diff --git a/compile.c b/compile.c
index 33b3b2d960..af4e9327ad 100644
--- a/compile.c
+++ b/compile.c
@@ -1443,13 +1443,15 @@ get_dyna_var_idx(const rb_iseq_t *iseq, ID id, int *level, int *ls)
 static int
 iseq_local_block_param_p(const rb_iseq_t *iseq, unsigned int idx, unsigned int level)
 {
+    const struct rb_iseq_constant_body *body;
     while (level > 0) {
 	iseq = iseq->body->parent_iseq;
 	level--;
     }
-    if (iseq->body->local_iseq == iseq && /* local variables */
-	iseq->body->param.flags.has_block &&
-	iseq->body->local_table_size - iseq->body->param.block_start == idx) {
+    body = iseq->body;
+    if (body->local_iseq == iseq && /* local variables */
+	body->param.flags.has_block &&
+	body->local_table_size - body->param.block_start == idx) {
 	return TRUE;
     }
     else {
@@ -1499,37 +1501,38 @@ iseq_add_setlocal(rb_iseq_t *iseq, LINK_ANCHOR *const seq, int line, int idx, in
 static void
 iseq_calc_param_size(rb_iseq_t *iseq)
 {
-    if (iseq->body->param.flags.has_opt ||
-	iseq->body->param.flags.has_post ||
-	iseq->body->param.flags.has_rest ||
-	iseq->body->param.flags.has_block ||
-	iseq->body->param.flags.has_kw ||
-	iseq->body->param.flags.has_kwrest) {
+    struct rb_iseq_constant_body *const body = iseq->body;
+    if (body->param.flags.has_opt ||
+	body->param.flags.has_post ||
+	body->param.flags.has_rest ||
+	body->param.flags.has_block ||
+	body->param.flags.has_kw ||
+	body->param.flags.has_kwrest) {
 
-	if (iseq->body->param.flags.has_block) {
-	    iseq->body->param.size = iseq->body->param.block_start + 1;
+	if (body->param.flags.has_block) {
+	    body->param.size = body->param.block_start + 1;
 	}
-	else if (iseq->body->param.flags.has_kwrest) {
-	    iseq->body->param.size = iseq->body->param.keyword->rest_start + 1;
+	else if (body->param.flags.has_kwrest) {
+	    body->param.size = body->param.keyword->rest_start + 1;
 	}
-	else if (iseq->body->param.flags.has_kw) {
-	    iseq->body->param.size = iseq->body->param.keyword->bits_start + 1;
+	else if (body->param.flags.has_kw) {
+	    body->param.size = body->param.keyword->bits_start + 1;
 	}
-	else if (iseq->body->param.flags.has_post) {
-	    iseq->body->param.size = iseq->body->param.post_start + iseq->body->param.post_num;
+	else if (body->param.flags.has_post) {
+	    body->param.size = body->param.post_start + body->param.post_num;
 	}
-	else if (iseq->body->param.flags.has_rest) {
-	    iseq->body->param.size = iseq->body->param.rest_start + 1;
+	else if (body->param.flags.has_rest) {
+	    body->param.size = body->param.rest_start + 1;
 	}
-	else if (iseq->body->param.flags.has_opt) {
-	    iseq->body->param.size = iseq->body->param.lead_num + iseq->body->param.opt_num;
+	else if (body->param.flags.has_opt) {
+	    body->param.size = body->param.lead_num + body->param.opt_num;
 	}
 	else {
 	    rb_bug("unreachable");
 	}
     }
     else {
-	iseq->body->param.size = iseq->body->param.lead_num;
+	body->param.size = body->param.lead_num;
     }
 }
 
@@ -1538,13 +1541,14 @@ iseq_set_arguments_keywords(rb_iseq_t *iseq, LINK_ANCHOR *const optargs,
 			    const struct rb_args_info *args, int arg_size)
 {
     const NODE *node = args->kw_args;
+    struct rb_iseq_constant_body *const body = iseq->body;
     struct rb_iseq_param_keyword *keyword;
     const VALUE default_values = rb_ary_tmp_new(1);
     const VALUE complex_mark = rb_str_tmp_new(0);
     int kw = 0, rkw = 0, di = 0, i;
 
-    iseq->body->param.flags.has_kw = TRUE;
-    iseq->body->param.keyword = keyword = ZALLOC_N(struct rb_iseq_param_keyword, 1);
+    body->param.flags.has_kw = TRUE;
+    body->param.keyword = keyword = ZALLOC_N(struct rb_iseq_param_keyword, 1);
 
     while (node) {
 	kw++;
@@ -1592,10 +1596,10 @@ iseq_set_arguments_keywords(rb_iseq_t *iseq, LINK_ANCHOR *const optargs,
 
     if (args->kw_rest_arg->nd_vid != 0) {
 	keyword->rest_start = arg_size++;
-	iseq->body->param.flags.has_kwrest = TRUE;
+	body->param.flags.has_kwrest = TRUE;
     }
     keyword->required_num = rkw;
-    keyword->table = &iseq->body->local_table[keyword->bits_start - keyword->num];
+    keyword->table = &body->local_table[keyword->bits_start - keyword->num];
 
