add circuitpython code

1 files changed, 3045 insertions, 0 deletions

diff --git a/circuitpython/py/emitnative.c b/circuitpython/py/emitnative.c
new file mode 100644
index 0000000..5946fcd
--- /dev/null
+++ b/circuitpython/py/emitnative.c
@@ -0,0 +1,3045 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2013, 2014 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+// Essentially normal Python has 1 type: Python objects
+// Viper has more than 1 type, and is just a more complicated (a superset of) Python.
+// If you declare everything in Viper as a Python object (ie omit type decls) then
+// it should in principle be exactly the same as Python native.
+// Having types means having more opcodes, like binary_op_nat_nat, binary_op_nat_obj etc.
+// In practice we won't have a VM but rather do this in asm which is actually very minimal.
+
+// Because it breaks strict Python equivalence it should be a completely separate
+// decorator.  It breaks equivalence because overflow on integers wraps around.
+// It shouldn't break equivalence if you don't use the new types, but since the
+// type decls might be used in normal Python for other reasons, it's probably safest,
+// cleanest and clearest to make it a separate decorator.
+
+// Actually, it does break equivalence because integers default to native integers,
+// not Python objects.
+
+// for x in l[0:8]: can be compiled into a native loop if l has pointer type
+
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+#include "py/emit.h"
+#include "py/nativeglue.h"
+#include "py/objstr.h"
+
+#if MICROPY_DEBUG_VERBOSE // print debugging info
+#define DEBUG_PRINT (1)
+#define DEBUG_printf DEBUG_printf
+#else // don't print debugging info
+#define DEBUG_printf(...) (void)0
+#endif
+
+#ifndef N_X64
+#define N_X64 (0)
+#endif
+
+#ifndef N_X86
+#define N_X86 (0)
+#endif
+
+#ifndef N_THUMB
+#define N_THUMB (0)
+#endif
+
+#ifndef N_ARM
+#define N_ARM (0)
+#endif
+
+#ifndef N_XTENSA
+#define N_XTENSA (0)
+#endif
+
+#ifndef N_NLR_SETJMP
+#define N_NLR_SETJMP (0)
+#endif
+
+#ifndef N_PRELUDE_AS_BYTES_OBJ
+#define N_PRELUDE_AS_BYTES_OBJ (0)
+#endif
+
+// wrapper around everything in this file
+#if N_X64 || N_X86 || N_THUMB || N_ARM || N_XTENSA || N_XTENSAWIN
+
+// C stack layout for native functions:
+//  0:                          nlr_buf_t [optional]
+//  emit->code_state_start:     mp_code_state_t
+//  emit->stack_start:          Python object stack             | emit->n_state
+//                              locals (reversed, L0 at end)    |
+//
+// C stack layout for native generator functions:
+//  0=emit->stack_start:        nlr_buf_t
+//
+//  Then REG_GENERATOR_STATE points to:
+//  0=emit->code_state_start:   mp_code_state_t
+//  emit->stack_start:          Python object stack             | emit->n_state
+//                              locals (reversed, L0 at end)    |
+//
+// C stack layout for viper functions:
+//  0:                          nlr_buf_t [optional]
+//  emit->code_state_start:     fun_obj, old_globals [optional]
+//  emit->stack_start:          Python object stack             | emit->n_state
+//                              locals (reversed, L0 at end)    |
+//                              (L0-L2 may be in regs instead)
+
+// Native emitter needs to know the following sizes and offsets of C structs (on the target):
+#if MICROPY_DYNAMIC_COMPILER
+#define SIZEOF_NLR_BUF (2 + mp_dynamic_compiler.nlr_buf_num_regs + 1) // the +1 is conservative in case MICROPY_ENABLE_PYSTACK enabled
+#else
+#define SIZEOF_NLR_BUF (sizeof(nlr_buf_t) / sizeof(uintptr_t))
+#endif
+#define SIZEOF_CODE_STATE (sizeof(mp_code_state_t) / sizeof(uintptr_t))
+#define OFFSETOF_CODE_STATE_STATE (offsetof(mp_code_state_t, state) / sizeof(uintptr_t))
+#define OFFSETOF_CODE_STATE_FUN_BC (offsetof(mp_code_state_t, fun_bc) / sizeof(uintptr_t))
+#define OFFSETOF_CODE_STATE_IP (offsetof(mp_code_state_t, ip) / sizeof(uintptr_t))
+#define OFFSETOF_CODE_STATE_SP (offsetof(mp_code_state_t, sp) / sizeof(uintptr_t))
+#define OFFSETOF_OBJ_FUN_BC_GLOBALS (offsetof(mp_obj_fun_bc_t, globals) / sizeof(uintptr_t))
+#define OFFSETOF_OBJ_FUN_BC_BYTECODE (offsetof(mp_obj_fun_bc_t, bytecode) / sizeof(uintptr_t))
+#define OFFSETOF_OBJ_FUN_BC_CONST_TABLE (offsetof(mp_obj_fun_bc_t, const_table) / sizeof(uintptr_t))
+
+// If not already defined, set parent args to same as child call registers
+#ifndef REG_PARENT_RET
+#define REG_PARENT_RET REG_RET
+#define REG_PARENT_ARG_1 REG_ARG_1
+#define REG_PARENT_ARG_2 REG_ARG_2
+#define REG_PARENT_ARG_3 REG_ARG_3
+#define REG_PARENT_ARG_4 REG_ARG_4
+#endif
+
+// Word index of nlr_buf_t.ret_val
+#define NLR_BUF_IDX_RET_VAL (1)
+
+// Whether the viper function needs access to fun_obj
+#define NEED_FUN_OBJ(emit) ((emit)->scope->exc_stack_size > 0 \
+    || ((emit)->scope->scope_flags & (MP_SCOPE_FLAG_REFGLOBALS | MP_SCOPE_FLAG_HASCONSTS)))
+
+// Whether the native/viper function needs to be wrapped in an exception handler
+#define NEED_GLOBAL_EXC_HANDLER(emit) ((emit)->scope->exc_stack_size > 0 \
+    || ((emit)->scope->scope_flags & (MP_SCOPE_FLAG_GENERATOR | MP_SCOPE_FLAG_REFGLOBALS)))
+
+// Whether registers can be used to store locals (only true if there are no
+// exception handlers, because otherwise an nlr_jump will restore registers to
+// their state at the start of the function and updates to locals will be lost)
+#define CAN_USE_REGS_FOR_LOCALS(emit) ((emit)->scope->exc_stack_size == 0 && !(emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR))
+
+// Indices within the local C stack for various variables
+#define LOCAL_IDX_EXC_VAL(emit) (NLR_BUF_IDX_RET_VAL)
+#define LOCAL_IDX_EXC_HANDLER_PC(emit) (NLR_BUF_IDX_LOCAL_1)
+#define LOCAL_IDX_EXC_HANDLER_UNWIND(emit) (NLR_BUF_IDX_LOCAL_2)
+#define LOCAL_IDX_RET_VAL(emit) (NLR_BUF_IDX_LOCAL_3)
+#define LOCAL_IDX_FUN_OBJ(emit) ((emit)->code_state_start + OFFSETOF_CODE_STATE_FUN_BC)
+#define LOCAL_IDX_OLD_GLOBALS(emit) ((emit)->code_state_start + OFFSETOF_CODE_STATE_IP)
+#define LOCAL_IDX_GEN_PC(emit) ((emit)->code_state_start + OFFSETOF_CODE_STATE_IP)
+#define LOCAL_IDX_LOCAL_VAR(emit, local_num) ((emit)->stack_start + (emit)->n_state - 1 - (local_num))
+
+#define REG_GENERATOR_STATE (REG_LOCAL_3)
+
+#define EMIT_NATIVE_VIPER_TYPE_ERROR(emit, ...) do { \
+        *emit->error_slot = mp_obj_new_exception_msg_varg(&mp_type_ViperTypeError, __VA_ARGS__); \
+} while (0)
+
+typedef enum {
+    STACK_VALUE,
+    STACK_REG,
+    STACK_IMM,
+} stack_info_kind_t;
+
+// these enums must be distinct and the bottom 4 bits
+// must correspond to the correct MP_NATIVE_TYPE_xxx value
+typedef enum {
+    VTYPE_PYOBJ = 0x00 | MP_NATIVE_TYPE_OBJ,
+    VTYPE_BOOL = 0x00 | MP_NATIVE_TYPE_BOOL,
+    VTYPE_INT = 0x00 | MP_NATIVE_TYPE_INT,
+    VTYPE_UINT = 0x00 | MP_NATIVE_TYPE_UINT,
+    VTYPE_PTR = 0x00 | MP_NATIVE_TYPE_PTR,
+    VTYPE_PTR8 = 0x00 | MP_NATIVE_TYPE_PTR8,
+    VTYPE_PTR16 = 0x00 | MP_NATIVE_TYPE_PTR16,
+    VTYPE_PTR32 = 0x00 | MP_NATIVE_TYPE_PTR32,
+
+    VTYPE_PTR_NONE = 0x50 | MP_NATIVE_TYPE_PTR,
+
+    VTYPE_UNBOUND = 0x60 | MP_NATIVE_TYPE_OBJ,
+    VTYPE_BUILTIN_CAST = 0x70 | MP_NATIVE_TYPE_OBJ,
+} vtype_kind_t;
+
+STATIC qstr vtype_to_qstr(vtype_kind_t vtype) {
+    switch (vtype) {
+        case VTYPE_PYOBJ:
+            return MP_QSTR_object;
+        case VTYPE_BOOL:
+            return MP_QSTR_bool;
+        case VTYPE_INT:
+            return MP_QSTR_int;
+        case VTYPE_UINT:
+            return MP_QSTR_uint;
+        case VTYPE_PTR:
+            return MP_QSTR_ptr;
+        case VTYPE_PTR8:
+            return MP_QSTR_ptr8;
+        case VTYPE_PTR16:
+            return MP_QSTR_ptr16;
+        case VTYPE_PTR32:
+            return MP_QSTR_ptr32;
+        case VTYPE_PTR_NONE:
+        default:
+            return MP_QSTR_None;
+    }
+}
+
+typedef struct _stack_info_t {
+    vtype_kind_t vtype;
+    stack_info_kind_t kind;
+    union {
+        int u_reg;
+        mp_int_t u_imm;
+    } data;
+} stack_info_t;
+
+#define UNWIND_LABEL_UNUSED (0x7fff)
+#define UNWIND_LABEL_DO_FINAL_UNWIND (0x7ffe)
+
+typedef struct _exc_stack_entry_t {
+    uint16_t label : 15;
+    uint16_t is_finally : 1;
+    uint16_t unwind_label : 15;
+    uint16_t is_active : 1;
+} exc_stack_entry_t;
+
+struct _emit_t {
+    mp_obj_t *error_slot;
+    uint *label_slot;
+    uint exit_label;
+    int pass;
+
+    bool do_viper_types;
+    bool prelude_offset_uses_u16_encoding;
+
+    mp_uint_t local_vtype_alloc;
+    vtype_kind_t *local_vtype;
+
+    mp_uint_t stack_info_alloc;
+    stack_info_t *stack_info;
+    vtype_kind_t saved_stack_vtype;
+
+    size_t exc_stack_alloc;
+    size_t exc_stack_size;
+    exc_stack_entry_t *exc_stack;
+
+    int prelude_offset;
+    int start_offset;
+    int n_state;
+    uint16_t code_state_start;
+    uint16_t stack_start;
+    int stack_size;
+    uint16_t n_cell;
+
+    uint16_t const_table_cur_obj;
+    uint16_t const_table_num_obj;
+    uint16_t const_table_cur_raw_code;
+    mp_uint_t *const_table;
+
+    #if MICROPY_PERSISTENT_CODE_SAVE
+    uint16_t qstr_link_cur;
+    mp_qstr_link_entry_t *qstr_link;
+    #endif
+
+    bool last_emit_was_return_value;
+
+    scope_t *scope;
+
+    ASM_T *as;
+};
+
+STATIC const uint8_t reg_local_table[REG_LOCAL_NUM] = {REG_LOCAL_1, REG_LOCAL_2, REG_LOCAL_3};
+
+STATIC void emit_native_global_exc_entry(emit_t *emit);
+STATIC void emit_native_global_exc_exit(emit_t *emit);
+STATIC void emit_native_load_const_obj(emit_t *emit, mp_obj_t obj);
+
+emit_t *EXPORT_FUN(new)(mp_obj_t * error_slot, uint *label_slot, mp_uint_t max_num_labels) {
+    emit_t *emit = m_new0(emit_t, 1);
+    emit->error_slot = error_slot;
+    emit->label_slot = label_slot;
+    emit->stack_info_alloc = 8;
+    emit->stack_info = m_new(stack_info_t, emit->stack_info_alloc);
+    emit->exc_stack_alloc = 8;
+    emit->exc_stack = m_new(exc_stack_entry_t, emit->exc_stack_alloc);
+    emit->as = m_new0(ASM_T, 1);
+    mp_asm_base_init(&emit->as->base, max_num_labels);
+    return emit;
+}
+
+void EXPORT_FUN(free)(emit_t * emit) {
+    mp_asm_base_deinit(&emit->as->base, false);
+    m_del_obj(ASM_T, emit->as);
+    m_del(exc_stack_entry_t, emit->exc_stack, emit->exc_stack_alloc);
+    m_del(vtype_kind_t, emit->local_vtype, emit->local_vtype_alloc);
+    m_del(stack_info_t, emit->stack_info, emit->stack_info_alloc);
+    m_del_obj(emit_t, emit);
+}
+
+STATIC void emit_call_with_imm_arg(emit_t *emit, mp_fun_kind_t fun_kind, mp_int_t arg_val, int arg_reg);
+
+STATIC void emit_native_mov_reg_const(emit_t *emit, int reg_dest, int const_val) {
+    ASM_LOAD_REG_REG_OFFSET(emit->as, reg_dest, REG_FUN_TABLE, const_val);
+}
+
+STATIC void emit_native_mov_state_reg(emit_t *emit, int local_num, int reg_src) {
+    if (emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR) {
+        ASM_STORE_REG_REG_OFFSET(emit->as, reg_src, REG_GENERATOR_STATE, local_num);
+    } else {
+        ASM_MOV_LOCAL_REG(emit->as, local_num, reg_src);
+    }
+}
+
+STATIC void emit_native_mov_reg_state(emit_t *emit, int reg_dest, int local_num) {
+    if (emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR) {
+        ASM_LOAD_REG_REG_OFFSET(emit->as, reg_dest, REG_GENERATOR_STATE, local_num);
+    } else {
+        ASM_MOV_REG_LOCAL(emit->as, reg_dest, local_num);
+    }
+}
+
+STATIC void emit_native_mov_reg_state_addr(emit_t *emit, int reg_dest, int local_num) {
+    if (emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR) {
+        ASM_MOV_REG_IMM(emit->as, reg_dest, local_num * ASM_WORD_SIZE);
+        ASM_ADD_REG_REG(emit->as, reg_dest, REG_GENERATOR_STATE);
+    } else {
+        ASM_MOV_REG_LOCAL_ADDR(emit->as, reg_dest, local_num);
+    }
+}
+
+STATIC void emit_native_mov_reg_qstr(emit_t *emit, int arg_reg, qstr qst) {
+    #if MICROPY_PERSISTENT_CODE_SAVE
+    size_t loc = ASM_MOV_REG_IMM_FIX_U16(emit->as, arg_reg, qst);
+    size_t link_idx = emit->qstr_link_cur++;
+    if (emit->pass == MP_PASS_EMIT) {
+        emit->qstr_link[link_idx].off = loc << 2 | 1;
+        emit->qstr_link[link_idx].qst = qst;
+    }
+    #else
+    ASM_MOV_REG_IMM(emit->as, arg_reg, qst);
+    #endif
+}
+
+STATIC void emit_native_mov_reg_qstr_obj(emit_t *emit, int reg_dest, qstr qst) {
+    #if MICROPY_PERSISTENT_CODE_SAVE
+    size_t loc = ASM_MOV_REG_IMM_FIX_WORD(emit->as, reg_dest, (mp_uint_t)MP_OBJ_NEW_QSTR(qst));
+    size_t link_idx = emit->qstr_link_cur++;
+    if (emit->pass == MP_PASS_EMIT) {
+        emit->qstr_link[link_idx].off = loc << 2 | 2;
+        emit->qstr_link[link_idx].qst = qst;
+    }
+    #else
+    ASM_MOV_REG_IMM(emit->as, reg_dest, (mp_uint_t)MP_OBJ_NEW_QSTR(qst));
+    #endif
+}
+
+#define emit_native_mov_state_imm_via(emit, local_num, imm, reg_temp) \
+    do { \
+        ASM_MOV_REG_IMM((emit)->as, (reg_temp), (imm)); \
+        emit_native_mov_state_reg((emit), (local_num), (reg_temp)); \
+    } while (false)
+
+#define emit_native_mov_state_imm_fix_u16_via(emit, local_num, imm, reg_temp) \
+    do { \
+        ASM_MOV_REG_IMM_FIX_U16((emit)->as, (reg_temp), (imm)); \
+        emit_native_mov_state_reg((emit), (local_num), (reg_temp)); \
+    } while (false)
+
+#define emit_native_mov_state_imm_fix_word_via(emit, local_num, imm, reg_temp) \
+    do { \
+        ASM_MOV_REG_IMM_FIX_WORD((emit)->as, (reg_temp), (imm)); \
+        emit_native_mov_state_reg((emit), (local_num), (reg_temp)); \
+    } while (false)
+
+STATIC void emit_native_start_pass(emit_t *emit, pass_kind_t pass, scope_t *scope) {
+    DEBUG_printf("start_pass(pass=%u, scope=%p)\n", pass, scope);
+
+    emit->pass = pass;
+    emit->do_viper_types = scope->emit_options == MP_EMIT_OPT_VIPER;
+    emit->stack_size = 0;
+    #if N_PRELUDE_AS_BYTES_OBJ
+    emit->const_table_cur_obj = emit->do_viper_types ? 0 : 1; // reserve first obj for prelude bytes obj
+    #else
+    emit->const_table_cur_obj = 0;
+    #endif
+    emit->const_table_cur_raw_code = 0;
+    #if MICROPY_PERSISTENT_CODE_SAVE
+    emit->qstr_link_cur = 0;
+    #endif
+    emit->last_emit_was_return_value = false;
+    emit->scope = scope;
+
+    // allocate memory for keeping track of the types of locals
+    if (emit->local_vtype_alloc < scope->num_locals) {
+        emit->local_vtype = m_renew(vtype_kind_t, emit->local_vtype, emit->local_vtype_alloc, scope->num_locals);
+        emit->local_vtype_alloc = scope->num_locals;
+    }
+
+    // set default type for arguments
+    mp_uint_t num_args = emit->scope->num_pos_args + emit->scope->num_kwonly_args;
+    if (scope->scope_flags & MP_SCOPE_FLAG_VARARGS) {
+        num_args += 1;
+    }
+    if (scope->scope_flags & MP_SCOPE_FLAG_VARKEYWORDS) {
+        num_args += 1;
+    }
+    for (mp_uint_t i = 0; i < num_args; i++) {
+        emit->local_vtype[i] = VTYPE_PYOBJ;
+    }
+
+    // Set viper type for arguments
+    if (emit->do_viper_types) {
+        for (int i = 0; i < emit->scope->id_info_len; ++i) {
+            id_info_t *id = &emit->scope->id_info[i];
+            if (id->flags & ID_FLAG_IS_PARAM) {
+                assert(id->local_num < emit->local_vtype_alloc);
+                emit->local_vtype[id->local_num] = id->flags >> ID_FLAG_VIPER_TYPE_POS;
+            }
+        }
+    }
+
+    // local variables begin unbound, and have unknown type
+    for (mp_uint_t i = num_args; i < emit->local_vtype_alloc; i++) {
+        emit->local_vtype[i] = VTYPE_UNBOUND;
+    }
+
+    // values on stack begin unbound
+    for (mp_uint_t i = 0; i < emit->stack_info_alloc; i++) {
+        emit->stack_info[i].kind = STACK_VALUE;
+        emit->stack_info[i].vtype = VTYPE_UNBOUND;
+    }
+
+    mp_asm_base_start_pass(&emit->as->base, pass == MP_PASS_EMIT ? MP_ASM_PASS_EMIT : MP_ASM_PASS_COMPUTE);
+
+    // generate code for entry to function
+
+    // Work out start of code state (mp_code_state_t or reduced version for viper)
+    emit->code_state_start = 0;
+    if (NEED_GLOBAL_EXC_HANDLER(emit)) {
+        emit->code_state_start = SIZEOF_NLR_BUF;
+    }
+
+    if (emit->do_viper_types) {
+        // Work out size of state (locals plus stack)
+        // n_state counts all stack and locals, even those in registers
+        emit->n_state = scope->num_locals + scope->stack_size;
+        int num_locals_in_regs = 0;
+        if (CAN_USE_REGS_FOR_LOCALS(emit)) {
+            num_locals_in_regs = scope->num_locals;
+            if (num_locals_in_regs > REG_LOCAL_NUM) {
+                num_locals_in_regs = REG_LOCAL_NUM;
+            }
+            // Need a spot for REG_LOCAL_3 if 4 or more args (see below)
+            if (scope->num_pos_args >= 4) {
+                --num_locals_in_regs;
+            }
+        }
+
+        // Work out where the locals and Python stack start within the C stack
+        if (NEED_GLOBAL_EXC_HANDLER(emit)) {
+            // Reserve 2 words for function object and old globals
+            emit->stack_start = emit->code_state_start + 2;
+        } else if (scope->scope_flags & MP_SCOPE_FLAG_HASCONSTS) {
