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36 results

mx25.h

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  • Forked from card10 / firmware
    Source project has a limited visibility.
    vm.c 42.79 KiB
    /*
     * This file is part of the Micro Python project, http://micropython.org/
     *
     * The MIT License (MIT)
     *
     * Copyright (c) 2013, 2014 Damien P. George
     * Copyright (c) 2014 Paul Sokolovsky
     *
     * 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.
     */
    
    #include <stdio.h>
    #include <string.h>
    #include <assert.h>
    #include <alloca.h>
    
    #include "mpconfig.h"
    #include "nlr.h"
    #include "misc.h"
    #include "qstr.h"
    #include "obj.h"
    #include "emitglue.h"
    #include "runtime.h"
    #include "bc0.h"
    #include "bc.h"
    #include "objgenerator.h"
    
    // With these macros you can tune the maximum number of function state bytes
    // that will be allocated on the stack.  Any function that needs more
    // than this will use the heap.
    #define VM_MAX_STATE_ON_STACK (10 * sizeof(machine_uint_t))
    
    #define DETECT_VM_STACK_OVERFLOW (0)
    #if 0
    #define TRACE(ip) mp_bytecode_print2(ip, 1);
    #else
    #define TRACE(ip)
    #endif
    
    // Value stack grows up (this makes it incompatible with native C stack, but
    // makes sure that arguments to functions are in natural order arg1..argN
    // (Python semantics mandates left-to-right evaluation order, including for
    // function arguments). Stack pointer is pre-incremented and points at the
    // top element.
    // Exception stack also grows up, top element is also pointed at.
    
    // Exception stack unwind reasons (WHY_* in CPython-speak)
    // TODO perhaps compress this to RETURN=0, JUMP>0, with number of unwinds
    // left to do encoded in the JUMP number
    typedef enum {
        UNWIND_RETURN = 1,
        UNWIND_JUMP,
    } mp_unwind_reason_t;
    
    #define DECODE_UINT do { \
        unum = 0; \
        do { \
            unum = (unum << 7) + (*ip & 0x7f); \
        } while ((*ip++ & 0x80) != 0); \
    } while (0)
    #define DECODE_ULABEL do { unum = (ip[0] | (ip[1] << 8)); ip += 2; } while (0)
    #define DECODE_SLABEL do { unum = (ip[0] | (ip[1] << 8)) - 0x8000; ip += 2; } while (0)
    #define DECODE_QSTR qstr qst = 0; \
        do { \
            qst = (qst << 7) + (*ip & 0x7f); \
        } while ((*ip++ & 0x80) != 0)
    #define DECODE_PTR do { \
        ip = (byte*)(((machine_uint_t)ip + sizeof(machine_uint_t) - 1) & (~(sizeof(machine_uint_t) - 1))); /* align ip */ \
        unum = *(machine_uint_t*)ip; \
        ip += sizeof(machine_uint_t); \
    } while (0)
    #define PUSH(val) *++sp = (val)
    #define POP() (*sp--)
    #define TOP() (*sp)
    #define SET_TOP(val) *sp = (val)
    
    #define PUSH_EXC_BLOCK() \
        DECODE_ULABEL; /* except labels are always forward */ \
        ++exc_sp; \
        exc_sp->opcode = *code_state->ip; \
        exc_sp->handler = ip + unum; \
        exc_sp->val_sp = MP_TAGPTR_MAKE(sp, currently_in_except_block); \
        exc_sp->prev_exc = MP_OBJ_NULL; \
        currently_in_except_block = 0; /* in a try block now */
    
    #define POP_EXC_BLOCK() \
        currently_in_except_block = MP_TAGPTR_TAG(exc_sp->val_sp); /* restore previous state */ \
        exc_sp--; /* pop back to previous exception handler */
    
    mp_vm_return_kind_t mp_execute_bytecode(const byte *code, const mp_obj_t *args, uint n_args,
                                                              const mp_obj_t *args2, uint n_args2, mp_obj_t *ret) {
        const byte *ip = code;
    
        // get code info size, and skip line number table
        machine_uint_t code_info_size = ip[0] | (ip[1] << 8) | (ip[2] << 16) | (ip[3] << 24);
        ip += code_info_size;
    
        // bytecode prelude: state size and exception stack size; 16 bit uints
        machine_uint_t n_state = ip[0] | (ip[1] << 8);
        machine_uint_t n_exc_stack = ip[2] | (ip[3] << 8);
        ip += 4;
    
        // allocate state for locals and stack
    #if DETECT_VM_STACK_OVERFLOW
        n_state += 1;
    #endif
    
        int state_size = n_state * sizeof(mp_obj_t) + n_exc_stack * sizeof(mp_exc_stack_t);
        mp_code_state *code_state;
        if (state_size > VM_MAX_STATE_ON_STACK) {
            code_state = m_new_obj_var(mp_code_state, byte, state_size);
        } else {
            code_state = alloca(sizeof(mp_code_state) + state_size);
        }
    
        code_state->code_info = code;
        code_state->sp = &code_state->state[0] - 1;
        code_state->exc_sp = (mp_exc_stack_t*)(code_state->state + n_state) - 1;
        code_state->n_state = n_state;
    