     {
 	VALUE *dvs = ALLOC_N(VALUE, RARRAY_LEN(default_values));
@@ -1620,6 +1624,7 @@ iseq_set_arguments(rb_iseq_t *iseq, LINK_ANCHOR *const optargs, const NODE *cons
     debugs("iseq_set_arguments: %s\n", node_args ? "" : "0");
 
     if (node_args) {
+	struct rb_iseq_constant_body *const body = iseq->body;
 	struct rb_args_info *args = node_args->nd_ainfo;
 	ID rest_id = 0;
 	int last_comma = 0;
@@ -1628,9 +1633,9 @@ iseq_set_arguments(rb_iseq_t *iseq, LINK_ANCHOR *const optargs, const NODE *cons
 
 	EXPECT_NODE("iseq_set_arguments", node_args, NODE_ARGS, COMPILE_NG);
 
-	iseq->body->param.lead_num = arg_size = (int)args->pre_args_num;
-	if (iseq->body->param.lead_num > 0) iseq->body->param.flags.has_lead = TRUE;
-	debugs("  - argc: %d\n", iseq->body->param.lead_num);
+	body->param.lead_num = arg_size = (int)args->pre_args_num;
+	if (body->param.lead_num > 0) body->param.flags.has_lead = TRUE;
+	debugs("  - argc: %d\n", body->param.lead_num);
 
 	rest_id = args->rest_arg;
 	if (rest_id == 1) {
@@ -1668,26 +1673,26 @@ iseq_set_arguments(rb_iseq_t *iseq, LINK_ANCHOR *const optargs, const NODE *cons
 	    }
 	    rb_ary_clear(labels);
 
-	    iseq->body->param.flags.has_opt = TRUE;
-	    iseq->body->param.opt_num = i;
-	    iseq->body->param.opt_table = opt_table;
+	    body->param.flags.has_opt = TRUE;
+	    body->param.opt_num = i;
+	    body->param.opt_table = opt_table;
 	    arg_size += i;
 	}
 
 	if (rest_id) {
-	    iseq->body->param.rest_start = arg_size++;
-	    iseq->body->param.flags.has_rest = TRUE;
-	    assert(iseq->body->param.rest_start != -1);
+	    body->param.rest_start = arg_size++;
+	    body->param.flags.has_rest = TRUE;
+	    assert(body->param.rest_start != -1);
 	}
 
 	if (args->first_post_arg) {
-	    iseq->body->param.post_start = arg_size;
-	    iseq->body->param.post_num = args->post_args_num;
-	    iseq->body->param.flags.has_post = TRUE;
+	    body->param.post_start = arg_size;
+	    body->param.post_num = args->post_args_num;
+	    body->param.flags.has_post = TRUE;
 	    arg_size += args->post_args_num;
 
-	    if (iseq->body->param.flags.has_rest) { /* TODO: why that? */
-		iseq->body->param.post_start = iseq->body->param.rest_start + 1;
+	    if (body->param.flags.has_rest) { /* TODO: why that? */
+		body->param.post_start = body->param.rest_start + 1;
 	    }
 	}
 
@@ -1697,17 +1702,17 @@ iseq_set_arguments(rb_iseq_t *iseq, LINK_ANCHOR *const optargs, const NODE *cons
 	else if (args->kw_rest_arg) {
 	    struct rb_iseq_param_keyword *keyword = ZALLOC_N(struct rb_iseq_param_keyword, 1);
 	    keyword->rest_start = arg_size++;
-	    iseq->body->param.keyword = keyword;
-	    iseq->body->param.flags.has_kwrest = TRUE;
+	    body->param.keyword = keyword;
+	    body->param.flags.has_kwrest = TRUE;
 	}
 
 	if (block_id) {
-	    iseq->body->param.block_start = arg_size++;
-	    iseq->body->param.flags.has_block = TRUE;
+	    body->param.block_start = arg_size++;
+	    body->param.flags.has_block = TRUE;
 	}
 
 	iseq_calc_param_size(iseq);
-	iseq->body->param.size = arg_size;
+	body->param.size = arg_size;
 
 	if (args->pre_init) { /* m_init */
 	    COMPILE_POPPED(optargs, "init arguments (m)", args->pre_init);
@@ -1716,16 +1721,16 @@ iseq_set_arguments(rb_iseq_t *iseq, LINK_ANCHOR *const optargs, const NODE *cons
 	    COMPILE_POPPED(optargs, "init arguments (p)", args->post_init);
 	}
 
-	if (iseq->body->type == ISEQ_TYPE_BLOCK) {
-	    if (iseq->body->param.flags.has_opt    == FALSE &&
-		iseq->body->param.flags.has_post   == FALSE &&
-		iseq->body->param.flags.has_rest   == FALSE &&
-		iseq->body->param.flags.has_kw     == FALSE &&
-		iseq->body->param.flags.has_kwrest == FALSE) {
+	if (body->type == ISEQ_TYPE_BLOCK) {
+	    if (body->param.flags.has_opt    == FALSE &&
+		body->param.flags.has_post   == FALSE &&
+		body->param.flags.has_rest   == FALSE &&
+		body->param.flags.has_kw     == FALSE &&
+		body->param.flags.has_kwrest == FALSE) {
 
