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

  vm_args.c - process method call arguments.

  $Author$

  Copyright (C) 2014- Yukihiro Matsumoto

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

NORETURN(static void raise_argument_error(rb_execution_context_t *ec, const rb_iseq_t *iseq, const VALUE exc));
NORETURN(static void argument_arity_error(rb_execution_context_t *ec, const rb_iseq_t *iseq, const int miss_argc, const int min_argc, const int max_argc));
NORETURN(static void argument_kw_error(rb_execution_context_t *ec, const rb_iseq_t *iseq, const char *error, const VALUE keys));
VALUE rb_keyword_error_new(const char *error, VALUE keys); /* class.c */
static VALUE method_missing(rb_execution_context_t *ec, VALUE obj, ID id, int argc, const VALUE *argv,
                            enum method_missing_reason call_status, int kw_splat);
const rb_callable_method_entry_t *rb_resolve_refined_method_callable(VALUE refinements, const rb_callable_method_entry_t *me);

struct args_info {
    /* basic args info */
    VALUE *argv;
    int argc;

    /* additional args info */
    int rest_index;
    int rest_dupped;
    const struct rb_callinfo_kwarg *kw_arg;
    VALUE *kw_argv;
    VALUE rest;
};

enum arg_setup_type {
    arg_setup_method,
    arg_setup_block
};

static inline void
arg_rest_dup(struct args_info *args)
{
    if (!args->rest_dupped) {
        args->rest = rb_ary_dup(args->rest);
        args->rest_dupped = TRUE;
    }
}

static inline int
args_argc(struct args_info *args)
{
    if (args->rest == Qfalse) {
        return args->argc;
    }
    else {
        return args->argc + RARRAY_LENINT(args->rest) - args->rest_index;
    }
}

static inline void
args_extend(struct args_info *args, const int min_argc)
{
    int i;

    if (args->rest) {
        arg_rest_dup(args);
        VM_ASSERT(args->rest_index == 0);
        for (i=args->argc + RARRAY_LENINT(args->rest); i<min_argc; i++) {
            rb_ary_push(args->rest, Qnil);
        }
    }
    else {
        for (i=args->argc; i<min_argc; i++) {
            args->argv[args->argc++] = Qnil;
        }
    }
}

static inline void
args_reduce(struct args_info *args, int over_argc)
{
    if (args->rest) {
        const long len = RARRAY_LEN(args->rest);

        if (len > over_argc) {
            arg_rest_dup(args);
            rb_ary_resize(args->rest, len - over_argc);
            return;
        }
        else {
            args->rest = Qfalse;
            over_argc -= len;
        }
    }

    VM_ASSERT(args->argc >= over_argc);
    args->argc -= over_argc;
}

static inline int
args_check_block_arg0(struct args_info *args)
{
    VALUE ary = Qnil;

    if (args->rest && RARRAY_LEN(args->rest) == 1) {
        VALUE arg0 = RARRAY_AREF(args->rest, 0);
        ary = rb_check_array_type(arg0);
    }
    else if (args->argc == 1) {
        VALUE arg0 = args->argv[0];
        ary = rb_check_array_type(arg0);
        args->argv[0] = arg0; /* see: https://bugs.ruby-lang.org/issues/8484 */
    }

    if (!NIL_P(ary)) {
        args->rest = ary;
        args->rest_index = 0;
        args->argc = 0;
        return TRUE;
    }

    return FALSE;
}

static inline void
args_copy(struct args_info *args)
{
    if (args->rest != Qfalse) {
        int argc = args->argc;
        args->argc = 0;
        arg_rest_dup(args);

        /*
         * argv: [m0, m1, m2, m3]
         * rest: [a0, a1, a2, a3, a4, a5]
         *                ^
         *                rest_index
         *
         * #=> first loop
         *
         * argv: [m0, m1]
         * rest: [m2, m3, a2, a3, a4, a5]
         *        ^
         *        rest_index
         *
         * #=> 2nd loop
         *
         * argv: [] (argc == 0)
         * rest: [m0, m1, m2, m3, a2, a3, a4, a5]
         *        ^
         *        rest_index
         */
        while (args->rest_index > 0 && argc > 0) {
            RARRAY_ASET(args->rest, --args->rest_index, args->argv[--argc]);
        }
        while (argc > 0) {
            rb_ary_unshift(args->rest, args->argv[--argc]);
        }
    }
    else if (args->argc > 0) {
        args->rest = rb_ary_new_from_values(args->argc, args->argv);
        args->rest_index = 0;
        args->rest_dupped = TRUE;
        args->argc = 0;
    }
}

static inline const VALUE *
args_rest_argv(struct args_info *args)
{
    return RARRAY_CONST_PTR(args->rest) + args->rest_index;
}

static inline VALUE
args_rest_array(struct args_info *args)
{
    VALUE ary;

    if (args->rest) {
        ary = rb_ary_behead(args->rest, args->rest_index);
        args->rest_index = 0;
        args->rest = 0;
    }
    else {
        ary = rb_ary_new();
    }
    return ary;
}

static int
args_kw_argv_to_hash(struct args_info *args)
{
    const struct rb_callinfo_kwarg *kw_arg = args->kw_arg;
    const VALUE *const passed_keywords = kw_arg->keywords;
    const int kw_len = kw_arg->keyword_len;
    VALUE h = rb_hash_new_with_size(kw_len);
    const int kw_start = args->argc - kw_len;
    const VALUE * const kw_argv = args->argv + kw_start;
    int i;

    args->argc = kw_start + 1;
    for (i=0; i<kw_len; i++) {
        rb_hash_aset(h, passed_keywords[i], kw_argv[i]);
    }

