diff --git a/py/Makefile b/py/Makefile
index 36d2a5036cc772ce1cad622833a48c1375a0fb4e..5b3eb17668657384b70ceda5b9ef7f95a71a0518 100644
--- a/py/Makefile
+++ b/py/Makefile
@@ -12,6 +12,7 @@ SRC = \
 	scope.c \
 	compile.c \
 	emitcommon.c \
+	emitpass1.c \
 	emitcpy.c \
 	emitbc.c \
 	asmx64.c \
@@ -19,7 +20,7 @@ SRC = \
 	emitthumb.c \
 	asmthumb.c \
 	runtime.c \
-	bc.c \
+	vm.c \
 	main.c \
 
 SRC_ASM = \
diff --git a/py/asmx64.h b/py/asmx64.h
index 4871dbff8a7ad06c332f908345eeee5295bc3e88..34d5a4835455d5041d2bd4c12a9b61be4e7d0131 100644
--- a/py/asmx64.h
+++ b/py/asmx64.h
@@ -26,7 +26,7 @@
 
 typedef struct _asm_x64_t asm_x64_t;
 
-asm_x64_t* asm_x64_new();
+asm_x64_t* asm_x64_new(uint max_num_labels);
 void asm_x64_free(asm_x64_t* as, bool free_code);
 void asm_x64_start_pass(asm_x64_t *as, int pass);
 void asm_x64_end_pass(asm_x64_t *as);
diff --git a/py/compile.c b/py/compile.c
index 5a90bdcf777ad9b23085fe4cf6c62306ffb4f74f..c6b195edeb4146da0a47133ab02bb822f76bcc86 100644
--- a/py/compile.c
+++ b/py/compile.c
@@ -39,6 +39,9 @@ typedef struct _compiler_t {
 
     pass_kind_t pass;
 
+    int next_label;
+    int max_num_labels;
+
     int break_label;
     int continue_label;
     int except_nest_level;
@@ -159,8 +162,12 @@ py_parse_node_t fold_constants(py_parse_node_t pn) {
 
 void compile_node(compiler_t *comp, py_parse_node_t pn);
 
-scope_t *scope_new_and_link(compiler_t *comp, scope_kind_t kind, py_parse_node_t pn) {
-    scope_t *scope = scope_new(kind, pn);
+static int comp_next_label(compiler_t *comp) {
+    return comp->next_label++;
+}
+
+static scope_t *scope_new_and_link(compiler_t *comp, scope_kind_t kind, py_parse_node_t pn) {
+    scope_t *scope = scope_new(kind, pn, rt_get_new_unique_code_id());
     scope->parent = comp->scope_cur;
     scope->next = NULL;
     if (comp->scope_head == NULL) {
@@ -175,7 +182,7 @@ scope_t *scope_new_and_link(compiler_t *comp, scope_kind_t kind, py_parse_node_t
     return scope;
 }
 
-int list_len(py_parse_node_t pn, int pn_kind) {
+static int list_len(py_parse_node_t pn, int pn_kind) {
     if (PY_PARSE_NODE_IS_NULL(pn)) {
         return 0;
     } else if (PY_PARSE_NODE_IS_LEAF(pn)) {
@@ -190,7 +197,7 @@ int list_len(py_parse_node_t pn, int pn_kind) {
     }
 }
 
-void apply_to_single_or_list(compiler_t *comp, py_parse_node_t pn, int pn_list_kind, void (*f)(compiler_t*, py_parse_node_t)) {
+static void apply_to_single_or_list(compiler_t *comp, py_parse_node_t pn, int pn_list_kind, void (*f)(compiler_t*, py_parse_node_t)) {
     if (PY_PARSE_NODE_IS_STRUCT(pn) && PY_PARSE_NODE_STRUCT_KIND((py_parse_node_struct_t*)pn) == pn_list_kind) {
         py_parse_node_struct_t *pns = (py_parse_node_struct_t*)pn;
         int num_nodes = PY_PARSE_NODE_STRUCT_NUM_NODES(pns);
@@ -202,7 +209,7 @@ void apply_to_single_or_list(compiler_t *comp, py_parse_node_t pn, int pn_list_k
     }
 }
 