+            // Reserve 1 word for function object, to access const table
+            emit->stack_start = emit->code_state_start + 1;
+        } else {
+            emit->stack_start = emit->code_state_start + 0;
+        }
+
+        // Entry to function
+        ASM_ENTRY(emit->as, emit->stack_start + emit->n_state - num_locals_in_regs);
+
+        #if N_X86
+        asm_x86_mov_arg_to_r32(emit->as, 0, REG_PARENT_ARG_1);
+        #endif
+
+        // Load REG_FUN_TABLE with a pointer to mp_fun_table, found in the const_table
+        ASM_LOAD_REG_REG_OFFSET(emit->as, REG_LOCAL_3, REG_PARENT_ARG_1, OFFSETOF_OBJ_FUN_BC_CONST_TABLE);
+        ASM_LOAD_REG_REG_OFFSET(emit->as, REG_FUN_TABLE, REG_LOCAL_3, 0);
+
+        // Store function object (passed as first arg) to stack if needed
+        if (NEED_FUN_OBJ(emit)) {
+            ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_FUN_OBJ(emit), REG_PARENT_ARG_1);
+        }
+
+        // Put n_args in REG_ARG_1, n_kw in REG_ARG_2, args array in REG_LOCAL_3
+        #if N_X86
+        asm_x86_mov_arg_to_r32(emit->as, 1, REG_ARG_1);
+        asm_x86_mov_arg_to_r32(emit->as, 2, REG_ARG_2);
+        asm_x86_mov_arg_to_r32(emit->as, 3, REG_LOCAL_3);
+        #else
+        ASM_MOV_REG_REG(emit->as, REG_ARG_1, REG_PARENT_ARG_2);
+        ASM_MOV_REG_REG(emit->as, REG_ARG_2, REG_PARENT_ARG_3);
+        ASM_MOV_REG_REG(emit->as, REG_LOCAL_3, REG_PARENT_ARG_4);
+        #endif
+
+        // Check number of args matches this function, and call mp_arg_check_num_sig if not
+        ASM_JUMP_IF_REG_NONZERO(emit->as, REG_ARG_2, *emit->label_slot + 4, true);
+        ASM_MOV_REG_IMM(emit->as, REG_ARG_3, scope->num_pos_args);
+        ASM_JUMP_IF_REG_EQ(emit->as, REG_ARG_1, REG_ARG_3, *emit->label_slot + 5);
+        mp_asm_base_label_assign(&emit->as->base, *emit->label_slot + 4);
+        ASM_MOV_REG_IMM(emit->as, REG_ARG_3, MP_OBJ_FUN_MAKE_SIG(scope->num_pos_args, scope->num_pos_args, false));
+        ASM_CALL_IND(emit->as, MP_F_ARG_CHECK_NUM_SIG);
+        mp_asm_base_label_assign(&emit->as->base, *emit->label_slot + 5);
+
+        // Store arguments into locals (reg or stack), converting to native if needed
+        for (int i = 0; i < emit->scope->num_pos_args; i++) {
+            int r = REG_ARG_1;
+            ASM_LOAD_REG_REG_OFFSET(emit->as, REG_ARG_1, REG_LOCAL_3, i);
+            if (emit->local_vtype[i] != VTYPE_PYOBJ) {
+                emit_call_with_imm_arg(emit, MP_F_CONVERT_OBJ_TO_NATIVE, emit->local_vtype[i], REG_ARG_2);
+                r = REG_RET;
+            }
+            // REG_LOCAL_3 points to the args array so be sure not to overwrite it if it's still needed
+            if (i < REG_LOCAL_NUM && CAN_USE_REGS_FOR_LOCALS(emit) && (i != 2 || emit->scope->num_pos_args == 3)) {
+                ASM_MOV_REG_REG(emit->as, reg_local_table[i], r);
+            } else {
+                emit_native_mov_state_reg(emit, LOCAL_IDX_LOCAL_VAR(emit, i), r);
+            }
+        }
+        // Get 3rd local from the stack back into REG_LOCAL_3 if this reg couldn't be written to above
+        if (emit->scope->num_pos_args >= 4 && CAN_USE_REGS_FOR_LOCALS(emit)) {
+            ASM_MOV_REG_LOCAL(emit->as, REG_LOCAL_3, LOCAL_IDX_LOCAL_VAR(emit, 2));
+        }
+
+        emit_native_global_exc_entry(emit);
+
+    } else {
+        // work out size of state (locals plus stack)
+        emit->n_state = scope->num_locals + scope->stack_size;
+
+        if (emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR) {
+            emit->code_state_start = 0;
+            emit->stack_start = SIZEOF_CODE_STATE;
+            #if N_PRELUDE_AS_BYTES_OBJ
+            // Load index of prelude bytes object in const_table
+            mp_asm_base_data(&emit->as->base, ASM_WORD_SIZE, (uintptr_t)(emit->scope->num_pos_args + emit->scope->num_kwonly_args + 1));
+            #else
+            mp_asm_base_data(&emit->as->base, ASM_WORD_SIZE, (uintptr_t)emit->prelude_offset);
+            #endif
+            mp_asm_base_data(&emit->as->base, ASM_WORD_SIZE, (uintptr_t)emit->start_offset);
+            ASM_ENTRY(emit->as, SIZEOF_NLR_BUF);
+
+            // Put address of code_state into REG_GENERATOR_STATE
+            #if N_X86
+            asm_x86_mov_arg_to_r32(emit->as, 0, REG_GENERATOR_STATE);
+            #else
+            ASM_MOV_REG_REG(emit->as, REG_GENERATOR_STATE, REG_PARENT_ARG_1);
+            #endif
+
+            // Put throw value into LOCAL_IDX_EXC_VAL slot, for yield/yield-from
+            #if N_X86
+            asm_x86_mov_arg_to_r32(emit->as, 1, REG_PARENT_ARG_2);
+            #endif
+            ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_VAL(emit), REG_PARENT_ARG_2);
+
+            // Load REG_FUN_TABLE with a pointer to mp_fun_table, found in the const_table
+            ASM_LOAD_REG_REG_OFFSET(emit->as, REG_TEMP0, REG_GENERATOR_STATE, LOCAL_IDX_FUN_OBJ(emit));
+            ASM_LOAD_REG_REG_OFFSET(emit->as, REG_TEMP0, REG_TEMP0, OFFSETOF_OBJ_FUN_BC_CONST_TABLE);
+            ASM_LOAD_REG_REG_OFFSET(emit->as, REG_FUN_TABLE, REG_TEMP0, emit->scope->num_pos_args + emit->scope->num_kwonly_args);
+        } else {
+            // The locals and stack start after the code_state structure
+            emit->stack_start = emit->code_state_start + SIZEOF_CODE_STATE;
+
+            // Allocate space on C-stack for code_state structure, which includes state
+            ASM_ENTRY(emit->as, emit->stack_start + emit->n_state);
+
+            // Prepare incoming arguments for call to mp_setup_code_state
+
+            #if N_X86
+            asm_x86_mov_arg_to_r32(emit->as, 0, REG_PARENT_ARG_1);
+            asm_x86_mov_arg_to_r32(emit->as, 1, REG_PARENT_ARG_2);
+            asm_x86_mov_arg_to_r32(emit->as, 2, REG_PARENT_ARG_3);
+            asm_x86_mov_arg_to_r32(emit->as, 3, REG_PARENT_ARG_4);
+            #endif
+
+            // Load REG_FUN_TABLE with a pointer to mp_fun_table, found in the const_table
+            ASM_LOAD_REG_REG_OFFSET(emit->as, REG_LOCAL_3, REG_PARENT_ARG_1, OFFSETOF_OBJ_FUN_BC_CONST_TABLE);
+            ASM_LOAD_REG_REG_OFFSET(emit->as, REG_FUN_TABLE, REG_LOCAL_3, emit->scope->num_pos_args + emit->scope->num_kwonly_args);
+
+            // Set code_state.fun_bc
+            ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_FUN_OBJ(emit), REG_PARENT_ARG_1);
+
+            // Set code_state.ip (offset from start of this function to prelude info)
+            int code_state_ip_local = emit->code_state_start + OFFSETOF_CODE_STATE_IP;
+            #if N_PRELUDE_AS_BYTES_OBJ
+            // Prelude is a bytes object in const_table; store ip = prelude->data - fun_bc->bytecode
+            ASM_LOAD_REG_REG_OFFSET(emit->as, REG_LOCAL_3, REG_LOCAL_3, emit->scope->num_pos_args + emit->scope->num_kwonly_args + 1);
+            ASM_LOAD_REG_REG_OFFSET(emit->as, REG_LOCAL_3, REG_LOCAL_3, offsetof(mp_obj_str_t, data) / sizeof(uintptr_t));
+            ASM_LOAD_REG_REG_OFFSET(emit->as, REG_PARENT_ARG_1, REG_PARENT_ARG_1, OFFSETOF_OBJ_FUN_BC_BYTECODE);
+            ASM_SUB_REG_REG(emit->as, REG_LOCAL_3, REG_PARENT_ARG_1);
+            emit_native_mov_state_reg(emit, code_state_ip_local, REG_LOCAL_3);
+            #else
+            if (emit->pass == MP_PASS_CODE_SIZE) {
+                // Commit to the encoding size based on the value of prelude_offset in this pass.
+                // By using 32768 as the cut-off it is highly unlikely that prelude_offset will
+                // grow beyond 65535 by the end of thiss pass, and so require the larger encoding.
+                emit->prelude_offset_uses_u16_encoding = emit->prelude_offset < 32768;
+            }
+            if (emit->prelude_offset_uses_u16_encoding) {
+                assert(emit->prelude_offset <= 65535);
+                emit_native_mov_state_imm_fix_u16_via(emit, code_state_ip_local, emit->prelude_offset, REG_PARENT_ARG_1);
+            } else {
+                emit_native_mov_state_imm_fix_word_via(emit, code_state_ip_local, emit->prelude_offset, REG_PARENT_ARG_1);
+            }
+            #endif
+
+            // Set code_state.n_state (only works on little endian targets due to n_state being uint16_t)
+            emit_native_mov_state_imm_via(emit, emit->code_state_start + offsetof(mp_code_state_t, n_state) / sizeof(uintptr_t), emit->n_state, REG_ARG_1);
+
+            // Put address of code_state into first arg
+            ASM_MOV_REG_LOCAL_ADDR(emit->as, REG_ARG_1, emit->code_state_start);
+
+            // Copy next 3 args if needed
+            #if REG_ARG_2 != REG_PARENT_ARG_2
+            ASM_MOV_REG_REG(emit->as, REG_ARG_2, REG_PARENT_ARG_2);
+            #endif
+            #if REG_ARG_3 != REG_PARENT_ARG_3
+            ASM_MOV_REG_REG(emit->as, REG_ARG_3, REG_PARENT_ARG_3);
+            #endif
+            #if REG_ARG_4 != REG_PARENT_ARG_4
+            ASM_MOV_REG_REG(emit->as, REG_ARG_4, REG_PARENT_ARG_4);
+            #endif
+
+            // Call mp_setup_code_state to prepare code_state structure
+            #if N_THUMB
+            asm_thumb_bl_ind(emit->as, MP_F_SETUP_CODE_STATE, ASM_THUMB_REG_R4);
+            #elif N_ARM
+            asm_arm_bl_ind(emit->as, MP_F_SETUP_CODE_STATE, ASM_ARM_REG_R4);
+            #else
+            ASM_CALL_IND(emit->as, MP_F_SETUP_CODE_STATE);
+            #endif
+        }
+
+        emit_native_global_exc_entry(emit);
+
+        // cache some locals in registers, but only if no exception handlers
+        if (CAN_USE_REGS_FOR_LOCALS(emit)) {
+            for (int i = 0; i < REG_LOCAL_NUM && i < scope->num_locals; ++i) {
+                ASM_MOV_REG_LOCAL(emit->as, reg_local_table[i], LOCAL_IDX_LOCAL_VAR(emit, i));
+            }
+        }
+
+        // set the type of closed over variables
+        for (mp_uint_t i = 0; i < scope->id_info_len; i++) {
+            id_info_t *id = &scope->id_info[i];
+            if (id->kind == ID_INFO_KIND_CELL) {
+                emit->local_vtype[id->local_num] = VTYPE_PYOBJ;
+            }
+        }
+
+        if (pass == MP_PASS_EMIT) {
+            // write argument names as qstr objects
+            // see comment in corresponding part of emitbc.c about the logic here
+            for (int i = 0; i < scope->num_pos_args + scope->num_kwonly_args; i++) {
+                qstr qst = MP_QSTR__star_;
+                for (int j = 0; j < scope->id_info_len; ++j) {
+                    id_info_t *id = &scope->id_info[j];
+                    if ((id->flags & ID_FLAG_IS_PARAM) && id->local_num == i) {
+                        qst = id->qst;
+                        break;
+                    }
+                }
+                emit->const_table[i] = (mp_uint_t)MP_OBJ_NEW_QSTR(qst);
+            }
+        }
+    }
+
+}
+
+static inline void emit_native_write_code_info_byte(emit_t *emit, byte val) {
+    mp_asm_base_data(&emit->as->base, 1, val);
+}
+
+STATIC void emit_native_end_pass(emit_t *emit) {
+    emit_native_global_exc_exit(emit);
+
+    if (!emit->do_viper_types) {
+        emit->prelude_offset = mp_asm_base_get_code_pos(&emit->as->base);
+
+        size_t n_state = emit->n_state;
+        size_t n_exc_stack = 0; // exc-stack not needed for native code
+        MP_BC_PRELUDE_SIG_ENCODE(n_state, n_exc_stack, emit->scope, emit_native_write_code_info_byte, emit);
+
+        #if MICROPY_PERSISTENT_CODE
+        size_t n_info = 4;
+        #else
+        size_t n_info = 1;
+        #endif
+        MP_BC_PRELUDE_SIZE_ENCODE(n_info, emit->n_cell, emit_native_write_code_info_byte, emit);
+
+        #if MICROPY_PERSISTENT_CODE
+        mp_asm_base_data(&emit->as->base, 1, emit->scope->simple_name);
+        mp_asm_base_data(&emit->as->base, 1, emit->scope->simple_name >> 8);
+        mp_asm_base_data(&emit->as->base, 1, emit->scope->source_file);
+        mp_asm_base_data(&emit->as->base, 1, emit->scope->source_file >> 8);
+        #else
+        mp_asm_base_data(&emit->as->base, 1, 1);
+        #endif
+
+        // bytecode prelude: initialise closed over variables
+        size_t cell_start = mp_asm_base_get_code_pos(&emit->as->base);
+        for (int i = 0; i < emit->scope->id_info_len; i++) {
+            id_info_t *id = &emit->scope->id_info[i];
+            if (id->kind == ID_INFO_KIND_CELL) {
+                assert(id->local_num <= 255);
+                mp_asm_base_data(&emit->as->base, 1, id->local_num); // write the local which should be converted to a cell
+            }
+        }
+        emit->n_cell = mp_asm_base_get_code_pos(&emit->as->base) - cell_start;
+
+        #if N_PRELUDE_AS_BYTES_OBJ
+        // Prelude bytes object is after qstr arg names and mp_fun_table
+        size_t table_off = emit->scope->num_pos_args + emit->scope->num_kwonly_args + 1;
+        if (emit->pass == MP_PASS_EMIT) {
+            void *buf = emit->as->base.code_base + emit->prelude_offset;
+            size_t n = emit->as->base.code_offset - emit->prelude_offset;
+            emit->const_table[table_off] = (uintptr_t)mp_obj_new_bytes(buf, n);
+        }
+        #endif
+    }
+
+    ASM_END_PASS(emit->as);
+
+    // check stack is back to zero size
+    assert(emit->stack_size == 0);
+    assert(emit->exc_stack_size == 0);
+
+    // Deal with const table accounting
+    assert(emit->pass <= MP_PASS_STACK_SIZE || (emit->const_table_num_obj == emit->const_table_cur_obj));
+    emit->const_table_num_obj = emit->const_table_cur_obj;
+    if (emit->pass == MP_PASS_CODE_SIZE) {
+        size_t const_table_alloc = 1 + emit->const_table_num_obj + emit->const_table_cur_raw_code;
+        size_t nqstr = 0;
+        if (!emit->do_viper_types) {
+            // Add room for qstr names of arguments
+            nqstr = emit->scope->num_pos_args + emit->scope->num_kwonly_args;
+            const_table_alloc += nqstr;
+        }
+        emit->const_table = m_new(mp_uint_t, const_table_alloc);
+        #if !MICROPY_DYNAMIC_COMPILER
+        // Store mp_fun_table pointer just after qstrs
+        // (but in dynamic-compiler mode eliminate dependency on mp_fun_table)
+        emit->const_table[nqstr] = (mp_uint_t)(uintptr_t)&mp_fun_table;
+        #endif
+
+        #if MICROPY_PERSISTENT_CODE_SAVE
+        size_t qstr_link_alloc = emit->qstr_link_cur;
+        if (qstr_link_alloc > 0) {
+            emit->qstr_link = m_new(mp_qstr_link_entry_t, qstr_link_alloc);
+        }
+        #endif
+    }
+
+    if (emit->pass == MP_PASS_EMIT) {
+        void *f = mp_asm_base_get_code(&emit->as->base);
+        mp_uint_t f_len = mp_asm_base_get_code_size(&emit->as->base);
+
+        mp_emit_glue_assign_native(emit->scope->raw_code,
+            emit->do_viper_types ? MP_CODE_NATIVE_VIPER : MP_CODE_NATIVE_PY,
+            f, f_len, emit->const_table,
+            #if MICROPY_PERSISTENT_CODE_SAVE
+            emit->prelude_offset,
+            emit->const_table_cur_obj, emit->const_table_cur_raw_code,
+            emit->qstr_link_cur, emit->qstr_link,
+            #endif
+            emit->scope->num_pos_args, emit->scope->scope_flags, 0);
+    }
+}
+
+STATIC bool emit_native_last_emit_was_return_value(emit_t *emit) {
+    return emit->last_emit_was_return_value;
+}
+
+STATIC void ensure_extra_stack(emit_t *emit, size_t delta) {
+    if (emit->stack_size + delta > emit->stack_info_alloc) {
+        size_t new_alloc = (emit->stack_size + delta + 8) & ~3;
+        emit->stack_info = m_renew(stack_info_t, emit->stack_info, emit->stack_info_alloc, new_alloc);
+        emit->stack_info_alloc = new_alloc;
+    }
+}
+
+STATIC void adjust_stack(emit_t *emit, mp_int_t stack_size_delta) {
+    assert((mp_int_t)emit->stack_size + stack_size_delta >= 0);
+    assert((mp_int_t)emit->stack_size + stack_size_delta <= (mp_int_t)emit->stack_info_alloc);
+    emit->stack_size += stack_size_delta;
+    if (emit->pass > MP_PASS_SCOPE && emit->stack_size > emit->scope->stack_size) {
+        emit->scope->stack_size = emit->stack_size;
+    }
+    #ifdef DEBUG_PRINT
+    DEBUG_printf("  adjust_stack; stack_size=%d+%d; stack now:", emit->stack_size - stack_size_delta, stack_size_delta);
+    for (int i = 0; i < emit->stack_size; i++) {
+        stack_info_t *si = &emit->stack_info[i];
+        DEBUG_printf(" (v=%d k=%d %d)", si->vtype, si->kind, si->data.u_reg);
+    }
+    DEBUG_printf("\n");
+    #endif
+}
+
+STATIC void emit_native_adjust_stack_size(emit_t *emit, mp_int_t delta) {
+    DEBUG_printf("adjust_stack_size(" INT_FMT ")\n", delta);
+    if (delta > 0) {
+        ensure_extra_stack(emit, delta);
+    }
+    // If we are adjusting the stack in a positive direction (pushing) then we
+    // need to fill in values for the stack kind and vtype of the newly-pushed
+    // entries.  These should be set to "value" (ie not reg or imm) because we
+    // should only need to adjust the stack due to a jump to this part in the
+    // code (and hence we have settled the stack before the jump).
