eval.c

nasm早期的源代码,比较简单是学习汇编和编译原理的好例子

            e = unknown_expr();
        else
            e = scalarvect(reloc_value(e) ^ reloc_value(f));
    }
    return e;
}

static expr *expr2(int critical)
{
    expr *e, *f;

    e = expr3(critical);
    if (!e)
        return NULL;

    while (i == '&') {
        i = scan(scpriv, tokval);
        f = expr3(critical);
        if (!f)
            return NULL;
        if (!(is_simple(e) || is_just_unknown(e)) ||
            !(is_simple(f) || is_just_unknown(f))) {
            error(ERR_NONFATAL, "`&' operator may only be applied to"
                  " scalar values");
        }
        if (is_just_unknown(e) || is_just_unknown(f))
            e = unknown_expr();
        else
            e = scalarvect(reloc_value(e) & reloc_value(f));
    }
    return e;
}

static expr *expr3(int critical)
{
    expr *e, *f;

    e = expr4(critical);
    if (!e)
        return NULL;

    while (i == TOKEN_SHL || i == TOKEN_SHR) {
        int j = i;
        i = scan(scpriv, tokval);
        f = expr4(critical);
        if (!f)
            return NULL;
        if (!(is_simple(e) || is_just_unknown(e)) ||
            !(is_simple(f) || is_just_unknown(f))) {
            error(ERR_NONFATAL, "shift operator may only be applied to"
                  " scalar values");
        } else if (is_just_unknown(e) || is_just_unknown(f)) {
            e = unknown_expr();
        } else
            switch (j) {
            case TOKEN_SHL:
                e = scalarvect(reloc_value(e) << reloc_value(f));
                break;
            case TOKEN_SHR:
                e = scalarvect(((uint64_t)reloc_value(e)) >>
                               reloc_value(f));
                break;
            }
    }
    return e;
}

static expr *expr4(int critical)
{
    expr *e, *f;

    e = expr5(critical);
    if (!e)
        return NULL;
    while (i == '+' || i == '-') {
        int j = i;
        i = scan(scpriv, tokval);
        f = expr5(critical);
        if (!f)
            return NULL;
        switch (j) {
        case '+':
            e = add_vectors(e, f);
            break;
        case '-':
            e = add_vectors(e, scalar_mult(f, -1L, false));
            break;
        }
    }
    return e;
}

static expr *expr5(int critical)
{
    expr *e, *f;

    e = expr6(critical);
    if (!e)
        return NULL;
    while (i == '*' || i == '/' || i == '%' ||
           i == TOKEN_SDIV || i == TOKEN_SMOD) {
        int j = i;
        i = scan(scpriv, tokval);
        f = expr6(critical);
        if (!f)
            return NULL;
        if (j != '*' && (!(is_simple(e) || is_just_unknown(e)) ||
                         !(is_simple(f) || is_just_unknown(f)))) {
            error(ERR_NONFATAL, "division operator may only be applied to"
                  " scalar values");
            return NULL;
        }
        if (j != '*' && !is_unknown(f) && reloc_value(f) == 0) {
            error(ERR_NONFATAL, "division by zero");
            return NULL;
        }
        switch (j) {
        case '*':
            if (is_simple(e))
                e = scalar_mult(f, reloc_value(e), true);
            else if (is_simple(f))
                e = scalar_mult(e, reloc_value(f), true);
            else if (is_just_unknown(e) && is_just_unknown(f))
                e = unknown_expr();
            else {
                error(ERR_NONFATAL, "unable to multiply two "
                      "non-scalar objects");
                return NULL;
            }
            break;
        case '/':
            if (is_just_unknown(e) || is_just_unknown(f))
                e = unknown_expr();
            else
                e = scalarvect(((uint64_t)reloc_value(e)) /
                               ((uint64_t)reloc_value(f)));
            break;
        case '%':
            if (is_just_unknown(e) || is_just_unknown(f))
                e = unknown_expr();
            else
                e = scalarvect(((uint64_t)reloc_value(e)) %
                               ((uint64_t)reloc_value(f)));
            break;
        case TOKEN_SDIV:
            if (is_just_unknown(e) || is_just_unknown(f))
                e = unknown_expr();
            else
                e = scalarvect(((int64_t)reloc_value(e)) /
                               ((int64_t)reloc_value(f)));
            break;
        case TOKEN_SMOD:
            if (is_just_unknown(e) || is_just_unknown(f))
                e = unknown_expr();
            else
                e = scalarvect(((int64_t)reloc_value(e)) %
                               ((int64_t)reloc_value(f)));
            break;
        }
    }
    return e;
}