        // init args
        for (uint i = 0; i < n_args; i++) {
            code_state->state[n_state - 1 - i] = args[i];
        }
        for (uint i = 0; i < n_args2; i++) {
            code_state->state[n_state - 1 - n_args - i] = args2[i];
        }
    
        // set rest of state to MP_OBJ_NULL
        for (uint i = 0; i < n_state - n_args - n_args2; i++) {
            code_state->state[i] = MP_OBJ_NULL;
        }
    
        // bytecode prelude: initialise closed over variables
        for (uint n_local = *ip++; n_local > 0; n_local--) {
            uint local_num = *ip++;
            code_state->state[n_state - 1 - local_num] = mp_obj_new_cell(code_state->state[n_state - 1 - local_num]);
        }
    
        code_state->ip = ip;
    
        // execute the byte code
        mp_vm_return_kind_t vm_return_kind = mp_execute_bytecode2(code_state, MP_OBJ_NULL);
    
    #if DETECT_VM_STACK_OVERFLOW
        if (vm_return_kind == MP_VM_RETURN_NORMAL) {
            if (code_state->sp < code_state->state) {
                printf("VM stack underflow: " INT_FMT "\n", code_state->sp - code_state->state);
                assert(0);
            }
        }
        // We can't check the case when an exception is returned in state[n_state - 1]
        // and there are no arguments, because in this case our detection slot may have
        // been overwritten by the returned exception (which is allowed).
        if (!(vm_return_kind == MP_VM_RETURN_EXCEPTION && n_args == 0 && n_args2 == 0)) {
            // Just check to see that we have at least 1 null object left in the state.
            bool overflow = true;
            for (uint i = 0; i < n_state - n_args - n_args2; i++) {
                if (code_state->state[i] == MP_OBJ_NULL) {
                    overflow = false;
                    break;
                }
            }
            if (overflow) {
                printf("VM stack overflow state=%p n_state+1=" UINT_FMT "\n", code_state->state, n_state);
                assert(0);
            }
        }
    #endif
    
        mp_vm_return_kind_t ret_kind;
        switch (vm_return_kind) {
            case MP_VM_RETURN_NORMAL:
                // return value is in *sp
                *ret = *code_state->sp;
                ret_kind = MP_VM_RETURN_NORMAL;
                break;
    
            case MP_VM_RETURN_EXCEPTION:
                // return value is in state[n_state - 1]
                *ret = code_state->state[n_state - 1];
                ret_kind = MP_VM_RETURN_EXCEPTION;
                break;
    
            case MP_VM_RETURN_YIELD: // byte-code shouldn't yield
            default:
                assert(0);
                *ret = mp_const_none;
                ret_kind = MP_VM_RETURN_NORMAL;
                break;
        }
    
        // free the state if it was allocated on the heap
        if (state_size > VM_MAX_STATE_ON_STACK) {
            m_del_var(mp_code_state, byte, state_size, code_state);
        }
        return ret_kind;
    }
    
    // fastn has items in reverse order (fastn[0] is local[0], fastn[-1] is local[1], etc)
    // sp points to bottom of stack which grows up
    // returns:
    //  MP_VM_RETURN_NORMAL, sp valid, return value in *sp
    //  MP_VM_RETURN_YIELD, ip, sp valid, yielded value in *sp
    //  MP_VM_RETURN_EXCEPTION, exception in fastn[0]
    mp_vm_return_kind_t mp_execute_bytecode2(mp_code_state *code_state, volatile mp_obj_t inject_exc) {
    #if MICROPY_OPT_COMPUTED_GOTO
        #include "vmentrytable.h"
        #define DISPATCH() do { \
            TRACE(ip); \
            code_state->ip = ip; \
            goto *entry_table[*ip++]; \
        } while(0)
        #define ENTRY(op) entry_##op
        #define ENTRY_DEFAULT entry_default
    #else
        #define DISPATCH() break
        #define ENTRY(op) case op
        #define ENTRY_DEFAULT default
    #endif
    
        // nlr_raise needs to be implemented as a goto, so that the C compiler's flow analyser
        // sees that it's possible for us to jump from the dispatch loop to the exception
        // handler.  Without this, the code may have a different stack layout in the dispatch
        // loop and the exception handler, leading to very obscure bugs.
        #define RAISE(o) do { nlr_pop(); nlr.ret_val = o; goto exception_handler; } while(0)
    
        // Pointers which are constant for particular invocation of mp_execute_bytecode2()
        mp_obj_t *const fastn = &code_state->state[code_state->n_state - 1];
        mp_exc_stack_t *const exc_stack = (mp_exc_stack_t*)(code_state->state + code_state->n_state);
    
        // variables that are visible to the exception handler (declared volatile)
        volatile bool currently_in_except_block = MP_TAGPTR_TAG(code_state->exc_sp); // 0 or 1, to detect nested exceptions
        mp_exc_stack_t *volatile exc_sp = MP_TAGPTR_PTR(code_state->exc_sp); // stack grows up, exc_sp points to top of stack
    