-		if (iseq->body->param.lead_num == 1 && last_comma == 0) {
+		if (body->param.lead_num == 1 && last_comma == 0) {
 		    /* {|a|} */
-		    iseq->body->param.flags.ambiguous_param0 = TRUE;
+		    body->param.flags.ambiguous_param0 = TRUE;
 		}
 	    }
 	}
@@ -1978,6 +1983,7 @@ static int
 iseq_set_sequence(rb_iseq_t *iseq, LINK_ANCHOR *const anchor)
 {
     struct iseq_insn_info_entry *insns_info;
+    struct rb_iseq_constant_body *const body = iseq->body;
     unsigned int *positions;
     LINK_ELEMENT *list;
     VALUE *generated_iseq;
@@ -2040,11 +2046,11 @@ iseq_set_sequence(rb_iseq_t *iseq, LINK_ANCHOR *const anchor)
     generated_iseq = ALLOC_N(VALUE, code_index);
     insns_info = ALLOC_N(struct iseq_insn_info_entry, insn_num);
     positions = ALLOC_N(unsigned int, insn_num);
-    iseq->body->is_entries = ZALLOC_N(union iseq_inline_storage_entry, iseq->body->is_size);
-    iseq->body->ci_entries = (struct rb_call_info *)ruby_xmalloc(sizeof(struct rb_call_info) * iseq->body->ci_size +
-								 sizeof(struct rb_call_info_with_kwarg) * iseq->body->ci_kw_size);
-    MEMZERO(iseq->body->ci_entries + iseq->body->ci_size, struct rb_call_info_with_kwarg,  iseq->body->ci_kw_size); /* need to clear ci_kw entries */
-    iseq->body->cc_entries = ZALLOC_N(struct rb_call_cache, iseq->body->ci_size + iseq->body->ci_kw_size);
+    body->is_entries = ZALLOC_N(union iseq_inline_storage_entry, body->is_size);
+    body->ci_entries = (struct rb_call_info *)ruby_xmalloc(sizeof(struct rb_call_info) * body->ci_size +
+								 sizeof(struct rb_call_info_with_kwarg) * body->ci_kw_size);
+    MEMZERO(body->ci_entries + body->ci_size, struct rb_call_info_with_kwarg,  body->ci_kw_size); /* need to clear ci_kw entries */
+    body->cc_entries = ZALLOC_N(struct rb_call_cache, body->ci_size + body->ci_kw_size);
 
     ISEQ_COMPILE_DATA(iseq)->ci_index = ISEQ_COMPILE_DATA(iseq)->ci_kw_index = 0;
 
@@ -2124,9 +2130,9 @@ iseq_set_sequence(rb_iseq_t *iseq, LINK_ANCHOR *const anchor)
 		      case TS_IC: /* inline cache */
 			{
 			    unsigned int ic_index = FIX2UINT(operands[j]);
-			    IC ic = (IC)&iseq->body->is_entries[ic_index];
-			    if (UNLIKELY(ic_index >= iseq->body->is_size)) {
-				rb_bug("iseq_set_sequence: ic_index overflow: index: %d, size: %d", ic_index, iseq->body->is_size);
+			    IC ic = (IC)&body->is_entries[ic_index];
+			    if (UNLIKELY(ic_index >= body->is_size)) {
+				rb_bug("iseq_set_sequence: ic_index overflow: index: %d, size: %d", ic_index, body->is_size);
 			    }
 			    generated_iseq[code_index + 1 + j] = (VALUE)ic;
 			    break;
@@ -2134,9 +2140,9 @@ iseq_set_sequence(rb_iseq_t *iseq, LINK_ANCHOR *const anchor)
 		      case TS_ISE: /* inline storage entry */
 			{
 			    unsigned int ic_index = FIX2UINT(operands[j]);
-			    IC ic = (IC)&iseq->body->is_entries[ic_index];
-			    if (UNLIKELY(ic_index >= iseq->body->is_size)) {
-				rb_bug("iseq_set_sequence: ic_index overflow: index: %d, size: %d", ic_index, iseq->body->is_size);
+			    IC ic = (IC)&body->is_entries[ic_index];
+			    if (UNLIKELY(ic_index >= body->is_size)) {
+				rb_bug("iseq_set_sequence: ic_index overflow: index: %d, size: %d", ic_index, body->is_size);
 			    }
 			    generated_iseq[code_index + 1 + j] = (VALUE)ic;
 			    FL_SET(iseq, ISEQ_MARKABLE_ISEQ);
@@ -2148,16 +2154,16 @@ iseq_set_sequence(rb_iseq_t *iseq, LINK_ANCHOR *const anchor)
 			    struct rb_call_info *ci;
 
 			    if (base_ci->flag & VM_CALL_KWARG) {
-				struct rb_call_info_with_kwarg *ci_kw_entries = (struct rb_call_info_with_kwarg *)&iseq->body->ci_entries[iseq->body->ci_size];
+				struct rb_call_info_with_kwarg *ci_kw_entries = (struct rb_call_info_with_kwarg *)&body->ci_entries[body->ci_size];
 				struct rb_call_info_with_kwarg *ci_kw = &ci_kw_entries[ISEQ_COMPILE_DATA(iseq)->ci_kw_index++];
 				*ci_kw = *((struct rb_call_info_with_kwarg *)base_ci);
 				ci = (struct rb_call_info *)ci_kw;
-				assert(ISEQ_COMPILE_DATA(iseq)->ci_kw_index <= iseq->body->ci_kw_size);
+				assert(ISEQ_COMPILE_DATA(iseq)->ci_kw_index <= body->ci_kw_size);
 			    }
 			    else {
-				ci = &iseq->body->ci_entries[ISEQ_COMPILE_DATA(iseq)->ci_index++];
+				ci = &body->ci_entries[ISEQ_COMPILE_DATA(iseq)->ci_index++];
 				*ci = *base_ci;
-				assert(ISEQ_COMPILE_DATA(iseq)->ci_index <= iseq->body->ci_size);
+				assert(ISEQ_COMPILE_DATA(iseq)->ci_index <= body->ci_size);
 			    }
 
