset_clear(ws) (ws)->len = 0;

/**
 * Removes the value @p val from the workset if present.
 */
static INLINE void workset_remove(workset_t *ws, ir_node *val) {
        int i;
        for(i=0; i<ws->len; ++i)
                if (ws->vals[i].irn == val) {
                        ws->vals[i] = ws->vals[--ws->len];
                        return;
                }
}

static INLINE int workset_contains(const workset_t *ws, ir_node *val) {
        int i;
        for(i=0; i<ws->len; ++i)
                if (ws->vals[i].irn == val)
                        return 1;
        return 0;
}

#define workset_foreach(ws, v)  for(ws->i=0; \
                                                                        v=(ws->i < ws->len) ? ws->vals[ws->i].irn : NULL, ws->i < ws->len; \
                                                                        ws->i++)

#define workset_set_time(ws, i, t) (ws)->vals[i].time=t
#define workset_set_length(ws, length) (ws)->len = length
#define workset_get_length(ws) ((ws)->len)
#define workset_get_val(ws, i) ((ws)->vals[i].irn)
#define workset_sort(ws) qsort((ws)->vals, (ws)->len, sizeof((ws)->vals[0]), loc_compare);


/**
 * Collects all values live-in at block @p blk and all phi results in this block.
 * Then it adds the best values (at most n_regs) to the ws.
 */
static void build_start_set(belady_env_t *bel, ir_node *blk) {
        workset_t *ws = bel->ws;
        ir_node *irn, *first;
        irn_live_t *li;
        int count;
        loc_t loc, *starters;
        struct obstack ob;

        obstack_init(&ob);

        /* get all values */
        first = sched_first(blk);
        count = 0;
        sched_foreach(blk, irn)
                if (is_Phi(irn) && arch_get_irn_reg_class(bel->arch, irn, 0) == bel->cls) {
                        loc.irn = irn;
                        loc.time = be_get_next_use(bel->uses, first, 0, irn);
                        obstack_grow(&ob, &loc, sizeof(loc));
                        count++;
                } else
                        break;

        live_foreach(blk, li)
                if (live_is_in(li) && arch_get_irn_reg_class(bel->arch, li->irn, 0) == bel->cls) {
                        loc.irn = (ir_node *)li->irn;
                        loc.time = be_get_next_use(bel->uses, first, 0, li->irn);
                        obstack_grow(&ob, &loc, sizeof(loc));
                        count++;
                }
        starters = obstack_finish(&ob);

        /* sort all values */
        qsort(starters, count, sizeof(starters[0]), loc_compare);

        /* copy the best ones to the ws */
        count = MIN(count, ws->bel->n_regs);
        workset_bulk_fill(ws, count, starters);

        obstack_free(&ob, NULL);
}

/**
 * Performs the actions neccessary to grant the request that:
 * - new_vals can be held in registers
 * - as few as possible other values are disposed
 * - the worst values get disposed
 *
 * @p is_usage indicates that the values in new_vals are used (not defined)
 * In this case reloads must be performed
 */
static void displace(belady_env_t *bel, workset_t *new_vals, int is_usage) {
        ir_node *val;
        int i, len, max_allowed, demand;
        workset_t *ws = bel->ws;
        ir_node **to_insert = alloca(bel->n_regs * sizeof(*to_insert));

        /*
         * 1. Identify the number of needed slots and the values to reload
         */
        demand = 0;
        workset_foreach(new_vals, val) {
                /* mark value as used */
                if (is_usage)
                        pset_insert_ptr(bel->used, val);

                if (!workset_contains(ws, val)) {
                        DBG((dbg, DBG_DECIDE, "    insert %+F\n", val));
                        to_insert[demand++] = val;

                        if (is_usage) {
                                spill_info_t si, *found;
                                reloader_t *rld;

                                /* find the spill info or create it */
                                si.spilled_node = val;
                                si.reloaders = NULL;
                                found = set_insert(bel->spills, &si, sizeof(si), HASH_PTR(si.spilled_node));

