[libfirm] / ir / ana / execfreq.c

/*
 * Copyright (C) 1995-2008 University of Karlsruhe.  All right reserved.
 *
 * This file is part of libFirm.
 *
 * This file may be distributed and/or modified under the terms of the
 * GNU General Public License version 2 as published by the Free Software
 * Foundation and appearing in the file LICENSE.GPL included in the
 * packaging of this file.
 *
 * Licensees holding valid libFirm Professional Edition licenses may use
 * this file in accordance with the libFirm Commercial License.
 * Agreement provided with the Software.
 *
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE.
 */

/**
 * @file
 * @brief       Compute an estimate of basic block executions.
 * @author      Adam M. Szalkowski
 * @date        28.05.2006
 * @version     $Id$
 */
#include "config.h"

#include <stdio.h>
#include <string.h>
#include <limits.h>
#include <math.h>

#include "gaussseidel.h"

#include "set.h"
#include "hashptr.h"
#include "debug.h"
#include "statev.h"
#include "dfs_t.h"
#include "absgraph.h"

#include "irprog_t.h"
#include "irgraph_t.h"
#include "irnode_t.h"
#include "irloop.h"
#include "irgwalk.h"
#include "iredges.h"
#include "irprintf.h"
#include "irtools.h"
#include "irhooks.h"

#include "execfreq.h"

/* enable to also solve the equations with Gauss-Jordan */
#undef COMPARE_AGAINST_GAUSSJORDAN

#ifdef COMPARE_AGAINST_GAUSSJORDAN
#include "gaussjordan.h"
#endif


#define EPSILON              1e-5
#define UNDEF(x)         (fabs(x) < EPSILON)
#define SEIDEL_TOLERANCE 1e-7

#define MAX_INT_FREQ 1000000

#define set_foreach(s,i) for((i)=set_first((s)); (i); (i)=set_next((s)))

typedef struct _freq_t {
        const ir_node    *irn;
        int               idx;
        double            freq;
} freq_t;

struct ir_exec_freq {
        set *set;
        hook_entry_t hook;
        double max;
        double min_non_zero;
        double m, b;
        unsigned infeasible : 1;
};

static int
cmp_freq(const void *a, const void *b, size_t size)
{
        const freq_t *p = a;
        const freq_t *q = b;
        (void) size;

        return !(p->irn == q->irn);
}

static freq_t *
set_find_freq(set * set, const ir_node * irn)
{
        freq_t     query;

        query.irn = irn;
        return set_find(set, &query, sizeof(query), HASH_PTR(irn));
}

static freq_t *
set_insert_freq(set * set, const ir_node * irn)
{
        freq_t query;

        query.irn = irn;
        query.freq = 0.0;
        query.idx  = -1;
        return set_insert(set, &query, sizeof(query), HASH_PTR(irn));
}

double
get_block_execfreq(const ir_exec_freq *ef, const ir_node * irn)
{
        if(!ef->infeasible) {
                set *freqs = ef->set;
                freq_t *freq;
                assert(is_Block(irn));
                freq = set_find_freq(freqs, irn);
                assert(freq);

                assert(freq->freq >= 0);
                return freq->freq;
        }

        return 1.0;
}

unsigned long
get_block_execfreq_ulong(const ir_exec_freq *ef, const ir_node *bb)
{
        double f       = get_block_execfreq(ef, bb);
        int res        = (int) (f > ef->min_non_zero ? ef->m * f + ef->b : 1.0);
        return res;
}

static double *
solve_lgs(gs_matrix_t *mat, double *x, int size)
{
        double init = 1.0 / size;
        double dev;
        int i, iter = 0;

        /* better convergence. */
        for (i = 0; i < size; ++i)
                x[i] = init;

        stat_ev_dbl("execfreq_matrix_size", size);
        stat_ev_tim_push();
        do {
                ++iter;
                dev = gs_matrix_gauss_seidel(mat, x, size);
        } while(fabs(dev) > SEIDEL_TOLERANCE);
        stat_ev_tim_pop("execfreq_seidel_time");
        stat_ev_dbl("execfreq_seidel_iter", iter);