-int list_get(py_parse_node_t *pn, int pn_kind, py_parse_node_t **nodes) {
+static int list_get(py_parse_node_t *pn, int pn_kind, py_parse_node_t **nodes) {
     if (PY_PARSE_NODE_IS_NULL(*pn)) {
         *nodes = NULL;
         return 0;
@@ -353,7 +360,7 @@ void c_if_cond_2(compiler_t *comp, py_parse_node_t pn, bool jump_if, int label,
         int n = PY_PARSE_NODE_STRUCT_NUM_NODES(pns);
         if (PY_PARSE_NODE_STRUCT_KIND(pns) == PN_or_test) {
             if (jump_if == false) {
-                int label2 = EMIT(label_new);
+                int label2 = comp_next_label(comp);
                 for (int i = 0; i < n - 1; i++) {
                     c_if_cond_2(comp, pns->nodes[i], true, label2, true);
                 }
@@ -371,7 +378,7 @@ void c_if_cond_2(compiler_t *comp, py_parse_node_t pn, bool jump_if, int label,
                     c_if_cond_2(comp, pns->nodes[i], false, label, true);
                 }
             } else {
-                int label2 = EMIT(label_new);
+                int label2 = comp_next_label(comp);
                 for (int i = 0; i < n - 1; i++) {
                     c_if_cond_2(comp, pns->nodes[i], false, label2, true);
                 }
@@ -893,7 +900,7 @@ void compile_return_stmt(compiler_t *comp, py_parse_node_struct_t *pns) {
         py_parse_node_struct_t *pns_test_if_expr = (py_parse_node_struct_t*)pns->nodes[0];
         py_parse_node_struct_t *pns_test_if_else = (py_parse_node_struct_t*)pns_test_if_expr->nodes[1];
 
-        int l_fail = EMIT(label_new);
+        int l_fail = comp_next_label(comp);
         c_if_cond(comp, pns_test_if_else->nodes[0], false, l_fail); // condition
         compile_node(comp, pns_test_if_expr->nodes[0]); // success value
         EMIT(return_value);
@@ -1073,7 +1080,7 @@ void compile_nonlocal_stmt(compiler_t *comp, py_parse_node_struct_t *pns) {
 }
 
 void compile_assert_stmt(compiler_t *comp, py_parse_node_struct_t *pns) {
-    int l_end = EMIT(label_new);
+    int l_end = comp_next_label(comp);
     c_if_cond(comp, pns->nodes[0], true, l_end);
     EMIT_COMMON(load_id, comp->qstr___class__, comp->qstr_assertion_error);
     if (!PY_PARSE_NODE_IS_NULL(pns->nodes[1])) {
@@ -1088,9 +1095,9 @@ void compile_assert_stmt(compiler_t *comp, py_parse_node_struct_t *pns) {
 void compile_if_stmt(compiler_t *comp, py_parse_node_struct_t *pns) {
     // TODO proper and/or short circuiting
 
-    int l_end = EMIT(label_new);
+    int l_end = comp_next_label(comp);
 
-    int l_fail = EMIT(label_new);
+    int l_fail = comp_next_label(comp);
     c_if_cond(comp, pns->nodes[0], false, l_fail); // if condition
 
     compile_node(comp, pns->nodes[1]); // if block
@@ -1113,7 +1120,7 @@ void compile_if_stmt(compiler_t *comp, py_parse_node_struct_t *pns) {
             int n = PY_PARSE_NODE_STRUCT_NUM_NODES(pns_elif);
             for (int i = 0; i < n; i++) {
                 py_parse_node_struct_t *pns_elif2 = (py_parse_node_struct_t*)pns_elif->nodes[i];
-                l_fail = EMIT(label_new);
+                l_fail = comp_next_label(comp);
                 c_if_cond(comp, pns_elif2->nodes[0], false, l_fail); // elif condition
 
                 compile_node(comp, pns_elif2->nodes[1]); // elif block
@@ -1126,7 +1133,7 @@ void compile_if_stmt(compiler_t *comp, py_parse_node_struct_t *pns) {
         } else {
             // a single elif block
 
-            l_fail = EMIT(label_new);
+            l_fail = comp_next_label(comp);
             c_if_cond(comp, pns_elif->nodes[0], false, l_fail); // elif condition
 
             compile_node(comp, pns_elif->nodes[1]); // elif block
@@ -1147,10 +1154,10 @@ void compile_while_stmt(compiler_t *comp, py_parse_node_struct_t *pns) {
     int old_break_label = comp->break_label;
     int old_continue_label = comp->continue_label;
 
-    int done_label = EMIT(label_new);
-    int end_label = EMIT(label_new);
-    int break_label = EMIT(label_new);
-    int continue_label = EMIT(label_new);
+    int done_label = comp_next_label(comp);
+    int end_label = comp_next_label(comp);
+    int break_label = comp_next_label(comp);
+    int continue_label = comp_next_label(comp);
 
     comp->break_label = break_label;
     comp->continue_label = continue_label;
@@ -1184,11 +1191,11 @@ void compile_for_stmt(compiler_t *comp, py_parse_node_struct_t *pns) {
     int old_break_label = comp->break_label;
     int old_continue_label = comp->continue_label;
 