                                /* insert the reloader into the linked list */
                                rld = obstack_alloc(&bel->ob, sizeof(*rld));
                                rld->reloader = bel->instr;
                                rld->next = found->reloaders;
                                found->reloaders = rld;
                        }
                } else
                        DBG((dbg, DBG_DECIDE, "    skip %+F\n", val));
        }
        DBG((dbg, DBG_DECIDE, "    demand = %d\n", demand));


        /*
         * 2. Make room for at least 'demand' slots
         */
        len = workset_get_length(ws);
        max_allowed = bel->n_regs - demand;

        /* Only make more free room if we do not have enough */
        if (len > max_allowed) {
                /* get current next-use distance */
                for (i=0; i<ws->len; ++i)
                        workset_set_time(ws, i, be_get_next_use(bel->uses, bel->instr, bel->instr_nr, workset_get_val(ws, i)));

                /* sort entries by increasing nextuse-distance*/
                workset_sort(ws);

                /* Logic for not needed live-ins: If a value is disposed
                   before its first usage, remove it from start workset */
                for (i=max_allowed; i<ws->len; ++i) {
                        ir_node *irn = ws->vals[i].irn;
                        if (!pset_find_ptr(bel->used, irn)) {
                                ir_node *curr_bb = get_nodes_block(bel->instr);
                                workset_t *ws_start = ((block_info_t *) get_irn_link(curr_bb))->ws_start;
                                workset_remove(ws_start, irn);

                                DBG((dbg, DBG_DECIDE, "    dispose %+F dumb\n", irn));
                        } else
                                DBG((dbg, DBG_DECIDE, "    dispose %+F\n", irn));
                }

                /* kill the last 'demand' entries in the array */
                workset_set_length(ws, max_allowed);
        }

        /*
         * 3. Insert the new values into the workset
         */
        workset_bulk_insert(bel->ws, demand, to_insert);
}

/**
 * For the given block @p blk, decide for each values
 * whether it is used from a register or is reloaded
 * before the use.
 */
static void decide(ir_node *blk, void *env) {
        belady_env_t *bel = env;
        workset_t *new_vals;
        ir_node *irn;
        block_info_t *blk_info = obstack_alloc(&bel->ob, sizeof(*blk_info));
        set_irn_link(blk, blk_info);

        DBG((dbg, DBG_DECIDE, "\n"));
        DBG((dbg, DBG_DECIDE, "Decide for %+F\n", blk));

        /* build starting-workset for this block */
        build_start_set(bel, blk);
        blk_info->ws_start = workset_clone(&bel->ob, bel->ws);
        DBG((dbg, DBG_WSETS, "Initial start workset for %+F:\n", blk));
        workset_foreach(blk_info->ws_start, irn)
                DBG((dbg, DBG_WSETS, "  %+F\n", irn));

        /* process the block from start to end */
        DBG((dbg, DBG_WSETS, "Processing...\n"));
        bel->used = pset_new_ptr(32);
        bel->instr_nr = 0;
        new_vals = new_workset(&bel->ob, bel);
        sched_foreach(blk, irn) {
                DBG((dbg, DBG_DECIDE, "  %+F\n", irn));

                /* projs are handled with the tuple value.
                 * Phis are no real instr (see insert_starters)
                 * instr_nr does not increase */
                if (is_Proj(irn) || is_Phi(irn))
                        continue;

                /* set instruction in the workset */
                bel->instr = irn;

                /* allocate all values _used_ by this instruction */
                workset_clear(new_vals);
                workset_bulk_insert(new_vals, get_irn_arity(irn)+1, get_irn_in(irn));
                displace(bel, new_vals, 1);

                /* allocate all values _defined_ by this instruction */
                workset_clear(new_vals);
                if (get_irn_mode(irn) == mode_T) { /* special handling for tuples and projs */
                        ir_node *proj;
                        for(proj=sched_next(irn); is_Proj(proj); proj=sched_next(proj))
                                workset_insert(new_vals, proj);
                } else {
                        workset_insert(new_vals, irn);
                }
                displace(bel, new_vals, 0);

                bel->instr_nr++;
        }
        del_pset(bel->used);