    args->argv[args->argc - 1] = h;

    return args->argc;
}

static inline void
args_setup_lead_parameters(struct args_info *args, int argc, VALUE *locals)
{
    if (args->argc >= argc) {
        /* do noting */
        args->argc -= argc;
        args->argv += argc;
    }
    else {
        int i, j;
        const VALUE *argv = args_rest_argv(args);

        for (i=args->argc, j=0; i<argc; i++, j++) {
            locals[i] = argv[j];
        }
        args->rest_index += argc - args->argc;
        args->argc = 0;
    }
}

static inline void
args_setup_post_parameters(struct args_info *args, int argc, VALUE *locals)
{
    long len;
    len = RARRAY_LEN(args->rest);
    MEMCPY(locals, RARRAY_CONST_PTR(args->rest) + len - argc, VALUE, argc);
    rb_ary_resize(args->rest, len - argc);
}

static inline int
args_setup_opt_parameters(struct args_info *args, int opt_max, VALUE *locals)
{
    int i;

    if (args->argc >= opt_max) {
        args->argc -= opt_max;
        args->argv += opt_max;
        i = opt_max;
    }
    else {
        int j;
        i = args->argc;
        args->argc = 0;

        if (args->rest) {
            int len = RARRAY_LENINT(args->rest);
            const VALUE *argv = RARRAY_CONST_PTR(args->rest);

            for (; i<opt_max && args->rest_index < len; i++, args->rest_index++) {
                locals[i] = argv[args->rest_index];
            }
        }

        /* initialize by nil */
        for (j=i; j<opt_max; j++) {
            locals[j] = Qnil;
        }
    }

    return i;
}

static inline void
args_setup_rest_parameter(struct args_info *args, VALUE *locals)
{
    *locals = args_rest_array(args);
}

static VALUE
make_unknown_kw_hash(const VALUE *passed_keywords, int passed_keyword_len, const VALUE *kw_argv)
{
    int i;
    VALUE obj = rb_ary_hidden_new(1);

    for (i=0; i<passed_keyword_len; i++) {
        if (!UNDEF_P(kw_argv[i])) {
            rb_ary_push(obj, passed_keywords[i]);
        }
    }
    return obj;
}

static VALUE
make_rest_kw_hash(const VALUE *passed_keywords, int passed_keyword_len, const VALUE *kw_argv)
{
    int i;
    VALUE obj = rb_hash_new_with_size(passed_keyword_len);

    for (i=0; i<passed_keyword_len; i++) {
        if (!UNDEF_P(kw_argv[i])) {
            rb_hash_aset(obj, passed_keywords[i], kw_argv[i]);
        }
    }
    return obj;
}

static inline int
args_setup_kw_parameters_lookup(const ID key, VALUE *ptr, const VALUE *const passed_keywords, VALUE *passed_values, const int passed_keyword_len)
{
    int i;
    const VALUE keyname = ID2SYM(key);

    for (i=0; i<passed_keyword_len; i++) {
        if (keyname == passed_keywords[i]) {
            *ptr = passed_values[i];
            passed_values[i] = Qundef;
            return TRUE;
        }
    }

    return FALSE;
}

#define KW_SPECIFIED_BITS_MAX (32-1) /* TODO: 32 -> Fixnum's max bits */

static void
args_setup_kw_parameters(rb_execution_context_t *const ec, const rb_iseq_t *const iseq,
                         VALUE *const passed_values, const int passed_keyword_len, const VALUE *const passed_keywords,
                         VALUE *const locals)
{
    const ID *acceptable_keywords = ISEQ_BODY(iseq)->param.keyword->table;
    const int req_key_num = ISEQ_BODY(iseq)->param.keyword->required_num;
    const int key_num = ISEQ_BODY(iseq)->param.keyword->num;
    const VALUE * const default_values = ISEQ_BODY(iseq)->param.keyword->default_values;
    VALUE missing = 0;
    int i, di, found = 0;
    int unspecified_bits = 0;
    VALUE unspecified_bits_value = Qnil;

    for (i=0; i<req_key_num; i++) {
        ID key = acceptable_keywords[i];
        if (args_setup_kw_parameters_lookup(key, &locals[i], passed_keywords, passed_values, passed_keyword_len)) {
            found++;
        }
        else {
            if (!missing) missing = rb_ary_hidden_new(1);
            rb_ary_push(missing, ID2SYM(key));
        }
    }

    if (missing) argument_kw_error(ec, iseq, "missing", missing);

    for (di=0; i<key_num; i++, di++) {
        if (args_setup_kw_parameters_lookup(acceptable_keywords[i], &locals[i], passed_keywords, passed_values, passed_keyword_len)) {
            found++;
        }
        else {
            if (UNDEF_P(default_values[di])) {
                locals[i] = Qnil;

                if (LIKELY(i < KW_SPECIFIED_BITS_MAX)) {
                    unspecified_bits |= 0x01 << di;
                }
                else {
                    if (NIL_P(unspecified_bits_value)) {
                        /* fixnum -> hash */
                        int j;
                        unspecified_bits_value = rb_hash_new();