-    int for_label = EMIT(label_new);
-    int pop_label = EMIT(label_new);
-    int end_label = EMIT(label_new);
+    int for_label = comp_next_label(comp);
+    int pop_label = comp_next_label(comp);
+    int end_label = comp_next_label(comp);
 
-    int break_label = EMIT(label_new);
+    int break_label = comp_next_label(comp);
 
     comp->continue_label = for_label;
     comp->break_label = break_label;
@@ -1224,22 +1231,22 @@ void compile_try_except(compiler_t *comp, py_parse_node_t pn_body, int n_except,
 
     // setup code
     int stack_size = EMIT(get_stack_size);
-    int l1 = EMIT(label_new);
-    int success_label = EMIT(label_new);
+    int l1 = comp_next_label(comp);
+    int success_label = comp_next_label(comp);
     comp->except_nest_level += 1; // for correct handling of continue
     EMIT(setup_except, l1);
     compile_node(comp, pn_body); // body
     EMIT(pop_block);
     EMIT(jump, success_label);
     EMIT(label_assign, l1);
-    int l2 = EMIT(label_new);
+    int l2 = comp_next_label(comp);
 
     for (int i = 0; i < n_except; i++) {
         assert(PY_PARSE_NODE_IS_STRUCT_KIND(pn_excepts[i], PN_try_stmt_except)); // should be
         py_parse_node_struct_t *pns_except = (py_parse_node_struct_t*)pn_excepts[i];
 
         qstr qstr_exception_local = 0;
-        int end_finally_label = EMIT(label_new);
+        int end_finally_label = comp_next_label(comp);
 
         if (PY_PARSE_NODE_IS_NULL(pns_except->nodes[0])) {
             // this is a catch all exception handler
@@ -1276,7 +1283,7 @@ void compile_try_except(compiler_t *comp, py_parse_node_t pn_body, int n_except,
 
         int l3;
         if (qstr_exception_local != 0) {
-            l3 = EMIT(label_new);
+            l3 = comp_next_label(comp);
             EMIT(setup_finally, l3);
         }
         compile_node(comp, pns_except->nodes[1]);
@@ -1307,7 +1314,7 @@ void compile_try_except(compiler_t *comp, py_parse_node_t pn_body, int n_except,
 void compile_try_finally(compiler_t *comp, py_parse_node_t pn_body, int n_except, py_parse_node_t *pn_except, py_parse_node_t pn_else, py_parse_node_t pn_finally) {
     // don't understand how the stack works with exceptions, so we force it to return to the correct value
     int stack_size = EMIT(get_stack_size);
-    int l_finally_block = EMIT(label_new);
+    int l_finally_block = comp_next_label(comp);
     EMIT(setup_finally, l_finally_block);
     if (n_except == 0) {
         assert(PY_PARSE_NODE_IS_NULL(pn_else));
@@ -1357,7 +1364,7 @@ void compile_with_stmt_helper(compiler_t *comp, int n, py_parse_node_t *nodes, p
         // no more pre-bits, compile the body of the with
         compile_node(comp, body);
     } else {
-        int l_end = EMIT(label_new);
+        int l_end = comp_next_label(comp);
         if (PY_PARSE_NODE_IS_STRUCT_KIND(nodes[0], PN_with_item)) {
             // this pre-bit is of the form "a as b"
             py_parse_node_struct_t *pns = (py_parse_node_struct_t*)nodes[0];
@@ -1490,8 +1497,8 @@ void compile_test_if_expr(compiler_t *comp, py_parse_node_struct_t *pns) {
     py_parse_node_struct_t *pns_test_if_else = (py_parse_node_struct_t*)pns->nodes[1];
 
     int stack_size = EMIT(get_stack_size);
-    int l_fail = EMIT(label_new);
-    int l_end = EMIT(label_new);
+    int l_fail = comp_next_label(comp);
+    int l_end = comp_next_label(comp);
     c_if_cond(comp, pns_test_if_else->nodes[0], false, l_fail); // condition
     compile_node(comp, pns->nodes[0]); // success value
     EMIT(jump, l_end);
@@ -1521,7 +1528,7 @@ void compile_lambdef(compiler_t *comp, py_parse_node_struct_t *pns) {
 }
 