+    for (mp_int_t i = 0; i < delta; i++) {
+        stack_info_t *si = &emit->stack_info[emit->stack_size + i];
+        si->kind = STACK_VALUE;
+        // TODO we don't know the vtype to use here.  At the moment this is a
+        // hack to get the case of multi comparison working.
+        if (delta == 1) {
+            si->vtype = emit->saved_stack_vtype;
+        } else {
+            si->vtype = VTYPE_PYOBJ;
+        }
+    }
+    adjust_stack(emit, delta);
+}
+
+STATIC void emit_native_set_source_line(emit_t *emit, mp_uint_t source_line) {
+    (void)emit;
+    (void)source_line;
+}
+
+// this must be called at start of emit functions
+STATIC void emit_native_pre(emit_t *emit) {
+    emit->last_emit_was_return_value = false;
+}
+
+// depth==0 is top, depth==1 is before top, etc
+STATIC stack_info_t *peek_stack(emit_t *emit, mp_uint_t depth) {
+    return &emit->stack_info[emit->stack_size - 1 - depth];
+}
+
+// depth==0 is top, depth==1 is before top, etc
+STATIC vtype_kind_t peek_vtype(emit_t *emit, mp_uint_t depth) {
+    if (emit->do_viper_types) {
+        return peek_stack(emit, depth)->vtype;
+    } else {
+        // Type is always PYOBJ even if the intermediate stored value is not
+        return VTYPE_PYOBJ;
+    }
+}
+
+// pos=1 is TOS, pos=2 is next, etc
+// use pos=0 for no skipping
+STATIC void need_reg_single(emit_t *emit, int reg_needed, int skip_stack_pos) {
+    skip_stack_pos = emit->stack_size - skip_stack_pos;
+    for (int i = 0; i < emit->stack_size; i++) {
+        if (i != skip_stack_pos) {
+            stack_info_t *si = &emit->stack_info[i];
+            if (si->kind == STACK_REG && si->data.u_reg == reg_needed) {
+                si->kind = STACK_VALUE;
+                emit_native_mov_state_reg(emit, emit->stack_start + i, si->data.u_reg);
+            }
+        }
+    }
+}
+
+// Ensures all unsettled registers that hold Python values are copied to the
+// concrete Python stack.  All registers are then free to use.
+STATIC void need_reg_all(emit_t *emit) {
+    for (int i = 0; i < emit->stack_size; i++) {
+        stack_info_t *si = &emit->stack_info[i];
+        if (si->kind == STACK_REG) {
+            DEBUG_printf("    reg(%u) to local(%u)\n", si->data.u_reg, emit->stack_start + i);
+            si->kind = STACK_VALUE;
+            emit_native_mov_state_reg(emit, emit->stack_start + i, si->data.u_reg);
+        }
+    }
+}
+
+STATIC vtype_kind_t load_reg_stack_imm(emit_t *emit, int reg_dest, const stack_info_t *si, bool convert_to_pyobj) {
+    if (!convert_to_pyobj && emit->do_viper_types) {
+        ASM_MOV_REG_IMM(emit->as, reg_dest, si->data.u_imm);
+        return si->vtype;
+    } else {
+        if (si->vtype == VTYPE_PYOBJ) {
+            ASM_MOV_REG_IMM(emit->as, reg_dest, si->data.u_imm);
+        } else if (si->vtype == VTYPE_BOOL) {
+            emit_native_mov_reg_const(emit, reg_dest, MP_F_CONST_FALSE_OBJ + si->data.u_imm);
+        } else if (si->vtype == VTYPE_INT || si->vtype == VTYPE_UINT) {
+            ASM_MOV_REG_IMM(emit->as, reg_dest, (uintptr_t)MP_OBJ_NEW_SMALL_INT(si->data.u_imm));
+        } else if (si->vtype == VTYPE_PTR_NONE) {
+            emit_native_mov_reg_const(emit, reg_dest, MP_F_CONST_NONE_OBJ);
+        } else {
+            mp_raise_NotImplementedError(MP_ERROR_TEXT("conversion to object"));
+        }
+        return VTYPE_PYOBJ;
+    }
+}
+
+// Copies all unsettled registers and immediates that are Python values into the
+// concrete Python stack.  This ensures the concrete Python stack holds valid
+// values for the current stack_size.
+// This function may clobber REG_TEMP1.
+STATIC void need_stack_settled(emit_t *emit) {
+    DEBUG_printf("  need_stack_settled; stack_size=%d\n", emit->stack_size);
+    need_reg_all(emit);
+    for (int i = 0; i < emit->stack_size; i++) {
+        stack_info_t *si = &emit->stack_info[i];
+        if (si->kind == STACK_IMM) {
+            DEBUG_printf("    imm(" INT_FMT ") to local(%u)\n", si->data.u_imm, emit->stack_start + i);
+            si->kind = STACK_VALUE;
+            // using REG_TEMP1 to avoid clobbering REG_TEMP0 (aka REG_RET)
+            si->vtype = load_reg_stack_imm(emit, REG_TEMP1, si, false);
+            emit_native_mov_state_reg(emit, emit->stack_start + i, REG_TEMP1);
+        }
+    }
+}
+
+// pos=1 is TOS, pos=2 is next, etc
+STATIC void emit_access_stack(emit_t *emit, int pos, vtype_kind_t *vtype, int reg_dest) {
+    need_reg_single(emit, reg_dest, pos);
+    stack_info_t *si = &emit->stack_info[emit->stack_size - pos];
+    *vtype = si->vtype;
+    switch (si->kind) {
+        case STACK_VALUE:
+            emit_native_mov_reg_state(emit, reg_dest, emit->stack_start + emit->stack_size - pos);
+            break;
+
+        case STACK_REG:
+            if (si->data.u_reg != reg_dest) {
+                ASM_MOV_REG_REG(emit->as, reg_dest, si->data.u_reg);
+            }
+            break;
+
+        case STACK_IMM:
+            *vtype = load_reg_stack_imm(emit, reg_dest, si, false);
+            break;
+    }
+}
+
+// does an efficient X=pop(); discard(); push(X)
+// needs a (non-temp) register in case the poped element was stored in the stack
+STATIC void emit_fold_stack_top(emit_t *emit, int reg_dest) {
+    stack_info_t *si = &emit->stack_info[emit->stack_size - 2];
+    si[0] = si[1];
+    if (si->kind == STACK_VALUE) {
+        // if folded element was on the stack we need to put it in a register
+        emit_native_mov_reg_state(emit, reg_dest, emit->stack_start + emit->stack_size - 1);
+        si->kind = STACK_REG;
+        si->data.u_reg = reg_dest;
+    }
+    adjust_stack(emit, -1);
+}
+
+// If stacked value is in a register and the register is not r1 or r2, then
+// *reg_dest is set to that register.  Otherwise the value is put in *reg_dest.
+STATIC void emit_pre_pop_reg_flexible(emit_t *emit, vtype_kind_t *vtype, int *reg_dest, int not_r1, int not_r2) {
+    emit->last_emit_was_return_value = false;
+    stack_info_t *si = peek_stack(emit, 0);
+    if (si->kind == STACK_REG && si->data.u_reg != not_r1 && si->data.u_reg != not_r2) {
+        *vtype = si->vtype;
+        *reg_dest = si->data.u_reg;
+        need_reg_single(emit, *reg_dest, 1);
+    } else {
+        emit_access_stack(emit, 1, vtype, *reg_dest);
+    }
+    adjust_stack(emit, -1);
+}
+
+STATIC void emit_pre_pop_discard(emit_t *emit) {
+    emit->last_emit_was_return_value = false;
+    adjust_stack(emit, -1);
+}
+
+STATIC void emit_pre_pop_reg(emit_t *emit, vtype_kind_t *vtype, int reg_dest) {
+    emit->last_emit_was_return_value = false;
+    emit_access_stack(emit, 1, vtype, reg_dest);
+    adjust_stack(emit, -1);
+}
+
+STATIC void emit_pre_pop_reg_reg(emit_t *emit, vtype_kind_t *vtypea, int rega, vtype_kind_t *vtypeb, int regb) {
+    emit_pre_pop_reg(emit, vtypea, rega);
+    emit_pre_pop_reg(emit, vtypeb, regb);
+}
+
+STATIC void emit_pre_pop_reg_reg_reg(emit_t *emit, vtype_kind_t *vtypea, int rega, vtype_kind_t *vtypeb, int regb, vtype_kind_t *vtypec, int regc) {
+    emit_pre_pop_reg(emit, vtypea, rega);
+    emit_pre_pop_reg(emit, vtypeb, regb);
+    emit_pre_pop_reg(emit, vtypec, regc);
+}
+
+STATIC void emit_post(emit_t *emit) {
+    (void)emit;
+}
+
+STATIC void emit_post_top_set_vtype(emit_t *emit, vtype_kind_t new_vtype) {
+    stack_info_t *si = &emit->stack_info[emit->stack_size - 1];
+    si->vtype = new_vtype;
+}
+
+STATIC void emit_post_push_reg(emit_t *emit, vtype_kind_t vtype, int reg) {
+    ensure_extra_stack(emit, 1);
+    stack_info_t *si = &emit->stack_info[emit->stack_size];
+    si->vtype = vtype;
+    si->kind = STACK_REG;
+    si->data.u_reg = reg;
+    adjust_stack(emit, 1);
+}
+
+STATIC void emit_post_push_imm(emit_t *emit, vtype_kind_t vtype, mp_int_t imm) {
+    ensure_extra_stack(emit, 1);
+    stack_info_t *si = &emit->stack_info[emit->stack_size];
+    si->vtype = vtype;
+    si->kind = STACK_IMM;
+    si->data.u_imm = imm;
+    adjust_stack(emit, 1);
+}
+
+STATIC void emit_post_push_reg_reg(emit_t *emit, vtype_kind_t vtypea, int rega, vtype_kind_t vtypeb, int regb) {
+    emit_post_push_reg(emit, vtypea, rega);
+    emit_post_push_reg(emit, vtypeb, regb);
+}
+
+STATIC void emit_post_push_reg_reg_reg(emit_t *emit, vtype_kind_t vtypea, int rega, vtype_kind_t vtypeb, int regb, vtype_kind_t vtypec, int regc) {
+    emit_post_push_reg(emit, vtypea, rega);
+    emit_post_push_reg(emit, vtypeb, regb);
+    emit_post_push_reg(emit, vtypec, regc);
+}
+
+STATIC void emit_post_push_reg_reg_reg_reg(emit_t *emit, vtype_kind_t vtypea, int rega, vtype_kind_t vtypeb, int regb, vtype_kind_t vtypec, int regc, vtype_kind_t vtyped, int regd) {
+    emit_post_push_reg(emit, vtypea, rega);
+    emit_post_push_reg(emit, vtypeb, regb);
+    emit_post_push_reg(emit, vtypec, regc);
+    emit_post_push_reg(emit, vtyped, regd);
+}
+
+STATIC void emit_call(emit_t *emit, mp_fun_kind_t fun_kind) {
+    need_reg_all(emit);
+    ASM_CALL_IND(emit->as, fun_kind);
+}
+
+STATIC void emit_call_with_imm_arg(emit_t *emit, mp_fun_kind_t fun_kind, mp_int_t arg_val, int arg_reg) {
+    need_reg_all(emit);
+    ASM_MOV_REG_IMM(emit->as, arg_reg, arg_val);
+    ASM_CALL_IND(emit->as, fun_kind);
+}
+
+STATIC void emit_call_with_2_imm_args(emit_t *emit, mp_fun_kind_t fun_kind, mp_int_t arg_val1, int arg_reg1, mp_int_t arg_val2, int arg_reg2) {
+    need_reg_all(emit);
+    ASM_MOV_REG_IMM(emit->as, arg_reg1, arg_val1);
+    ASM_MOV_REG_IMM(emit->as, arg_reg2, arg_val2);
+    ASM_CALL_IND(emit->as, fun_kind);
+}
+
+STATIC void emit_call_with_qstr_arg(emit_t *emit, mp_fun_kind_t fun_kind, qstr qst, int arg_reg) {
+    need_reg_all(emit);
+    emit_native_mov_reg_qstr(emit, arg_reg, qst);
+    ASM_CALL_IND(emit->as, fun_kind);
+}
+
+// vtype of all n_pop objects is VTYPE_PYOBJ
+// Will convert any items that are not VTYPE_PYOBJ to this type and put them back on the stack.
+// If any conversions of non-immediate values are needed, then it uses REG_ARG_1, REG_ARG_2 and REG_RET.
+// Otherwise, it does not use any temporary registers (but may use reg_dest before loading it with stack pointer).
+STATIC void emit_get_stack_pointer_to_reg_for_pop(emit_t *emit, mp_uint_t reg_dest, mp_uint_t n_pop) {
+    need_reg_all(emit);
+
+    // First, store any immediate values to their respective place on the stack.
+    for (mp_uint_t i = 0; i < n_pop; i++) {
+        stack_info_t *si = &emit->stack_info[emit->stack_size - 1 - i];
+        // must push any imm's to stack
+        // must convert them to VTYPE_PYOBJ for viper code
+        if (si->kind == STACK_IMM) {
+            si->kind = STACK_VALUE;
+            si->vtype = load_reg_stack_imm(emit, reg_dest, si, true);
+            emit_native_mov_state_reg(emit, emit->stack_start + emit->stack_size - 1 - i, reg_dest);
+        }
+
+        // verify that this value is on the stack
+        assert(si->kind == STACK_VALUE);
+    }
+
+    // Second, convert any non-VTYPE_PYOBJ to that type.
+    for (mp_uint_t i = 0; i < n_pop; i++) {
+        stack_info_t *si = &emit->stack_info[emit->stack_size - 1 - i];
+        if (si->vtype != VTYPE_PYOBJ) {
+            mp_uint_t local_num = emit->stack_start + emit->stack_size - 1 - i;
+            emit_native_mov_reg_state(emit, REG_ARG_1, local_num);
+            emit_call_with_imm_arg(emit, MP_F_CONVERT_NATIVE_TO_OBJ, si->vtype, REG_ARG_2); // arg2 = type
+            emit_native_mov_state_reg(emit, local_num, REG_RET);
+            si->vtype = VTYPE_PYOBJ;
+            DEBUG_printf("  convert_native_to_obj(local_num=" UINT_FMT ")\n", local_num);
+        }
+    }
+
+    // Adujust the stack for a pop of n_pop items, and load the stack pointer into reg_dest.