 			    generated_iseq[code_index + 1 + j] = (VALUE)ci;
@@ -2165,7 +2171,7 @@ iseq_set_sequence(rb_iseq_t *iseq, LINK_ANCHOR *const anchor)
 			}
 		      case TS_CALLCACHE:
 			{
-			    struct rb_call_cache *cc = &iseq->body->cc_entries[ISEQ_COMPILE_DATA(iseq)->ci_index + ISEQ_COMPILE_DATA(iseq)->ci_kw_index - 1];
+			    struct rb_call_cache *cc = &body->cc_entries[ISEQ_COMPILE_DATA(iseq)->ci_index + ISEQ_COMPILE_DATA(iseq)->ci_kw_index - 1];
 			    generated_iseq[code_index + 1 + j] = (VALUE)cc;
 			    break;
 			}
@@ -2243,19 +2249,19 @@ iseq_set_sequence(rb_iseq_t *iseq, LINK_ANCHOR *const anchor)
 	list = list->next;
     }
 
-    iseq->body->iseq_encoded = (void *)generated_iseq;
-    iseq->body->iseq_size = code_index;
-    iseq->body->stack_max = stack_max;
+    body->iseq_encoded = (void *)generated_iseq;
+    body->iseq_size = code_index;
+    body->stack_max = stack_max;
 
     /* get rid of memory leak when REALLOC failed */
-    iseq->body->insns_info.body = insns_info;
-    iseq->body->insns_info.positions = positions;
+    body->insns_info.body = insns_info;
+    body->insns_info.positions = positions;
 
     REALLOC_N(insns_info, struct iseq_insn_info_entry, insns_info_index);
-    iseq->body->insns_info.body = insns_info;
+    body->insns_info.body = insns_info;
     REALLOC_N(positions, unsigned int, insns_info_index);
-    iseq->body->insns_info.positions = positions;
-    iseq->body->insns_info.size = insns_info_index;
+    body->insns_info.positions = positions;
+    body->insns_info.size = insns_info_index;
 
     return COMPILE_OK;
 }
@@ -4833,6 +4839,7 @@ number_literal_p(const NODE *n)
 static int
 compile_if(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *const node, int popped, const enum node_type type)
 {
+    struct rb_iseq_constant_body *const body = iseq->body;
     const NODE *const node_body = type == NODE_IF ? node->nd_body : node->nd_else;
     const NODE *const node_else = type == NODE_IF ? node->nd_else : node->nd_body;
 
@@ -4858,20 +4865,20 @@ compile_if(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *const node, int
     compile_branch_condition(iseq, cond_seq, node->nd_cond,
 			     then_label, else_label);
 
-    ci_size = iseq->body->ci_size;
-    ci_kw_size = iseq->body->ci_kw_size;
+    ci_size = body->ci_size;
+    ci_kw_size = body->ci_kw_size;
     CHECK(COMPILE_(then_seq, "then", node_body, popped));
     if (!then_label->refcnt) {
-        iseq->body->ci_size = ci_size;
-        iseq->body->ci_kw_size = ci_kw_size;
+        body->ci_size = ci_size;
+        body->ci_kw_size = ci_kw_size;
     }
 
-    ci_size = iseq->body->ci_size;
-    ci_kw_size = iseq->body->ci_kw_size;
+    ci_size = body->ci_size;
+    ci_kw_size = body->ci_kw_size;
     CHECK(COMPILE_(else_seq, "else", node_else, popped));
     if (!else_label->refcnt) {
-        iseq->body->ci_size = ci_size;
-        iseq->body->ci_kw_size = ci_kw_size;
+        body->ci_size = ci_size;
+        body->ci_kw_size = ci_kw_size;
     }
 
     ADD_SEQ(ret, cond_seq);
@@ -5776,6 +5783,7 @@ iseq_compile_each0(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *node, in
 {
     const int line = (int)nd_line(node);
     const enum node_type type = nd_type(node);
+    struct rb_iseq_constant_body *const body = iseq->body;
 
     if (ISEQ_COMPILE_DATA(iseq)->last_line == line) {
 	/* ignore */
@@ -5879,7 +5887,7 @@ iseq_compile_each0(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *node, in
 
       case NODE_LASGN:{
 	ID id = node->nd_vid;
-	int idx = iseq->body->local_iseq->body->local_table_size - get_local_var_idx(iseq, id);
+	int idx = body->local_iseq->body->local_table_size - get_local_var_idx(iseq, id);
 
 	debugs("lvar: %s idx: %d\n", rb_id2name(id), idx);
 	CHECK(COMPILE(ret, "rvalue", node->nd_value));
@@ -6513,46 +6521,48 @@ iseq_compile_each0(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *node, in
 	else {
 	    /* NODE_ZSUPER */
 	    int i;
-	    const rb_iseq_t *liseq = iseq->body->local_iseq;
+	    const rb_iseq_t *liseq = body->local_iseq;
+	    const struct rb_iseq_constant_body *const local_body = liseq->body;
+	    const struct rb_iseq_param_keyword *const local_kwd = local_body->param.keyword;
 	    int lvar_level = get_lvar_level(iseq);
 