                        for (j=0; j<KW_SPECIFIED_BITS_MAX; j++) {
                            if (unspecified_bits & (0x01 << j)) {
                                rb_hash_aset(unspecified_bits_value, INT2FIX(j), Qtrue);
                            }
                        }
                    }
                    rb_hash_aset(unspecified_bits_value, INT2FIX(di), Qtrue);
                }
            }
            else {
                locals[i] = default_values[di];
            }
        }
    }

    if (ISEQ_BODY(iseq)->param.flags.has_kwrest) {
        const int rest_hash_index = key_num + 1;
        locals[rest_hash_index] = make_rest_kw_hash(passed_keywords, passed_keyword_len, passed_values);
    }
    else {
        if (found != passed_keyword_len) {
            VALUE keys = make_unknown_kw_hash(passed_keywords, passed_keyword_len, passed_values);
            argument_kw_error(ec, iseq, "unknown", keys);
        }
    }

    if (NIL_P(unspecified_bits_value)) {
        unspecified_bits_value = INT2FIX(unspecified_bits);
    }
    locals[key_num] = unspecified_bits_value;
}

static void
args_setup_kw_parameters_from_kwsplat(rb_execution_context_t *const ec, const rb_iseq_t *const iseq,
                         VALUE keyword_hash, VALUE *const locals, bool remove_hash_value)
{
    const ID *acceptable_keywords = ISEQ_BODY(iseq)->param.keyword->table;
    const int req_key_num = ISEQ_BODY(iseq)->param.keyword->required_num;
    const int key_num = ISEQ_BODY(iseq)->param.keyword->num;
    const VALUE * const default_values = ISEQ_BODY(iseq)->param.keyword->default_values;
    VALUE missing = 0;
    int i, di;
    int unspecified_bits = 0;
    size_t keyword_size = RHASH_SIZE(keyword_hash);
    VALUE unspecified_bits_value = Qnil;

    for (i=0; i<req_key_num; i++) {
        VALUE key = ID2SYM(acceptable_keywords[i]);
        VALUE value;
        if (remove_hash_value) {
            value = rb_hash_delete_entry(keyword_hash, key);
        }
        else {
            value = rb_hash_lookup2(keyword_hash, key, Qundef);
        }

        if (!UNDEF_P(value)) {
            keyword_size--;
            locals[i] = value;
        }
        else {
            if (!missing) missing = rb_ary_hidden_new(1);
            rb_ary_push(missing, key);
        }
    }

    if (missing) argument_kw_error(ec, iseq, "missing", missing);

    for (di=0; i<key_num; i++, di++) {
        VALUE key = ID2SYM(acceptable_keywords[i]);
        VALUE value;
        if (remove_hash_value) {
            value = rb_hash_delete_entry(keyword_hash, key);
        }
        else {
            value = rb_hash_lookup2(keyword_hash, key, Qundef);
        }

        if (!UNDEF_P(value)) {
            keyword_size--;
            locals[i] = value;
        }
        else {
            if (UNDEF_P(default_values[di])) {
                locals[i] = Qnil;

                if (LIKELY(i < KW_SPECIFIED_BITS_MAX)) {
                    unspecified_bits |= 0x01 << di;
                }
                else {
                    if (NIL_P(unspecified_bits_value)) {
                        /* fixnum -> hash */
                        int j;
                        unspecified_bits_value = rb_hash_new();

                        for (j=0; j<KW_SPECIFIED_BITS_MAX; j++) {
                            if (unspecified_bits & (0x01 << j)) {
                                rb_hash_aset(unspecified_bits_value, INT2FIX(j), Qtrue);
                            }
                        }
                    }
                    rb_hash_aset(unspecified_bits_value, INT2FIX(di), Qtrue);
                }
            }
            else {
                locals[i] = default_values[di];
            }
        }
    }

    if (ISEQ_BODY(iseq)->param.flags.has_kwrest) {
        const int rest_hash_index = key_num + 1;
        locals[rest_hash_index] = keyword_hash;
    }
    else {
        if (!remove_hash_value) {
            if (keyword_size != 0) {
                /* Recurse with duplicated keyword hash in remove mode.
                 * This is simpler than writing code to check which entries in the hash do not match.
                 * This will raise an exception, so the additional performance impact shouldn't be material.
                 */
                args_setup_kw_parameters_from_kwsplat(ec, iseq, rb_hash_dup(keyword_hash), locals, true);
            }
        }
        else if (!RHASH_EMPTY_P(keyword_hash)) {
            argument_kw_error(ec, iseq, "unknown", rb_hash_keys(keyword_hash));
        }
    }

    if (NIL_P(unspecified_bits_value)) {
        unspecified_bits_value = INT2FIX(unspecified_bits);
    }
    locals[key_num] = unspecified_bits_value;
}

static inline void
args_setup_kw_rest_parameter(VALUE keyword_hash, VALUE *locals, int kw_flag, bool anon_kwrest)
{
    if (NIL_P(keyword_hash)) {
        if (!anon_kwrest) {
            keyword_hash = rb_hash_new();
        }
    }
    else if (!(kw_flag & VM_CALL_KW_SPLAT_MUT)) {
        keyword_hash = rb_hash_dup(keyword_hash);
    }
    locals[0] = keyword_hash;
}

static inline void
args_setup_block_parameter(const rb_execution_context_t *ec, struct rb_calling_info *calling, VALUE *locals)
{
    VALUE block_handler = calling->block_handler;
    *locals = rb_vm_bh_to_procval(ec, block_handler);
}

static inline int
ignore_keyword_hash_p(VALUE keyword_hash, const rb_iseq_t * const iseq, unsigned int * kw_flag, VALUE * converted_keyword_hash)
{
    if (keyword_hash == Qnil) {
        goto ignore;
    }
    else if (!RB_TYPE_P(keyword_hash, T_HASH)) {
        keyword_hash = rb_to_hash_type(keyword_hash);
    }
    else if (UNLIKELY(ISEQ_BODY(iseq)->param.flags.anon_kwrest)) {
        if (!ISEQ_BODY(iseq)->param.flags.has_kw) {
            *kw_flag |= VM_CALL_KW_SPLAT_MUT;
        }
    }