        /* Remember end-workset for this block */
        blk_info->ws_end = workset_clone(&bel->ob, bel->ws);
        DBG((dbg, DBG_WSETS, "Start workset for %+F:\n", blk));
        workset_foreach(blk_info->ws_start, irn)
                DBG((dbg, DBG_WSETS, "  %+F\n", irn));
        DBG((dbg, DBG_WSETS, "End workset for %+F:\n", blk));
        workset_foreach(blk_info->ws_end, irn)
                DBG((dbg, DBG_WSETS, "  %+F\n", irn));
}

/**
 * 'decide' is block-local and makes assumtions
 * about the set of live-ins. Thus we must adapt the
 * live-outs to the live-ins at each block-border.
 */
static void fix_block_borders(ir_node *blk, void *env) {
        belady_env_t *bel = env;
        int i, max;

        DBG((dbg, DBG_FIX, "\n"));
        DBG((dbg, DBG_FIX, "Fixing %+F\n", blk));

        workset_t *wsb = ((block_info_t *)get_irn_link(blk))->ws_start;

        /* process all pred blocks */
        for (i=0, max=get_irn_arity(blk); i<max; ++i) {
                ir_node *irnb, *irnp, *pred = get_Block_cfgpred_block(blk, i);
                workset_t *wsp = ((block_info_t *)get_irn_link(pred))->ws_end;

                DBG((dbg, DBG_FIX, "  Pred %+F\n", pred));

                workset_foreach(wsb, irnb) {
                        spill_info_t si, *found;
                        reloader_t *rld;

                        /* if irnb is a phi of the current block we reload
                         * the corresponding argument, else irnb itself */
                        if(is_Phi(irnb) && blk == get_nodes_block(irnb))
                                irnb = get_irn_n(irnb, i);

                        /* check if irnb is in a register at end of pred */
                        workset_foreach(wsp, irnp)
                                if (irnb == irnp)
                                        goto next_value;

                        /* irnb is in memory at the end of pred, so we have to reload it */

                        /* find the spill info or create it */
                        si.spilled_node = irnb;
                        si.reloaders = NULL;
                        found = set_insert(bel->spills, &si, sizeof(si), HASH_PTR(si.spilled_node));

                        /* insert the reloader into the linked list.
                         * the schedule position depends on the cf-situation of the block */
                        rld = obstack_alloc(&bel->ob, sizeof(*rld));
                        rld->reloader = (max==1) ? sched_skip(sched_first(blk), 1, sched_skip_phi_predicator, NULL) : pred;
                        rld->next = found->reloaders;
                        found->reloaders = rld;

                        DBG((dbg, DBG_FIX, "    reload %+F before %+F\n", irnb, rld->reloader));

next_value:
                        /*epsilon statement :)*/;
                }
        }
}

static INLINE spill_ctx_t *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 INLINE ir_node *spill_irn(belady_env_t *bel, ir_node *irn, ir_node *ctx_irn) {
        spill_ctx_t *ctx;
        DBG((dbg, DBG_SPILL, "spill_irn %+F\n", irn));

        ctx = get_spill_ctx(bel->spill_ctxs, irn, ctx_irn);
        if(!ctx->spill)
                ctx->spill = be_spill(bel->factory, bel->arch, 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 *spill_phi(belady_env_t *bel, 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 = get_irn_irg(bl);
        spill_ctx_t *ctx;

        assert(is_Phi(phi));
        DBG((dbg, DBG_SPILL, "spill_phi %+F\n", phi));

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

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

                /* 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(bel->mem_phis, arg))
                                sub_res = spill_phi(bel, arg, ctx_irn);
                        else
                                sub_res = spill_irn(bel, arg, ctx_irn);

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

static ir_node *spill_node(belady_env_t *bel, ir_node *to_spill) {
        ir_node *res;
        if (pset_find_ptr(bel->mem_phis, to_spill))
                res = spill_phi(bel, to_spill, to_spill);
        else
                res = spill_irn(bel, to_spill, to_spill);

        return res;
}

static void insert_spills_reloads(ir_graph *irg, belady_env_t *bel) {
        ir_node *irn;
        spill_info_t *si;
        struct obstack ob;
        obstack_init(&ob);