+    adjust_stack(emit, -n_pop);
+    emit_native_mov_reg_state_addr(emit, reg_dest, emit->stack_start + emit->stack_size);
+}
+
+// vtype of all n_push objects is VTYPE_PYOBJ
+STATIC void emit_get_stack_pointer_to_reg_for_push(emit_t *emit, mp_uint_t reg_dest, mp_uint_t n_push) {
+    need_reg_all(emit);
+    ensure_extra_stack(emit, n_push);
+    for (mp_uint_t i = 0; i < n_push; i++) {
+        emit->stack_info[emit->stack_size + i].kind = STACK_VALUE;
+        emit->stack_info[emit->stack_size + i].vtype = VTYPE_PYOBJ;
+    }
+    emit_native_mov_reg_state_addr(emit, reg_dest, emit->stack_start + emit->stack_size);
+    adjust_stack(emit, n_push);
+}
+
+STATIC void emit_native_push_exc_stack(emit_t *emit, uint label, bool is_finally) {
+    if (emit->exc_stack_size + 1 > emit->exc_stack_alloc) {
+        size_t new_alloc = emit->exc_stack_alloc + 4;
+        emit->exc_stack = m_renew(exc_stack_entry_t, emit->exc_stack, emit->exc_stack_alloc, new_alloc);
+        emit->exc_stack_alloc = new_alloc;
+    }
+
+    exc_stack_entry_t *e = &emit->exc_stack[emit->exc_stack_size++];
+    e->label = label;
+    e->is_finally = is_finally;
+    e->unwind_label = UNWIND_LABEL_UNUSED;
+    e->is_active = true;
+
+    ASM_MOV_REG_PCREL(emit->as, REG_RET, label);
+    ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_PC(emit), REG_RET);
+}
+
+STATIC void emit_native_leave_exc_stack(emit_t *emit, bool start_of_handler) {
+    assert(emit->exc_stack_size > 0);
+
+    // Get current exception handler and deactivate it
+    exc_stack_entry_t *e = &emit->exc_stack[emit->exc_stack_size - 1];
+    e->is_active = false;
+
+    // Find next innermost active exception handler, to restore as current handler
+    for (--e; e >= emit->exc_stack && !e->is_active; --e) {
+    }
+
+    // Update the PC of the new exception handler
+    if (e < emit->exc_stack) {
+        // No active handler, clear handler PC to zero
+        if (start_of_handler) {
+            // Optimisation: PC is already cleared by global exc handler
+            return;
+        }
+        ASM_XOR_REG_REG(emit->as, REG_RET, REG_RET);
+    } else {
+        // Found new active handler, get its PC
+        ASM_MOV_REG_PCREL(emit->as, REG_RET, e->label);
+    }
+    ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_PC(emit), REG_RET);
+}
+
+STATIC exc_stack_entry_t *emit_native_pop_exc_stack(emit_t *emit) {
+    assert(emit->exc_stack_size > 0);
+    exc_stack_entry_t *e = &emit->exc_stack[--emit->exc_stack_size];
+    assert(e->is_active == false);
+    return e;
+}
+
+STATIC void emit_load_reg_with_ptr(emit_t *emit, int reg, mp_uint_t ptr, size_t table_off) {
+    if (!emit->do_viper_types) {
+        // Skip qstr names of arguments
+        table_off += emit->scope->num_pos_args + emit->scope->num_kwonly_args;
+    }
+    if (emit->pass == MP_PASS_EMIT) {
+        emit->const_table[table_off] = ptr;
+    }
+    emit_native_mov_reg_state(emit, REG_TEMP0, LOCAL_IDX_FUN_OBJ(emit));
+    ASM_LOAD_REG_REG_OFFSET(emit->as, REG_TEMP0, REG_TEMP0, OFFSETOF_OBJ_FUN_BC_CONST_TABLE);
+    ASM_LOAD_REG_REG_OFFSET(emit->as, reg, REG_TEMP0, table_off);
+}
+
+STATIC void emit_load_reg_with_object(emit_t *emit, int reg, mp_obj_t obj) {
+    // First entry is for mp_fun_table
+    size_t table_off = 1 + emit->const_table_cur_obj++;
+    emit_load_reg_with_ptr(emit, reg, (mp_uint_t)obj, table_off);
+}
+
+STATIC void emit_load_reg_with_raw_code(emit_t *emit, int reg, mp_raw_code_t *rc) {
+    // First entry is for mp_fun_table, then constant objects
+    size_t table_off = 1 + emit->const_table_num_obj + emit->const_table_cur_raw_code++;
+    emit_load_reg_with_ptr(emit, reg, (mp_uint_t)rc, table_off);
+}
+
+STATIC void emit_native_label_assign(emit_t *emit, mp_uint_t l) {
+    DEBUG_printf("label_assign(" UINT_FMT ")\n", l);
+
+    bool is_finally = false;
+    if (emit->exc_stack_size > 0) {
+        exc_stack_entry_t *e = &emit->exc_stack[emit->exc_stack_size - 1];
+        is_finally = e->is_finally && e->label == l;
+    }
+
+    if (is_finally) {
+        // Label is at start of finally handler: store TOS into exception slot
+        vtype_kind_t vtype;
+        emit_pre_pop_reg(emit, &vtype, REG_TEMP0);
+        ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_VAL(emit), REG_TEMP0);
+    }
+
+    emit_native_pre(emit);
+    // need to commit stack because we can jump here from elsewhere
+    need_stack_settled(emit);
+    mp_asm_base_label_assign(&emit->as->base, l);
+    emit_post(emit);
+
+    if (is_finally) {
+        // Label is at start of finally handler: pop exception stack
+        emit_native_leave_exc_stack(emit, false);
+    }
+}
+
+STATIC void emit_native_global_exc_entry(emit_t *emit) {
+    // Note: 4 labels are reserved for this function, starting at *emit->label_slot
+
+    emit->exit_label = *emit->label_slot;
+
+    if (NEED_GLOBAL_EXC_HANDLER(emit)) {
+        mp_uint_t nlr_label = *emit->label_slot + 1;
+        mp_uint_t start_label = *emit->label_slot + 2;
+        mp_uint_t global_except_label = *emit->label_slot + 3;
+
+        if (!(emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR)) {
+            // Set new globals
+            emit_native_mov_reg_state(emit, REG_ARG_1, LOCAL_IDX_FUN_OBJ(emit));
+            ASM_LOAD_REG_REG_OFFSET(emit->as, REG_ARG_1, REG_ARG_1, OFFSETOF_OBJ_FUN_BC_GLOBALS);
+            emit_call(emit, MP_F_NATIVE_SWAP_GLOBALS);
+
+            // Save old globals (or NULL if globals didn't change)
+            emit_native_mov_state_reg(emit, LOCAL_IDX_OLD_GLOBALS(emit), REG_RET);
+        }
+
+        if (emit->scope->exc_stack_size == 0) {
+            if (!(emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR)) {
+                // Optimisation: if globals didn't change don't push the nlr context
+                ASM_JUMP_IF_REG_ZERO(emit->as, REG_RET, start_label, false);
+            }
+
+            // Wrap everything in an nlr context
+            ASM_MOV_REG_LOCAL_ADDR(emit->as, REG_ARG_1, 0);
+            emit_call(emit, MP_F_NLR_PUSH);
+            #if N_NLR_SETJMP
+            ASM_MOV_REG_LOCAL_ADDR(emit->as, REG_ARG_1, 2);
+            emit_call(emit, MP_F_SETJMP);
+            #endif
+            ASM_JUMP_IF_REG_ZERO(emit->as, REG_RET, start_label, true);
+        } else {
+            // Clear the unwind state
+            ASM_XOR_REG_REG(emit->as, REG_TEMP0, REG_TEMP0);
+            ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_UNWIND(emit), REG_TEMP0);
+
+            // Put PC of start code block into REG_LOCAL_1
+            ASM_MOV_REG_PCREL(emit->as, REG_LOCAL_1, start_label);
+
+            // Wrap everything in an nlr context
+            emit_native_label_assign(emit, nlr_label);
+            ASM_MOV_REG_LOCAL(emit->as, REG_LOCAL_2, LOCAL_IDX_EXC_HANDLER_UNWIND(emit));
+            ASM_MOV_REG_LOCAL_ADDR(emit->as, REG_ARG_1, 0);
+            emit_call(emit, MP_F_NLR_PUSH);
+            #if N_NLR_SETJMP
+            ASM_MOV_REG_LOCAL_ADDR(emit->as, REG_ARG_1, 2);
+            emit_call(emit, MP_F_SETJMP);
+            #endif
+            ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_UNWIND(emit), REG_LOCAL_2);
+            ASM_JUMP_IF_REG_NONZERO(emit->as, REG_RET, global_except_label, true);
+
+            // Clear PC of current code block, and jump there to resume execution
+            ASM_XOR_REG_REG(emit->as, REG_TEMP0, REG_TEMP0);
+            ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_PC(emit), REG_TEMP0);
+            ASM_JUMP_REG(emit->as, REG_LOCAL_1);
+
+            // Global exception handler: check for valid exception handler
+            emit_native_label_assign(emit, global_except_label);
+            #if N_NLR_SETJMP
+            // Reload REG_FUN_TABLE, since it may be clobbered by longjmp
+            emit_native_mov_reg_state(emit, REG_LOCAL_1, LOCAL_IDX_FUN_OBJ(emit));
+            ASM_LOAD_REG_REG_OFFSET(emit->as, REG_LOCAL_1, REG_LOCAL_1, offsetof(mp_obj_fun_bc_t, const_table) / sizeof(uintptr_t));
+            ASM_LOAD_REG_REG_OFFSET(emit->as, REG_FUN_TABLE, REG_LOCAL_1, emit->scope->num_pos_args + emit->scope->num_kwonly_args);
+            #endif
+            ASM_MOV_REG_LOCAL(emit->as, REG_LOCAL_1, LOCAL_IDX_EXC_HANDLER_PC(emit));
+            ASM_JUMP_IF_REG_NONZERO(emit->as, REG_LOCAL_1, nlr_label, false);
+        }
+
+        if (!(emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR)) {
+            // Restore old globals
+            emit_native_mov_reg_state(emit, REG_ARG_1, LOCAL_IDX_OLD_GLOBALS(emit));
+            emit_call(emit, MP_F_NATIVE_SWAP_GLOBALS);
+        }
+
+        if (emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR) {
+            // Store return value in state[0]
+            ASM_MOV_REG_LOCAL(emit->as, REG_TEMP0, LOCAL_IDX_EXC_VAL(emit));
+            ASM_STORE_REG_REG_OFFSET(emit->as, REG_TEMP0, REG_GENERATOR_STATE, OFFSETOF_CODE_STATE_STATE);
+
+            // Load return kind
+            ASM_MOV_REG_IMM(emit->as, REG_PARENT_RET, MP_VM_RETURN_EXCEPTION);
+
+            ASM_EXIT(emit->as);
+        } else {
+            // Re-raise exception out to caller
+            ASM_MOV_REG_LOCAL(emit->as, REG_ARG_1, LOCAL_IDX_EXC_VAL(emit));
+            emit_call(emit, MP_F_NATIVE_RAISE);
+        }
+
+        // Label for start of function
+        emit_native_label_assign(emit, start_label);
+
+        if (emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR) {
+            emit_native_mov_reg_state(emit, REG_TEMP0, LOCAL_IDX_GEN_PC(emit));
+            ASM_JUMP_REG(emit->as, REG_TEMP0);
+            emit->start_offset = mp_asm_base_get_code_pos(&emit->as->base);
+
+            // This is the first entry of the generator
+
+            // Check LOCAL_IDX_EXC_VAL for any injected value
+            ASM_MOV_REG_LOCAL(emit->as, REG_ARG_1, LOCAL_IDX_EXC_VAL(emit));
+            emit_call(emit, MP_F_NATIVE_RAISE);
+        }
+    }
+}
+
+STATIC void emit_native_global_exc_exit(emit_t *emit) {
+    // Label for end of function
+    emit_native_label_assign(emit, emit->exit_label);
+
+    if (NEED_GLOBAL_EXC_HANDLER(emit)) {
+        // Get old globals
+        if (!(emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR)) {
+            emit_native_mov_reg_state(emit, REG_ARG_1, LOCAL_IDX_OLD_GLOBALS(emit));
+
+            if (emit->scope->exc_stack_size == 0) {
+                // Optimisation: if globals didn't change then don't restore them and don't do nlr_pop
+                ASM_JUMP_IF_REG_ZERO(emit->as, REG_ARG_1, emit->exit_label + 1, false);
+            }
+
+            // Restore old globals
+            emit_call(emit, MP_F_NATIVE_SWAP_GLOBALS);
+        }
+
+        // Pop the nlr context
+        emit_call(emit, MP_F_NLR_POP);
+
+        if (!(emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR)) {
+            if (emit->scope->exc_stack_size == 0) {
+                // Destination label for above optimisation
+                emit_native_label_assign(emit, emit->exit_label + 1);
+            }
+        }
+
+        // Load return value
+        ASM_MOV_REG_LOCAL(emit->as, REG_PARENT_RET, LOCAL_IDX_RET_VAL(emit));
+    }
+
+    ASM_EXIT(emit->as);
+}
+
+STATIC void emit_native_import_name(emit_t *emit, qstr qst) {
+    DEBUG_printf("import_name %s\n", qstr_str(qst));
+
+    // get arguments from stack: arg2 = fromlist, arg3 = level
+    // If using viper types these arguments must be converted to proper objects, and
+    // to accomplish this viper types are turned off for the emit_pre_pop_reg_reg call.
+    bool orig_do_viper_types = emit->do_viper_types;
+    emit->do_viper_types = false;
+    vtype_kind_t vtype_fromlist;
+    vtype_kind_t vtype_level;
+    emit_pre_pop_reg_reg(emit, &vtype_fromlist, REG_ARG_2, &vtype_level, REG_ARG_3);
+    assert(vtype_fromlist == VTYPE_PYOBJ);
+    assert(vtype_level == VTYPE_PYOBJ);
+    emit->do_viper_types = orig_do_viper_types;
+
+    emit_call_with_qstr_arg(emit, MP_F_IMPORT_NAME, qst, REG_ARG_1); // arg1 = import name
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+}
+
+STATIC void emit_native_import_from(emit_t *emit, qstr qst) {
+    DEBUG_printf("import_from %s\n", qstr_str(qst));
+    emit_native_pre(emit);
+    vtype_kind_t vtype_module;
+    emit_access_stack(emit, 1, &vtype_module, REG_ARG_1); // arg1 = module
+    assert(vtype_module == VTYPE_PYOBJ);
+    emit_call_with_qstr_arg(emit, MP_F_IMPORT_FROM, qst, REG_ARG_2); // arg2 = import name
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+}
+
+STATIC void emit_native_import_star(emit_t *emit) {
+    DEBUG_printf("import_star\n");
+    vtype_kind_t vtype_module;
+    emit_pre_pop_reg(emit, &vtype_module, REG_ARG_1); // arg1 = module
+    assert(vtype_module == VTYPE_PYOBJ);
+    emit_call(emit, MP_F_IMPORT_ALL);
+    emit_post(emit);
+}
+
+STATIC void emit_native_import(emit_t *emit, qstr qst, int kind) {
+    if (kind == MP_EMIT_IMPORT_NAME) {
+        emit_native_import_name(emit, qst);
+    } else if (kind == MP_EMIT_IMPORT_FROM) {
+        emit_native_import_from(emit, qst);
+    } else {
+        emit_native_import_star(emit);
+    }
+}
+
+STATIC void emit_native_load_const_tok(emit_t *emit, mp_token_kind_t tok) {
+    DEBUG_printf("load_const_tok(tok=%u)\n", tok);
+    if (tok == MP_TOKEN_ELLIPSIS) {
+        #if MICROPY_PERSISTENT_CODE_SAVE
+        emit_native_load_const_obj(emit, MP_OBJ_FROM_PTR(&mp_const_ellipsis_obj));
+        #else
+        emit_post_push_imm(emit, VTYPE_PYOBJ, (mp_uint_t)MP_OBJ_FROM_PTR(&mp_const_ellipsis_obj));
+        #endif
+    } else {
+        emit_native_pre(emit);
+        if (tok == MP_TOKEN_KW_NONE) {
+            emit_post_push_imm(emit, VTYPE_PTR_NONE, 0);
+        } else {
+            emit_post_push_imm(emit, VTYPE_BOOL, tok == MP_TOKEN_KW_FALSE ? 0 : 1);
+        }
+    }
+}
+
+STATIC void emit_native_load_const_small_int(emit_t *emit, mp_int_t arg) {
+    DEBUG_printf("load_const_small_int(int=" INT_FMT ")\n", arg);
+    emit_native_pre(emit);
+    emit_post_push_imm(emit, VTYPE_INT, arg);
+}
+
+STATIC void emit_native_load_const_str(emit_t *emit, qstr qst) {
+    emit_native_pre(emit);
+    // TODO: Eventually we want to be able to work with raw pointers in viper to
+    // do native array access.  For now we just load them as any other object.
+    /*
+    if (emit->do_viper_types) {
+        // load a pointer to the asciiz string?
+        emit_post_push_imm(emit, VTYPE_PTR, (mp_uint_t)qstr_str(qst));
+    } else
+    */
+    {
+        need_reg_single(emit, REG_TEMP0, 0);
+        emit_native_mov_reg_qstr_obj(emit, REG_TEMP0, qst);
+        emit_post_push_reg(emit, VTYPE_PYOBJ, REG_TEMP0);
+    }
+}
+
+STATIC void emit_native_load_const_obj(emit_t *emit, mp_obj_t obj) {
+    emit->scope->scope_flags |= MP_SCOPE_FLAG_HASCONSTS;
+    emit_native_pre(emit);
+    need_reg_single(emit, REG_RET, 0);
+    emit_load_reg_with_object(emit, REG_RET, obj);
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+}
+
+STATIC void emit_native_load_null(emit_t *emit) {
+    emit_native_pre(emit);
+    emit_post_push_imm(emit, VTYPE_PYOBJ, 0);
+}
+
+STATIC void emit_native_load_fast(emit_t *emit, qstr qst, mp_uint_t local_num) {
+    DEBUG_printf("load_fast(%s, " UINT_FMT ")\n", qstr_str(qst), local_num);
+    vtype_kind_t vtype = emit->local_vtype[local_num];
+    if (vtype == VTYPE_UNBOUND) {
+        EMIT_NATIVE_VIPER_TYPE_ERROR(emit, MP_ERROR_TEXT("local '%q' used before type known"), qst);
+    }
+    emit_native_pre(emit);
+    if (local_num < REG_LOCAL_NUM && CAN_USE_REGS_FOR_LOCALS(emit)) {
+        emit_post_push_reg(emit, vtype, reg_local_table[local_num]);
+    } else {
+        need_reg_single(emit, REG_TEMP0, 0);
+        emit_native_mov_reg_state(emit, REG_TEMP0, LOCAL_IDX_LOCAL_VAR(emit, local_num));
+        emit_post_push_reg(emit, vtype, REG_TEMP0);
+    }
+}
+
+STATIC void emit_native_load_deref(emit_t *emit, qstr qst, mp_uint_t local_num) {
+    DEBUG_printf("load_deref(%s, " UINT_FMT ")\n", qstr_str(qst), local_num);
+    need_reg_single(emit, REG_RET, 0);
+    emit_native_load_fast(emit, qst, local_num);
+    vtype_kind_t vtype;
+    int reg_base = REG_RET;
+    emit_pre_pop_reg_flexible(emit, &vtype, &reg_base, -1, -1);
+    ASM_LOAD_REG_REG_OFFSET(emit->as, REG_RET, reg_base, 1);
+    // closed over vars are always Python objects
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+}
+
+STATIC void emit_native_load_local(emit_t *emit, qstr qst, mp_uint_t local_num, int kind) {
+    if (kind == MP_EMIT_IDOP_LOCAL_FAST) {
+        emit_native_load_fast(emit, qst, local_num);
+    } else {
+        emit_native_load_deref(emit, qst, local_num);
+    }
+}
+
+STATIC void emit_native_load_global(emit_t *emit, qstr qst, int kind) {
+    MP_STATIC_ASSERT(MP_F_LOAD_NAME + MP_EMIT_IDOP_GLOBAL_NAME == MP_F_LOAD_NAME);
+    MP_STATIC_ASSERT(MP_F_LOAD_NAME + MP_EMIT_IDOP_GLOBAL_GLOBAL == MP_F_LOAD_GLOBAL);
+    emit_native_pre(emit);
+    if (kind == MP_EMIT_IDOP_GLOBAL_NAME) {
+        DEBUG_printf("load_name(%s)\n", qstr_str(qst));
+    } else {
+        DEBUG_printf("load_global(%s)\n", qstr_str(qst));
+        if (emit->do_viper_types) {
+            // check for builtin casting operators
+            int native_type = mp_native_type_from_qstr(qst);
+            if (native_type >= MP_NATIVE_TYPE_BOOL) {
+                emit_post_push_imm(emit, VTYPE_BUILTIN_CAST, native_type);
+                return;
+            }
+        }
+    }
+    emit_call_with_qstr_arg(emit, MP_F_LOAD_NAME + kind, qst, REG_ARG_1);
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+}
+
+STATIC void emit_native_load_attr(emit_t *emit, qstr qst) {
+    // depends on type of subject:
+    //  - integer, function, pointer to integers: error
+    //  - pointer to structure: get member, quite easy
+    //  - Python object: call mp_load_attr, and needs to be typed to convert result
+    vtype_kind_t vtype_base;
+    emit_pre_pop_reg(emit, &vtype_base, REG_ARG_1); // arg1 = base
+    assert(vtype_base == VTYPE_PYOBJ);
+    emit_call_with_qstr_arg(emit, MP_F_LOAD_ATTR, qst, REG_ARG_2); // arg2 = attribute name
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+}
+
+STATIC void emit_native_load_method(emit_t *emit, qstr qst, bool is_super) {
+    if (is_super) {
+        emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_2, 3); // arg2 = dest ptr
+        emit_get_stack_pointer_to_reg_for_push(emit, REG_ARG_2, 2); // arg2 = dest ptr
+        emit_call_with_qstr_arg(emit, MP_F_LOAD_SUPER_METHOD, qst, REG_ARG_1); // arg1 = method name
+    } else {
+        vtype_kind_t vtype_base;
+        emit_pre_pop_reg(emit, &vtype_base, REG_ARG_1); // arg1 = base
+        assert(vtype_base == VTYPE_PYOBJ);
+        emit_get_stack_pointer_to_reg_for_push(emit, REG_ARG_3, 2); // arg3 = dest ptr
+        emit_call_with_qstr_arg(emit, MP_F_LOAD_METHOD, qst, REG_ARG_2); // arg2 = method name
+    }
+}
+
+STATIC void emit_native_load_build_class(emit_t *emit) {
+    emit_native_pre(emit);
+    emit_call(emit, MP_F_LOAD_BUILD_CLASS);
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+}
+
+STATIC void emit_native_load_subscr(emit_t *emit) {
+    DEBUG_printf("load_subscr\n");
+    // need to compile: base[index]
+
+    // pop: index, base
+    // optimise case where index is an immediate
+    vtype_kind_t vtype_base = peek_vtype(emit, 1);
+
+    if (vtype_base == VTYPE_PYOBJ) {
+        // standard Python subscr
+        // TODO factor this implicit cast code with other uses of it
+        vtype_kind_t vtype_index = peek_vtype(emit, 0);
+        if (vtype_index == VTYPE_PYOBJ) {
+            emit_pre_pop_reg(emit, &vtype_index, REG_ARG_2);
+        } else {
+            emit_pre_pop_reg(emit, &vtype_index, REG_ARG_1);
+            emit_call_with_imm_arg(emit, MP_F_CONVERT_NATIVE_TO_OBJ, vtype_index, REG_ARG_2); // arg2 = type
+            ASM_MOV_REG_REG(emit->as, REG_ARG_2, REG_RET);
+        }
+        emit_pre_pop_reg(emit, &vtype_base, REG_ARG_1);
+        emit_call_with_imm_arg(emit, MP_F_OBJ_SUBSCR, (mp_uint_t)MP_OBJ_SENTINEL, REG_ARG_3);
+        emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+    } else {
+        // viper load
+        // TODO The different machine architectures have very different
+        // capabilities and requirements for loads, so probably best to
+        // write a completely separate load-optimiser for each one.
