gwj / at91sam9263 · Files

/*
 * Tiny Code Generator for QEMU
 *
 * Copyright (c) 2008 Fabrice Bellard
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

/* define it to suppress various consistency checks (faster) */
#define NDEBUG

/* define it to use liveness analysis (better code) */
#define USE_LIVENESS_ANALYSIS

#include <assert.h>
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <inttypes.h>

#ifdef _WIN32
#include <malloc.h>
#endif

#ifdef _AIX
#include <alloca.h>
#endif

#include "config.h"

#include "qemu-common.h"

#include "cache-utils.h"

/* Note: the long term plan is to reduce the dependancies on the QEMU
   CPU definitions. Currently they are used for qemu_ld/st
   instructions */
#define NO_CPU_IO_DEFS
#include "cpu.h"
#include "exec-all.h"

#include "tcg-op.h"
#include "elf.h"


static void patch_reloc(uint8_t *code_ptr, int type, 

                        tcg_target_long value, tcg_target_long addend);

TCGOpDef tcg_op_defs[] = {
#define DEF(s, n, copy_size) { #s, 0, 0, n, n, 0, copy_size },
#define DEF2(s, iargs, oargs, cargs, flags) { #s, iargs, oargs, cargs, iargs + oargs + cargs, flags, 0 },
#include "tcg-opc.h"
#undef DEF
#undef DEF2
};

static TCGRegSet tcg_target_available_regs[2];
static TCGRegSet tcg_target_call_clobber_regs;

/* XXX: move that inside the context */
uint16_t *gen_opc_ptr;
TCGArg *gen_opparam_ptr;

static inline void tcg_out8(TCGContext *s, uint8_t v)
{
    *s->code_ptr++ = v;
}

static inline void tcg_out16(TCGContext *s, uint16_t v)
{
    *(uint16_t *)s->code_ptr = v;
    s->code_ptr += 2;
}

static inline void tcg_out32(TCGContext *s, uint32_t v)
{
    *(uint32_t *)s->code_ptr = v;
    s->code_ptr += 4;
}

/* label relocation processing */

void tcg_out_reloc(TCGContext *s, uint8_t *code_ptr, int type, 
                   int label_index, long addend)
{
    TCGLabel *l;
    TCGRelocation *r;

    l = &s->labels[label_index];
    if (l->has_value) {

        /* FIXME: This may break relocations on RISC targets that
           modify instruction fields in place.  The caller may not have 
           written the initial value.  */

        patch_reloc(code_ptr, type, l->u.value, addend);

    } else {
        /* add a new relocation entry */
        r = tcg_malloc(sizeof(TCGRelocation));
        r->type = type;
        r->ptr = code_ptr;
        r->addend = addend;
        r->next = l->u.first_reloc;
        l->u.first_reloc = r;
    }
}

static void tcg_out_label(TCGContext *s, int label_index, 
                          tcg_target_long value)
{
    TCGLabel *l;
    TCGRelocation *r;

    l = &s->labels[label_index];
    if (l->has_value)
        tcg_abort();
    r = l->u.first_reloc;
    while (r != NULL) {

        patch_reloc(r->ptr, r->type, value, r->addend);

        r = r->next;
    }
    l->has_value = 1;
    l->u.value = value;
}

int gen_new_label(void)
{
    TCGContext *s = &tcg_ctx;
    int idx;
    TCGLabel *l;

    if (s->nb_labels >= TCG_MAX_LABELS)
        tcg_abort();
    idx = s->nb_labels++;
    l = &s->labels[idx];
    l->has_value = 0;
    l->u.first_reloc = NULL;
    return idx;
}

#include "tcg-target.c"