        // outer exception handling loop
        for (;;) {
            nlr_buf_t nlr;
    outer_dispatch_loop:
            if (nlr_push(&nlr) == 0) {
                // local variables that are not visible to the exception handler
                const byte *ip = code_state->ip;
                mp_obj_t *sp = code_state->sp;
                machine_uint_t unum;
                mp_obj_t obj_shared;
    
                // If we have exception to inject, now that we finish setting up
                // execution context, raise it. This works as if RAISE_VARARGS
                // bytecode was executed.
                // Injecting exc into yield from generator is a special case,
                // handled by MP_BC_YIELD_FROM itself
                if (inject_exc != MP_OBJ_NULL && *ip != MP_BC_YIELD_FROM) {
                    mp_obj_t exc = inject_exc;
                    inject_exc = MP_OBJ_NULL;
                    exc = mp_make_raise_obj(exc);
                    RAISE(exc);
                }
    
                // loop to execute byte code
                for (;;) {
    dispatch_loop:
    #if MICROPY_OPT_COMPUTED_GOTO
                    DISPATCH();
    #else
                    TRACE(ip);
                    code_state->ip = ip;
                    switch (*ip++) {
    #endif
    
                    ENTRY(MP_BC_LOAD_CONST_FALSE):
                        PUSH(mp_const_false);
                        DISPATCH();
    
                    ENTRY(MP_BC_LOAD_CONST_NONE):
                        PUSH(mp_const_none);
                        DISPATCH();
    
                    ENTRY(MP_BC_LOAD_CONST_TRUE):
                        PUSH(mp_const_true);
                        DISPATCH();
    
                    ENTRY(MP_BC_LOAD_CONST_ELLIPSIS):
                        PUSH((mp_obj_t)&mp_const_ellipsis_obj);
                        DISPATCH();
    
                    ENTRY(MP_BC_LOAD_CONST_SMALL_INT): {
                        machine_int_t num = 0;
                        if ((ip[0] & 0x40) != 0) {
                            // Number is negative
                            num--;
                        }
                        do {
                            num = (num << 7) | (*ip & 0x7f);
                        } while ((*ip++ & 0x80) != 0);
                        PUSH(MP_OBJ_NEW_SMALL_INT(num));
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_LOAD_CONST_INT): {
                        DECODE_QSTR;
                        PUSH(mp_load_const_int(qst));
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_LOAD_CONST_DEC): {
                        DECODE_QSTR;
                        PUSH(mp_load_const_dec(qst));
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_LOAD_CONST_BYTES): {
                        DECODE_QSTR;
                        PUSH(mp_load_const_bytes(qst));
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_LOAD_CONST_STRING): {
                        DECODE_QSTR;
                        PUSH(mp_load_const_str(qst));
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_LOAD_NULL):
                        PUSH(MP_OBJ_NULL);
                        DISPATCH();
    
                    ENTRY(MP_BC_LOAD_FAST_0):
                        obj_shared = fastn[0];
                        goto load_check;
    
                    ENTRY(MP_BC_LOAD_FAST_1):
                        obj_shared = fastn[-1];
                        goto load_check;
    
                    ENTRY(MP_BC_LOAD_FAST_2):
                        obj_shared = fastn[-2];
                        goto load_check;
    
                    ENTRY(MP_BC_LOAD_FAST_N):
                        DECODE_UINT;
                        obj_shared = fastn[-unum];
                        load_check:
                        if (obj_shared == MP_OBJ_NULL) {
                            local_name_error: {
                                mp_obj_t obj = mp_obj_new_exception_msg(&mp_type_NameError, "local variable referenced before assignment");
                                RAISE(obj);
                            }
                        }
                        PUSH(obj_shared);
                        DISPATCH();
    
                    ENTRY(MP_BC_LOAD_DEREF):
                        DECODE_UINT;
                        obj_shared = mp_obj_cell_get(fastn[-unum]);
                        goto load_check;
    
                    ENTRY(MP_BC_LOAD_NAME): {
                        DECODE_QSTR;
                        PUSH(mp_load_name(qst));
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_LOAD_GLOBAL): {
                        DECODE_QSTR;
                        PUSH(mp_load_global(qst));
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_LOAD_ATTR): {
                        DECODE_QSTR;
                        SET_TOP(mp_load_attr(TOP(), qst));
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_LOAD_METHOD): {
                        DECODE_QSTR;
                        mp_load_method(*sp, qst, sp);
                        sp += 1;
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_LOAD_BUILD_CLASS):
                        PUSH(mp_load_build_class());
                        DISPATCH();
    
                    ENTRY(MP_BC_LOAD_SUBSCR): {
                        mp_obj_t index = POP();
                        SET_TOP(mp_obj_subscr(TOP(), index, MP_OBJ_SENTINEL));
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_STORE_FAST_0):
                        fastn[0] = POP();
                        DISPATCH();
    