+        stack_info_t *top = peek_stack(emit, 0);
+        if (top->vtype == VTYPE_INT && top->kind == STACK_IMM) {
+            // index is an immediate
+            mp_int_t index_value = top->data.u_imm;
+            emit_pre_pop_discard(emit); // discard index
+            int reg_base = REG_ARG_1;
+            int reg_index = REG_ARG_2;
+            emit_pre_pop_reg_flexible(emit, &vtype_base, &reg_base, reg_index, reg_index);
+            need_reg_single(emit, REG_RET, 0);
+            switch (vtype_base) {
+                case VTYPE_PTR8: {
+                    // pointer to 8-bit memory
+                    // TODO optimise to use thumb ldrb r1, [r2, r3]
+                    if (index_value != 0) {
+                        // index is non-zero
+                        #if N_THUMB
+                        if (index_value > 0 && index_value < 32) {
+                            asm_thumb_ldrb_rlo_rlo_i5(emit->as, REG_RET, reg_base, index_value);
+                            break;
+                        }
+                        #endif
+                        ASM_MOV_REG_IMM(emit->as, reg_index, index_value);
+                        ASM_ADD_REG_REG(emit->as, reg_index, reg_base); // add index to base
+                        reg_base = reg_index;
+                    }
+                    ASM_LOAD8_REG_REG(emit->as, REG_RET, reg_base); // load from (base+index)
+                    break;
+                }
+                case VTYPE_PTR16: {
+                    // pointer to 16-bit memory
+                    if (index_value != 0) {
+                        // index is a non-zero immediate
+                        #if N_THUMB
+                        if (index_value > 0 && index_value < 32) {
+                            asm_thumb_ldrh_rlo_rlo_i5(emit->as, REG_RET, reg_base, index_value);
+                            break;
+                        }
+                        #endif
+                        ASM_MOV_REG_IMM(emit->as, reg_index, index_value << 1);
+                        ASM_ADD_REG_REG(emit->as, reg_index, reg_base); // add 2*index to base
+                        reg_base = reg_index;
+                    }
+                    ASM_LOAD16_REG_REG(emit->as, REG_RET, reg_base); // load from (base+2*index)
+                    break;
+                }
+                case VTYPE_PTR32: {
+                    // pointer to 32-bit memory
+                    if (index_value != 0) {
+                        // index is a non-zero immediate
+                        #if N_THUMB
+                        if (index_value > 0 && index_value < 32) {
+                            asm_thumb_ldr_rlo_rlo_i5(emit->as, REG_RET, reg_base, index_value);
+                            break;
+                        }
+                        #endif
+                        ASM_MOV_REG_IMM(emit->as, reg_index, index_value << 2);
+                        ASM_ADD_REG_REG(emit->as, reg_index, reg_base); // add 4*index to base
+                        reg_base = reg_index;
+                    }
+                    ASM_LOAD32_REG_REG(emit->as, REG_RET, reg_base); // load from (base+4*index)
+                    break;
+                }
+                default:
+                    EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+                        MP_ERROR_TEXT("can't load from '%q'"), vtype_to_qstr(vtype_base));
+            }
+        } else {
+            // index is not an immediate
+            vtype_kind_t vtype_index;
+            int reg_index = REG_ARG_2;
+            emit_pre_pop_reg_flexible(emit, &vtype_index, &reg_index, REG_ARG_1, REG_ARG_1);
+            emit_pre_pop_reg(emit, &vtype_base, REG_ARG_1);
+            need_reg_single(emit, REG_RET, 0);
+            if (vtype_index != VTYPE_INT && vtype_index != VTYPE_UINT) {
+                EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+                    MP_ERROR_TEXT("can't load with '%q' index"), vtype_to_qstr(vtype_index));
+            }
+            switch (vtype_base) {
+                case VTYPE_PTR8: {
+                    // pointer to 8-bit memory
+                    // TODO optimise to use thumb ldrb r1, [r2, r3]
+                    ASM_ADD_REG_REG(emit->as, REG_ARG_1, reg_index); // add index to base
+                    ASM_LOAD8_REG_REG(emit->as, REG_RET, REG_ARG_1); // store value to (base+index)
+                    break;
+                }
+                case VTYPE_PTR16: {
+                    // pointer to 16-bit memory
+                    ASM_ADD_REG_REG(emit->as, REG_ARG_1, reg_index); // add index to base
+                    ASM_ADD_REG_REG(emit->as, REG_ARG_1, reg_index); // add index to base
+                    ASM_LOAD16_REG_REG(emit->as, REG_RET, REG_ARG_1); // load from (base+2*index)
+                    break;
+                }
+                case VTYPE_PTR32: {
+                    // pointer to word-size memory
+                    ASM_ADD_REG_REG(emit->as, REG_ARG_1, reg_index); // add index to base
+                    ASM_ADD_REG_REG(emit->as, REG_ARG_1, reg_index); // add index to base
+                    ASM_ADD_REG_REG(emit->as, REG_ARG_1, reg_index); // add index to base
+                    ASM_ADD_REG_REG(emit->as, REG_ARG_1, reg_index); // add index to base
+                    ASM_LOAD32_REG_REG(emit->as, REG_RET, REG_ARG_1); // load from (base+4*index)
+                    break;
+                }
+                default:
+                    EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+                        MP_ERROR_TEXT("can't load from '%q'"), vtype_to_qstr(vtype_base));
+            }
+        }
+        emit_post_push_reg(emit, VTYPE_INT, REG_RET);
+    }
+}
+
+STATIC void emit_native_store_fast(emit_t *emit, qstr qst, mp_uint_t local_num) {
+    vtype_kind_t vtype;
+    if (local_num < REG_LOCAL_NUM && CAN_USE_REGS_FOR_LOCALS(emit)) {
+        emit_pre_pop_reg(emit, &vtype, reg_local_table[local_num]);
+    } else {
+        emit_pre_pop_reg(emit, &vtype, REG_TEMP0);
+        emit_native_mov_state_reg(emit, LOCAL_IDX_LOCAL_VAR(emit, local_num), REG_TEMP0);
+    }
+    emit_post(emit);
+
+    // check types
+    if (emit->local_vtype[local_num] == VTYPE_UNBOUND) {
+        // first time this local is assigned, so give it a type of the object stored in it
+        emit->local_vtype[local_num] = vtype;
+    } else if (emit->local_vtype[local_num] != vtype) {
+        // type of local is not the same as object stored in it
+        EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+            MP_ERROR_TEXT("local '%q' has type '%q' but source is '%q'"),
+            qst, vtype_to_qstr(emit->local_vtype[local_num]), vtype_to_qstr(vtype));
+    }
+}
+
+STATIC void emit_native_store_deref(emit_t *emit, qstr qst, mp_uint_t local_num) {
+    DEBUG_printf("store_deref(%s, " UINT_FMT ")\n", qstr_str(qst), local_num);
+    need_reg_single(emit, REG_TEMP0, 0);
+    need_reg_single(emit, REG_TEMP1, 0);
+    emit_native_load_fast(emit, qst, local_num);
+    vtype_kind_t vtype;
+    int reg_base = REG_TEMP0;
+    emit_pre_pop_reg_flexible(emit, &vtype, &reg_base, -1, -1);
+    int reg_src = REG_TEMP1;
+    emit_pre_pop_reg_flexible(emit, &vtype, &reg_src, reg_base, reg_base);
+    ASM_STORE_REG_REG_OFFSET(emit->as, reg_src, reg_base, 1);
+    emit_post(emit);
+}
+
+STATIC void emit_native_store_local(emit_t *emit, qstr qst, mp_uint_t local_num, int kind) {
+    if (kind == MP_EMIT_IDOP_LOCAL_FAST) {
+        emit_native_store_fast(emit, qst, local_num);
+    } else {
+        emit_native_store_deref(emit, qst, local_num);
+    }
+}
+
+STATIC void emit_native_store_global(emit_t *emit, qstr qst, int kind) {
+    MP_STATIC_ASSERT(MP_F_STORE_NAME + MP_EMIT_IDOP_GLOBAL_NAME == MP_F_STORE_NAME);
+    MP_STATIC_ASSERT(MP_F_STORE_NAME + MP_EMIT_IDOP_GLOBAL_GLOBAL == MP_F_STORE_GLOBAL);
+    if (kind == MP_EMIT_IDOP_GLOBAL_NAME) {
+        // mp_store_name, but needs conversion of object (maybe have mp_viper_store_name(obj, type))
+        vtype_kind_t vtype;
+        emit_pre_pop_reg(emit, &vtype, REG_ARG_2);
+        assert(vtype == VTYPE_PYOBJ);
+    } else {
+        vtype_kind_t vtype = peek_vtype(emit, 0);
+        if (vtype == VTYPE_PYOBJ) {
+            emit_pre_pop_reg(emit, &vtype, REG_ARG_2);
+        } else {
+            emit_pre_pop_reg(emit, &vtype, REG_ARG_1);
+            emit_call_with_imm_arg(emit, MP_F_CONVERT_NATIVE_TO_OBJ, vtype, REG_ARG_2); // arg2 = type
+            ASM_MOV_REG_REG(emit->as, REG_ARG_2, REG_RET);
+        }
+    }
+    emit_call_with_qstr_arg(emit, MP_F_STORE_NAME + kind, qst, REG_ARG_1); // arg1 = name
+    emit_post(emit);
+}
+
+STATIC void emit_native_store_attr(emit_t *emit, qstr qst) {
+    vtype_kind_t vtype_base, vtype_val;
+    emit_pre_pop_reg_reg(emit, &vtype_base, REG_ARG_1, &vtype_val, REG_ARG_3); // arg1 = base, arg3 = value
+    assert(vtype_base == VTYPE_PYOBJ);
+    assert(vtype_val == VTYPE_PYOBJ);
+    emit_call_with_qstr_arg(emit, MP_F_STORE_ATTR, qst, REG_ARG_2); // arg2 = attribute name
+    emit_post(emit);
+}
+
+STATIC void emit_native_store_subscr(emit_t *emit) {
+    DEBUG_printf("store_subscr\n");
+    // need to compile: base[index] = value
+
+    // pop: index, base, value
+    // optimise case where index is an immediate
+    vtype_kind_t vtype_base = peek_vtype(emit, 1);
+
+    if (vtype_base == VTYPE_PYOBJ) {
+        // standard Python subscr
+        vtype_kind_t vtype_index = peek_vtype(emit, 0);
+        vtype_kind_t vtype_value = peek_vtype(emit, 2);
+        if (vtype_index != VTYPE_PYOBJ || vtype_value != VTYPE_PYOBJ) {
+            // need to implicitly convert non-objects to objects
+            // TODO do this properly
+            emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_1, 3);
+            adjust_stack(emit, 3);
+        }
+        emit_pre_pop_reg_reg_reg(emit, &vtype_index, REG_ARG_2, &vtype_base, REG_ARG_1, &vtype_value, REG_ARG_3);
+        emit_call(emit, MP_F_OBJ_SUBSCR);
+    } else {
+        // viper store
+        // TODO The different machine architectures have very different
+        // capabilities and requirements for stores, so probably best to
+        // write a completely separate store-optimiser for each one.
+        stack_info_t *top = peek_stack(emit, 0);
+        if (top->vtype == VTYPE_INT && top->kind == STACK_IMM) {
+            // index is an immediate
+            mp_int_t index_value = top->data.u_imm;
+            emit_pre_pop_discard(emit); // discard index
+            vtype_kind_t vtype_value;
+            int reg_base = REG_ARG_1;
+            int reg_index = REG_ARG_2;
+            int reg_value = REG_ARG_3;
+            emit_pre_pop_reg_flexible(emit, &vtype_base, &reg_base, reg_index, reg_value);
+            #if N_X64 || N_X86
+            // special case: x86 needs byte stores to be from lower 4 regs (REG_ARG_3 is EDX)
+            emit_pre_pop_reg(emit, &vtype_value, reg_value);
+            #else
+            emit_pre_pop_reg_flexible(emit, &vtype_value, &reg_value, reg_base, reg_index);
+            #endif
+            if (vtype_value != VTYPE_BOOL && vtype_value != VTYPE_INT && vtype_value != VTYPE_UINT) {
+                EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+                    MP_ERROR_TEXT("can't store '%q'"), vtype_to_qstr(vtype_value));
+            }
+            switch (vtype_base) {
+                case VTYPE_PTR8: {
+                    // pointer to 8-bit memory
+                    // TODO optimise to use thumb strb r1, [r2, r3]
+                    if (index_value != 0) {
+                        // index is non-zero
+                        #if N_THUMB
+                        if (index_value > 0 && index_value < 32) {
+                            asm_thumb_strb_rlo_rlo_i5(emit->as, reg_value, reg_base, index_value);
+                            break;
+                        }
+                        #endif
+                        ASM_MOV_REG_IMM(emit->as, reg_index, index_value);
+                        #if N_ARM
+                        asm_arm_strb_reg_reg_reg(emit->as, reg_value, reg_base, reg_index);
+                        return;
+                        #endif
+                        ASM_ADD_REG_REG(emit->as, reg_index, reg_base); // add index to base
+                        reg_base = reg_index;
+                    }
+                    ASM_STORE8_REG_REG(emit->as, reg_value, reg_base); // store value to (base+index)
+                    break;
+                }
+                case VTYPE_PTR16: {
+                    // pointer to 16-bit memory
+                    if (index_value != 0) {
+                        // index is a non-zero immediate
+                        #if N_THUMB
+                        if (index_value > 0 && index_value < 32) {
+                            asm_thumb_strh_rlo_rlo_i5(emit->as, reg_value, reg_base, index_value);
+                            break;
+                        }
+                        #endif
+                        ASM_MOV_REG_IMM(emit->as, reg_index, index_value << 1);
+                        ASM_ADD_REG_REG(emit->as, reg_index, reg_base); // add 2*index to base
+                        reg_base = reg_index;
+                    }
+                    ASM_STORE16_REG_REG(emit->as, reg_value, reg_base); // store value to (base+2*index)
+                    break;
+                }
+                case VTYPE_PTR32: {
+                    // pointer to 32-bit memory
+                    if (index_value != 0) {
+                        // index is a non-zero immediate
+                        #if N_THUMB
+                        if (index_value > 0 && index_value < 32) {
+                            asm_thumb_str_rlo_rlo_i5(emit->as, reg_value, reg_base, index_value);
+                            break;
+                        }
+                        #endif
+                        #if N_ARM
+                        ASM_MOV_REG_IMM(emit->as, reg_index, index_value);
+                        asm_arm_str_reg_reg_reg(emit->as, reg_value, reg_base, reg_index);
+                        return;
+                        #endif
+                        ASM_MOV_REG_IMM(emit->as, reg_index, index_value << 2);
+                        ASM_ADD_REG_REG(emit->as, reg_index, reg_base); // add 4*index to base
+                        reg_base = reg_index;
+                    }
+                    ASM_STORE32_REG_REG(emit->as, reg_value, reg_base); // store value to (base+4*index)
+                    break;
+                }
+                default:
+                    EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+                        MP_ERROR_TEXT("can't store to '%q'"), vtype_to_qstr(vtype_base));
+            }
+        } else {
+            // index is not an immediate
+            vtype_kind_t vtype_index, vtype_value;
+            int reg_index = REG_ARG_2;
+            int reg_value = REG_ARG_3;
+            emit_pre_pop_reg_flexible(emit, &vtype_index, &reg_index, REG_ARG_1, reg_value);
+            emit_pre_pop_reg(emit, &vtype_base, REG_ARG_1);
+            if (vtype_index != VTYPE_INT && vtype_index != VTYPE_UINT) {
+                EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+                    MP_ERROR_TEXT("can't store with '%q' index"), vtype_to_qstr(vtype_index));
+            }
+            #if N_X64 || N_X86
+            // special case: x86 needs byte stores to be from lower 4 regs (REG_ARG_3 is EDX)
+            emit_pre_pop_reg(emit, &vtype_value, reg_value);
+            #else
+            emit_pre_pop_reg_flexible(emit, &vtype_value, &reg_value, REG_ARG_1, reg_index);
+            #endif
+            if (vtype_value != VTYPE_BOOL && vtype_value != VTYPE_INT && vtype_value != VTYPE_UINT) {
+                EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+                    MP_ERROR_TEXT("can't store '%q'"), vtype_to_qstr(vtype_value));
+            }
+            switch (vtype_base) {
+                case VTYPE_PTR8: {
+                    // pointer to 8-bit memory
+                    // TODO optimise to use thumb strb r1, [r2, r3]
+                    #if N_ARM
+                    asm_arm_strb_reg_reg_reg(emit->as, reg_value, REG_ARG_1, reg_index);
+                    break;
+                    #endif
+                    ASM_ADD_REG_REG(emit->as, REG_ARG_1, reg_index); // add index to base
+                    ASM_STORE8_REG_REG(emit->as, reg_value, REG_ARG_1); // store value to (base+index)
+                    break;
+                }
+                case VTYPE_PTR16: {
+                    // pointer to 16-bit memory
+                    #if N_ARM
+                    asm_arm_strh_reg_reg_reg(emit->as, reg_value, REG_ARG_1, reg_index);
+                    break;
+                    #endif
+                    ASM_ADD_REG_REG(emit->as, REG_ARG_1, reg_index); // add index to base
+                    ASM_ADD_REG_REG(emit->as, REG_ARG_1, reg_index); // add index to base
+                    ASM_STORE16_REG_REG(emit->as, reg_value, REG_ARG_1); // store value to (base+2*index)
+                    break;
+                }
+                case VTYPE_PTR32: {
+                    // pointer to 32-bit memory
+                    #if N_ARM
+                    asm_arm_str_reg_reg_reg(emit->as, reg_value, REG_ARG_1, reg_index);
+                    break;
+                    #endif
+                    ASM_ADD_REG_REG(emit->as, REG_ARG_1, reg_index); // add index to base
+                    ASM_ADD_REG_REG(emit->as, REG_ARG_1, reg_index); // add index to base
+                    ASM_ADD_REG_REG(emit->as, REG_ARG_1, reg_index); // add index to base
+                    ASM_ADD_REG_REG(emit->as, REG_ARG_1, reg_index); // add index to base
+                    ASM_STORE32_REG_REG(emit->as, reg_value, REG_ARG_1); // store value to (base+4*index)
+                    break;
+                }
+                default:
+                    EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+                        MP_ERROR_TEXT("can't store to '%q'"), vtype_to_qstr(vtype_base));
+            }
+        }
+
+    }
+}
+
+STATIC void emit_native_delete_local(emit_t *emit, qstr qst, mp_uint_t local_num, int kind) {
+    if (kind == MP_EMIT_IDOP_LOCAL_FAST) {
+        // TODO: This is not compliant implementation. We could use MP_OBJ_SENTINEL
+        // to mark deleted vars but then every var would need to be checked on
+        // each access. Very inefficient, so just set value to None to enable GC.