-	    argc = liseq->body->param.lead_num;
+	    argc = local_body->param.lead_num;
 
 	    /* normal arguments */
-	    for (i = 0; i < liseq->body->param.lead_num; i++) {
-		int idx = liseq->body->local_table_size - i;
+	    for (i = 0; i < local_body->param.lead_num; i++) {
+		int idx = local_body->local_table_size - i;
 		ADD_GETLOCAL(args, line, idx, lvar_level);
 	    }
 
-	    if (liseq->body->param.flags.has_opt) {
+	    if (local_body->param.flags.has_opt) {
 		/* optional arguments */
 		int j;
-		for (j = 0; j < liseq->body->param.opt_num; j++) {
-		    int idx = liseq->body->local_table_size - (i + j);
+		for (j = 0; j < local_body->param.opt_num; j++) {
+		    int idx = local_body->local_table_size - (i + j);
 		    ADD_GETLOCAL(args, line, idx, lvar_level);
 		}
 		i += j;
 		argc = i;
 	    }
-	    if (liseq->body->param.flags.has_rest) {
+	    if (local_body->param.flags.has_rest) {
 		/* rest argument */
-		int idx = liseq->body->local_table_size - liseq->body->param.rest_start;
+		int idx = local_body->local_table_size - local_body->param.rest_start;
 
 		ADD_GETLOCAL(args, line, idx, lvar_level);
 		ADD_INSN1(args, line, splatarray, Qfalse);
 
-		argc = liseq->body->param.rest_start + 1;
+		argc = local_body->param.rest_start + 1;
 		flag |= VM_CALL_ARGS_SPLAT;
 	    }
-	    if (liseq->body->param.flags.has_post) {
+	    if (local_body->param.flags.has_post) {
 		/* post arguments */
-		int post_len = liseq->body->param.post_num;
-		int post_start = liseq->body->param.post_start;
+		int post_len = local_body->param.post_num;
+		int post_start = local_body->param.post_start;
 
-		if (liseq->body->param.flags.has_rest) {
+		if (local_body->param.flags.has_rest) {
 		    int j;
 		    for (j=0; j<post_len; j++) {
-			int idx = liseq->body->local_table_size - (post_start + j);
+			int idx = local_body->local_table_size - (post_start + j);
 			ADD_GETLOCAL(args, line, idx, lvar_level);
 		    }
 		    ADD_INSN1(args, line, newarray, INT2FIX(j));
@@ -6562,46 +6572,46 @@ iseq_compile_each0(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *node, in
 		else {
 		    int j;
 		    for (j=0; j<post_len; j++) {
-			int idx = liseq->body->local_table_size - (post_start + j);
+			int idx = local_body->local_table_size - (post_start + j);
 			ADD_GETLOCAL(args, line, idx, lvar_level);
 		    }
 		    argc = post_len + post_start;
 		}
 	    }
 
-	    if (liseq->body->param.flags.has_kw) { /* TODO: support keywords */
-		int local_size = liseq->body->local_table_size;
+	    if (local_body->param.flags.has_kw) { /* TODO: support keywords */
+		int local_size = local_body->local_table_size;
 		argc++;
 
 		ADD_INSN1(args, line, putspecialobject, INT2FIX(VM_SPECIAL_OBJECT_VMCORE));
 
-		if (liseq->body->param.flags.has_kwrest) {
-		    int idx = liseq->body->local_table_size - liseq->body->param.keyword->rest_start;
+		if (local_body->param.flags.has_kwrest) {
+		    int idx = local_body->local_table_size - local_kwd->rest_start;
 		    ADD_GETLOCAL(args, line, idx, lvar_level);
 		    ADD_SEND (args, line, rb_intern("dup"), INT2FIX(0));
 		}
 		else {
 		    ADD_INSN1(args, line, newhash, INT2FIX(0));
 		}
-		for (i = 0; i < liseq->body->param.keyword->num; ++i) {
-		    ID id = liseq->body->param.keyword->table[i];
+		for (i = 0; i < local_kwd->num; ++i) {
+		    ID id = local_kwd->table[i];
 		    int idx = local_size - get_local_var_idx(liseq, id);
 		    ADD_INSN1(args, line, putobject, ID2SYM(id));
 		    ADD_GETLOCAL(args, line, idx, lvar_level);
 		}
 		ADD_SEND(args, line, id_core_hash_merge_ptr, INT2FIX(i * 2 + 1));
-		if (liseq->body->param.flags.has_rest) {
+		if (local_body->param.flags.has_rest) {
 		    ADD_INSN1(args, line, newarray, INT2FIX(1));
 		    ADD_INSN (args, line, concatarray);
 		    --argc;
 		}
 	    }
-	    else if (liseq->body->param.flags.has_kwrest) {
-		int idx = liseq->body->local_table_size - liseq->body->param.keyword->rest_start;
+	    else if (local_body->param.flags.has_kwrest) {
+		int idx = local_body->local_table_size - local_kwd->rest_start;
 		ADD_GETLOCAL(args, line, idx, lvar_level);
 