/* pool based memory allocation */
void *tcg_malloc_internal(TCGContext *s, int size)
{
    TCGPool *p;
    int pool_size;

    if (size > TCG_POOL_CHUNK_SIZE) {
        /* big malloc: insert a new pool (XXX: could optimize) */
        p = qemu_malloc(sizeof(TCGPool) + size);
        p->size = size;
        if (s->pool_current)
            s->pool_current->next = p;
        else
            s->pool_first = p;
        p->next = s->pool_current;
    } else {
        p = s->pool_current;
        if (!p) {
            p = s->pool_first;
            if (!p)
                goto new_pool;
        } else {
            if (!p->next) {
            new_pool:
                pool_size = TCG_POOL_CHUNK_SIZE;
                p = qemu_malloc(sizeof(TCGPool) + pool_size);
                p->size = pool_size;
                p->next = NULL;
                if (s->pool_current) 
                    s->pool_current->next = p;
                else
                    s->pool_first = p;
            } else {
                p = p->next;
            }
        }
    }
    s->pool_current = p;
    s->pool_cur = p->data + size;
    s->pool_end = p->data + p->size;
    return p->data;
}

void tcg_pool_reset(TCGContext *s)
{
    s->pool_cur = s->pool_end = NULL;
    s->pool_current = NULL;
}

void tcg_context_init(TCGContext *s)
{
    int op, total_args, n;
    TCGOpDef *def;
    TCGArgConstraint *args_ct;
    int *sorted_args;

    memset(s, 0, sizeof(*s));
    s->temps = s->static_temps;
    s->nb_globals = 0;

    /* Count total number of arguments and allocate the corresponding
       space */
    total_args = 0;
    for(op = 0; op < NB_OPS; op++) {
        def = &tcg_op_defs[op];
        n = def->nb_iargs + def->nb_oargs;
        total_args += n;
    }

    args_ct = qemu_malloc(sizeof(TCGArgConstraint) * total_args);
    sorted_args = qemu_malloc(sizeof(int) * total_args);

    for(op = 0; op < NB_OPS; op++) {
        def = &tcg_op_defs[op];
        def->args_ct = args_ct;
        def->sorted_args = sorted_args;
        n = def->nb_iargs + def->nb_oargs;
        sorted_args += n;
        args_ct += n;
    }

    tcg_target_init(s);

    /* init global prologue and epilogue */
    s->code_buf = code_gen_prologue;
    s->code_ptr = s->code_buf;
    tcg_target_qemu_prologue(s);
    flush_icache_range((unsigned long)s->code_buf, 
                       (unsigned long)s->code_ptr);

}

void tcg_set_frame(TCGContext *s, int reg,
                   tcg_target_long start, tcg_target_long size)
{
    s->frame_start = start;
    s->frame_end = start + size;
    s->frame_reg = reg;
}

void tcg_func_start(TCGContext *s)
{

    int i;

    tcg_pool_reset(s);
    s->nb_temps = s->nb_globals;

    for(i = 0; i < (TCG_TYPE_COUNT * 2); i++)

        s->first_free_temp[i] = -1;

    s->labels = tcg_malloc(sizeof(TCGLabel) * TCG_MAX_LABELS);
    s->nb_labels = 0;
    s->current_frame_offset = s->frame_start;

    gen_opc_ptr = gen_opc_buf;
    gen_opparam_ptr = gen_opparam_buf;
}

static inline void tcg_temp_alloc(TCGContext *s, int n)
{
    if (n > TCG_MAX_TEMPS)
        tcg_abort();
}

static inline int tcg_global_reg_new_internal(TCGType type, int reg,
                                              const char *name)

{
    TCGContext *s = &tcg_ctx;
    TCGTemp *ts;
    int idx;

#if TCG_TARGET_REG_BITS == 32
    if (type != TCG_TYPE_I32)
        tcg_abort();
#endif
    if (tcg_regset_test_reg(s->reserved_regs, reg))
        tcg_abort();
    idx = s->nb_globals;
    tcg_temp_alloc(s, s->nb_globals + 1);
    ts = &s->temps[s->nb_globals];
    ts->base_type = type;
    ts->type = type;
    ts->fixed_reg = 1;
    ts->reg = reg;
    ts->name = name;
    s->nb_globals++;
    tcg_regset_set_reg(s->reserved_regs, reg);

    return idx;
}

TCGv_i32 tcg_global_reg_new_i32(int reg, const char *name)
{
    int idx;

    idx = tcg_global_reg_new_internal(TCG_TYPE_I32, reg, name);
    return MAKE_TCGV_I32(idx);
}