static expr *eval_floatize(enum floatize type)
{
    uint8_t result[16], *p;	/* Up to 128 bits */
    static const struct {
	int bytes, start, len;
    } formats[] = {
	{  2, 0, 2 },		/* FLOAT_16 */
	{  4, 0, 4 },		/* FLOAT_32 */
	{  8, 0, 8 },		/* FLOAT_64 */
	{ 10, 0, 8 },		/* FLOAT_80M */
	{ 10, 8, 2 },		/* FLOAT_80E */
	{ 16, 0, 8 },		/* FLOAT_128L */
	{ 16, 8, 8 },		/* FLOAT_128H */
    };
    int sign = 1;
    int64_t val;
    int j;
	
    i = scan(scpriv, tokval);
    if (i != '(') {
	error(ERR_NONFATAL, "expecting `('");
	return NULL;
    }
    i = scan(scpriv, tokval);
    if (i == '-' || i == '+') {
	sign = (i == '-') ? -1 : 1;
	i = scan(scpriv, tokval);
    }
    if (i != TOKEN_FLOAT) {
	error(ERR_NONFATAL, "expecting floating-point number");
	return NULL;
    }
    if (!float_const(tokval->t_charptr, sign, result,
		     formats[type].bytes, error))
	return NULL;
    i = scan(scpriv, tokval);
    if (i != ')') {
	error(ERR_NONFATAL, "expecting `)'");
	return NULL;
    }

    p = result+formats[type].start+formats[type].len;
    val = 0;
    for (j = formats[type].len; j; j--) {
	p--;
	val = (val << 8) + *p;
    }

    begintemp();
    addtotemp(EXPR_SIMPLE, val);

    i = scan(scpriv, tokval);
    return finishtemp();
}

static expr *expr6(int critical)
{
    int32_t type;
    expr *e;
    int32_t label_seg, label_ofs;

    switch (i) {
    case '-':
        i = scan(scpriv, tokval);
        e = expr6(critical);
        if (!e)
            return NULL;
        return scalar_mult(e, -1L, false);


    case '+':
        i = scan(scpriv, tokval);
        return expr6(critical);

    case '~':
        i = scan(scpriv, tokval);
        e = expr6(critical);
        if (!e)
            return NULL;
        if (is_just_unknown(e))
            return unknown_expr();
        else if (!is_simple(e)) {
            error(ERR_NONFATAL, "`~' operator may only be applied to"
                  " scalar values");
            return NULL;
        }
        return scalarvect(~reloc_value(e));

    case '!':
        i = scan(scpriv, tokval);
        e = expr6(critical);
        if (!e)
            return NULL;
        if (is_just_unknown(e))
            return unknown_expr();
        else if (!is_simple(e)) {
            error(ERR_NONFATAL, "`!' operator may only be applied to"
                  " scalar values");
            return NULL;
        }
        return scalarvect(!reloc_value(e));

    case TOKEN_SEG:
        i = scan(scpriv, tokval);
        e = expr6(critical);
        if (!e)
            return NULL;
        e = segment_part(e);
        if (!e)
            return NULL;
        if (is_unknown(e) && critical) {
            error(ERR_NONFATAL, "unable to determine segment base");
            return NULL;
        }
        return e;

    case TOKEN_FLOATIZE:
	return eval_floatize(tokval->t_integer);

    case '(':
        i = scan(scpriv, tokval);
        e = bexpr(critical);
        if (!e)
            return NULL;
        if (i != ')') {
            error(ERR_NONFATAL, "expecting `)'");
            return NULL;
        }
        i = scan(scpriv, tokval);
        return e;