    if (RHASH_EMPTY_P(keyword_hash) && !ISEQ_BODY(iseq)->param.flags.has_kwrest) {
        goto ignore;
    }

    if (!(*kw_flag & VM_CALL_KW_SPLAT_MUT) &&
        (ISEQ_BODY(iseq)->param.flags.has_kwrest ||
         ISEQ_BODY(iseq)->param.flags.ruby2_keywords)) {
        *kw_flag |= VM_CALL_KW_SPLAT_MUT;
        keyword_hash = rb_hash_dup(keyword_hash);
    }
    *converted_keyword_hash = keyword_hash;

    if (!(ISEQ_BODY(iseq)->param.flags.has_kw) &&
        !(ISEQ_BODY(iseq)->param.flags.has_kwrest) &&
        RHASH_EMPTY_P(keyword_hash)) {
      ignore:
        *kw_flag &= ~(VM_CALL_KW_SPLAT | VM_CALL_KW_SPLAT_MUT);
        return 1;
    }
    else {
        return 0;
    }
}

static VALUE
check_kwrestarg(VALUE keyword_hash, unsigned int *kw_flag)
{
    if (!(*kw_flag & VM_CALL_KW_SPLAT_MUT)) {
        *kw_flag |= VM_CALL_KW_SPLAT_MUT;
        return rb_hash_dup(keyword_hash);
    }
    else {
        return keyword_hash;
    }
}

static void
flatten_rest_args(rb_execution_context_t * const ec, struct args_info *args, VALUE * const locals, unsigned int *ci_flag)
{
    const VALUE *argv = RARRAY_CONST_PTR(args->rest);
    int j, i=args->argc, rest_len = RARRAY_LENINT(args->rest)-1;
    args->argc += rest_len;
    if (rest_len) {
        CHECK_VM_STACK_OVERFLOW(ec->cfp, rest_len+1);
        for (i, j=0; rest_len > 0; rest_len--, i++, j++) {
            locals[i] = argv[j];
        }
    }
    args->rest = Qfalse;
    *ci_flag &= ~VM_CALL_ARGS_SPLAT;
}

static int
setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * const iseq,
                         struct rb_calling_info *const calling,
                         const struct rb_callinfo *ci,
                         VALUE * const locals, const enum arg_setup_type arg_setup_type)
{
    const int min_argc = ISEQ_BODY(iseq)->param.lead_num + ISEQ_BODY(iseq)->param.post_num;
    const int max_argc = (ISEQ_BODY(iseq)->param.flags.has_rest == FALSE) ? min_argc + ISEQ_BODY(iseq)->param.opt_num : UNLIMITED_ARGUMENTS;
    int given_argc;
    unsigned int ci_flag = vm_ci_flag(ci);
    unsigned int kw_flag = ci_flag & (VM_CALL_KWARG | VM_CALL_KW_SPLAT | VM_CALL_KW_SPLAT_MUT);
    int opt_pc = 0, allow_autosplat = !kw_flag;
    struct args_info args_body, *args;
    VALUE keyword_hash = Qnil;
    VALUE * const orig_sp = ec->cfp->sp;
    unsigned int i;
    VALUE flag_keyword_hash = 0;
    VALUE splat_flagged_keyword_hash = 0;
    VALUE converted_keyword_hash = 0;
    VALUE rest_last = 0;

    vm_check_canary(ec, orig_sp);
    /*
     * Extend SP for GC.
     *
     * [pushed values] [uninitialized values]
     * <- ci->argc -->
     * <- ISEQ_BODY(iseq)->param.size------------>
     * ^ locals        ^ sp
     *
     * =>
     * [pushed values] [initialized values  ]
     * <- ci->argc -->
     * <- ISEQ_BODY(iseq)->param.size------------>
     * ^ locals                             ^ sp
     */
    for (i=calling->argc; i<ISEQ_BODY(iseq)->param.size; i++) {
        locals[i] = Qnil;
    }
    ec->cfp->sp = &locals[i];

    /* setup args */
    args = &args_body;
    given_argc = args->argc = calling->argc;
    args->argv = locals;
    args->rest_dupped = ci_flag & VM_CALL_ARGS_SPLAT_MUT;

    if (UNLIKELY(ISEQ_BODY(iseq)->param.flags.anon_rest)) {
        if ((ci_flag & VM_CALL_ARGS_SPLAT) &&
                given_argc == ISEQ_BODY(iseq)->param.lead_num + (kw_flag ? 2 : 1) &&
                !ISEQ_BODY(iseq)->param.flags.has_opt &&
                !ISEQ_BODY(iseq)->param.flags.has_post &&
                !ISEQ_BODY(iseq)->param.flags.ruby2_keywords &&
                (!kw_flag ||
                !ISEQ_BODY(iseq)->param.flags.has_kw ||
                !ISEQ_BODY(iseq)->param.flags.has_kwrest ||
                !ISEQ_BODY(iseq)->param.flags.accepts_no_kwarg)) {
            args->rest_dupped = true;
        }
    }

    if (kw_flag & VM_CALL_KWARG) {
        args->kw_arg = vm_ci_kwarg(ci);

        if (ISEQ_BODY(iseq)->param.flags.has_kw) {
            int kw_len = args->kw_arg->keyword_len;
            /* copy kw_argv */
            args->kw_argv = ALLOCA_N(VALUE, kw_len);
            args->argc -= kw_len;
            given_argc -= kw_len;
            MEMCPY(args->kw_argv, locals + args->argc, VALUE, kw_len);
        }
        else {
            args->kw_argv = NULL;
            given_argc = args_kw_argv_to_hash(args);
            kw_flag |= VM_CALL_KW_SPLAT | VM_CALL_KW_SPLAT_MUT;
        }
    }
    else {
        args->kw_arg = NULL;
        args->kw_argv = NULL;
    }