                    ENTRY(MP_BC_STORE_FAST_1):
                        fastn[-1] = POP();
                        DISPATCH();
    
                    ENTRY(MP_BC_STORE_FAST_2):
                        fastn[-2] = POP();
                        DISPATCH();
    
                    ENTRY(MP_BC_STORE_FAST_N):
                        DECODE_UINT;
                        fastn[-unum] = POP();
                        DISPATCH();
    
                    ENTRY(MP_BC_STORE_DEREF):
                        DECODE_UINT;
                        mp_obj_cell_set(fastn[-unum], POP());
                        DISPATCH();
    
                    ENTRY(MP_BC_STORE_NAME): {
                        DECODE_QSTR;
                        mp_store_name(qst, POP());
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_STORE_GLOBAL): {
                        DECODE_QSTR;
                        mp_store_global(qst, POP());
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_STORE_ATTR): {
                        DECODE_QSTR;
                        mp_store_attr(sp[0], qst, sp[-1]);
                        sp -= 2;
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_STORE_SUBSCR):
                        mp_obj_subscr(sp[-1], sp[0], sp[-2]);
                        sp -= 3;
                        DISPATCH();
    
                    ENTRY(MP_BC_DELETE_FAST):
                        DECODE_UINT;
                        if (fastn[-unum] == MP_OBJ_NULL) {
                            goto local_name_error;
                        }
                        fastn[-unum] = MP_OBJ_NULL;
                        DISPATCH();
    
                    ENTRY(MP_BC_DELETE_DEREF):
                        DECODE_UINT;
                        if (mp_obj_cell_get(fastn[-unum]) == MP_OBJ_NULL) {
                            goto local_name_error;
                        }
                        mp_obj_cell_set(fastn[-unum], MP_OBJ_NULL);
                        DISPATCH();
    
                    ENTRY(MP_BC_DELETE_NAME): {
                        DECODE_QSTR;
                        mp_delete_name(qst);
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_DELETE_GLOBAL): {
                        DECODE_QSTR;
                        mp_delete_global(qst);
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_DUP_TOP): {
                        mp_obj_t top = TOP();
                        PUSH(top);
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_DUP_TOP_TWO):
                        sp += 2;
                        sp[0] = sp[-2];
                        sp[-1] = sp[-3];
                        DISPATCH();
    
                    ENTRY(MP_BC_POP_TOP):
                        sp -= 1;
                        DISPATCH();
    
                    ENTRY(MP_BC_ROT_TWO): {
                        mp_obj_t top = sp[0];
                        sp[0] = sp[-1];
                        sp[-1] = top;
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_ROT_THREE): {
                        mp_obj_t top = sp[0];
                        sp[0] = sp[-1];
                        sp[-1] = sp[-2];
                        sp[-2] = top;
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_JUMP):
                        DECODE_SLABEL;
                        ip += unum;
                        DISPATCH();
    
                    ENTRY(MP_BC_POP_JUMP_IF_TRUE):
                        DECODE_SLABEL;
                        if (mp_obj_is_true(POP())) {
                            ip += unum;
                        }
                        DISPATCH();
    
                    ENTRY(MP_BC_POP_JUMP_IF_FALSE):
                        DECODE_SLABEL;
                        if (!mp_obj_is_true(POP())) {
                            ip += unum;
                        }
                        DISPATCH();
    
                    ENTRY(MP_BC_JUMP_IF_TRUE_OR_POP):
                        DECODE_SLABEL;
                        if (mp_obj_is_true(TOP())) {
                            ip += unum;
                        } else {
                            sp--;
                        }
                        DISPATCH();
    
                    ENTRY(MP_BC_JUMP_IF_FALSE_OR_POP):
                        DECODE_SLABEL;
                        if (mp_obj_is_true(TOP())) {
                            sp--;
                        } else {
                            ip += unum;
                        }
                        DISPATCH();
    