        /* get all special spilled phis */
        for(si = set_first(bel->spills); si; si = set_next(bel->spills)) {
                irn = si->spilled_node;
                if (is_Phi(irn)) {
                        ir_node *blk = get_nodes_block(irn);
                        workset_t *sws = ((block_info_t *)get_irn_link(blk))->ws_start;
                        if (!workset_contains(sws, irn))
                                pset_insert_ptr(bel->mem_phis, irn);
                }
        }

        /* process each spilled node */
        for(si = set_first(bel->spills); si; si = set_next(bel->spills)) {
                reloader_t *rld;
                ir_node **reloads;
                int n_reloads = 0;
                ir_mode *mode = get_irn_mode(si->spilled_node);

                /* go through all reloads for this spill */
                for(rld = si->reloaders; rld; rld = rld->next) {
                        /* the spill for this reloader */
                        ir_node *spill   = spill_node(bel, si->spilled_node);

                        /* the reload */
                        ir_node *bl      = is_Block(rld->reloader) ? rld->reloader : get_nodes_block(rld->reloader);
                        ir_node *reload  = new_Reload(bel->factory, bel->cls, irg, bl, mode, spill);
                        pset_insert_ptr(bel->reloads, reload);

                        /* remember the reaload */
                        obstack_ptr_grow(&ob, reload);
                        sched_add_before(rld->reloader, reload);
                        n_reloads++;
                }

                assert(n_reloads > 0);
                reloads = obstack_finish(&ob);
                be_introduce_copies_ignore(bel->session->dom_front, si->spilled_node, n_reloads, reloads, bel->mem_phis);
                obstack_free(&ob, reloads);
        }

        obstack_free(&ob, NULL);

        /* remove all special phis form the irg and the schedule */
        for(irn = pset_first(bel->mem_phis); irn; irn = pset_next(bel->mem_phis)) {
                int i, n;
                for(i = 0, n = get_irn_arity(irn); i < n; ++i)
                        set_irn_n(irn, i, new_r_Bad(irg));
                sched_remove(irn);
        }
}

/**
 * Removes all used reloads from bel->reloads.
 * The remaining nodes in bel->reloads will be removed from the graph.
 */
static void rescue_used_reloads(ir_node *irn, void *env) {
        pset *rlds = ((belady_env_t *)env)->reloads;
        if (pset_find_ptr(rlds, irn))
                pset_remove_ptr(rlds, irn);
}

void be_spill_belady(const be_main_session_env_t *session, const arch_register_class_t *cls) {
        ir_node *irn;

        dbg = firm_dbg_register("ir.be.spillbelady");
        firm_dbg_set_mask(dbg, DEBUG_LVL);

        /* init belady env */
        belady_env_t *bel = alloca(sizeof(*bel));
        obstack_init(&bel->ob);
        bel->session = session;
        bel->factory = session->main_env->node_factory;
        bel->arch = session->main_env->arch_env;
        bel->cls = cls;
        bel->n_regs = arch_register_class_n_regs(cls);
        bel->ws = new_workset(&bel->ob, bel);
        bel->uses = be_begin_uses(session->irg, session->main_env->arch_env, cls);
        bel->spills = new_set(set_cmp_spillinfo, 32);
        bel->spill_ctxs = new_set(set_cmp_spillctx, 32);
        bel->mem_phis = pset_new_ptr_default();
        bel->reloads = pset_new_ptr_default();

        /* do the work */
        irg_block_walk_graph(session->irg, decide, NULL, bel);
        irg_block_walk_graph(session->irg, fix_block_borders, NULL, bel);
        insert_spills_reloads(session->irg, bel);

        /* find all unused reloads and remove them from the schedule */
        irg_walk_graph(session->irg, rescue_used_reloads, NULL, bel);
        for(irn = pset_first(bel->reloads); irn; irn = pset_next(bel->reloads))
                sched_remove(irn);

        /* clean up */
        del_pset(bel->reloads);
        del_pset(bel->mem_phis);
        del_set(bel->spill_ctxs);
        del_set(bel->spills);
        be_end_uses(bel->uses);
        obstack_free(&bel->ob, NULL);
}