    if ((ci_flag & VM_CALL_ARGS_SPLAT) && (ci_flag & VM_CALL_KW_SPLAT)) {
        // f(*a, **kw)
        args->rest_index = 0;
        keyword_hash = locals[--args->argc];
        args->rest = locals[--args->argc];

        if (ignore_keyword_hash_p(keyword_hash, iseq, &kw_flag, &converted_keyword_hash)) {
            keyword_hash = Qnil;
        }
        else if (UNLIKELY(ISEQ_BODY(iseq)->param.flags.ruby2_keywords)) {
            converted_keyword_hash = check_kwrestarg(converted_keyword_hash, &kw_flag);
            flag_keyword_hash = converted_keyword_hash;
            arg_rest_dup(args);
            rb_ary_push(args->rest, converted_keyword_hash);
            keyword_hash = Qnil;
        }
        else if (!ISEQ_BODY(iseq)->param.flags.has_kwrest && !ISEQ_BODY(iseq)->param.flags.has_kw) {
            converted_keyword_hash = check_kwrestarg(converted_keyword_hash, &kw_flag);
            if (ISEQ_BODY(iseq)->param.flags.has_rest) {
                arg_rest_dup(args);
                rb_ary_push(args->rest, converted_keyword_hash);
                keyword_hash = Qnil;
            }
            else {
                // Avoid duping rest when not necessary
                // Copy rest elements and converted keyword hash directly to VM stack
                const VALUE *argv = RARRAY_CONST_PTR(args->rest);
                int j, i=args->argc, rest_len = RARRAY_LENINT(args->rest);
                if (rest_len) {
                    CHECK_VM_STACK_OVERFLOW(ec->cfp, rest_len+1);
                    given_argc += rest_len;
                    args->argc += rest_len;
                    for (j=0; rest_len > 0; rest_len--, i++, j++) {
                        locals[i] = argv[j];
                    }
                }
                locals[i] = converted_keyword_hash;
                given_argc--;
                args->argc++;
                args->rest = Qfalse;
                ci_flag &= ~(VM_CALL_ARGS_SPLAT|VM_CALL_KW_SPLAT);
                keyword_hash = Qnil;
                goto arg_splat_and_kw_splat_flattened;
            }
        }
        else {
            keyword_hash = converted_keyword_hash;
        }

        int len = RARRAY_LENINT(args->rest);
        given_argc += len - 2;
    }
    else if (ci_flag & VM_CALL_ARGS_SPLAT) {
        // f(*a)
        args->rest_index = 0;
        args->rest = locals[--args->argc];
        int len = RARRAY_LENINT(args->rest);
        given_argc += len - 1;

        if (!kw_flag && len > 0) {
            rest_last = RARRAY_AREF(args->rest, len - 1);
            if (RB_TYPE_P(rest_last, T_HASH) && FL_TEST_RAW(rest_last, RHASH_PASS_AS_KEYWORDS)) {
                // def f(**kw); a = [..., kw]; g(*a)
                splat_flagged_keyword_hash = rest_last;
                if (!(RHASH_EMPTY_P(rest_last) || ISEQ_BODY(iseq)->param.flags.has_kw) || (ISEQ_BODY(iseq)->param.flags.has_kwrest)) {
                    rest_last = rb_hash_dup(rest_last);
                }
                kw_flag |= VM_CALL_KW_SPLAT | VM_CALL_KW_SPLAT_MUT;

                // Unset rest_dupped set by anon_rest as we may need to modify splat in this case
                args->rest_dupped = false;

                if (ignore_keyword_hash_p(rest_last, iseq, &kw_flag, &converted_keyword_hash)) {
                    if (ISEQ_BODY(iseq)->param.flags.has_rest) {
                        // Only duplicate/modify splat array if it will be used
                        arg_rest_dup(args);
                        rb_ary_pop(args->rest);
                    }
                    else if (arg_setup_type == arg_setup_block && !ISEQ_BODY(iseq)->param.flags.has_kwrest) {
                        // Avoid hash allocation for empty hashes
                        // Copy rest elements except empty keyword hash directly to VM stack
                        flatten_rest_args(ec, args, locals, &ci_flag);
                        keyword_hash = Qnil;
                        kw_flag = 0;
                    }
                    given_argc--;
                }
                else if (!ISEQ_BODY(iseq)->param.flags.has_rest) {
                    // Avoid duping rest when not necessary
                    // Copy rest elements and converted keyword hash directly to VM stack
                    flatten_rest_args(ec, args, locals, &ci_flag);

                    if (ISEQ_BODY(iseq)->param.flags.has_kw || ISEQ_BODY(iseq)->param.flags.has_kwrest) {
                        given_argc--;
                        keyword_hash = converted_keyword_hash;
                    }
                    else {
                        locals[args->argc] = converted_keyword_hash;
                        args->argc += 1;
                        keyword_hash = Qnil;
                        kw_flag = 0;
                    }
                }
                else {
                    if (rest_last != converted_keyword_hash) {
                        rest_last = converted_keyword_hash;
                        arg_rest_dup(args);
                        RARRAY_ASET(args->rest, len - 1, rest_last);
                    }

                    if (ISEQ_BODY(iseq)->param.flags.ruby2_keywords && rest_last) {
                        flag_keyword_hash = rest_last;
                    }
                    else if (ISEQ_BODY(iseq)->param.flags.has_kw || ISEQ_BODY(iseq)->param.flags.has_kwrest) {
                        arg_rest_dup(args);
                        rb_ary_pop(args->rest);
                        given_argc--;
                        keyword_hash = rest_last;
                    }
                }
            }
        }
    }
    else {
        args->rest = Qfalse;