                    ENTRY(MP_BC_SETUP_WITH): {
                        mp_obj_t obj = TOP();
                        SET_TOP(mp_load_attr(obj, MP_QSTR___exit__));
                        mp_load_method(obj, MP_QSTR___enter__, sp + 1);
                        mp_obj_t ret = mp_call_method_n_kw(0, 0, sp + 1);
                        PUSH_EXC_BLOCK();
                        PUSH(ret);
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_WITH_CLEANUP): {
                        // Arriving here, there's "exception control block" on top of stack,
                        // and __exit__ bound method underneath it. Bytecode calls __exit__,
                        // and "deletes" it off stack, shifting "exception control block"
                        // to its place.
                        static const mp_obj_t no_exc[] = {mp_const_none, mp_const_none, mp_const_none};
                        if (TOP() == mp_const_none) {
                            sp--;
                            mp_obj_t obj = TOP();
                            SET_TOP(mp_const_none);
                            mp_call_function_n_kw(obj, 3, 0, no_exc);
                        } else if (MP_OBJ_IS_SMALL_INT(TOP())) {
                            mp_obj_t cause = POP();
                            switch (MP_OBJ_SMALL_INT_VALUE(cause)) {
                                case UNWIND_RETURN: {
                                    mp_obj_t retval = POP();
                                    mp_call_function_n_kw(TOP(), 3, 0, no_exc);
                                    SET_TOP(retval);
                                    PUSH(cause);
                                    break;
                                }
                                case UNWIND_JUMP: {
                                    mp_call_function_n_kw(sp[-2], 3, 0, no_exc);
                                    // Pop __exit__ boundmethod at sp[-2]
                                    sp[-2] = sp[-1];
                                    sp[-1] = sp[0];
                                    SET_TOP(cause);
                                    break;
                                }
                                default:
                                    assert(0);
                            }
                        } else if (mp_obj_is_exception_type(TOP())) {
                            mp_obj_t args[3] = {sp[0], sp[-1], sp[-2]};
                            mp_obj_t ret_value = mp_call_function_n_kw(sp[-3], 3, 0, args);
                            // Pop __exit__ boundmethod at sp[-3]
                            // TODO: Once semantics is proven, optimize for case when ret_value == True
                            sp[-3] = sp[-2];
                            sp[-2] = sp[-1];
                            sp[-1] = sp[0];
                            sp--;
                            if (mp_obj_is_true(ret_value)) {
                                // This is what CPython does
                                //PUSH(MP_OBJ_NEW_SMALL_INT(UNWIND_SILENCED));
                                // But what we need to do is - pop exception from value stack...
                                sp -= 3;
                                // ... pop "with" exception handler, and signal END_FINALLY
                                // to just execute finally handler normally (by pushing None
                                // on value stack)
                                assert(exc_sp >= exc_stack);
                                assert(exc_sp->opcode == MP_BC_SETUP_WITH);
                                POP_EXC_BLOCK();
                                PUSH(mp_const_none);
                            }
                        } else {
                            assert(0);
                        }
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_UNWIND_JUMP):
                        DECODE_SLABEL;
                        PUSH((void*)(ip + unum)); // push destination ip for jump
                        PUSH((void*)(machine_uint_t)(*ip)); // push number of exception handlers to unwind (0x80 bit set if we also need to pop stack)
    unwind_jump:
                        unum = (machine_uint_t)POP(); // get number of exception handlers to unwind
                        while ((unum & 0x7f) > 0) {
                            unum -= 1;
                            assert(exc_sp >= exc_stack);
                            if (exc_sp->opcode == MP_BC_SETUP_FINALLY || exc_sp->opcode == MP_BC_SETUP_WITH) {
                                // We're going to run "finally" code as a coroutine
                                // (not calling it recursively). Set up a sentinel
                                // on a stack so it can return back to us when it is
                                // done (when END_FINALLY reached).
                                PUSH((void*)unum); // push number of exception handlers left to unwind
                                PUSH(MP_OBJ_NEW_SMALL_INT(UNWIND_JUMP)); // push sentinel
                                ip = exc_sp->handler; // get exception handler byte code address
                                exc_sp--; // pop exception handler
                                goto dispatch_loop; // run the exception handler
                            }
                            exc_sp--;
                        }
                        ip = (const byte*)POP(); // pop destination ip for jump
                        if (unum != 0) {
                            sp--;
                        }
                        DISPATCH();
    
                    // matched against: POP_BLOCK or POP_EXCEPT (anything else?)
                    ENTRY(MP_BC_SETUP_EXCEPT):
                    ENTRY(MP_BC_SETUP_FINALLY):
                        PUSH_EXC_BLOCK();
                        DISPATCH();
    
                    ENTRY(MP_BC_END_FINALLY):
                        // not fully implemented
                        // if TOS is an exception, reraises the exception (3 values on TOS)
                        // if TOS is None, just pops it and continues
                        // if TOS is an integer, does something else
                        // else error
                        if (mp_obj_is_exception_type(TOP())) {
                            RAISE(sp[-1]);
                        }
                        if (TOP() == mp_const_none) {
                            sp--;
                        } else if (MP_OBJ_IS_SMALL_INT(TOP())) {
                            // We finished "finally" coroutine and now dispatch back
                            // to our caller, based on TOS value
                            mp_unwind_reason_t reason = MP_OBJ_SMALL_INT_VALUE(POP());
                            switch (reason) {
                                case UNWIND_RETURN:
                                    goto unwind_return;
                                case UNWIND_JUMP:
                                    goto unwind_jump;
                            }
                            assert(0);
                        } else {
                            assert(0);
                        }
                        DISPATCH();
    
                    ENTRY(MP_BC_GET_ITER):
                        SET_TOP(mp_getiter(TOP()));
                        DISPATCH();
    
                    ENTRY(MP_BC_FOR_ITER): {
                        DECODE_ULABEL; // the jump offset if iteration finishes; for labels are always forward
                        code_state->sp = sp;
                        assert(TOP());
                        mp_obj_t value = mp_iternext_allow_raise(TOP());
                        if (value == MP_OBJ_STOP_ITERATION) {
                            --sp; // pop the exhausted iterator
                            ip += unum; // jump to after for-block
                        } else {
                            PUSH(value); // push the next iteration value
                        }
                        DISPATCH();
                    }
    