TCGv_i64 tcg_global_reg_new_i64(int reg, const char *name)
{
    int idx;

    idx = tcg_global_reg_new_internal(TCG_TYPE_I64, reg, name);
    return MAKE_TCGV_I64(idx);

}

#if TCG_TARGET_REG_BITS == 32
/* temporary hack to avoid register shortage for tcg_qemu_st64() */

TCGv_i64 tcg_global_reg2_new_hack(TCGType type, int reg1, int reg2,
                                  const char *name)

{
    TCGContext *s = &tcg_ctx;
    TCGTemp *ts;
    int idx;
    char buf[64];

    if (type != TCG_TYPE_I64)
        tcg_abort();
    idx = s->nb_globals;
    tcg_temp_alloc(s, s->nb_globals + 2);
    ts = &s->temps[s->nb_globals];
    ts->base_type = type;
    ts->type = TCG_TYPE_I32;
    ts->fixed_reg = 1;
    ts->reg = reg1;
    pstrcpy(buf, sizeof(buf), name);
    pstrcat(buf, sizeof(buf), "_0");
    ts->name = strdup(buf);

    ts++;
    ts->base_type = type;
    ts->type = TCG_TYPE_I32;
    ts->fixed_reg = 1;
    ts->reg = reg2;
    pstrcpy(buf, sizeof(buf), name);
    pstrcat(buf, sizeof(buf), "_1");
    ts->name = strdup(buf);

    s->nb_globals += 2;

    return MAKE_TCGV_I64(idx);

}
#endif

static inline int tcg_global_mem_new_internal(TCGType type, int reg,
                                              tcg_target_long offset,
                                              const char *name)

{
    TCGContext *s = &tcg_ctx;
    TCGTemp *ts;
    int idx;

    idx = s->nb_globals;
#if TCG_TARGET_REG_BITS == 32
    if (type == TCG_TYPE_I64) {
        char buf[64];

        tcg_temp_alloc(s, s->nb_globals + 2);

        ts = &s->temps[s->nb_globals];
        ts->base_type = type;
        ts->type = TCG_TYPE_I32;
        ts->fixed_reg = 0;
        ts->mem_allocated = 1;
        ts->mem_reg = reg;
#ifdef TCG_TARGET_WORDS_BIGENDIAN
        ts->mem_offset = offset + 4;
#else
        ts->mem_offset = offset;
#endif
        pstrcpy(buf, sizeof(buf), name);
        pstrcat(buf, sizeof(buf), "_0");
        ts->name = strdup(buf);
        ts++;

        ts->base_type = type;
        ts->type = TCG_TYPE_I32;
        ts->fixed_reg = 0;
        ts->mem_allocated = 1;
        ts->mem_reg = reg;
#ifdef TCG_TARGET_WORDS_BIGENDIAN
        ts->mem_offset = offset;
#else
        ts->mem_offset = offset + 4;
#endif
        pstrcpy(buf, sizeof(buf), name);
        pstrcat(buf, sizeof(buf), "_1");
        ts->name = strdup(buf);

        s->nb_globals += 2;
    } else
#endif
    {
        tcg_temp_alloc(s, s->nb_globals + 1);
        ts = &s->temps[s->nb_globals];
        ts->base_type = type;
        ts->type = type;
        ts->fixed_reg = 0;
        ts->mem_allocated = 1;
        ts->mem_reg = reg;
        ts->mem_offset = offset;
        ts->name = name;
        s->nb_globals++;
    }

    return idx;
}

TCGv_i32 tcg_global_mem_new_i32(int reg, tcg_target_long offset,
                                const char *name)
{
    int idx;

    idx = tcg_global_mem_new_internal(TCG_TYPE_I32, reg, offset, name);
    return MAKE_TCGV_I32(idx);
}

TCGv_i64 tcg_global_mem_new_i64(int reg, tcg_target_long offset,
                                const char *name)
{
    int idx;

    idx = tcg_global_mem_new_internal(TCG_TYPE_I64, reg, offset, name);
    return MAKE_TCGV_I64(idx);

}

static inline int tcg_temp_new_internal(TCGType type, int temp_local)