        if (args->argc > 0 && (kw_flag & VM_CALL_KW_SPLAT)) {
            // f(**kw)
            VALUE last_arg = args->argv[args->argc-1];
            if (ignore_keyword_hash_p(last_arg, iseq, &kw_flag, &converted_keyword_hash)) {
                args->argc--;
                given_argc--;
            }
            else {
                if (!(kw_flag & VM_CALL_KW_SPLAT_MUT) && !ISEQ_BODY(iseq)->param.flags.has_kw) {
                    converted_keyword_hash = rb_hash_dup(converted_keyword_hash);
                    kw_flag |= VM_CALL_KW_SPLAT_MUT;
                }

                if (last_arg != converted_keyword_hash) {
                    last_arg = converted_keyword_hash;
                    args->argv[args->argc-1] = last_arg;
                }

                if (ISEQ_BODY(iseq)->param.flags.ruby2_keywords) {
                    flag_keyword_hash = last_arg;
                }
                else if (ISEQ_BODY(iseq)->param.flags.has_kw || ISEQ_BODY(iseq)->param.flags.has_kwrest) {
                    args->argc--;
                    given_argc--;
                    keyword_hash = last_arg;
                }
            }
        }
    }

    if (flag_keyword_hash) {
        FL_SET_RAW(flag_keyword_hash, RHASH_PASS_AS_KEYWORDS);
    }

  arg_splat_and_kw_splat_flattened:
    if (kw_flag && ISEQ_BODY(iseq)->param.flags.accepts_no_kwarg) {
        rb_raise(rb_eArgError, "no keywords accepted");
    }

    switch (arg_setup_type) {
      case arg_setup_method:
        break; /* do nothing special */
      case arg_setup_block:
        if (given_argc == 1 &&
            allow_autosplat &&
            !splat_flagged_keyword_hash &&
            (min_argc > 0 || ISEQ_BODY(iseq)->param.opt_num > 1) &&
            !ISEQ_BODY(iseq)->param.flags.ambiguous_param0 &&
            !((ISEQ_BODY(iseq)->param.flags.has_kw ||
               ISEQ_BODY(iseq)->param.flags.has_kwrest)
               && max_argc == 1) &&
            args_check_block_arg0(args)) {
            given_argc = RARRAY_LENINT(args->rest);
        }
        break;
    }

    /* argc check */
    if (given_argc < min_argc) {
        if (arg_setup_type == arg_setup_block) {
            CHECK_VM_STACK_OVERFLOW(ec->cfp, min_argc);
            given_argc = min_argc;
            args_extend(args, min_argc);
        }
        else {
            argument_arity_error(ec, iseq, given_argc, min_argc, max_argc);
        }
    }

    if (given_argc > max_argc && max_argc != UNLIMITED_ARGUMENTS) {
        if (arg_setup_type == arg_setup_block) {
            /* truncate */
            args_reduce(args, given_argc - max_argc);
            given_argc = max_argc;
        }
        else {
            argument_arity_error(ec, iseq, given_argc, min_argc, max_argc);
        }
    }

    if (ISEQ_BODY(iseq)->param.flags.has_lead) {
        args_setup_lead_parameters(args, ISEQ_BODY(iseq)->param.lead_num, locals + 0);
    }

    if (ISEQ_BODY(iseq)->param.flags.has_rest || ISEQ_BODY(iseq)->param.flags.has_post){
        args_copy(args);
    }

    if (ISEQ_BODY(iseq)->param.flags.has_post) {
        args_setup_post_parameters(args, ISEQ_BODY(iseq)->param.post_num, locals + ISEQ_BODY(iseq)->param.post_start);
    }

    if (ISEQ_BODY(iseq)->param.flags.has_opt) {
        int opt = args_setup_opt_parameters(args, ISEQ_BODY(iseq)->param.opt_num, locals + ISEQ_BODY(iseq)->param.lead_num);
        opt_pc = (int)ISEQ_BODY(iseq)->param.opt_table[opt];
    }

    if (ISEQ_BODY(iseq)->param.flags.has_rest) {
        args_setup_rest_parameter(args, locals + ISEQ_BODY(iseq)->param.rest_start);
        VALUE ary = *(locals + ISEQ_BODY(iseq)->param.rest_start);
        VALUE index = RARRAY_LEN(ary) - 1;
        if (splat_flagged_keyword_hash &&
            !ISEQ_BODY(iseq)->param.flags.ruby2_keywords &&
            !ISEQ_BODY(iseq)->param.flags.has_kw &&
            !ISEQ_BODY(iseq)->param.flags.has_kwrest &&
            RARRAY_AREF(ary, index) == splat_flagged_keyword_hash) {
            ((struct RHash *)rest_last)->basic.flags &= ~RHASH_PASS_AS_KEYWORDS;
            RARRAY_ASET(ary, index, rest_last);
        }
    }

    if (ISEQ_BODY(iseq)->param.flags.has_kw) {
        VALUE * const klocals = locals + ISEQ_BODY(iseq)->param.keyword->bits_start - ISEQ_BODY(iseq)->param.keyword->num;