#ifdef COMPARE_AGAINST_GAUSSJORDAN
        {
                double *nw = XMALLOCN(double, size * size);
                double *nx = XMALLOCNZ(double, size);

                gs_matrix_export(mat, nw, size);

                stat_ev_tim_push();
                firm_gaussjordansolve(nw, nx, size);
                stat_ev_tim_pop("execfreq_jordan_time");

                xfree(nw);
                xfree(nx);
        }
#endif

        return x;
}

/*
 * Determine probability that predecessor pos takes this cf edge.
 */
static double
get_cf_probability(ir_node *bb, int pos, double loop_weight)
{
        double           sum = 0.0;
        double           cur = 1.0;
        double           inv_loop_weight = 1./loop_weight;
        const ir_node   *pred = get_Block_cfgpred_block(bb, pos);
        const ir_loop   *pred_loop;
        int              pred_depth;
        const ir_edge_t *edge;
        const ir_loop   *loop;
        int              depth;
        int              d;

        if (is_Bad(pred))
                return 0;

        loop       = get_irn_loop(bb);
        depth      = get_loop_depth(loop);
        pred_loop  = get_irn_loop(pred);
        pred_depth = get_loop_depth(pred_loop);

        for (d = depth; d < pred_depth; ++d) {
                cur *= inv_loop_weight;
        }

        foreach_block_succ(pred, edge) {
                const ir_node *succ       = get_edge_src_irn(edge);
                const ir_loop *succ_loop  = get_irn_loop(succ);
                int            succ_depth = get_loop_depth(succ_loop);

                double         fac = 1.0;
                for (d = succ_depth; d < pred_depth; ++d) {
                        fac *= inv_loop_weight;
                }
                sum += fac;
        }

        return cur/sum;
}

static void exec_freq_node_info(void *ctx, FILE *f, const ir_node *irn)
{
        if(is_Block(irn)) {
                ir_exec_freq *ef = ctx;
                fprintf(f, "execution frequency: %g/%lu\n", get_block_execfreq(ef, irn), get_block_execfreq_ulong(ef, irn));
        }
}

ir_exec_freq *create_execfreq(ir_graph *irg)
{
        ir_exec_freq *execfreq = XMALLOCZ(ir_exec_freq);
        execfreq->set = new_set(cmp_freq, 32);

        memset(&execfreq->hook, 0, sizeof(execfreq->hook));
        execfreq->hook.context = execfreq;
        execfreq->hook.hook._hook_node_info = exec_freq_node_info;
        register_hook(hook_node_info, &execfreq->hook);
        (void) irg;

        return execfreq;
}

void set_execfreq(ir_exec_freq *execfreq, const ir_node *block, double freq)
{
        freq_t *f = set_insert_freq(execfreq->set, block);
        f->freq = freq;
}

static void collect_blocks(ir_node *bl, void *data)
{
        set *freqs = data;
        set_insert_freq(freqs, bl);
}

ir_exec_freq *
compute_execfreq(ir_graph * irg, double loop_weight)
{
        gs_matrix_t  *mat;
        int           size;
        int           idx;
        freq_t       *freq, *s, *e;
        ir_exec_freq *ef;
        set          *freqs;
        dfs_t        *dfs;
        double       *x;
        double        norm;

        /*
         * compute a DFS.
         * using a toposort on the CFG (without back edges) will propagate
         * the values better for the gauss/seidel iteration.
         * => they can "flow" from start to end.
         */
        dfs = dfs_new(&absgraph_irg_cfg_succ, irg);
        ef = XMALLOCZ(ir_exec_freq);
        ef->min_non_zero = HUGE_VAL; /* initialize with a reasonable large number. */
        freqs = ef->set = new_set(cmp_freq, dfs_get_n_nodes(dfs));