 void compile_or_test(compiler_t *comp, py_parse_node_struct_t *pns) {
-    int l_end = EMIT(label_new);
+    int l_end = comp_next_label(comp);
     int n = PY_PARSE_NODE_STRUCT_NUM_NODES(pns);
     for (int i = 0; i < n; i += 1) {
         compile_node(comp, pns->nodes[i]);
@@ -1533,7 +1540,7 @@ void compile_or_test(compiler_t *comp, py_parse_node_struct_t *pns) {
 }
 
 void compile_and_test(compiler_t *comp, py_parse_node_struct_t *pns) {
-    int l_end = EMIT(label_new);
+    int l_end = comp_next_label(comp);
     int n = PY_PARSE_NODE_STRUCT_NUM_NODES(pns);
     for (int i = 0; i < n; i += 1) {
         compile_node(comp, pns->nodes[i]);
@@ -1556,7 +1563,7 @@ void compile_comparison(compiler_t *comp, py_parse_node_struct_t *pns) {
     bool multi = (num_nodes > 3);
     int l_fail = 0;
     if (multi) {
-        l_fail = EMIT(label_new);
+        l_fail = comp_next_label(comp);
     }
     for (int i = 1; i + 1 < num_nodes; i += 2) {
         compile_node(comp, pns->nodes[i + 1]);
@@ -1602,7 +1609,7 @@ void compile_comparison(compiler_t *comp, py_parse_node_struct_t *pns) {
         }
     }
     if (multi) {
-        int l_end = EMIT(label_new);
+        int l_end = comp_next_label(comp);
         EMIT(jump, l_end);
         EMIT(label_assign, l_fail);
         EMIT(rot_two);
@@ -2255,8 +2262,8 @@ void compile_scope_comp_iter(compiler_t *comp, py_parse_node_t pn_iter, py_parse
         // for loop
         py_parse_node_struct_t *pns_comp_for2 = (py_parse_node_struct_t*)pn_iter;
         compile_node(comp, pns_comp_for2->nodes[1]);
-        int l_end2 = EMIT(label_new);
-        int l_top2 = EMIT(label_new);
+        int l_end2 = comp_next_label(comp);
+        int l_top2 = comp_next_label(comp);
         EMIT(get_iter);
         EMIT(label_assign, l_top2);
         EMIT(for_iter, l_end2);
@@ -2302,6 +2309,7 @@ void check_for_doc_string(compiler_t *comp, py_parse_node_t pn) {
 void compile_scope(compiler_t *comp, scope_t *scope, pass_kind_t pass) {
     comp->pass = pass;
     comp->scope_cur = scope;
+    comp->next_label = 1;
     EMIT(start_pass, pass, scope);
 
     if (comp->pass == PASS_1) {
@@ -2377,8 +2385,8 @@ void compile_scope(compiler_t *comp, scope_t *scope, pass_kind_t pass) {
             EMIT(build_set, 0);
         }
 
-        int l_end = EMIT(label_new);
-        int l_top = EMIT(label_new);
+        int l_end = comp_next_label(comp);
+        int l_top = comp_next_label(comp);
         EMIT_COMMON(load_id, comp->qstr___class__, qstr_arg);
         EMIT(label_assign, l_top);
         EMIT(for_iter, l_end);
@@ -2431,6 +2439,11 @@ void compile_scope(compiler_t *comp, scope_t *scope, pass_kind_t pass) {
     }
 
     EMIT(end_pass);
+
+    // update maximim number of labels needed
+    if (comp->next_label > comp->max_num_labels) {
+        comp->max_num_labels = comp->next_label;
+    }
 }
 
 void compile_scope_compute_things(compiler_t *comp, scope_t *scope) {
@@ -2489,15 +2502,14 @@ void py_compile(py_parse_node_t pn) {
     comp->qstr___doc__ = qstr_from_strn_copy("__doc__", 7);
     comp->qstr_assertion_error = qstr_from_strn_copy("AssertionError", 14);
 
+    comp->max_num_labels = 0;
     comp->break_label = 0;
     comp->continue_label = 0;
     comp->except_nest_level = 0;
     comp->scope_head = NULL;
     comp->scope_cur = NULL;
 
-    emit_new_cpython(&comp->emit, &comp->emit_method_table);
-    //emit_new_bc(&comp->emit, &comp->emit_method_table);
-    //emit_new_x64(&comp->emit, &comp->emit_method_table);
+    emit_pass1_new(&comp->emit, &comp->emit_method_table);
 
     pn = fold_constants(pn);
     scope_new_and_link(comp, SCOPE_MODULE, pn);
@@ -2510,6 +2522,10 @@ void py_compile(py_parse_node_t pn) {
         compile_scope_compute_things(comp, s);
     }
 