+        emit_native_load_const_tok(emit, MP_TOKEN_KW_NONE);
+        emit_native_store_fast(emit, qst, local_num);
+    } else {
+        // TODO implement me!
+    }
+}
+
+STATIC void emit_native_delete_global(emit_t *emit, qstr qst, int kind) {
+    MP_STATIC_ASSERT(MP_F_DELETE_NAME + MP_EMIT_IDOP_GLOBAL_NAME == MP_F_DELETE_NAME);
+    MP_STATIC_ASSERT(MP_F_DELETE_NAME + MP_EMIT_IDOP_GLOBAL_GLOBAL == MP_F_DELETE_GLOBAL);
+    emit_native_pre(emit);
+    emit_call_with_qstr_arg(emit, MP_F_DELETE_NAME + kind, qst, REG_ARG_1);
+    emit_post(emit);
+}
+
+STATIC void emit_native_delete_attr(emit_t *emit, qstr qst) {
+    vtype_kind_t vtype_base;
+    emit_pre_pop_reg(emit, &vtype_base, REG_ARG_1); // arg1 = base
+    assert(vtype_base == VTYPE_PYOBJ);
+    ASM_XOR_REG_REG(emit->as, REG_ARG_3, REG_ARG_3); // arg3 = value (null for delete)
+    emit_call_with_qstr_arg(emit, MP_F_STORE_ATTR, qst, REG_ARG_2); // arg2 = attribute name
+    emit_post(emit);
+}
+
+STATIC void emit_native_delete_subscr(emit_t *emit) {
+    vtype_kind_t vtype_index, vtype_base;
+    emit_pre_pop_reg_reg(emit, &vtype_index, REG_ARG_2, &vtype_base, REG_ARG_1); // index, base
+    assert(vtype_index == VTYPE_PYOBJ);
+    assert(vtype_base == VTYPE_PYOBJ);
+    emit_call_with_imm_arg(emit, MP_F_OBJ_SUBSCR, (mp_uint_t)MP_OBJ_NULL, REG_ARG_3);
+}
+
+STATIC void emit_native_subscr(emit_t *emit, int kind) {
+    if (kind == MP_EMIT_SUBSCR_LOAD) {
+        emit_native_load_subscr(emit);
+    } else if (kind == MP_EMIT_SUBSCR_STORE) {
+        emit_native_store_subscr(emit);
+    } else {
+        emit_native_delete_subscr(emit);
+    }
+}
+
+STATIC void emit_native_attr(emit_t *emit, qstr qst, int kind) {
+    if (kind == MP_EMIT_ATTR_LOAD) {
+        emit_native_load_attr(emit, qst);
+    } else if (kind == MP_EMIT_ATTR_STORE) {
+        emit_native_store_attr(emit, qst);
+    } else {
+        emit_native_delete_attr(emit, qst);
+    }
+}
+
+STATIC void emit_native_dup_top(emit_t *emit) {
+    DEBUG_printf("dup_top\n");
+    vtype_kind_t vtype;
+    int reg = REG_TEMP0;
+    emit_pre_pop_reg_flexible(emit, &vtype, &reg, -1, -1);
+    emit_post_push_reg_reg(emit, vtype, reg, vtype, reg);
+}
+
+STATIC void emit_native_dup_top_two(emit_t *emit) {
+    vtype_kind_t vtype0, vtype1;
+    emit_pre_pop_reg_reg(emit, &vtype0, REG_TEMP0, &vtype1, REG_TEMP1);
+    emit_post_push_reg_reg_reg_reg(emit, vtype1, REG_TEMP1, vtype0, REG_TEMP0, vtype1, REG_TEMP1, vtype0, REG_TEMP0);
+}
+
+STATIC void emit_native_pop_top(emit_t *emit) {
+    DEBUG_printf("pop_top\n");
+    emit_pre_pop_discard(emit);
+    emit_post(emit);
+}
+
+STATIC void emit_native_rot_two(emit_t *emit) {
+    DEBUG_printf("rot_two\n");
+    vtype_kind_t vtype0, vtype1;
+    emit_pre_pop_reg_reg(emit, &vtype0, REG_TEMP0, &vtype1, REG_TEMP1);
+    emit_post_push_reg_reg(emit, vtype0, REG_TEMP0, vtype1, REG_TEMP1);
+}
+
+STATIC void emit_native_rot_three(emit_t *emit) {
+    DEBUG_printf("rot_three\n");
+    vtype_kind_t vtype0, vtype1, vtype2;
+    emit_pre_pop_reg_reg_reg(emit, &vtype0, REG_TEMP0, &vtype1, REG_TEMP1, &vtype2, REG_TEMP2);
+    emit_post_push_reg_reg_reg(emit, vtype0, REG_TEMP0, vtype2, REG_TEMP2, vtype1, REG_TEMP1);
+}
+
+STATIC void emit_native_jump(emit_t *emit, mp_uint_t label) {
+    DEBUG_printf("jump(label=" UINT_FMT ")\n", label);
+    emit_native_pre(emit);
+    // need to commit stack because we are jumping elsewhere
+    need_stack_settled(emit);
+    ASM_JUMP(emit->as, label);
+    emit_post(emit);
+}
+
+STATIC void emit_native_jump_helper(emit_t *emit, bool cond, mp_uint_t label, bool pop) {
+    vtype_kind_t vtype = peek_vtype(emit, 0);
+    if (vtype == VTYPE_PYOBJ) {
+        emit_pre_pop_reg(emit, &vtype, REG_ARG_1);
+        if (!pop) {
+            adjust_stack(emit, 1);
+        }
+        emit_call(emit, MP_F_OBJ_IS_TRUE);
+    } else {
+        emit_pre_pop_reg(emit, &vtype, REG_RET);
+        if (!pop) {
+            adjust_stack(emit, 1);
+        }
+        if (!(vtype == VTYPE_BOOL || vtype == VTYPE_INT || vtype == VTYPE_UINT)) {
+            EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+                MP_ERROR_TEXT("can't implicitly convert '%q' to 'bool'"), vtype_to_qstr(vtype));
+        }
+    }
+    // For non-pop need to save the vtype so that emit_native_adjust_stack_size
+    // can use it.  This is a bit of a hack.
+    if (!pop) {
+        emit->saved_stack_vtype = vtype;
+    }
+    // need to commit stack because we may jump elsewhere
+    need_stack_settled(emit);
+    // Emit the jump
+    if (cond) {
+        ASM_JUMP_IF_REG_NONZERO(emit->as, REG_RET, label, vtype == VTYPE_PYOBJ);
+    } else {
+        ASM_JUMP_IF_REG_ZERO(emit->as, REG_RET, label, vtype == VTYPE_PYOBJ);
+    }
+    if (!pop) {
+        adjust_stack(emit, -1);
+    }
+    emit_post(emit);
+}
+
+STATIC void emit_native_pop_jump_if(emit_t *emit, bool cond, mp_uint_t label) {
+    DEBUG_printf("pop_jump_if(cond=%u, label=" UINT_FMT ")\n", cond, label);
+    emit_native_jump_helper(emit, cond, label, true);
+}
+
+STATIC void emit_native_jump_if_or_pop(emit_t *emit, bool cond, mp_uint_t label) {
+    DEBUG_printf("jump_if_or_pop(cond=%u, label=" UINT_FMT ")\n", cond, label);
+    emit_native_jump_helper(emit, cond, label, false);
+}
+
+STATIC void emit_native_unwind_jump(emit_t *emit, mp_uint_t label, mp_uint_t except_depth) {
+    if (except_depth > 0) {
+        exc_stack_entry_t *first_finally = NULL;
+        exc_stack_entry_t *prev_finally = NULL;
+        exc_stack_entry_t *e = &emit->exc_stack[emit->exc_stack_size - 1];
+        for (; except_depth > 0; --except_depth, --e) {
+            if (e->is_finally && e->is_active) {
+                // Found an active finally handler
+                if (first_finally == NULL) {
+                    first_finally = e;
+                }
+                if (prev_finally != NULL) {
+                    // Mark prev finally as needed to unwind a jump
+                    prev_finally->unwind_label = e->label;
+                }
+                prev_finally = e;
+            }
+        }
+        if (prev_finally == NULL) {
+            // No finally, handle the jump ourselves
+            // First, restore the exception handler address for the jump
+            if (e < emit->exc_stack) {
+                ASM_XOR_REG_REG(emit->as, REG_RET, REG_RET);
+            } else {
+                ASM_MOV_REG_PCREL(emit->as, REG_RET, e->label);
+            }
+            ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_PC(emit), REG_RET);
+        } else {
+            // Last finally should do our jump for us
+            // Mark finally as needing to decide the type of jump
+            prev_finally->unwind_label = UNWIND_LABEL_DO_FINAL_UNWIND;
+            ASM_MOV_REG_PCREL(emit->as, REG_RET, label & ~MP_EMIT_BREAK_FROM_FOR);
+            ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_UNWIND(emit), REG_RET);
+            // Cancel any active exception (see also emit_native_pop_except_jump)
+            ASM_MOV_REG_IMM(emit->as, REG_RET, (mp_uint_t)MP_OBJ_NULL);
+            ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_VAL(emit), REG_RET);
+            // Jump to the innermost active finally
+            label = first_finally->label;
+        }
+    }
+    emit_native_jump(emit, label & ~MP_EMIT_BREAK_FROM_FOR);
+}
+
+STATIC void emit_native_setup_with(emit_t *emit, mp_uint_t label) {
+    // the context manager is on the top of the stack
+    // stack: (..., ctx_mgr)
+
+    // get __exit__ method
+    vtype_kind_t vtype;
+    emit_access_stack(emit, 1, &vtype, REG_ARG_1); // arg1 = ctx_mgr
+    assert(vtype == VTYPE_PYOBJ);
+    emit_get_stack_pointer_to_reg_for_push(emit, REG_ARG_3, 2); // arg3 = dest ptr
+    emit_call_with_qstr_arg(emit, MP_F_LOAD_METHOD, MP_QSTR___exit__, REG_ARG_2);
+    // stack: (..., ctx_mgr, __exit__, self)
+
+    emit_pre_pop_reg(emit, &vtype, REG_ARG_3); // self
+    emit_pre_pop_reg(emit, &vtype, REG_ARG_2); // __exit__
+    emit_pre_pop_reg(emit, &vtype, REG_ARG_1); // ctx_mgr
+    emit_post_push_reg(emit, vtype, REG_ARG_2); // __exit__
+    emit_post_push_reg(emit, vtype, REG_ARG_3); // self
+    // stack: (..., __exit__, self)
+    // REG_ARG_1=ctx_mgr
+
+    // get __enter__ method
+    emit_get_stack_pointer_to_reg_for_push(emit, REG_ARG_3, 2); // arg3 = dest ptr
+    emit_call_with_qstr_arg(emit, MP_F_LOAD_METHOD, MP_QSTR___enter__, REG_ARG_2); // arg2 = method name
+    // stack: (..., __exit__, self, __enter__, self)
+
+    // call __enter__ method
+    emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_3, 2); // pointer to items, including meth and self
+    emit_call_with_2_imm_args(emit, MP_F_CALL_METHOD_N_KW, 0, REG_ARG_1, 0, REG_ARG_2);
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET); // push return value of __enter__
+    // stack: (..., __exit__, self, as_value)
+
+    // need to commit stack because we may jump elsewhere
+    need_stack_settled(emit);
+    emit_native_push_exc_stack(emit, label, true);
+
+    emit_native_dup_top(emit);
+    // stack: (..., __exit__, self, as_value, as_value)
+}
+
+STATIC void emit_native_setup_block(emit_t *emit, mp_uint_t label, int kind) {
+    if (kind == MP_EMIT_SETUP_BLOCK_WITH) {
+        emit_native_setup_with(emit, label);
+    } else {
+        // Set up except and finally
+        emit_native_pre(emit);
+        need_stack_settled(emit);
+        emit_native_push_exc_stack(emit, label, kind == MP_EMIT_SETUP_BLOCK_FINALLY);
+        emit_post(emit);
+    }
+}
+
+STATIC void emit_native_with_cleanup(emit_t *emit, mp_uint_t label) {
+    // Note: 3 labels are reserved for this function, starting at *emit->label_slot
+
+    // stack: (..., __exit__, self, as_value)
+    emit_native_pre(emit);
+    emit_native_leave_exc_stack(emit, false);
+    adjust_stack(emit, -1);
+    // stack: (..., __exit__, self)
+
+    // Label for case where __exit__ is called from an unwind jump
+    emit_native_label_assign(emit, *emit->label_slot + 2);
+
+    // call __exit__
+    emit_post_push_imm(emit, VTYPE_PTR_NONE, 0);
+    emit_post_push_imm(emit, VTYPE_PTR_NONE, 0);
+    emit_post_push_imm(emit, VTYPE_PTR_NONE, 0);
+    emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_3, 5);
+    emit_call_with_2_imm_args(emit, MP_F_CALL_METHOD_N_KW, 3, REG_ARG_1, 0, REG_ARG_2);
+
+    // Replace exc with None and finish
+    emit_native_jump(emit, *emit->label_slot);
+
+    // nlr_catch
+    // Don't use emit_native_label_assign because this isn't a real finally label
+    mp_asm_base_label_assign(&emit->as->base, label);
+
+    // Leave with's exception handler
+    emit_native_leave_exc_stack(emit, true);
+
+    // Adjust stack counter for: __exit__, self (implicitly discard as_value which is above self)
+    emit_native_adjust_stack_size(emit, 2);
+    // stack: (..., __exit__, self)
+
+    ASM_MOV_REG_LOCAL(emit->as, REG_ARG_1, LOCAL_IDX_EXC_VAL(emit)); // get exc
+
+    // Check if exc is MP_OBJ_NULL (i.e. zero) and jump to non-exc handler if it is
+    ASM_JUMP_IF_REG_ZERO(emit->as, REG_ARG_1, *emit->label_slot + 2, false);
+
+    ASM_LOAD_REG_REG_OFFSET(emit->as, REG_ARG_2, REG_ARG_1, 0); // get type(exc)
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_ARG_2); // push type(exc)
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_ARG_1); // push exc value
+    emit_post_push_imm(emit, VTYPE_PTR_NONE, 0); // traceback info
+    // Stack: (..., __exit__, self, type(exc), exc, traceback)
+
+    // call __exit__ method
+    emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_3, 5);
+    emit_call_with_2_imm_args(emit, MP_F_CALL_METHOD_N_KW, 3, REG_ARG_1, 0, REG_ARG_2);
+    // Stack: (...)
+
+    // If REG_RET is true then we need to replace exception with None (swallow exception)
+    if (REG_ARG_1 != REG_RET) {
+        ASM_MOV_REG_REG(emit->as, REG_ARG_1, REG_RET);
+    }
+    emit_call(emit, MP_F_OBJ_IS_TRUE);
+    ASM_JUMP_IF_REG_ZERO(emit->as, REG_RET, *emit->label_slot + 1, true);
+
+    // Replace exception with MP_OBJ_NULL.
+    emit_native_label_assign(emit, *emit->label_slot);
+    ASM_MOV_REG_IMM(emit->as, REG_TEMP0, (mp_uint_t)MP_OBJ_NULL);
+    ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_VAL(emit), REG_TEMP0);
+
+    // end of with cleanup nlr_catch block
+    emit_native_label_assign(emit, *emit->label_slot + 1);
+
+    // Exception is in nlr_buf.ret_val slot
+}
+
+STATIC void emit_native_end_finally(emit_t *emit) {
+    // logic:
+    //   exc = pop_stack
+    //   if exc == None: pass
+    //   else: raise exc
+    // the check if exc is None is done in the MP_F_NATIVE_RAISE stub
+    emit_native_pre(emit);
+    ASM_MOV_REG_LOCAL(emit->as, REG_ARG_1, LOCAL_IDX_EXC_VAL(emit));
+    emit_call(emit, MP_F_NATIVE_RAISE);
+
+    // Get state for this finally and see if we need to unwind
+    exc_stack_entry_t *e = emit_native_pop_exc_stack(emit);
+    if (e->unwind_label != UNWIND_LABEL_UNUSED) {
+        ASM_MOV_REG_LOCAL(emit->as, REG_RET, LOCAL_IDX_EXC_HANDLER_UNWIND(emit));
+        ASM_JUMP_IF_REG_ZERO(emit->as, REG_RET, *emit->label_slot, false);
+        if (e->unwind_label == UNWIND_LABEL_DO_FINAL_UNWIND) {
+            ASM_JUMP_REG(emit->as, REG_RET);
+        } else {
+            emit_native_jump(emit, e->unwind_label);
+        }
+        emit_native_label_assign(emit, *emit->label_slot);
+    }
+
+    emit_post(emit);
+}
+
+STATIC void emit_native_get_iter(emit_t *emit, bool use_stack) {
+    // perhaps the difficult one, as we want to rewrite for loops using native code
+    // in cases where we iterate over a Python object, can we use normal runtime calls?