{
    TCGContext *s = &tcg_ctx;
    TCGTemp *ts;

    int idx, k;

    k = type;
    if (temp_local)
        k += TCG_TYPE_COUNT;
    idx = s->first_free_temp[k];

    if (idx != -1) {
        /* There is already an available temp with the
           right type */
        ts = &s->temps[idx];

        s->first_free_temp[k] = ts->next_free_temp;

        ts->temp_allocated = 1;

        assert(ts->temp_local == temp_local);

    } else {
        idx = s->nb_temps;

#if TCG_TARGET_REG_BITS == 32

        if (type == TCG_TYPE_I64) {

            tcg_temp_alloc(s, s->nb_temps + 2);

            ts = &s->temps[s->nb_temps];
            ts->base_type = type;
            ts->type = TCG_TYPE_I32;
            ts->temp_allocated = 1;

            ts->temp_local = temp_local;

            ts->name = NULL;
            ts++;
            ts->base_type = TCG_TYPE_I32;
            ts->type = TCG_TYPE_I32;
            ts->temp_allocated = 1;

            ts->temp_local = temp_local;

            ts->name = NULL;
            s->nb_temps += 2;
        } else

#endif

        {
            tcg_temp_alloc(s, s->nb_temps + 1);
            ts = &s->temps[s->nb_temps];
            ts->base_type = type;
            ts->type = type;
            ts->temp_allocated = 1;

            ts->temp_local = temp_local;

            ts->name = NULL;
            s->nb_temps++;
        }

    }

    return idx;

}

TCGv_i32 tcg_temp_new_internal_i32(int temp_local)
{
    int idx;

    idx = tcg_temp_new_internal(TCG_TYPE_I32, temp_local);
    return MAKE_TCGV_I32(idx);
}

TCGv_i64 tcg_temp_new_internal_i64(int temp_local)
{
    int idx;

    idx = tcg_temp_new_internal(TCG_TYPE_I64, temp_local);
    return MAKE_TCGV_I64(idx);
}

static inline void tcg_temp_free_internal(int idx)

{
    TCGContext *s = &tcg_ctx;
    TCGTemp *ts;

    int k;

    assert(idx >= s->nb_globals && idx < s->nb_temps);

    ts = &s->temps[idx];

    assert(ts->temp_allocated != 0);
    ts->temp_allocated = 0;

    k = ts->base_type;
    if (ts->temp_local)
        k += TCG_TYPE_COUNT;
    ts->next_free_temp = s->first_free_temp[k];
    s->first_free_temp[k] = idx;

}

void tcg_temp_free_i32(TCGv_i32 arg)
{
    tcg_temp_free_internal(GET_TCGV_I32(arg));
}

void tcg_temp_free_i64(TCGv_i64 arg)
{
    tcg_temp_free_internal(GET_TCGV_I64(arg));
}

TCGv_i32 tcg_const_i32(int32_t val)

{

    TCGv_i32 t0;
    t0 = tcg_temp_new_i32();

    tcg_gen_movi_i32(t0, val);
    return t0;
}

TCGv_i64 tcg_const_i64(int64_t val)

{

    TCGv_i64 t0;
    t0 = tcg_temp_new_i64();

    tcg_gen_movi_i64(t0, val);
    return t0;

}

TCGv_i32 tcg_const_local_i32(int32_t val)

{

    TCGv_i32 t0;
    t0 = tcg_temp_local_new_i32();

    tcg_gen_movi_i32(t0, val);
    return t0;
}

TCGv_i64 tcg_const_local_i64(int64_t val)

{

    TCGv_i64 t0;
    t0 = tcg_temp_local_new_i64();

    tcg_gen_movi_i64(t0, val);
    return t0;
}

void tcg_register_helper(void *func, const char *name)
{
    TCGContext *s = &tcg_ctx;
    int n;
    if ((s->nb_helpers + 1) > s->allocated_helpers) {
        n = s->allocated_helpers;
        if (n == 0) {
            n = 4;
        } else {
            n *= 2;
        }
        s->helpers = realloc(s->helpers, n * sizeof(TCGHelperInfo));
        s->allocated_helpers = n;
    }

    s->helpers[s->nb_helpers].func = (tcg_target_ulong)func;

    s->helpers[s->nb_helpers].name = name;
    s->nb_helpers++;
}

/* Note: we convert the 64 bit args to 32 bit and do some alignment
   and endian swap. Maybe it would be better to do the alignment
   and endian swap in tcg_reg_alloc_call(). */

void tcg_gen_callN(TCGContext *s, TCGv_ptr func, unsigned int flags,
                   int sizemask, TCGArg ret, int nargs, TCGArg *args)