+    //emit_cpython_new(&comp->emit, &comp->emit_method_table, comp->max_num_labels);
+    emit_bc_new(&comp->emit, &comp->emit_method_table, comp->max_num_labels);
+    //emit_new_x64(&comp->emit, &comp->emit_method_table, comp->max_num_labels);
+
     for (scope_t *s = comp->scope_head; s != NULL; s = s->next) {
         compile_scope(comp, s, PASS_2);
         compile_scope(comp, s, PASS_3);
diff --git a/py/emit.h b/py/emit.h
index dcafbc08d798ee6041e2be10f7c3577be5b9b313..b2d451efdbf5c838ed1c28699ec016f4fdb73fe4 100644
--- a/py/emit.h
+++ b/py/emit.h
@@ -113,10 +113,13 @@ void emit_common_load_id(pass_kind_t pass, scope_t *scope, emit_t *emit, const e
 void emit_common_store_id(pass_kind_t pass, scope_t *scope, emit_t *emit, const emit_method_table_t *emit_method_table, qstr qstr);
 void emit_common_delete_id(pass_kind_t pass, scope_t *scope, emit_t *emit, const emit_method_table_t *emit_method_table, qstr qstr);
 
-void emit_new_cpython(emit_t **emit, const emit_method_table_t **emit_method_table);
-void emit_new_bc(emit_t **emit, const emit_method_table_t **emit_method_table);
-void emit_new_x64(emit_t **emit, const emit_method_table_t **emit_method_table);
-void emit_new_thumb(emit_t **emit, const emit_method_table_t **emit_method_table);
+void emit_pass1_new(emit_t **emit, const emit_method_table_t **emit_method_table);
+uint emit_pass1_get_max_num_labels(emit_t *emit);
+
+void emit_cpython_new(emit_t **emit_out, const emit_method_table_t **emit_method_table_out, uint max_num_labels);
+void emit_bc_new(emit_t **emit, const emit_method_table_t **emit_method_table, uint max_num_labels);
+void emit_x64_new(emit_t **emit, const emit_method_table_t **emit_method_table, uint max_num_labels);
+void emit_thumb_new(emit_t **emit, const emit_method_table_t **emit_method_table, uint max_num_labels);
 
 /*
 void emit_set_native_types(emitter_t *emit, bool do_native_types);
diff --git a/py/emitbc.c b/py/emitbc.c
index 27540f18de7c178326db259673ab44ef758e6967..fae394bd9e634042f946f7a0d1b54ba13d442fac 100644
--- a/py/emitbc.c
+++ b/py/emitbc.c
@@ -13,7 +13,7 @@
 #include "scope.h"
 #include "runtime.h"
 #include "emit.h"
-#include "bc.h"
+#include "vm.h"
 
 struct _emit_t {
     pass_kind_t pass;
@@ -23,7 +23,7 @@ struct _emit_t {
 
     scope_t *scope;
 
-    int max_num_labels;
+    uint max_num_labels;
     uint *label_offsets;
 
     uint code_offset;
@@ -49,15 +49,8 @@ static void emit_bc_start_pass(emit_t *emit, pass_kind_t pass, scope_t *scope) {
     emit->stack_size = 0;
     emit->last_emit_was_return_value = false;
     emit->scope = scope;
-    if (pass == PASS_1) {
-        scope->unique_code_id = rt_get_new_unique_code_id();
-    } else if (pass > PASS_1) {
-        if (emit->label_offsets == NULL) {
-            emit->label_offsets = m_new(uint, emit->max_num_labels);
-        }
-        if (pass == PASS_2) {
-            memset(emit->label_offsets, -1, emit->max_num_labels * sizeof(uint));
-        }
+    if (pass == PASS_2) {
+        memset(emit->label_offsets, -1, emit->max_num_labels * sizeof(uint));
     }
     emit->code_offset = 0;
 }
@@ -68,13 +61,7 @@ static void emit_bc_end_pass(emit_t *emit) {
         printf("ERROR: stack size not back to zero; got %d\n", emit->stack_size);
     }
 