                    // matched against: SETUP_EXCEPT, SETUP_FINALLY, SETUP_WITH
                    ENTRY(MP_BC_POP_BLOCK):
                        // we are exiting an exception handler, so pop the last one of the exception-stack
                        assert(exc_sp >= exc_stack);
                        POP_EXC_BLOCK();
                        DISPATCH();
    
                    // matched against: SETUP_EXCEPT
                    ENTRY(MP_BC_POP_EXCEPT):
                        // TODO need to work out how blocks work etc
                        // pops block, checks it's an exception block, and restores the stack, saving the 3 exception values to local threadstate
                        assert(exc_sp >= exc_stack);
                        assert(currently_in_except_block);
                        //sp = (mp_obj_t*)(*exc_sp--);
                        //exc_sp--; // discard ip
                        POP_EXC_BLOCK();
                        //sp -= 3; // pop 3 exception values
                        DISPATCH();
    
                    ENTRY(MP_BC_NOT):
                        if (TOP() == mp_const_true) {
                            SET_TOP(mp_const_false);
                        } else {
                            SET_TOP(mp_const_true);
                        }
                        DISPATCH();
    
                    ENTRY(MP_BC_UNARY_OP):
                        unum = *ip++;
                        SET_TOP(mp_unary_op(unum, TOP()));
                        DISPATCH();
    
                    ENTRY(MP_BC_BINARY_OP): {
                        unum = *ip++;
                        mp_obj_t rhs = POP();
                        mp_obj_t lhs = TOP();
                        SET_TOP(mp_binary_op(unum, lhs, rhs));
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_BUILD_TUPLE):
                        DECODE_UINT;
                        sp -= unum - 1;
                        SET_TOP(mp_obj_new_tuple(unum, sp));
                        DISPATCH();
    
                    ENTRY(MP_BC_BUILD_LIST):
                        DECODE_UINT;
                        sp -= unum - 1;
                        SET_TOP(mp_obj_new_list(unum, sp));
                        DISPATCH();
    
                    ENTRY(MP_BC_LIST_APPEND):
                        DECODE_UINT;
                        // I think it's guaranteed by the compiler that sp[unum] is a list
                        mp_obj_list_append(sp[-unum], sp[0]);
                        sp--;
                        DISPATCH();
    
                    ENTRY(MP_BC_BUILD_MAP):
                        DECODE_UINT;
                        PUSH(mp_obj_new_dict(unum));
                        DISPATCH();
    
                    ENTRY(MP_BC_STORE_MAP):
                        sp -= 2;
                        mp_obj_dict_store(sp[0], sp[2], sp[1]);
                        DISPATCH();
    
                    ENTRY(MP_BC_MAP_ADD):
                        DECODE_UINT;
                        // I think it's guaranteed by the compiler that sp[-unum - 1] is a map
                        mp_obj_dict_store(sp[-unum - 1], sp[0], sp[-1]);
                        sp -= 2;
                        DISPATCH();
    
    #if MICROPY_PY_BUILTINS_SET
                    ENTRY(MP_BC_BUILD_SET):
                        DECODE_UINT;
                        sp -= unum - 1;
                        SET_TOP(mp_obj_new_set(unum, sp));
                        DISPATCH();
    
                    ENTRY(MP_BC_SET_ADD):
                        DECODE_UINT;
                        // I think it's guaranteed by the compiler that sp[-unum] is a set
                        mp_obj_set_store(sp[-unum], sp[0]);
                        sp--;
                        DISPATCH();
    #endif
    
    #if MICROPY_PY_BUILTINS_SLICE
                    ENTRY(MP_BC_BUILD_SLICE):
                        DECODE_UINT;
                        if (unum == 2) {
                            mp_obj_t stop = POP();
                            mp_obj_t start = TOP();
                            SET_TOP(mp_obj_new_slice(start, stop, mp_const_none));
                        } else {
                            mp_obj_t step = POP();
                            mp_obj_t stop = POP();
                            mp_obj_t start = TOP();
                            SET_TOP(mp_obj_new_slice(start, stop, step));
                        }
                        DISPATCH();
    #endif
    
                    ENTRY(MP_BC_UNPACK_SEQUENCE):
                        DECODE_UINT;
                        mp_unpack_sequence(sp[0], unum, sp);
                        sp += unum - 1;
                        DISPATCH();
    
                    ENTRY(MP_BC_UNPACK_EX):
                        DECODE_UINT;
                        mp_unpack_ex(sp[0], unum, sp);
                        sp += (unum & 0xff) + ((unum >> 8) & 0xff);
                        DISPATCH();
    
                    ENTRY(MP_BC_MAKE_FUNCTION):
                        DECODE_PTR;
                        PUSH(mp_make_function_from_raw_code((mp_raw_code_t*)unum, MP_OBJ_NULL, MP_OBJ_NULL));
                        DISPATCH();
    