 		ADD_SEND (args, line, rb_intern("dup"), INT2FIX(0));
-		if (liseq->body->param.flags.has_rest) {
+		if (local_body->param.flags.has_rest) {
 		    ADD_INSN1(args, line, newarray, INT2FIX(1));
 		    ADD_INSN (args, line, concatarray);
 		}
@@ -6679,8 +6689,8 @@ iseq_compile_each0(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *node, in
 	struct rb_call_info_kw_arg *keywords = NULL;
 
 	INIT_ANCHOR(args);
-	if (iseq->body->type == ISEQ_TYPE_TOP ||
-	    iseq->body->type == ISEQ_TYPE_MAIN) {
+	if (body->type == ISEQ_TYPE_TOP ||
+	    body->type == ISEQ_TYPE_MAIN) {
 	    COMPILE_ERROR(ERROR_ARGS "Invalid yield");
 	    goto ng;
 	}
@@ -6704,7 +6714,7 @@ iseq_compile_each0(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *node, in
       case NODE_LVAR:{
 	if (!popped) {
 	    ID id = node->nd_vid;
-	    int idx = iseq->body->local_iseq->body->local_table_size - get_local_var_idx(iseq, id);
+	    int idx = body->local_iseq->body->local_table_size - get_local_var_idx(iseq, id);
 
 	    debugs("id: %s idx: %d\n", rb_id2name(id), idx);
 	    ADD_GETLOCAL(ret, line, idx, get_lvar_level(iseq));
@@ -6747,7 +6757,7 @@ iseq_compile_each0(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *node, in
 
 	if (ISEQ_COMPILE_DATA(iseq)->option->inline_const_cache) {
 	    LABEL *lend = NEW_LABEL(line);
-	    int ic_index = iseq->body->is_size++;
+	    int ic_index = body->is_size++;
 
 	    ADD_INSN2(ret, line, getinlinecache, lend, INT2FIX(ic_index));
 	    ADD_INSN1(ret, line, getconstant, ID2SYM(node->nd_vid));
@@ -6924,7 +6934,7 @@ iseq_compile_each0(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *node, in
 	break;
       }
       case NODE_ONCE:{
-	int ic_index = iseq->body->is_size++;
+	int ic_index = body->is_size++;
 	const rb_iseq_t *block_iseq;
 	block_iseq = NEW_CHILD_ISEQ(node->nd_body, make_name_for_block(iseq), ISEQ_TYPE_PLAIN, line);
 
@@ -7097,7 +7107,7 @@ iseq_compile_each0(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *node, in
 	if (rb_is_const_id(node->nd_mid)) {
 	    /* constant */
 	    LABEL *lend = NEW_LABEL(line);
-	    int ic_index = iseq->body->is_size++;
+	    int ic_index = body->is_size++;
 
 	    DECL_ANCHOR(pref);
 	    DECL_ANCHOR(body);
@@ -7138,7 +7148,7 @@ iseq_compile_each0(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *node, in
       }
       case NODE_COLON3:{
 	LABEL *lend = NEW_LABEL(line);
-	int ic_index = iseq->body->is_size++;
+	int ic_index = body->is_size++;
 
 	debugi("colon3#nd_mid", node->nd_mid);
 
@@ -7224,7 +7234,7 @@ iseq_compile_each0(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *node, in
       }
       case NODE_ERRINFO:{
 	if (!popped) {
-	    if (iseq->body->type == ISEQ_TYPE_RESCUE) {
+	    if (body->type == ISEQ_TYPE_RESCUE) {
 		ADD_GETLOCAL(ret, line, LVAR_ERRINFO, 0);
 	    }
 	    else {
@@ -7256,7 +7266,7 @@ iseq_compile_each0(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *node, in
 	/* compiled to:
 	 *   ONCE{ rb_mRubyVMFrozenCore::core#set_postexe{ ... } }
 	 */
-	int is_index = iseq->body->is_size++;
+	int is_index = body->is_size++;
 	const rb_iseq_t *once_iseq =
 	    new_child_iseq_ifunc(iseq, IFUNC_NEW(build_postexe_iseq, node->nd_body, 0),
 				 rb_fstring(make_name_for_block(iseq)), iseq, ISEQ_TYPE_BLOCK, line);
@@ -7290,8 +7300,8 @@ iseq_compile_each0(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *node, in
 		 *   kw = default_value
 		 * end
 		 */
-		int kw_bits_idx = iseq->body->local_table_size - iseq->body->param.keyword->bits_start;
-		int keyword_idx = iseq->body->param.keyword->num;
+		int kw_bits_idx = body->local_table_size - body->param.keyword->bits_start;
+		int keyword_idx = body->param.keyword->num;
 