-    if (emit->pass == PASS_1) {
-        // calculate number of labels need
-        if (emit->next_label > emit->max_num_labels) {
-            emit->max_num_labels = emit->next_label;
-        }
-
-    } else if (emit->pass == PASS_2) {
+    if (emit->pass == PASS_2) {
         // calculate size of code in bytes
         emit->code_size = emit->code_offset;
         emit->code_base = m_new(byte, emit->code_size);
@@ -160,17 +147,13 @@ int emit_bc_get_stack_size(emit_t *emit) {
 }
 
 static void emit_bc_set_stack_size(emit_t *emit, int size) {
-    if (emit->pass > PASS_1) {
-        emit->stack_size = size;
-    }
+    emit->stack_size = size;
 }
 
 static void emit_pre(emit_t *emit, int stack_size_delta) {
-    if (emit->pass > PASS_1) {
-        emit->stack_size += stack_size_delta;
-        if (emit->stack_size > emit->scope->stack_size) {
-            emit->scope->stack_size = emit->stack_size;
-        }
+    emit->stack_size += stack_size_delta;
+    if (emit->stack_size > emit->scope->stack_size) {
+        emit->scope->stack_size = emit->stack_size;
     }
     emit->last_emit_was_return_value = false;
 }
@@ -181,17 +164,15 @@ static int emit_bc_label_new(emit_t *emit) {
 
 static void emit_bc_label_assign(emit_t *emit, int l) {
     emit_pre(emit, 0);
-    if (emit->pass > PASS_1) {
-        assert(l < emit->max_num_labels);
-        if (emit->pass == PASS_2) {
-            // assign label offset
-            assert(emit->label_offsets[l] == -1);
-            emit->label_offsets[l] = emit->code_offset;
-        } else if (emit->pass == PASS_3) {
-            // ensure label offset has not changed from PASS_2 to PASS_3
-            assert(emit->label_offsets[l] == emit->code_offset);
-            //printf("l%d: (at %d)\n", l, emit->code_offset);
-        }
+    assert(l < emit->max_num_labels);
+    if (emit->pass == PASS_2) {
+        // assign label offset
+        assert(emit->label_offsets[l] == -1);
+        emit->label_offsets[l] = emit->code_offset;
+    } else if (emit->pass == PASS_3) {
+        // ensure label offset has not changed from PASS_2 to PASS_3
+        assert(emit->label_offsets[l] == emit->code_offset);
+        //printf("l%d: (at %d)\n", l, emit->code_offset);
     }
 }
 
@@ -773,10 +754,10 @@ static const emit_method_table_t emit_bc_method_table = {
     emit_bc_yield_from,
 };
 
-void emit_new_bc(emit_t **emit_out, const emit_method_table_t **emit_method_table_out) {
+void emit_bc_new(emit_t **emit_out, const emit_method_table_t **emit_method_table_out, uint max_num_labels) {
     emit_t *emit = m_new(emit_t, 1);
-    emit->max_num_labels = 0;
-    emit->label_offsets = NULL;
+    emit->max_num_labels = max_num_labels;
+    emit->label_offsets = m_new(uint, emit->max_num_labels);
     emit->code_offset = 0;
     emit->code_size = 0;
     emit->code_base = NULL;
diff --git a/py/emitcpy.c b/py/emitcpy.c
index 1c600ac5771689921b0b2ff684ea8463f6dbac88..72f4d4daa96c52c4f35a2ed57625796f4191ee60 100644
--- a/py/emitcpy.c
+++ b/py/emitcpy.c
@@ -25,7 +25,7 @@ struct _emit_t {
 
     scope_t *scope;
 
-    int max_num_labels;
+    uint max_num_labels;
     int *label_offsets;
 };
 
@@ -39,13 +39,8 @@ static void emit_cpy_start_pass(emit_t *emit, pass_kind_t pass, scope_t *scope)
     emit->stack_size = 0;
     emit->last_emit_was_return_value = false;
     emit->scope = scope;
-    if (pass > PASS_1) {
-        if (emit->label_offsets == NULL) {
-            emit->label_offsets = m_new(int, emit->max_num_labels);
-        }
-        if (pass == PASS_2) {
-            memset(emit->label_offsets, -1, emit->max_num_labels * sizeof(int));
-        }
+    if (pass == PASS_2) {
+        memset(emit->label_offsets, -1, emit->max_num_labels * sizeof(int));
     }
 }
 