                    ENTRY(MP_BC_MAKE_FUNCTION_DEFARGS): {
                        DECODE_PTR;
                        // Stack layout: def_tuple def_dict <- TOS
                        mp_obj_t def_dict = POP();
                        SET_TOP(mp_make_function_from_raw_code((mp_raw_code_t*)unum, TOP(), def_dict));
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_MAKE_CLOSURE): {
                        DECODE_PTR;
                        machine_uint_t n_closed_over = *ip++;
                        // Stack layout: closed_overs <- TOS
                        sp -= n_closed_over - 1;
                        SET_TOP(mp_make_closure_from_raw_code((mp_raw_code_t*)unum, n_closed_over, sp));
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_MAKE_CLOSURE_DEFARGS): {
                        DECODE_PTR;
                        machine_uint_t n_closed_over = *ip++;
                        // Stack layout: def_tuple def_dict closed_overs <- TOS
                        sp -= 2 + n_closed_over - 1;
                        SET_TOP(mp_make_closure_from_raw_code((mp_raw_code_t*)unum, 0x100 | n_closed_over, sp));
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_CALL_FUNCTION):
                        DECODE_UINT;
                        // unum & 0xff == n_positional
                        // (unum >> 8) & 0xff == n_keyword
                        sp -= (unum & 0xff) + ((unum >> 7) & 0x1fe);
                        SET_TOP(mp_call_function_n_kw(*sp, unum & 0xff, (unum >> 8) & 0xff, sp + 1));
                        DISPATCH();
    
                    ENTRY(MP_BC_CALL_FUNCTION_VAR_KW):
                        DECODE_UINT;
                        // unum & 0xff == n_positional
                        // (unum >> 8) & 0xff == n_keyword
                        // We have folowing stack layout here:
                        // fun arg0 arg1 ... kw0 val0 kw1 val1 ... seq dict <- TOS
                        sp -= (unum & 0xff) + ((unum >> 7) & 0x1fe) + 2;
                        SET_TOP(mp_call_method_n_kw_var(false, unum, sp));
                        DISPATCH();
    
                    ENTRY(MP_BC_CALL_METHOD):
                        DECODE_UINT;
                        // unum & 0xff == n_positional
                        // (unum >> 8) & 0xff == n_keyword
                        sp -= (unum & 0xff) + ((unum >> 7) & 0x1fe) + 1;
                        SET_TOP(mp_call_method_n_kw(unum & 0xff, (unum >> 8) & 0xff, sp));
                        DISPATCH();
    
                    ENTRY(MP_BC_CALL_METHOD_VAR_KW):
                        DECODE_UINT;
                        // unum & 0xff == n_positional
                        // (unum >> 8) & 0xff == n_keyword
                        // We have folowing stack layout here:
                        // fun self arg0 arg1 ... kw0 val0 kw1 val1 ... seq dict <- TOS
                        sp -= (unum & 0xff) + ((unum >> 7) & 0x1fe) + 3;
                        SET_TOP(mp_call_method_n_kw_var(true, unum, sp));
                        DISPATCH();
    
                    ENTRY(MP_BC_RETURN_VALUE):
    unwind_return:
                        while (exc_sp >= exc_stack) {
                            if (exc_sp->opcode == MP_BC_SETUP_FINALLY || exc_sp->opcode == MP_BC_SETUP_WITH) {
                                // We're going to run "finally" code as a coroutine
                                // (not calling it recursively). Set up a sentinel
                                // on a stack so it can return back to us when it is
                                // done (when END_FINALLY reached).
                                PUSH(MP_OBJ_NEW_SMALL_INT(UNWIND_RETURN));
                                ip = exc_sp->handler;
                                // We don't need to do anything with sp, finally is just
                                // syntactic sugar for sequential execution??
                                // sp =
                                exc_sp--;
                                goto dispatch_loop;
                            }
                            exc_sp--;
                        }
                        nlr_pop();
                        code_state->sp = sp;
                        assert(exc_sp == exc_stack - 1);
                        return MP_VM_RETURN_NORMAL;
    
                    ENTRY(MP_BC_RAISE_VARARGS): {
                        unum = *ip++;
                        mp_obj_t obj;
                        assert(unum <= 1);
                        if (unum == 0) {
                            // search for the inner-most previous exception, to reraise it
                            obj = MP_OBJ_NULL;
                            for (mp_exc_stack_t *e = exc_sp; e >= exc_stack; e--) {
                                if (e->prev_exc != MP_OBJ_NULL) {
                                    obj = e->prev_exc;
                                    break;
                                }
                            }
                            if (obj == MP_OBJ_NULL) {
                                obj = mp_obj_new_exception_msg(&mp_type_RuntimeError, "No active exception to reraise");
                                RAISE(obj);
                            }
                        } else {
                            obj = POP();
                        }
                        obj = mp_make_raise_obj(obj);
                        RAISE(obj);
                    }
    
                    ENTRY(MP_BC_YIELD_VALUE):
    yield:
                        nlr_pop();
                        code_state->ip = ip;
                        code_state->sp = sp;
                        code_state->exc_sp = MP_TAGPTR_MAKE(exc_sp, currently_in_except_block);
                        return MP_VM_RETURN_YIELD;
    