 		ADD_INSN2(ret, line, checkkeyword, INT2FIX(kw_bits_idx + VM_ENV_DATA_SIZE - 1), INT2FIX(keyword_idx));
 		ADD_INSNL(ret, line, branchif, end_label);
@@ -8159,20 +8169,22 @@ rb_dvar_defined(ID id, const struct rb_block *base_block)
     const rb_iseq_t *iseq;
 
     if (base_block && (iseq = vm_block_iseq(base_block)) != NULL) {
-	while (iseq->body->type == ISEQ_TYPE_BLOCK ||
-	       iseq->body->type == ISEQ_TYPE_RESCUE ||
-	       iseq->body->type == ISEQ_TYPE_ENSURE ||
-	       iseq->body->type == ISEQ_TYPE_EVAL ||
-	       iseq->body->type == ISEQ_TYPE_MAIN
+	const struct rb_iseq_constant_body *body = iseq->body;
+	while (body->type == ISEQ_TYPE_BLOCK ||
+	       body->type == ISEQ_TYPE_RESCUE ||
+	       body->type == ISEQ_TYPE_ENSURE ||
+	       body->type == ISEQ_TYPE_EVAL ||
+	       body->type == ISEQ_TYPE_MAIN
 	       ) {
 	    unsigned int i;
 
-	    for (i = 0; i < iseq->body->local_table_size; i++) {
-		if (iseq->body->local_table[i] == id) {
+	    for (i = 0; i < body->local_table_size; i++) {
+		if (body->local_table[i] == id) {
 		    return 1;
 		}
 	    }
-	    iseq = iseq->body->parent_iseq;
+	    iseq = body->parent_iseq;
+	    body = iseq->body;
 	}
     }
     return 0;
@@ -8185,10 +8197,10 @@ rb_local_defined(ID id, const struct rb_block *base_block)
 
     if (base_block && (iseq = vm_block_iseq(base_block)) != NULL) {
 	unsigned int i;
-	iseq = iseq->body->local_iseq;
+	const struct rb_iseq_constant_body *const body = iseq->body->local_iseq->body;
 
-	for (i=0; i<iseq->body->local_table_size; i++) {
-	    if (iseq->body->local_table[i] == id) {
+	for (i=0; i<body->local_table_size; i++) {
+	    if (body->local_table[i] == id) {
 		return 1;
 	    }
 	}
@@ -8242,10 +8254,11 @@ for_self_aref(rb_iseq_t *iseq, LINK_ANCHOR *const ret, VALUE a)
 {
     const accessor_args *const args = (void *)a;
     const int line = args->line;
+    struct rb_iseq_constant_body *const body = iseq->body;
 
     iseq_set_local_table(iseq, 0);
-    iseq->body->param.lead_num = 0;
-    iseq->body->param.size = 0;
+    body->param.lead_num = 0;
+    body->param.size = 0;
 
     ADD_INSN1(ret, line, putobject, args->arg);
     ADD_INSN1(ret, line, opt_call_c_function, (VALUE)args->func);
@@ -8257,11 +8270,12 @@ for_self_aset(rb_iseq_t *iseq, LINK_ANCHOR *const ret, VALUE a)
 {
     const accessor_args *const args = (void *)a;
     const int line = args->line;
+    struct rb_iseq_constant_body *const body = iseq->body;
     static const ID vars[] = {1, idUScore};
 
     iseq_set_local_table(iseq, vars);
-    iseq->body->param.lead_num = 1;
-    iseq->body->param.size = 1;
+    body->param.lead_num = 1;
+    body->param.size = 1;
 
     ADD_GETLOCAL(ret, line, numberof(vars)-1, 0);
     ADD_INSN1(ret, line, putobject, args->arg);
@@ -8513,7 +8527,8 @@ ibf_load_gentry(const struct ibf_load *load, const struct rb_global_entry *entry
 static VALUE *
 ibf_dump_code(struct ibf_dump *dump, const rb_iseq_t *iseq)
 {
-    const int iseq_size = iseq->body->iseq_size;
+    const struct rb_iseq_constant_body *const body = iseq->body;
+    const int iseq_size = body->iseq_size;
     int code_index;
     VALUE *code;
     const VALUE *orig_code = rb_iseq_original_iseq(iseq);
@@ -8541,8 +8556,8 @@ ibf_dump_code(struct ibf_dump *dump, const rb_iseq_t *iseq)
 	      case TS_ISE:
 		{
 		    unsigned int i;
-		    for (i=0; i<iseq->body->is_size; i++) {
-			if (op == (VALUE)&iseq->body->is_entries[i]) {
+		    for (i=0; i<body->is_size; i++) {
+			if (op == (VALUE)&body->is_entries[i]) {
 			    break;
 			}
 		    }
@@ -8583,10 +8598,10 @@ ibf_load_code(const struct ibf_load *load, const rb_iseq_t *iseq, const struct r
     VALUE *code = IBF_R(body->iseq_encoded, VALUE, iseq_size);
 
     struct rb_iseq_constant_body *load_body = iseq->body;
-    struct rb_call_info *ci_entries = iseq->body->ci_entries;
-    struct rb_call_info_with_kwarg *ci_kw_entries = (struct rb_call_info_with_kwarg *)&iseq->body->ci_entries[iseq->body->ci_size];
-    struct rb_call_cache *cc_entries = iseq->body->cc_entries;
-    union iseq_inline_storage_entry *is_entries = iseq->body->is_entries;
+    struct rb_call_info *ci_entries = load_body->ci_entries;
+    struct rb_call_info_with_kwarg *ci_kw_entries = (struct rb_call_info_with_kwarg *)&load_body->ci_entries[load_body->ci_size];
+    struct rb_call_cache *cc_entries = load_body->cc_entries;
+    union iseq_inline_storage_entry *is_entries = load_body->is_entries;
 