@@ -54,13 +49,6 @@ static void emit_cpy_end_pass(emit_t *emit) {
     if (emit->stack_size != 0) {
         printf("ERROR: stack size not back to zero; got %d\n", emit->stack_size);
     }
-
-    // calculate number of labels need
-    if (emit->pass == PASS_1) {
-        if (emit->next_label > emit->max_num_labels) {
-            emit->max_num_labels = emit->next_label;
-        }
-    }
 }
 
 static bool emit_cpy_last_emit_was_return_value(emit_t *emit) {
@@ -77,7 +65,7 @@ static void emit_cpy_set_stack_size(emit_t *emit, int size) {
 
 static void emit_pre(emit_t *emit, int stack_size_delta, int byte_code_size) {
     emit->stack_size += stack_size_delta;
-    if (emit->pass > PASS_1 && emit->stack_size > emit->scope->stack_size) {
+    if (emit->stack_size > emit->scope->stack_size) {
         emit->scope->stack_size = emit->stack_size;
     }
     emit->last_emit_was_return_value = false;
@@ -97,17 +85,15 @@ static int emit_cpy_label_new(emit_t *emit) {
 
 static void emit_cpy_label_assign(emit_t *emit, int l) {
     emit_pre(emit, 0, 0);
-    if (emit->pass > PASS_1) {
-        assert(l < emit->max_num_labels);
-        if (emit->pass == PASS_2) {
-            // assign label offset
-            assert(emit->label_offsets[l] == -1);
-            emit->label_offsets[l] = emit->byte_code_offset;
-        } else if (emit->pass == PASS_3) {
-            // ensure label offset has not changed from PASS_2 to PASS_3
-            assert(emit->label_offsets[l] == emit->byte_code_offset);
-            //printf("l%d: (at %d)\n", l, emit->byte_code_offset);
-        }
+    assert(l < emit->max_num_labels);
+    if (emit->pass == PASS_2) {
+        // assign label offset
+        assert(emit->label_offsets[l] == -1);
+        emit->label_offsets[l] = emit->byte_code_offset;
+    } else if (emit->pass == PASS_3) {
+        // ensure label offset has not changed from PASS_2 to PASS_3
+        assert(emit->label_offsets[l] == emit->byte_code_offset);
+        //printf("l%d: (at %d)\n", l, emit->byte_code_offset);
     }
 }
 
@@ -921,10 +907,10 @@ static const emit_method_table_t emit_cpy_method_table = {
     emit_cpy_yield_from,
 };
 
-void emit_new_cpython(emit_t **emit_out, const emit_method_table_t **emit_method_table_out) {
+void emit_cpython_new(emit_t **emit_out, const emit_method_table_t **emit_method_table_out, uint max_num_labels) {
     emit_t *emit = m_new(emit_t, 1);
-    emit->max_num_labels = 0;
-    emit->label_offsets = NULL;
+    emit->max_num_labels = max_num_labels;
+    emit->label_offsets = m_new(int, max_num_labels);
 
     *emit_out = emit;
     *emit_method_table_out = &emit_cpy_method_table;
diff --git a/py/emitthumb.c b/py/emitthumb.c
index cad6b650440ca5536bb550778c5c79fbb608667c..9bccda8016c7d46a9448fccaa083ba68fcc722d7 100644
--- a/py/emitthumb.c
+++ b/py/emitthumb.c
@@ -57,9 +57,6 @@ void emit_start_pass(emitter_t *emit, pass_kind_t pass, scope_t *scope) {
     emit->last_emit_was_return_value = false;
     emit->need_to_push = NEED_TO_PUSH_NOTHING;
     emit->scope = scope;
-    if (pass == PASS_1) {
-        scope->unique_code_id = rt_get_new_unique_code_id();
-    }
 
     asm_thumb_start_pass(emit->as, pass);
 
diff --git a/py/emitx64.c b/py/emitx64.c
index 38d519063e19c6e174002755383377d7497ac2a0..c9307dc00d4b21bc8e006c0fb146498255ee234d 100644
--- a/py/emitx64.c
+++ b/py/emitx64.c
@@ -64,9 +64,6 @@ static void emit_x64_start_pass(emit_t *emit, pass_kind_t pass, scope_t *scope)
     emit->last_emit_was_return_value = false;
     emit->need_to_push = NEED_TO_PUSH_NOTHING;
     emit->scope = scope;
-    if (pass == PASS_1) {
-        scope->unique_code_id = rt_get_new_unique_code_id();
-    }
 
     asm_x64_start_pass(emit->as, pass);
 
@@ -763,9 +760,9 @@ static const emit_method_table_t emit_x64_method_table = {
     emit_x64_yield_from,
 };
 
-void emit_new_x64(emit_t **emit_out, const emit_method_table_t **emit_method_table_out) {
+void emit_x64_new(emit_t **emit_out, const emit_method_table_t **emit_method_table_out, uint max_num_labels) {
     emit_t *emit = m_new(emit_t, 1);
-    emit->as = asm_x64_new();
+    emit->as = asm_x64_new(max_num_labels);
     emit->do_native_types = false;
 