        /*
         * Populate the exec freq set.
         * The DFS cannot be used alone, since the CFG might not be connected
         * due to unreachable code.
         */
        irg_block_walk_graph(irg, collect_blocks, NULL, freqs);

        construct_cf_backedges(irg);
        edges_assure(irg);

        size = dfs_get_n_nodes(dfs);
        mat  = gs_new_matrix(size, size);
        x    = XMALLOCN(double, size);

        for (idx = dfs_get_n_nodes(dfs) - 1; idx >= 0; --idx) {
                ir_node *bb = (ir_node *) dfs_get_post_num_node(dfs, size - idx - 1);
                freq_t *freq;
                int i;

                freq = set_insert_freq(freqs, bb);
                freq->idx = idx;

                /* Sum of (execution frequency of predecessor * probability of cf edge) ... */
                for(i = get_Block_n_cfgpreds(bb) - 1; i >= 0; --i) {
                        ir_node *pred = get_Block_cfgpred_block(bb, i);
                        int pred_idx  = size - dfs_get_post_num(dfs, pred) - 1;

                        gs_matrix_set(mat, idx, pred_idx, get_cf_probability(bb, i, loop_weight));
                }
                /* ... equals my execution frequency */
                gs_matrix_set(mat, idx, idx, -1.0);
        }

        dfs_free(dfs);

        /*
         * Add an edge from end to start.
         * The problem is then an eigenvalue problem:
         * Solve A*x = 1*x => (A-I)x = 0
         */
        s = set_find_freq(freqs, get_irg_start_block(irg));
        e = set_find_freq(freqs, get_irg_end_block(irg));
        if (e->idx >= 0)
                gs_matrix_set(mat, s->idx, e->idx, 1.0);

        /* solve the system and delete the matrix */
        solve_lgs(mat, x, size);
        gs_delete_matrix(mat);

        /*
         * compute the normalization factor.
         * 1.0 / exec freq of start block.
         */
        norm = x[s->idx] != 0.0 ? 1.0 / x[s->idx] : 1.0;

        ef->max = 0.0;
        set_foreach(freqs, freq) {
                int idx = freq->idx;

                /* take abs because it sometimes can be -0 in case of endless loops */
                freq->freq = fabs(x[idx]) * norm;

                /* get the maximum exec freq */
                ef->max = MAX(ef->max, freq->freq);

                /* Get the minimum non-zero execution frequency. */
                if(freq->freq > 0.0)
                        ef->min_non_zero = MIN(ef->min_non_zero, freq->freq);
        }

        /* compute m and b of the transformation used to convert the doubles into scaled ints */
        {
                double smallest_diff = 1.0;

                double l2 = ef->min_non_zero;
                double h2 = ef->max;
                double l1 = 1.0;
                double h1 = MAX_INT_FREQ;

                double *fs = malloc(set_count(freqs) * sizeof(fs[0]));
                int i, j, n = 0;

                set_foreach(freqs, freq)
                        fs[n++] = freq->freq;

                /*
                 * find the smallest difference of the execution frequencies
                 * we try to ressolve it with 1 integer.
                 */
                for(i = 0; i < n; ++i) {
                        if(fs[i] <= 0.0)
                                continue;

                        for(j = i + 1; j < n; ++j) {
                                double diff = fabs(fs[i] - fs[j]);

                                if(!UNDEF(diff))
                                        smallest_diff = MIN(diff, smallest_diff);
                        }
                }

                /* according to that the slope of the translation function is 1.0 / smallest diff */
                ef->m = 1.0 / smallest_diff;

                /* the abscissa is then given by */
                ef->b = l1 - ef->m * l2;

                /*
                 * if the slope is so high that the largest integer would be larger than MAX_INT_FREQ
                 * set the largest int freq to that upper limit and recompute the translation function
                 */
                if(ef->m * h2 + ef->b > MAX_INT_FREQ) {
                        ef->m = (h1 - l1) / (h2 - l2);
                        ef->b = l1 - ef->m * l2;
                }

                free(fs);
        }

        memset(&ef->hook, 0, sizeof(ef->hook));
        ef->hook.context = ef;
        ef->hook.hook._hook_node_info = exec_freq_node_info;
        register_hook(hook_node_info, &ef->hook);

        xfree(x);

        return ef;
}

void
free_execfreq(ir_exec_freq *ef)
{
        del_set(ef->set);
        unregister_hook(hook_node_info, &ef->hook);
        free(ef);
}