     load_body->iseq_encoded = code;
     load_body->iseq_size = 0;
@@ -8761,12 +8776,13 @@ ibf_load_insns_info_positions(const struct ibf_load *load, const struct rb_iseq_
 static ID *
 ibf_dump_local_table(struct ibf_dump *dump, const rb_iseq_t *iseq)
 {
-    const int size = iseq->body->local_table_size;
+    const struct rb_iseq_constant_body *const body = iseq->body;
+    const int size = body->local_table_size;
     ID *table = ALLOCA_N(ID, size);
     int i;
 
     for (i=0; i<size; i++) {
-	table[i] = ibf_dump_id(dump, iseq->body->local_table[i]);
+	table[i] = ibf_dump_id(dump, body->local_table[i]);
     }
 
     return IBF_W(table, ID, size);
@@ -8834,9 +8850,10 @@ ibf_load_catch_table(const struct ibf_load *load, const struct rb_iseq_constant_
 static struct rb_call_info *
 ibf_dump_ci_entries(struct ibf_dump *dump, const rb_iseq_t *iseq)
 {
-    const unsigned int ci_size = iseq->body->ci_size;
-    const unsigned int ci_kw_size = iseq->body->ci_kw_size;
-    const struct rb_call_info *ci_entries = iseq->body->ci_entries;
+    const struct rb_iseq_constant_body *const body = iseq->body;
+    const unsigned int ci_size = body->ci_size;
+    const unsigned int ci_kw_size = body->ci_kw_size;
+    const struct rb_call_info *ci_entries = body->ci_entries;
     struct rb_call_info *dump_ci_entries;
     struct rb_call_info_with_kwarg *dump_ci_kw_entries;
     int byte_size = ci_size * sizeof(struct rb_call_info) +
diff --git a/iseq.c b/iseq.c
index 8b9da6c4d0..c01d94f9d3 100644
--- a/iseq.c
+++ b/iseq.c
@@ -228,12 +228,13 @@ rb_iseq_mark(const rb_iseq_t *iseq)
 	RUBY_MARK_UNLESS_NULL((VALUE)body->parent_iseq);
 
 	if (body->param.flags.has_kw && ISEQ_COMPILE_DATA(iseq) == NULL) {
+	    const struct rb_iseq_param_keyword *const keyword = body->param.keyword;
 	    int i, j;
 
-	    i = body->param.keyword->required_num;
+	    i = keyword->required_num;
 
-	    for (j = 0; i < body->param.keyword->num; i++, j++) {
-		VALUE obj = body->param.keyword->default_values[j];
+	    for (j = 0; i < keyword->num; i++, j++) {
+		VALUE obj = keyword->default_values[j];
 		if (!SPECIAL_CONST_P(obj)) {
 		    rb_gc_mark(obj);
 		}
@@ -2706,6 +2707,7 @@ rb_iseq_parameters(const rb_iseq_t *iseq, int is_proc)
 {
     int i, r;
     const struct rb_iseq_constant_body *const body = iseq->body;
+    const struct rb_iseq_param_keyword *const keyword = body->param.keyword;
     VALUE a, args = rb_ary_new2(body->param.size);
     ID req, opt, rest, block, key, keyrest;
 #define PARAM_TYPE(type) rb_ary_push(a = rb_ary_new2(2), ID2SYM(type))
@@ -2757,29 +2759,29 @@ rb_iseq_parameters(const rb_iseq_t *iseq, int is_proc)
     }
     if (body->param.flags.has_kw) {
 	i = 0;
-	if (body->param.keyword->required_num > 0) {
+	if (keyword->required_num > 0) {
 	    ID keyreq;
 	    CONST_ID(keyreq, "keyreq");
-	    for (; i < body->param.keyword->required_num; i++) {
+	    for (; i < keyword->required_num; i++) {
 		PARAM_TYPE(keyreq);
-		if (rb_id2str(body->param.keyword->table[i])) {
-		    rb_ary_push(a, ID2SYM(body->param.keyword->table[i]));
+		if (rb_id2str(keyword->table[i])) {
+		    rb_ary_push(a, ID2SYM(keyword->table[i]));
 		}
 		rb_ary_push(args, a);
 	    }
 	}
 	CONST_ID(key, "key");
-	for (; i < body->param.keyword->num; i++) {
+	for (; i < keyword->num; i++) {
 	    PARAM_TYPE(key);
-	    if (rb_id2str(body->param.keyword->table[i])) {
-		rb_ary_push(a, ID2SYM(body->param.keyword->table[i]));
+	    if (rb_id2str(keyword->table[i])) {
+		rb_ary_push(a, ID2SYM(keyword->table[i]));
 	    }
 	    rb_ary_push(args, a);
 	}
     }
     if (body->param.flags.has_kwrest) {
 	CONST_ID(keyrest, "keyrest");
-	rb_ary_push(args, PARAM(body->param.keyword->rest_start, keyrest));
+	rb_ary_push(args, PARAM(keyword->rest_start, keyrest));
     }
     if (body->param.flags.has_block) {
 	CONST_ID(block, "block");