     *emit_out = emit;
diff --git a/py/runtime.c b/py/runtime.c
index bf2e2ee0651a007c7564949705eb20827354260b..21f3c8c50adc8261035bb7fbed16763d1661d03f 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -7,7 +7,7 @@
 #include "misc.h"
 #include "machine.h"
 #include "runtime.h"
-#include "bc.h"
+#include "vm.h"
 
 #define DEBUG_printf(args...) (void)0
 //#define DEBUG_printf(args...) printf(args)
@@ -372,7 +372,7 @@ void rt_assign_native_code(int unique_code_id, py_fun_t fun, uint len, int n_arg
     if (unique_codes == NULL) {
         unique_codes = m_new(py_code_t, next_unique_code_id);
     }
-    assert(unique_code_id < next_unique_code_id);
+    assert(1 <= unique_code_id && unique_code_id < next_unique_code_id);
     unique_codes[unique_code_id].kind = PY_CODE_NATIVE;
     unique_codes[unique_code_id].n_args = n_args;
     unique_codes[unique_code_id].u_native.fun = fun;
@@ -635,7 +635,8 @@ py_obj_t rt_compare_op(int op, py_obj_t lhs, py_obj_t rhs) {
 }
 
 py_obj_t rt_make_function_from_id(int unique_code_id) {
-    if (unique_code_id >= next_unique_code_id) {
+    DEBUG_OP_printf("make_function_from_id %d\n", unique_code_id);
+    if (unique_code_id < 1 || unique_code_id >= next_unique_code_id) {
         // illegal code id
         return py_const_none;
     }
diff --git a/py/scope.c b/py/scope.c
index 5773ae0b44d9174c63ffbef558cb9f6e735dfeed..57a7e6875dd9bcb80798dd8a135d371f5400a7ed 100644
--- a/py/scope.c
+++ b/py/scope.c
@@ -8,7 +8,7 @@
 #include "parse.h"
 #include "scope.h"
 
-scope_t *scope_new(scope_kind_t kind, py_parse_node_t pn) {
+scope_t *scope_new(scope_kind_t kind, py_parse_node_t pn, uint unique_code_id) {
     scope_t *scope = m_new(scope_t, 1);
     scope->kind = kind;
     scope->parent = NULL;
@@ -52,7 +52,7 @@ scope_t *scope_new(scope_kind_t kind, py_parse_node_t pn) {
     scope->num_dict_params = 0;
     */
     scope->num_locals = 0;
-    scope->unique_code_id = 0;
+    scope->unique_code_id = unique_code_id;
 
     return scope;
 }
diff --git a/py/scope.h b/py/scope.h
index cb5e606c3387ea72b455527f108c4aaf3ffa27cc..f9ad748d97a7d3124c5d2db9b2f30796e5b12c46 100644
--- a/py/scope.h
+++ b/py/scope.h
@@ -46,10 +46,10 @@ typedef struct _scope_t {
     */
     int num_locals;
     int stack_size;
-    int unique_code_id;
+    uint unique_code_id;
 } scope_t;
 
-scope_t *scope_new(scope_kind_t kind, py_parse_node_t pn);
+scope_t *scope_new(scope_kind_t kind, py_parse_node_t pn, uint unique_code_id);
 id_info_t *scope_find_or_add_id(scope_t *scope, qstr qstr, bool *added);
 id_info_t *scope_find(scope_t *scope, qstr qstr);
 id_info_t *scope_find_global(scope_t *scope, qstr qstr);
diff --git a/py/bc.c b/py/vm.c
similarity index 99%
rename from py/bc.c
rename to py/vm.c
index 1edd911ab6f9e97cef3b76c695f938eada739b9e..63a478fcf3861472235ffb3d5674e7cfa30a91b8 100644
--- a/py/bc.c
+++ b/py/vm.c
@@ -7,7 +7,7 @@
 #include "misc.h"
 #include "machine.h"
 #include "runtime.h"
-#include "bc.h"
+#include "vm.h"
 
 #define DECODE_UINT do { unum = *ip++; if (unum > 127) { unum = ((unum & 0x3f) << 8) | (*ip++); } } while (0)
 #define DECODE_QSTR do { qstr = *ip++; if (qstr > 127) { qstr = ((qstr & 0x3f) << 8) | (*ip++); } } while (0)
diff --git a/py/bc.h b/py/vm.h
similarity index 100%
rename from py/bc.h
rename to py/vm.h