    case TOKEN_NUM:
    case TOKEN_REG:
    case TOKEN_ID:
    case TOKEN_HERE:
    case TOKEN_BASE:
        begintemp();
        switch (i) {
        case TOKEN_NUM:
            addtotemp(EXPR_SIMPLE, tokval->t_integer);
            break;
        case TOKEN_REG:
            addtotemp(tokval->t_integer, 1L);
            if (hint && hint->type == EAH_NOHINT)
                hint->base = tokval->t_integer, hint->type = EAH_MAKEBASE;
            break;
        case TOKEN_ID:
        case TOKEN_HERE:
        case TOKEN_BASE:
            /*
             * If !location->known, this indicates that no
             * symbol, Here or Base references are valid because we
             * are in preprocess-only mode.
             */
            if (!location->known) {
                error(ERR_NONFATAL,
                      "%s not supported in preprocess-only mode",
                      (i == TOKEN_ID ? "symbol references" :
                       i == TOKEN_HERE ? "`$'" : "`$$'"));
                addtotemp(EXPR_UNKNOWN, 1L);
                break;
            }

            type = EXPR_SIMPLE; /* might get overridden by UNKNOWN */
            if (i == TOKEN_BASE) {
                label_seg = in_abs_seg ? abs_seg : location->segment;
                label_ofs = 0;
            } else if (i == TOKEN_HERE) {
                label_seg = in_abs_seg ? abs_seg : location->segment;
                label_ofs = in_abs_seg ? abs_offset : location->offset;
            } else {
                if (!labelfunc(tokval->t_charptr, &label_seg, &label_ofs)) {
                    if (critical == 2) {
                        error(ERR_NONFATAL, "symbol `%s' undefined",
                              tokval->t_charptr);
                        return NULL;
                    } else if (critical == 1) {
                        error(ERR_NONFATAL,
                              "symbol `%s' not defined before use",
                              tokval->t_charptr);
                        return NULL;
                    } else {
                        if (opflags)
                            *opflags |= 1;
                        type = EXPR_UNKNOWN;
                        label_seg = NO_SEG;
                        label_ofs = 1;
                    }
                }
                if (opflags && is_extern(tokval->t_charptr))
                    *opflags |= OPFLAG_EXTERN;
            }
            addtotemp(type, label_ofs);
            if (label_seg != NO_SEG)
                addtotemp(EXPR_SEGBASE + label_seg, 1L);
            break;
        }
        i = scan(scpriv, tokval);
        return finishtemp();

    default:
        error(ERR_NONFATAL, "expression syntax error");
        return NULL;
    }
}

void eval_global_info(struct ofmt *output, lfunc lookup_label,
                      struct location * locp)
{
    outfmt = output;
    labelfunc = lookup_label;
    location = locp;
}

expr *evaluate(scanner sc, void *scprivate, struct tokenval *tv,
               int *fwref, int critical, efunc report_error,
               struct eval_hints *hints)
{
    expr *e;
    expr *f = NULL;

    hint = hints;
    if (hint)
        hint->type = EAH_NOHINT;

    if (critical & CRITICAL) {
        critical &= ~CRITICAL;
        bexpr = rexp0;
    } else
        bexpr = expr0;

    scan = sc;
    scpriv = scprivate;
    tokval = tv;
    error = report_error;
    opflags = fwref;

    if (tokval->t_type == TOKEN_INVALID)
        i = scan(scpriv, tokval);
    else
        i = tokval->t_type;

    while (ntempexprs)          /* initialize temporary storage */
        nasm_free(tempexprs[--ntempexprs]);

    e = bexpr(critical);
    if (!e)
        return NULL;

    if (i == TOKEN_WRT) {
        i = scan(scpriv, tokval);       /* eat the WRT */
        f = expr6(critical);
        if (!f)
            return NULL;
    }
    e = scalar_mult(e, 1L, false);      /* strip far-absolute segment part */
    if (f) {
        expr *g;
        if (is_just_unknown(f))
            g = unknown_expr();
        else {
            int64_t value;
            begintemp();
            if (!is_reloc(f)) {
                error(ERR_NONFATAL, "invalid right-hand operand to WRT");
                return NULL;
            }
            value = reloc_seg(f);
            if (value == NO_SEG)
                value = reloc_value(f) | SEG_ABS;
            else if (!(value & SEG_ABS) && !(value % 2) && critical) {
                error(ERR_NONFATAL, "invalid right-hand operand to WRT");
                return NULL;
            }
            addtotemp(EXPR_WRT, value);
            g = finishtemp();
        }
        e = add_vectors(e, g);
    }
    return e;
}