        if (args->kw_argv != NULL) {
            const struct rb_callinfo_kwarg *kw_arg = args->kw_arg;
            args_setup_kw_parameters(ec, iseq, args->kw_argv, kw_arg->keyword_len, kw_arg->keywords, klocals);
        }
        else if (!NIL_P(keyword_hash)) {
            bool remove_hash_value = false;
            if (ISEQ_BODY(iseq)->param.flags.has_kwrest) {
                keyword_hash = check_kwrestarg(keyword_hash, &kw_flag);
                remove_hash_value = true;
            }
            args_setup_kw_parameters_from_kwsplat(ec, iseq, keyword_hash, klocals, remove_hash_value);
        }
        else {
#if VM_CHECK_MODE > 0
            if (args_argc(args) != 0) {
                VM_ASSERT(ci_flag & VM_CALL_ARGS_SPLAT);
                VM_ASSERT(!(ci_flag & (VM_CALL_KWARG | VM_CALL_KW_SPLAT | VM_CALL_KW_SPLAT_MUT)));
                VM_ASSERT(!kw_flag);
                VM_ASSERT(!ISEQ_BODY(iseq)->param.flags.has_rest);
                VM_ASSERT(RARRAY_LENINT(args->rest) > 0);
                VM_ASSERT(RB_TYPE_P(rest_last, T_HASH));
                VM_ASSERT(FL_TEST_RAW(rest_last, RHASH_PASS_AS_KEYWORDS));
                VM_ASSERT(args_argc(args) == 1);
            }
#endif
            args_setup_kw_parameters(ec, iseq, NULL, 0, NULL, klocals);
        }
    }
    else if (ISEQ_BODY(iseq)->param.flags.has_kwrest) {
        args_setup_kw_rest_parameter(keyword_hash, locals + ISEQ_BODY(iseq)->param.keyword->rest_start,
            kw_flag, ISEQ_BODY(iseq)->param.flags.anon_kwrest);
    }
    else if (!NIL_P(keyword_hash) && RHASH_SIZE(keyword_hash) > 0 && arg_setup_type == arg_setup_method) {
        argument_kw_error(ec, iseq, "unknown", rb_hash_keys(keyword_hash));
    }

    if (ISEQ_BODY(iseq)->param.flags.has_block) {
        if (ISEQ_BODY(iseq)->local_iseq == iseq) {
            /* Do nothing */
        }
        else {
            args_setup_block_parameter(ec, calling, locals + ISEQ_BODY(iseq)->param.block_start);
        }
    }

#if 0
    {
        int i;
        for (i=0; i<ISEQ_BODY(iseq)->param.size; i++) {
            ruby_debug_printf("local[%d] = %p\n", i, (void *)locals[i]);
        }
    }
#endif

    ec->cfp->sp = orig_sp;
    return opt_pc;
}

static void
raise_argument_error(rb_execution_context_t *ec, const rb_iseq_t *iseq, const VALUE exc)
{
    VALUE at;

    if (iseq) {
        vm_push_frame(ec, iseq, VM_FRAME_MAGIC_DUMMY | VM_ENV_FLAG_LOCAL, Qnil /* self */,
                      VM_BLOCK_HANDLER_NONE /* specval*/, Qfalse /* me or cref */,
                      ISEQ_BODY(iseq)->iseq_encoded,
                      ec->cfp->sp, 0, 0 /* stack_max */);
        at = rb_ec_backtrace_object(ec);
        rb_backtrace_use_iseq_first_lineno_for_last_location(at);
        rb_vm_pop_frame(ec);
    }
    else {
        at = rb_ec_backtrace_object(ec);
    }

    rb_ivar_set(exc, idBt_locations, at);
    rb_exc_set_backtrace(exc, at);
    rb_exc_raise(exc);
}

static void
argument_arity_error(rb_execution_context_t *ec, const rb_iseq_t *iseq, const int miss_argc, const int min_argc, const int max_argc)
{
    VALUE exc = rb_arity_error_new(miss_argc, min_argc, max_argc);
    if (ISEQ_BODY(iseq)->param.flags.has_kw) {
        const struct rb_iseq_param_keyword *const kw = ISEQ_BODY(iseq)->param.keyword;
        const ID *keywords = kw->table;
        int req_key_num = kw->required_num;
        if (req_key_num > 0) {
            static const char required[] = "; required keywords";
            VALUE mesg = rb_attr_get(exc, idMesg);
            rb_str_resize(mesg, RSTRING_LEN(mesg)-1);
            rb_str_cat(mesg, required, sizeof(required) - 1 - (req_key_num == 1));
            rb_str_cat_cstr(mesg, ":");
            do {
                rb_str_cat_cstr(mesg, " ");
                rb_str_append(mesg, rb_id2str(*keywords++));
                rb_str_cat_cstr(mesg, ",");
            } while (--req_key_num);
            RSTRING_PTR(mesg)[RSTRING_LEN(mesg)-1] = ')';
        }
    }
    raise_argument_error(ec, iseq, exc);
}

static void
argument_kw_error(rb_execution_context_t *ec, const rb_iseq_t *iseq, const char *error, const VALUE keys)
{
    raise_argument_error(ec, iseq, rb_keyword_error_new(error, keys));
}

static VALUE
vm_to_proc(VALUE proc)
{
    if (UNLIKELY(!rb_obj_is_proc(proc))) {
        VALUE b;
        const rb_callable_method_entry_t *me =
            rb_callable_method_entry_with_refinements(CLASS_OF(proc), idTo_proc, NULL);

        if (me) {
            b = rb_vm_call0(GET_EC(), proc, idTo_proc, 0, NULL, me, RB_NO_KEYWORDS);
        }
        else {
            /* NOTE: calling method_missing */
            b = rb_check_convert_type_with_id(proc, T_DATA, "Proc", idTo_proc);
        }

        if (NIL_P(b) || !rb_obj_is_proc(b)) {
            rb_raise(rb_eTypeError,
                     "wrong argument type %s (expected Proc)",
                     rb_obj_classname(proc));
        }
        return b;
    }
    else {
        return proc;
    }
}