+
+    vtype_kind_t vtype;
+    emit_pre_pop_reg(emit, &vtype, REG_ARG_1);
+    assert(vtype == VTYPE_PYOBJ);
+    if (use_stack) {
+        emit_get_stack_pointer_to_reg_for_push(emit, REG_ARG_2, MP_OBJ_ITER_BUF_NSLOTS);
+        emit_call(emit, MP_F_NATIVE_GETITER);
+    } else {
+        // mp_getiter will allocate the iter_buf on the heap
+        ASM_MOV_REG_IMM(emit->as, REG_ARG_2, 0);
+        emit_call(emit, MP_F_NATIVE_GETITER);
+        emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+    }
+}
+
+STATIC void emit_native_for_iter(emit_t *emit, mp_uint_t label) {
+    emit_native_pre(emit);
+    emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_1, MP_OBJ_ITER_BUF_NSLOTS);
+    adjust_stack(emit, MP_OBJ_ITER_BUF_NSLOTS);
+    emit_call(emit, MP_F_NATIVE_ITERNEXT);
+    #if MICROPY_DEBUG_MP_OBJ_SENTINELS
+    ASM_MOV_REG_IMM(emit->as, REG_TEMP1, (mp_uint_t)MP_OBJ_STOP_ITERATION);
+    ASM_JUMP_IF_REG_EQ(emit->as, REG_RET, REG_TEMP1, label);
+    #else
+    MP_STATIC_ASSERT(MP_OBJ_STOP_ITERATION == 0);
+    ASM_JUMP_IF_REG_ZERO(emit->as, REG_RET, label, false);
+    #endif
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+}
+
+STATIC void emit_native_for_iter_end(emit_t *emit) {
+    // adjust stack counter (we get here from for_iter ending, which popped the value for us)
+    emit_native_pre(emit);
+    adjust_stack(emit, -MP_OBJ_ITER_BUF_NSLOTS);
+    emit_post(emit);
+}
+
+STATIC void emit_native_pop_except_jump(emit_t *emit, mp_uint_t label, bool within_exc_handler) {
+    if (within_exc_handler) {
+        // Cancel any active exception so subsequent handlers don't see it
+        ASM_MOV_REG_IMM(emit->as, REG_TEMP0, (mp_uint_t)MP_OBJ_NULL);
+        ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_VAL(emit), REG_TEMP0);
+    } else {
+        emit_native_leave_exc_stack(emit, false);
+    }
+    emit_native_jump(emit, label);
+}
+
+STATIC void emit_native_unary_op(emit_t *emit, mp_unary_op_t op) {
+    vtype_kind_t vtype;
+    emit_pre_pop_reg(emit, &vtype, REG_ARG_2);
+    if (vtype == VTYPE_PYOBJ) {
+        emit_call_with_imm_arg(emit, MP_F_UNARY_OP, op, REG_ARG_1);
+        emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+    } else {
+        adjust_stack(emit, 1);
+        EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+            MP_ERROR_TEXT("unary op %q not implemented"), mp_unary_op_method_name[op]);
+    }
+}
+
+STATIC void emit_native_binary_op(emit_t *emit, mp_binary_op_t op) {
+    DEBUG_printf("binary_op(" UINT_FMT ")\n", op);
+    vtype_kind_t vtype_lhs = peek_vtype(emit, 1);
+    vtype_kind_t vtype_rhs = peek_vtype(emit, 0);
+    if ((vtype_lhs == VTYPE_INT || vtype_lhs == VTYPE_UINT)
+        && (vtype_rhs == VTYPE_INT || vtype_rhs == VTYPE_UINT)) {
+        // for integers, inplace and normal ops are equivalent, so use just normal ops
+        if (MP_BINARY_OP_INPLACE_OR <= op && op <= MP_BINARY_OP_INPLACE_POWER) {
+            op += MP_BINARY_OP_OR - MP_BINARY_OP_INPLACE_OR;
+        }
+
+        #if N_X64 || N_X86
+        // special cases for x86 and shifting
+        if (op == MP_BINARY_OP_LSHIFT || op == MP_BINARY_OP_RSHIFT) {
+            #if N_X64
+            emit_pre_pop_reg_reg(emit, &vtype_rhs, ASM_X64_REG_RCX, &vtype_lhs, REG_RET);
+            #else
+            emit_pre_pop_reg_reg(emit, &vtype_rhs, ASM_X86_REG_ECX, &vtype_lhs, REG_RET);
+            #endif
+            if (op == MP_BINARY_OP_LSHIFT) {
+                ASM_LSL_REG(emit->as, REG_RET);
+            } else {
+                if (vtype_lhs == VTYPE_UINT) {
+                    ASM_LSR_REG(emit->as, REG_RET);
+                } else {
+                    ASM_ASR_REG(emit->as, REG_RET);
+                }
+            }
+            emit_post_push_reg(emit, vtype_lhs, REG_RET);
+            return;
+        }
+        #endif
+
+        // special cases for floor-divide and module because we dispatch to helper functions
+        if (op == MP_BINARY_OP_FLOOR_DIVIDE || op == MP_BINARY_OP_MODULO) {
+            emit_pre_pop_reg_reg(emit, &vtype_rhs, REG_ARG_2, &vtype_lhs, REG_ARG_1);
+            if (vtype_lhs != VTYPE_INT) {
+                EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+                    MP_ERROR_TEXT("div/mod not implemented for uint"), mp_binary_op_method_name[op]);
+            }
+            if (op == MP_BINARY_OP_FLOOR_DIVIDE) {
+                emit_call(emit, MP_F_SMALL_INT_FLOOR_DIVIDE);
+            } else {
+                emit_call(emit, MP_F_SMALL_INT_MODULO);
+            }
+            emit_post_push_reg(emit, VTYPE_INT, REG_RET);
+            return;
+        }
+
+        int reg_rhs = REG_ARG_3;
+        emit_pre_pop_reg_flexible(emit, &vtype_rhs, &reg_rhs, REG_RET, REG_ARG_2);
+        emit_pre_pop_reg(emit, &vtype_lhs, REG_ARG_2);
+
+        #if !(N_X64 || N_X86)
+        if (op == MP_BINARY_OP_LSHIFT || op == MP_BINARY_OP_RSHIFT) {
+            if (op == MP_BINARY_OP_LSHIFT) {
+                ASM_LSL_REG_REG(emit->as, REG_ARG_2, reg_rhs);
+            } else {
+                if (vtype_lhs == VTYPE_UINT) {
+                    ASM_LSR_REG_REG(emit->as, REG_ARG_2, reg_rhs);
+                } else {
+                    ASM_ASR_REG_REG(emit->as, REG_ARG_2, reg_rhs);
+                }
+            }
+            emit_post_push_reg(emit, vtype_lhs, REG_ARG_2);
+            return;
+        }
+        #endif
+
+        if (op == MP_BINARY_OP_OR) {
+            ASM_OR_REG_REG(emit->as, REG_ARG_2, reg_rhs);
+            emit_post_push_reg(emit, vtype_lhs, REG_ARG_2);
+        } else if (op == MP_BINARY_OP_XOR) {
+            ASM_XOR_REG_REG(emit->as, REG_ARG_2, reg_rhs);
+            emit_post_push_reg(emit, vtype_lhs, REG_ARG_2);
+        } else if (op == MP_BINARY_OP_AND) {
+            ASM_AND_REG_REG(emit->as, REG_ARG_2, reg_rhs);
+            emit_post_push_reg(emit, vtype_lhs, REG_ARG_2);
+        } else if (op == MP_BINARY_OP_ADD) {
+            ASM_ADD_REG_REG(emit->as, REG_ARG_2, reg_rhs);
+            emit_post_push_reg(emit, vtype_lhs, REG_ARG_2);
+        } else if (op == MP_BINARY_OP_SUBTRACT) {
+            ASM_SUB_REG_REG(emit->as, REG_ARG_2, reg_rhs);
+            emit_post_push_reg(emit, vtype_lhs, REG_ARG_2);
+        } else if (op == MP_BINARY_OP_MULTIPLY) {
+            ASM_MUL_REG_REG(emit->as, REG_ARG_2, reg_rhs);
+            emit_post_push_reg(emit, vtype_lhs, REG_ARG_2);
+        } else if (MP_BINARY_OP_LESS <= op && op <= MP_BINARY_OP_NOT_EQUAL) {
+            // comparison ops are (in enum order):
+            //  MP_BINARY_OP_LESS
+            //  MP_BINARY_OP_MORE
+            //  MP_BINARY_OP_EQUAL
+            //  MP_BINARY_OP_LESS_EQUAL
+            //  MP_BINARY_OP_MORE_EQUAL
+            //  MP_BINARY_OP_NOT_EQUAL
+
+            if (vtype_lhs != vtype_rhs) {
+                EMIT_NATIVE_VIPER_TYPE_ERROR(emit, MP_ERROR_TEXT("comparison of int and uint"));
+            }
+
+            size_t op_idx = op - MP_BINARY_OP_LESS + (vtype_lhs == VTYPE_UINT ? 0 : 6);
+
+            need_reg_single(emit, REG_RET, 0);
+            #if N_X64
+            asm_x64_xor_r64_r64(emit->as, REG_RET, REG_RET);
+            asm_x64_cmp_r64_with_r64(emit->as, reg_rhs, REG_ARG_2);
+            static byte ops[6 + 6] = {
+                // unsigned
+                ASM_X64_CC_JB,
+                ASM_X64_CC_JA,
+                ASM_X64_CC_JE,
+                ASM_X64_CC_JBE,
+                ASM_X64_CC_JAE,
+                ASM_X64_CC_JNE,
+                // signed
+                ASM_X64_CC_JL,
+                ASM_X64_CC_JG,
+                ASM_X64_CC_JE,
+                ASM_X64_CC_JLE,
+                ASM_X64_CC_JGE,
+                ASM_X64_CC_JNE,
+            };
+            asm_x64_setcc_r8(emit->as, ops[op_idx], REG_RET);
+            #elif N_X86
+            asm_x86_xor_r32_r32(emit->as, REG_RET, REG_RET);
+            asm_x86_cmp_r32_with_r32(emit->as, reg_rhs, REG_ARG_2);
+            static byte ops[6 + 6] = {
+                // unsigned
+                ASM_X86_CC_JB,
+                ASM_X86_CC_JA,
+                ASM_X86_CC_JE,
+                ASM_X86_CC_JBE,
+                ASM_X86_CC_JAE,
+                ASM_X86_CC_JNE,
+                // signed
+                ASM_X86_CC_JL,
+                ASM_X86_CC_JG,
+                ASM_X86_CC_JE,
+                ASM_X86_CC_JLE,
+                ASM_X86_CC_JGE,
+                ASM_X86_CC_JNE,
+            };
+            asm_x86_setcc_r8(emit->as, ops[op_idx], REG_RET);
+            #elif N_THUMB
+            asm_thumb_cmp_rlo_rlo(emit->as, REG_ARG_2, reg_rhs);
+            #if MICROPY_EMIT_THUMB_ARMV7M
+            static uint16_t ops[6 + 6] = {
+                // unsigned
+                ASM_THUMB_OP_ITE_CC,
+                ASM_THUMB_OP_ITE_HI,
+                ASM_THUMB_OP_ITE_EQ,
+                ASM_THUMB_OP_ITE_LS,
+                ASM_THUMB_OP_ITE_CS,
+                ASM_THUMB_OP_ITE_NE,
+                // signed
+                ASM_THUMB_OP_ITE_LT,
+                ASM_THUMB_OP_ITE_GT,
+                ASM_THUMB_OP_ITE_EQ,
+                ASM_THUMB_OP_ITE_LE,
+                ASM_THUMB_OP_ITE_GE,
+                ASM_THUMB_OP_ITE_NE,
+            };
+            asm_thumb_op16(emit->as, ops[op_idx]);
+            asm_thumb_mov_rlo_i8(emit->as, REG_RET, 1);
+            asm_thumb_mov_rlo_i8(emit->as, REG_RET, 0);
+            #else
+            static uint16_t ops[6 + 6] = {
+                // unsigned
+                ASM_THUMB_CC_CC,
+                ASM_THUMB_CC_HI,
+                ASM_THUMB_CC_EQ,
+                ASM_THUMB_CC_LS,
+                ASM_THUMB_CC_CS,
+                ASM_THUMB_CC_NE,
+                // signed
+                ASM_THUMB_CC_LT,
+                ASM_THUMB_CC_GT,
+                ASM_THUMB_CC_EQ,
+                ASM_THUMB_CC_LE,
+                ASM_THUMB_CC_GE,
+                ASM_THUMB_CC_NE,
+            };
+            asm_thumb_bcc_rel9(emit->as, ops[op_idx], 6);
+            asm_thumb_mov_rlo_i8(emit->as, REG_RET, 0);
+            asm_thumb_b_rel12(emit->as, 4);
+            asm_thumb_mov_rlo_i8(emit->as, REG_RET, 1);
+            #endif
+            #elif N_ARM
+            asm_arm_cmp_reg_reg(emit->as, REG_ARG_2, reg_rhs);
+            static uint ccs[6 + 6] = {
+                // unsigned
+                ASM_ARM_CC_CC,
+                ASM_ARM_CC_HI,
+                ASM_ARM_CC_EQ,
+                ASM_ARM_CC_LS,
+                ASM_ARM_CC_CS,
+                ASM_ARM_CC_NE,
+                // signed
+                ASM_ARM_CC_LT,
+                ASM_ARM_CC_GT,
+                ASM_ARM_CC_EQ,
+                ASM_ARM_CC_LE,
+                ASM_ARM_CC_GE,
+                ASM_ARM_CC_NE,
+            };
+            asm_arm_setcc_reg(emit->as, REG_RET, ccs[op_idx]);
+            #elif N_XTENSA || N_XTENSAWIN
+            static uint8_t ccs[6 + 6] = {
+                // unsigned
+                ASM_XTENSA_CC_LTU,
+                0x80 | ASM_XTENSA_CC_LTU, // for GTU we'll swap args
+                ASM_XTENSA_CC_EQ,
+                0x80 | ASM_XTENSA_CC_GEU, // for LEU we'll swap args
+                ASM_XTENSA_CC_GEU,
+                ASM_XTENSA_CC_NE,
+                // signed
+                ASM_XTENSA_CC_LT,
+                0x80 | ASM_XTENSA_CC_LT, // for GT we'll swap args
+                ASM_XTENSA_CC_EQ,
+                0x80 | ASM_XTENSA_CC_GE, // for LE we'll swap args
+                ASM_XTENSA_CC_GE,
+                ASM_XTENSA_CC_NE,
+            };
+            uint8_t cc = ccs[op_idx];
+            if ((cc & 0x80) == 0) {
+                asm_xtensa_setcc_reg_reg_reg(emit->as, cc, REG_RET, REG_ARG_2, reg_rhs);
+            } else {
+                asm_xtensa_setcc_reg_reg_reg(emit->as, cc & ~0x80, REG_RET, reg_rhs, REG_ARG_2);
+            }
+            #else
+            #error not implemented
+            #endif
+            emit_post_push_reg(emit, VTYPE_BOOL, REG_RET);
+        } else {
+            // TODO other ops not yet implemented
+            adjust_stack(emit, 1);
+            EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+                MP_ERROR_TEXT("binary op %q not implemented"), mp_binary_op_method_name[op]);
+        }
+    } else if (vtype_lhs == VTYPE_PYOBJ && vtype_rhs == VTYPE_PYOBJ) {
+        emit_pre_pop_reg_reg(emit, &vtype_rhs, REG_ARG_3, &vtype_lhs, REG_ARG_2);
+        bool invert = false;
+        if (op == MP_BINARY_OP_NOT_IN) {
+            invert = true;
+            op = MP_BINARY_OP_IN;
+        } else if (op == MP_BINARY_OP_IS_NOT) {
+            invert = true;
+            op = MP_BINARY_OP_IS;
+        }
+        emit_call_with_imm_arg(emit, MP_F_BINARY_OP, op, REG_ARG_1);
+        if (invert) {
+            ASM_MOV_REG_REG(emit->as, REG_ARG_2, REG_RET);
+            emit_call_with_imm_arg(emit, MP_F_UNARY_OP, MP_UNARY_OP_NOT, REG_ARG_1);
+        }
+        emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+    } else {
+        adjust_stack(emit, -1);
+        EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+            MP_ERROR_TEXT("can't do binary op between '%q' and '%q'"),
+            vtype_to_qstr(vtype_lhs), vtype_to_qstr(vtype_rhs));
+    }
+}
+
+#if MICROPY_PY_BUILTINS_SLICE
+STATIC void emit_native_build_slice(emit_t *emit, mp_uint_t n_args);
+#endif
+
+STATIC void emit_native_build(emit_t *emit, mp_uint_t n_args, int kind) {
+    // for viper: call runtime, with types of args
+    //   if wrapped in byte_array, or something, allocates memory and fills it
+    MP_STATIC_ASSERT(MP_F_BUILD_TUPLE + MP_EMIT_BUILD_TUPLE == MP_F_BUILD_TUPLE);
+    MP_STATIC_ASSERT(MP_F_BUILD_TUPLE + MP_EMIT_BUILD_LIST == MP_F_BUILD_LIST);
+    MP_STATIC_ASSERT(MP_F_BUILD_TUPLE + MP_EMIT_BUILD_MAP == MP_F_BUILD_MAP);
+    MP_STATIC_ASSERT(MP_F_BUILD_TUPLE + MP_EMIT_BUILD_SET == MP_F_BUILD_SET);
+    #if MICROPY_PY_BUILTINS_SLICE
+    if (kind == MP_EMIT_BUILD_SLICE) {
+        emit_native_build_slice(emit, n_args);
+        return;
+    }
+    #endif
+    emit_native_pre(emit);
+    if (kind == MP_EMIT_BUILD_TUPLE || kind == MP_EMIT_BUILD_LIST || kind == MP_EMIT_BUILD_SET) {
+        emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_2, n_args); // pointer to items
+    }
+    emit_call_with_imm_arg(emit, MP_F_BUILD_TUPLE + kind, n_args, REG_ARG_1);
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET); // new tuple/list/map/set
+}
+
+STATIC void emit_native_store_map(emit_t *emit) {
+    vtype_kind_t vtype_key, vtype_value, vtype_map;
+    emit_pre_pop_reg_reg_reg(emit, &vtype_key, REG_ARG_2, &vtype_value, REG_ARG_3, &vtype_map, REG_ARG_1); // key, value, map
+    assert(vtype_key == VTYPE_PYOBJ);
+    assert(vtype_value == VTYPE_PYOBJ);
+    assert(vtype_map == VTYPE_PYOBJ);
+    emit_call(emit, MP_F_STORE_MAP);
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET); // map
+}
+
+#if MICROPY_PY_BUILTINS_SLICE
+STATIC void emit_native_build_slice(emit_t *emit, mp_uint_t n_args) {
+    DEBUG_printf("build_slice %d\n", n_args);
+    if (n_args == 2) {
+        vtype_kind_t vtype_start, vtype_stop;
+        emit_pre_pop_reg_reg(emit, &vtype_stop, REG_ARG_2, &vtype_start, REG_ARG_1); // arg1 = start, arg2 = stop
+        assert(vtype_start == VTYPE_PYOBJ);
+        assert(vtype_stop == VTYPE_PYOBJ);
+        emit_native_mov_reg_const(emit, REG_ARG_3, MP_F_CONST_NONE_OBJ); // arg3 = step
+    } else {
+        assert(n_args == 3);
+        vtype_kind_t vtype_start, vtype_stop, vtype_step;
+        emit_pre_pop_reg_reg_reg(emit, &vtype_step, REG_ARG_3, &vtype_stop, REG_ARG_2, &vtype_start, REG_ARG_1); // arg1 = start, arg2 = stop, arg3 = step
+        assert(vtype_start == VTYPE_PYOBJ);
+        assert(vtype_stop == VTYPE_PYOBJ);
+        assert(vtype_step == VTYPE_PYOBJ);
+    }
+    emit_call(emit, MP_F_NEW_SLICE);
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+}
+#endif
+