{

    int call_type;
    int i;
    int real_args;
    int nb_rets;
    TCGArg *nparam;
    *gen_opc_ptr++ = INDEX_op_call;
    nparam = gen_opparam_ptr++;
    call_type = (flags & TCG_CALL_TYPE_MASK);
    if (ret != TCG_CALL_DUMMY_ARG) {
#if TCG_TARGET_REG_BITS < 64
        if (sizemask & 1) {

#ifdef TCG_TARGET_WORDS_BIGENDIAN

            *gen_opparam_ptr++ = ret + 1;
            *gen_opparam_ptr++ = ret;

#else

            *gen_opparam_ptr++ = ret;
            *gen_opparam_ptr++ = ret + 1;

#endif

            nb_rets = 2;
        } else
#endif
        {
            *gen_opparam_ptr++ = ret;
            nb_rets = 1;

        }

    } else {
        nb_rets = 0;

    }

    real_args = 0;
    for (i = 0; i < nargs; i++) {
#if TCG_TARGET_REG_BITS < 64
        if (sizemask & (2 << i)) {

#ifdef TCG_TARGET_I386
            /* REGPARM case: if the third parameter is 64 bit, it is
               allocated on the stack */

            if (i == 2 && call_type == TCG_CALL_TYPE_REGPARM) {

                call_type = TCG_CALL_TYPE_REGPARM_2;
                flags = (flags & ~TCG_CALL_TYPE_MASK) | call_type;
            }

#endif

#ifdef TCG_TARGET_CALL_ALIGN_ARGS
            /* some targets want aligned 64 bit args */

            if (real_args & 1) {

                *gen_opparam_ptr++ = TCG_CALL_DUMMY_ARG;

                real_args++;

            }
#endif

#ifdef TCG_TARGET_WORDS_BIGENDIAN

            *gen_opparam_ptr++ = args[i] + 1;
            *gen_opparam_ptr++ = args[i];

#else

            *gen_opparam_ptr++ = args[i];
            *gen_opparam_ptr++ = args[i] + 1;

#endif

            real_args += 2;
        } else

#endif

        {
            *gen_opparam_ptr++ = args[i];
            real_args++;

        }
    }

    *gen_opparam_ptr++ = GET_TCGV_PTR(func);

    *gen_opparam_ptr++ = flags;

    *nparam = (nb_rets << 16) | (real_args + 1);

    /* total parameters, needed to go backward in the instruction stream */
    *gen_opparam_ptr++ = 1 + nb_rets + real_args + 3;

}

#if TCG_TARGET_REG_BITS == 32

void tcg_gen_shifti_i64(TCGv_i64 ret, TCGv_i64 arg1,

                        int c, int right, int arith)
{

    if (c == 0) {

        tcg_gen_mov_i32(TCGV_LOW(ret), TCGV_LOW(arg1));

        tcg_gen_mov_i32(TCGV_HIGH(ret), TCGV_HIGH(arg1));
    } else if (c >= 32) {

        c -= 32;
        if (right) {
            if (arith) {

                tcg_gen_sari_i32(TCGV_LOW(ret), TCGV_HIGH(arg1), c);

                tcg_gen_sari_i32(TCGV_HIGH(ret), TCGV_HIGH(arg1), 31);

            } else {

                tcg_gen_shri_i32(TCGV_LOW(ret), TCGV_HIGH(arg1), c);

                tcg_gen_movi_i32(TCGV_HIGH(ret), 0);

            }
        } else {

            tcg_gen_shli_i32(TCGV_HIGH(ret), TCGV_LOW(arg1), c);
            tcg_gen_movi_i32(TCGV_LOW(ret), 0);