static VALUE
refine_sym_proc_call(RB_BLOCK_CALL_FUNC_ARGLIST(yielded_arg, callback_arg))
{
    VALUE obj;
    ID mid;
    const rb_callable_method_entry_t *me = 0; /* for hidden object case */
    rb_execution_context_t *ec;
    const VALUE symbol = RARRAY_AREF(callback_arg, 0);
    const VALUE refinements = RARRAY_AREF(callback_arg, 1);
    int kw_splat = RB_PASS_CALLED_KEYWORDS;
    VALUE klass;

    if (argc-- < 1) {
        rb_raise(rb_eArgError, "no receiver given");
    }
    obj = *argv++;

    mid = SYM2ID(symbol);
    for (klass = CLASS_OF(obj); klass; klass = RCLASS_SUPER(klass)) {
        me = rb_callable_method_entry(klass, mid);
        if (me) {
            me = rb_resolve_refined_method_callable(refinements, me);
            if (me) break;
        }
    }

    ec = GET_EC();
    if (!NIL_P(blockarg)) {
        vm_passed_block_handler_set(ec, blockarg);
    }
    if (!me) {
        return method_missing(ec, obj, mid, argc, argv, MISSING_NOENTRY, kw_splat);
    }
    return rb_vm_call0(ec, obj, mid, argc, argv, me, kw_splat);
}

static VALUE
vm_caller_setup_arg_block(const rb_execution_context_t *ec, rb_control_frame_t *reg_cfp,
                          const struct rb_callinfo *ci, const rb_iseq_t *blockiseq, const int is_super)
{
    if (vm_ci_flag(ci) & VM_CALL_ARGS_BLOCKARG) {
        VALUE block_code = *(--reg_cfp->sp);

        if (NIL_P(block_code)) {
            return VM_BLOCK_HANDLER_NONE;
        }
        else if (block_code == rb_block_param_proxy) {
            return VM_CF_BLOCK_HANDLER(reg_cfp);
        }
        else if (SYMBOL_P(block_code) && rb_method_basic_definition_p(rb_cSymbol, idTo_proc)) {
            const rb_cref_t *cref = vm_env_cref(reg_cfp->ep);
            if (cref && !NIL_P(cref->refinements)) {
                VALUE ref = cref->refinements;
                VALUE func = rb_hash_lookup(ref, block_code);
                if (NIL_P(func)) {
                    /* TODO: limit cached funcs */
                    VALUE callback_arg = rb_ary_hidden_new(2);
                    rb_ary_push(callback_arg, block_code);
                    rb_ary_push(callback_arg, ref);
                    OBJ_FREEZE(callback_arg);
                    func = rb_func_lambda_new(refine_sym_proc_call, callback_arg, 1, UNLIMITED_ARGUMENTS);
                    rb_hash_aset(ref, block_code, func);
                }
                block_code = func;
            }
            return block_code;
        }
        else {
            return vm_to_proc(block_code);
        }
    }
    else if (blockiseq != NULL) { /* likely */
        struct rb_captured_block *captured = VM_CFP_TO_CAPTURED_BLOCK(reg_cfp);
        captured->code.iseq = blockiseq;
        return VM_BH_FROM_ISEQ_BLOCK(captured);
    }
    else {
        if (is_super) {
            return GET_BLOCK_HANDLER();
        }
        else {
            return VM_BLOCK_HANDLER_NONE;
        }
    }
}

static void vm_adjust_stack_forwarding(const struct rb_execution_context_struct *ec, struct rb_control_frame_struct *cfp, int argc, VALUE splat);

static VALUE
vm_caller_setup_fwd_args(const rb_execution_context_t *ec, rb_control_frame_t *reg_cfp,
                    CALL_DATA cd, const rb_iseq_t *blockiseq, const int is_super,
                    struct rb_forwarding_call_data *adjusted_cd, struct rb_callinfo *adjusted_ci)
{
    CALL_INFO site_ci = cd->ci;
    VALUE bh = Qundef;

    RUBY_ASSERT(ISEQ_BODY(ISEQ_BODY(GET_ISEQ())->local_iseq)->param.flags.forwardable);
    CALL_INFO caller_ci = (CALL_INFO)TOPN(0);

    unsigned int site_argc = vm_ci_argc(site_ci);
    unsigned int site_flag = vm_ci_flag(site_ci);
    ID site_mid = vm_ci_mid(site_ci);

    unsigned int caller_argc = vm_ci_argc(caller_ci);
    unsigned int caller_flag = vm_ci_flag(caller_ci);
    const struct rb_callinfo_kwarg * kw = vm_ci_kwarg(caller_ci);

    VALUE splat = Qfalse;

    if (site_flag & VM_CALL_ARGS_SPLAT) {
        // If we're called with args_splat, the top 1 should be an array
        splat = TOPN(1);
        site_argc += (RARRAY_LEN(splat) - 1);
    }

    // Need to setup the block in case of e.g. `super { :block }`
    if (is_super && blockiseq) {
        bh = vm_caller_setup_arg_block(ec, GET_CFP(), site_ci, blockiseq, is_super);
    }
    else {
        bh = VM_ENV_BLOCK_HANDLER(GET_LEP());
    }

    vm_adjust_stack_forwarding(ec, GET_CFP(), caller_argc, splat);

    *adjusted_ci = VM_CI_ON_STACK(
            site_mid,
            ((caller_flag & ~VM_CALL_ARGS_SIMPLE) | (site_flag & (VM_CALL_FCALL | VM_CALL_FORWARDING))),
            site_argc + caller_argc,
            kw
            );

    adjusted_cd->cd.ci = adjusted_ci;
    adjusted_cd->cd.cc = cd->cc;
    adjusted_cd->caller_ci = caller_ci;

    return bh;
}