+STATIC void emit_native_store_comp(emit_t *emit, scope_kind_t kind, mp_uint_t collection_index) {
+    mp_fun_kind_t f;
+    if (kind == SCOPE_LIST_COMP) {
+        vtype_kind_t vtype_item;
+        emit_pre_pop_reg(emit, &vtype_item, REG_ARG_2);
+        assert(vtype_item == VTYPE_PYOBJ);
+        f = MP_F_LIST_APPEND;
+    #if MICROPY_PY_BUILTINS_SET
+    } else if (kind == SCOPE_SET_COMP) {
+        vtype_kind_t vtype_item;
+        emit_pre_pop_reg(emit, &vtype_item, REG_ARG_2);
+        assert(vtype_item == VTYPE_PYOBJ);
+        f = MP_F_STORE_SET;
+    #endif
+    } else {
+        // SCOPE_DICT_COMP
+        vtype_kind_t vtype_key, vtype_value;
+        emit_pre_pop_reg_reg(emit, &vtype_key, REG_ARG_2, &vtype_value, REG_ARG_3);
+        assert(vtype_key == VTYPE_PYOBJ);
+        assert(vtype_value == VTYPE_PYOBJ);
+        f = MP_F_STORE_MAP;
+    }
+    vtype_kind_t vtype_collection;
+    emit_access_stack(emit, collection_index, &vtype_collection, REG_ARG_1);
+    assert(vtype_collection == VTYPE_PYOBJ);
+    emit_call(emit, f);
+    emit_post(emit);
+}
+
+STATIC void emit_native_unpack_sequence(emit_t *emit, mp_uint_t n_args) {
+    DEBUG_printf("unpack_sequence %d\n", n_args);
+    vtype_kind_t vtype_base;
+    emit_pre_pop_reg(emit, &vtype_base, REG_ARG_1); // arg1 = seq
+    assert(vtype_base == VTYPE_PYOBJ);
+    emit_get_stack_pointer_to_reg_for_push(emit, REG_ARG_3, n_args); // arg3 = dest ptr
+    emit_call_with_imm_arg(emit, MP_F_UNPACK_SEQUENCE, n_args, REG_ARG_2); // arg2 = n_args
+}
+
+STATIC void emit_native_unpack_ex(emit_t *emit, mp_uint_t n_left, mp_uint_t n_right) {
+    DEBUG_printf("unpack_ex %d %d\n", n_left, n_right);
+    vtype_kind_t vtype_base;
+    emit_pre_pop_reg(emit, &vtype_base, REG_ARG_1); // arg1 = seq
+    assert(vtype_base == VTYPE_PYOBJ);
+    emit_get_stack_pointer_to_reg_for_push(emit, REG_ARG_3, n_left + n_right + 1); // arg3 = dest ptr
+    emit_call_with_imm_arg(emit, MP_F_UNPACK_EX, n_left | (n_right << 8), REG_ARG_2); // arg2 = n_left + n_right
+}
+
+STATIC void emit_native_make_function(emit_t *emit, scope_t *scope, mp_uint_t n_pos_defaults, mp_uint_t n_kw_defaults) {
+    // call runtime, with type info for args, or don't support dict/default params, or only support Python objects for them
+    emit_native_pre(emit);
+    if (n_pos_defaults == 0 && n_kw_defaults == 0) {
+        need_reg_all(emit);
+        ASM_MOV_REG_IMM(emit->as, REG_ARG_2, (mp_uint_t)MP_OBJ_NULL);
+        ASM_MOV_REG_IMM(emit->as, REG_ARG_3, (mp_uint_t)MP_OBJ_NULL);
+    } else {
+        vtype_kind_t vtype_def_tuple, vtype_def_dict;
+        emit_pre_pop_reg_reg(emit, &vtype_def_dict, REG_ARG_3, &vtype_def_tuple, REG_ARG_2);
+        assert(vtype_def_tuple == VTYPE_PYOBJ);
+        assert(vtype_def_dict == VTYPE_PYOBJ);
+        need_reg_all(emit);
+    }
+    emit_load_reg_with_raw_code(emit, REG_ARG_1, scope->raw_code);
+    ASM_CALL_IND(emit->as, MP_F_MAKE_FUNCTION_FROM_RAW_CODE);
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+}
+
+STATIC void emit_native_make_closure(emit_t *emit, scope_t *scope, mp_uint_t n_closed_over, mp_uint_t n_pos_defaults, mp_uint_t n_kw_defaults) {
+    emit_native_pre(emit);
+    if (n_pos_defaults == 0 && n_kw_defaults == 0) {
+        emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_3, n_closed_over);
+        ASM_MOV_REG_IMM(emit->as, REG_ARG_2, n_closed_over);
+    } else {
+        emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_3, n_closed_over + 2);
+        ASM_MOV_REG_IMM(emit->as, REG_ARG_2, 0x100 | n_closed_over);
+    }
+    emit_load_reg_with_raw_code(emit, REG_ARG_1, scope->raw_code);
+    ASM_CALL_IND(emit->as, MP_F_MAKE_CLOSURE_FROM_RAW_CODE);
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+}
+
+STATIC void emit_native_call_function(emit_t *emit, mp_uint_t n_positional, mp_uint_t n_keyword, mp_uint_t star_flags) {
+    DEBUG_printf("call_function(n_pos=" UINT_FMT ", n_kw=" UINT_FMT ", star_flags=" UINT_FMT ")\n", n_positional, n_keyword, star_flags);
+
+    // TODO: in viper mode, call special runtime routine with type info for args,
+    // and wanted type info for return, to remove need for boxing/unboxing
+
+    emit_native_pre(emit);
+    vtype_kind_t vtype_fun = peek_vtype(emit, n_positional + 2 * n_keyword);
+    if (vtype_fun == VTYPE_BUILTIN_CAST) {
+        // casting operator
+        assert(n_positional == 1 && n_keyword == 0);
+        assert(!star_flags);
+        DEBUG_printf("  cast to %d\n", vtype_fun);
+        vtype_kind_t vtype_cast = peek_stack(emit, 1)->data.u_imm;
+        switch (peek_vtype(emit, 0)) {
+            case VTYPE_PYOBJ: {
+                vtype_kind_t vtype;
+                emit_pre_pop_reg(emit, &vtype, REG_ARG_1);
+                emit_pre_pop_discard(emit);
+                emit_call_with_imm_arg(emit, MP_F_CONVERT_OBJ_TO_NATIVE, vtype_cast, REG_ARG_2); // arg2 = type
+                emit_post_push_reg(emit, vtype_cast, REG_RET);
+                break;
+            }
+            case VTYPE_BOOL:
+            case VTYPE_INT:
+            case VTYPE_UINT:
+            case VTYPE_PTR:
+            case VTYPE_PTR8:
+            case VTYPE_PTR16:
+            case VTYPE_PTR32:
+            case VTYPE_PTR_NONE:
+                emit_fold_stack_top(emit, REG_ARG_1);
+                emit_post_top_set_vtype(emit, vtype_cast);
+                break;
+            default:
+                // this can happen when casting a cast: int(int)
+                mp_raise_NotImplementedError(MP_ERROR_TEXT("casting"));
+        }
+    } else {
+        assert(vtype_fun == VTYPE_PYOBJ);
+        if (star_flags) {
+            emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_3, n_positional + 2 * n_keyword + 3); // pointer to args
+            emit_call_with_2_imm_args(emit, MP_F_CALL_METHOD_N_KW_VAR, 0, REG_ARG_1, n_positional | (n_keyword << 8), REG_ARG_2);
+            emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+        } else {
+            if (n_positional != 0 || n_keyword != 0) {
+                emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_3, n_positional + 2 * n_keyword); // pointer to args
+            }
+            emit_pre_pop_reg(emit, &vtype_fun, REG_ARG_1); // the function
+            emit_call_with_imm_arg(emit, MP_F_NATIVE_CALL_FUNCTION_N_KW, n_positional | (n_keyword << 8), REG_ARG_2);
+            emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+        }
+    }
+}
+
+STATIC void emit_native_call_method(emit_t *emit, mp_uint_t n_positional, mp_uint_t n_keyword, mp_uint_t star_flags) {
+    if (star_flags) {
+        emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_3, n_positional + 2 * n_keyword + 4); // pointer to args
+        emit_call_with_2_imm_args(emit, MP_F_CALL_METHOD_N_KW_VAR, 1, REG_ARG_1, n_positional | (n_keyword << 8), REG_ARG_2);
+        emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+    } else {
+        emit_native_pre(emit);
+        emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_3, 2 + n_positional + 2 * n_keyword); // pointer to items, including meth and self
+        emit_call_with_2_imm_args(emit, MP_F_CALL_METHOD_N_KW, n_positional, REG_ARG_1, n_keyword, REG_ARG_2);
+        emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
+    }
+}
+
+STATIC void emit_native_return_value(emit_t *emit) {
+    DEBUG_printf("return_value\n");
+
+    if (emit->scope->scope_flags & MP_SCOPE_FLAG_GENERATOR) {
+        // Save pointer to current stack position for caller to access return value
+        emit_get_stack_pointer_to_reg_for_pop(emit, REG_TEMP0, 1);
+        emit_native_mov_state_reg(emit, OFFSETOF_CODE_STATE_SP, REG_TEMP0);
+
+        // Put return type in return value slot
+        ASM_MOV_REG_IMM(emit->as, REG_TEMP0, MP_VM_RETURN_NORMAL);
+        ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_RET_VAL(emit), REG_TEMP0);
+
+        // Do the unwinding jump to get to the return handler
+        emit_native_unwind_jump(emit, emit->exit_label, emit->exc_stack_size);
+        emit->last_emit_was_return_value = true;
+        return;
+    }
+
+    if (emit->do_viper_types) {
+        vtype_kind_t return_vtype = emit->scope->scope_flags >> MP_SCOPE_FLAG_VIPERRET_POS;
+        if (peek_vtype(emit, 0) == VTYPE_PTR_NONE) {
+            emit_pre_pop_discard(emit);
+            if (return_vtype == VTYPE_PYOBJ) {
+                emit_native_mov_reg_const(emit, REG_PARENT_RET, MP_F_CONST_NONE_OBJ);
+            } else {
+                ASM_MOV_REG_IMM(emit->as, REG_ARG_1, 0);
+            }
+        } else {
+            vtype_kind_t vtype;
+            emit_pre_pop_reg(emit, &vtype, return_vtype == VTYPE_PYOBJ ? REG_PARENT_RET : REG_ARG_1);
+            if (vtype != return_vtype) {
+                EMIT_NATIVE_VIPER_TYPE_ERROR(emit,
+                    MP_ERROR_TEXT("return expected '%q' but got '%q'"),
+                    vtype_to_qstr(return_vtype), vtype_to_qstr(vtype));
+            }
+        }
+        if (return_vtype != VTYPE_PYOBJ) {
+            emit_call_with_imm_arg(emit, MP_F_CONVERT_NATIVE_TO_OBJ, return_vtype, REG_ARG_2);
+            #if REG_RET != REG_PARENT_RET
+            ASM_MOV_REG_REG(emit->as, REG_PARENT_RET, REG_RET);
+            #endif
+        }
+    } else {
+        vtype_kind_t vtype;
+        emit_pre_pop_reg(emit, &vtype, REG_PARENT_RET);
+        assert(vtype == VTYPE_PYOBJ);
+    }
+    if (NEED_GLOBAL_EXC_HANDLER(emit)) {
+        // Save return value for the global exception handler to use
+        ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_RET_VAL(emit), REG_PARENT_RET);
+    }
+    emit_native_unwind_jump(emit, emit->exit_label, emit->exc_stack_size);
+    emit->last_emit_was_return_value = true;
+}
+
+STATIC void emit_native_raise_varargs(emit_t *emit, mp_uint_t n_args) {
+    (void)n_args;
+    assert(n_args == 1);
+    vtype_kind_t vtype_exc;
+    emit_pre_pop_reg(emit, &vtype_exc, REG_ARG_1); // arg1 = object to raise
+    if (vtype_exc != VTYPE_PYOBJ) {
+        EMIT_NATIVE_VIPER_TYPE_ERROR(emit, MP_ERROR_TEXT("must raise an object"));
+    }
+    // TODO probably make this 1 call to the runtime (which could even call convert, native_raise(obj, type))
+    emit_call(emit, MP_F_NATIVE_RAISE);
+}
+
+STATIC void emit_native_yield(emit_t *emit, int kind) {
+    // Note: 1 (yield) or 3 (yield from) labels are reserved for this function, starting at *emit->label_slot
+
+    if (emit->do_viper_types) {
+        mp_raise_NotImplementedError(MP_ERROR_TEXT("native yield"));
+    }
+    emit->scope->scope_flags |= MP_SCOPE_FLAG_GENERATOR;
+
+    need_stack_settled(emit);
+
+    if (kind == MP_EMIT_YIELD_FROM) {
+
+        // Top of yield-from loop, conceptually implementing:
+        //     for item in generator:
+        //         yield item
+
+        // Jump to start of loop
+        emit_native_jump(emit, *emit->label_slot + 2);
+
+        // Label for top of loop
+        emit_native_label_assign(emit, *emit->label_slot + 1);
+    }
+
+    // Save pointer to current stack position for caller to access yielded value
+    emit_get_stack_pointer_to_reg_for_pop(emit, REG_TEMP0, 1);
+    emit_native_mov_state_reg(emit, OFFSETOF_CODE_STATE_SP, REG_TEMP0);
+
+    // Put return type in return value slot
+    ASM_MOV_REG_IMM(emit->as, REG_TEMP0, MP_VM_RETURN_YIELD);
+    ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_RET_VAL(emit), REG_TEMP0);
+
+    // Save re-entry PC
+    ASM_MOV_REG_PCREL(emit->as, REG_TEMP0, *emit->label_slot);
+    emit_native_mov_state_reg(emit, LOCAL_IDX_GEN_PC(emit), REG_TEMP0);
+
+    // Jump to exit handler
+    ASM_JUMP(emit->as, emit->exit_label);
+
+    // Label re-entry point
+    mp_asm_base_label_assign(&emit->as->base, *emit->label_slot);
+
+    // Re-open any active exception handler
+    if (emit->exc_stack_size > 0) {
+        // Find innermost active exception handler, to restore as current handler
+        exc_stack_entry_t *e = &emit->exc_stack[emit->exc_stack_size - 1];
+        for (; e >= emit->exc_stack; --e) {
+            if (e->is_active) {
+                // Found active handler, get its PC
+                ASM_MOV_REG_PCREL(emit->as, REG_RET, e->label);
+                ASM_MOV_LOCAL_REG(emit->as, LOCAL_IDX_EXC_HANDLER_PC(emit), REG_RET);
+                break;
+            }
+        }
+    }
+
+    emit_native_adjust_stack_size(emit, 1); // send_value
+
+    if (kind == MP_EMIT_YIELD_VALUE) {
+        // Check LOCAL_IDX_EXC_VAL for any injected value
+        ASM_MOV_REG_LOCAL(emit->as, REG_ARG_1, LOCAL_IDX_EXC_VAL(emit));
+        emit_call(emit, MP_F_NATIVE_RAISE);
+    } else {
+        // Label loop entry
+        emit_native_label_assign(emit, *emit->label_slot + 2);
+
+        // Get the next item from the delegate generator
+        vtype_kind_t vtype;
+        emit_pre_pop_reg(emit, &vtype, REG_ARG_2); // send_value
+        emit_access_stack(emit, 1, &vtype, REG_ARG_1); // generator
+        ASM_MOV_REG_LOCAL(emit->as, REG_ARG_3, LOCAL_IDX_EXC_VAL(emit)); // throw_value
+        emit_post_push_reg(emit, VTYPE_PYOBJ, REG_ARG_3);
+        emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_3, 1); // ret_value
+        emit_call(emit, MP_F_NATIVE_YIELD_FROM);
+
+        // If returned non-zero then generator continues
+        ASM_JUMP_IF_REG_NONZERO(emit->as, REG_RET, *emit->label_slot + 1, true);
+
+        // Pop exhausted gen, replace with ret_value
+        emit_native_adjust_stack_size(emit, 1); // ret_value
+        emit_fold_stack_top(emit, REG_ARG_1);
+    }
+}
+
+STATIC void emit_native_start_except_handler(emit_t *emit) {
+    // Protected block has finished so leave the current exception handler
+    emit_native_leave_exc_stack(emit, true);
+
+    // Get and push nlr_buf.ret_val
+    ASM_MOV_REG_LOCAL(emit->as, REG_TEMP0, LOCAL_IDX_EXC_VAL(emit));
+    emit_post_push_reg(emit, VTYPE_PYOBJ, REG_TEMP0);
+}
+
+STATIC void emit_native_end_except_handler(emit_t *emit) {
+    adjust_stack(emit, -1); // pop the exception (end_finally didn't use it)
+}
+
+const emit_method_table_t EXPORT_FUN(method_table) = {
+    #if MICROPY_DYNAMIC_COMPILER
+    EXPORT_FUN(new),
+    EXPORT_FUN(free),
+    #endif
+
+    emit_native_start_pass,
+    emit_native_end_pass,
+    emit_native_last_emit_was_return_value,
+    emit_native_adjust_stack_size,
+    emit_native_set_source_line,
+
+    {
+        emit_native_load_local,
+        emit_native_load_global,
+    },
+    {
+        emit_native_store_local,
+        emit_native_store_global,
+    },
+    {
+        emit_native_delete_local,
+        emit_native_delete_global,
+    },
+
+    emit_native_label_assign,
+    emit_native_import,
+    emit_native_load_const_tok,
+    emit_native_load_const_small_int,
+    emit_native_load_const_str,
+    emit_native_load_const_obj,
+    emit_native_load_null,
+    emit_native_load_method,
+    emit_native_load_build_class,
+    emit_native_subscr,
+    emit_native_attr,
+    emit_native_dup_top,
+    emit_native_dup_top_two,
+    emit_native_pop_top,
+    emit_native_rot_two,
+    emit_native_rot_three,
+    emit_native_jump,
+    emit_native_pop_jump_if,
+    emit_native_jump_if_or_pop,
+    emit_native_unwind_jump,
+    emit_native_setup_block,
+    emit_native_with_cleanup,
+    emit_native_end_finally,
+    emit_native_get_iter,
+    emit_native_for_iter,
+    emit_native_for_iter_end,
+    emit_native_pop_except_jump,
+    emit_native_unary_op,
+    emit_native_binary_op,
+    emit_native_build,
+    emit_native_store_map,
+    emit_native_store_comp,
+    emit_native_unpack_sequence,
+    emit_native_unpack_ex,
+    emit_native_make_function,
+    emit_native_make_closure,
+    emit_native_call_function,
+    emit_native_call_method,
+    emit_native_return_value,
+    emit_native_raise_varargs,
+    emit_native_yield,
+
+    emit_native_start_except_handler,
+    emit_native_end_except_handler,
+};
+
+#endif