        }
    } else {

        TCGv_i32 t0, t1;

        t0 = tcg_temp_new_i32();
        t1 = tcg_temp_new_i32();

        if (right) {

            tcg_gen_shli_i32(t0, TCGV_HIGH(arg1), 32 - c);

            if (arith)

                tcg_gen_sari_i32(t1, TCGV_HIGH(arg1), c);

            else

                tcg_gen_shri_i32(t1, TCGV_HIGH(arg1), c);

            tcg_gen_shri_i32(TCGV_LOW(ret), TCGV_LOW(arg1), c);
            tcg_gen_or_i32(TCGV_LOW(ret), TCGV_LOW(ret), t0);

            tcg_gen_mov_i32(TCGV_HIGH(ret), t1);

        } else {

            tcg_gen_shri_i32(t0, TCGV_LOW(arg1), 32 - c);

            /* Note: ret can be the same as arg1, so we use t1 */

            tcg_gen_shli_i32(t1, TCGV_LOW(arg1), c);

            tcg_gen_shli_i32(TCGV_HIGH(ret), TCGV_HIGH(arg1), c);
            tcg_gen_or_i32(TCGV_HIGH(ret), TCGV_HIGH(ret), t0);

            tcg_gen_mov_i32(TCGV_LOW(ret), t1);

        }

        tcg_temp_free_i32(t0);
        tcg_temp_free_i32(t1);

    }
}

#endif

static void tcg_reg_alloc_start(TCGContext *s)

{
    int i;
    TCGTemp *ts;
    for(i = 0; i < s->nb_globals; i++) {
        ts = &s->temps[i];
        if (ts->fixed_reg) {
            ts->val_type = TEMP_VAL_REG;
        } else {
            ts->val_type = TEMP_VAL_MEM;
        }
    }

    for(i = s->nb_globals; i < s->nb_temps; i++) {
        ts = &s->temps[i];
        ts->val_type = TEMP_VAL_DEAD;
        ts->mem_allocated = 0;
        ts->fixed_reg = 0;
    }

    for(i = 0; i < TCG_TARGET_NB_REGS; i++) {
        s->reg_to_temp[i] = -1;
    }
}

static char *tcg_get_arg_str_idx(TCGContext *s, char *buf, int buf_size,
                                 int idx)

{
    TCGTemp *ts;

    ts = &s->temps[idx];
    if (idx < s->nb_globals) {
        pstrcpy(buf, buf_size, ts->name);

    } else {

        if (ts->temp_local) 
            snprintf(buf, buf_size, "loc%d", idx - s->nb_globals);
        else
            snprintf(buf, buf_size, "tmp%d", idx - s->nb_globals);

    }
    return buf;
}

char *tcg_get_arg_str_i32(TCGContext *s, char *buf, int buf_size, TCGv_i32 arg)
{
    return tcg_get_arg_str_idx(s, buf, buf_size, GET_TCGV_I32(arg));
}

char *tcg_get_arg_str_i64(TCGContext *s, char *buf, int buf_size, TCGv_i64 arg)

{

    return tcg_get_arg_str_idx(s, buf, buf_size, GET_TCGV_I64(arg));

}

static int helper_cmp(const void *p1, const void *p2)

{

    const TCGHelperInfo *th1 = p1;
    const TCGHelperInfo *th2 = p2;
    if (th1->func < th2->func)
        return -1;
    else if (th1->func == th2->func)
        return 0;
    else
        return 1;

}

/* find helper definition (Note: A hash table would be better) */
static TCGHelperInfo *tcg_find_helper(TCGContext *s, tcg_target_ulong val)

{

    int m, m_min, m_max;

    TCGHelperInfo *th;

    tcg_target_ulong v;

    if (unlikely(!s->helpers_sorted)) {
        qsort(s->helpers, s->nb_helpers, sizeof(TCGHelperInfo), 
              helper_cmp);
        s->helpers_sorted = 1;
    }

    /* binary search */
    m_min = 0;
    m_max = s->nb_helpers - 1;
    while (m_min <= m_max) {
        m = (m_min + m_max) >> 1;
        th = &s->helpers[m];
        v = th->func;
        if (v == val)
            return th;
        else if (val < v) {
            m_max = m - 1;
        } else {
            m_min = m + 1;

        }
    }