                    ENTRY(MP_BC_YIELD_FROM): {
    //#define EXC_MATCH(exc, type) MP_OBJ_IS_TYPE(exc, type)
    #define EXC_MATCH(exc, type) mp_obj_exception_match(exc, type)
    #define GENERATOR_EXIT_IF_NEEDED(t) if (t != MP_OBJ_NULL && EXC_MATCH(t, &mp_type_GeneratorExit)) { RAISE(t); }
                        mp_vm_return_kind_t ret_kind;
                        mp_obj_t send_value = POP();
                        mp_obj_t t_exc = MP_OBJ_NULL;
                        mp_obj_t ret_value;
                        if (inject_exc != MP_OBJ_NULL) {
                            t_exc = inject_exc;
                            inject_exc = MP_OBJ_NULL;
                            ret_kind = mp_resume(TOP(), MP_OBJ_NULL, t_exc, &ret_value);
                        } else {
                            ret_kind = mp_resume(TOP(), send_value, MP_OBJ_NULL, &ret_value);
                        }
    
                        if (ret_kind == MP_VM_RETURN_YIELD) {
                            ip--;
                            PUSH(ret_value);
                            goto yield;
                        }
                        if (ret_kind == MP_VM_RETURN_NORMAL) {
                            // Pop exhausted gen
                            sp--;
                            if (ret_value == MP_OBJ_NULL) {
                                // Optimize StopIteration
                                // TODO: get StopIteration's value
                                PUSH(mp_const_none);
                            } else {
                                PUSH(ret_value);
                            }
    
                            // If we injected GeneratorExit downstream, then even
                            // if it was swallowed, we re-raise GeneratorExit
                            GENERATOR_EXIT_IF_NEEDED(t_exc);
                            DISPATCH();
                        }
                        if (ret_kind == MP_VM_RETURN_EXCEPTION) {
                            // Pop exhausted gen
                            sp--;
                            if (EXC_MATCH(ret_value, &mp_type_StopIteration)) {
                                PUSH(mp_obj_exception_get_value(ret_value));
                                // If we injected GeneratorExit downstream, then even
                                // if it was swallowed, we re-raise GeneratorExit
                                GENERATOR_EXIT_IF_NEEDED(t_exc);
                                DISPATCH();
                            } else {
                                RAISE(ret_value);
                            }
                        }
                    }
    
                    ENTRY(MP_BC_IMPORT_NAME): {
                        DECODE_QSTR;
                        mp_obj_t obj = POP();
                        SET_TOP(mp_import_name(qst, obj, TOP()));
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_IMPORT_FROM): {
                        DECODE_QSTR;
                        mp_obj_t obj = mp_import_from(TOP(), qst);
                        PUSH(obj);
                        DISPATCH();
                    }
    
                    ENTRY(MP_BC_IMPORT_STAR):
                        mp_import_all(POP());
                        DISPATCH();
    
                    ENTRY_DEFAULT: {
                        mp_obj_t obj = mp_obj_new_exception_msg(&mp_type_NotImplementedError, "byte code not implemented");
                        nlr_pop();
                        fastn[0] = obj;
                        return MP_VM_RETURN_EXCEPTION;
                    }
    
    #if !MICROPY_OPT_COMPUTED_GOTO
                    } // switch
    #endif
                } // for loop
    
            } else {
    exception_handler:
                // exception occurred
    
                // check if it's a StopIteration within a for block
                if (*code_state->ip == MP_BC_FOR_ITER && mp_obj_is_subclass_fast(mp_obj_get_type(nlr.ret_val), &mp_type_StopIteration)) {
                    const byte *ip = code_state->ip + 1;
                    machine_uint_t unum;
                    DECODE_ULABEL; // the jump offset if iteration finishes; for labels are always forward
                    code_state->ip = ip + unum; // jump to after for-block
                    code_state->sp -= 1; // pop the exhausted iterator
                    goto outer_dispatch_loop; // continue with dispatch loop
                }
    
                // set file and line number that the exception occurred at
                // TODO: don't set traceback for exceptions re-raised by END_FINALLY.
                // But consider how to handle nested exceptions.
                // TODO need a better way of not adding traceback to constant objects (right now, just GeneratorExit_obj and MemoryError_obj)
                if (mp_obj_is_exception_instance(nlr.ret_val) && nlr.ret_val != &mp_const_GeneratorExit_obj && nlr.ret_val != &mp_const_MemoryError_obj) {
                    const byte *code_info = code_state->code_info;
                    machine_uint_t code_info_size = code_info[0] | (code_info[1] << 8) | (code_info[2] << 16) | (code_info[3] << 24);
                    qstr source_file = code_info[4] | (code_info[5] << 8) | (code_info[6] << 16) | (code_info[7] << 24);
                    qstr block_name = code_info[8] | (code_info[9] << 8) | (code_info[10] << 16) | (code_info[11] << 24);
                    machine_uint_t source_line = 0;
                    machine_uint_t bc = code_state->ip - code_info - code_info_size;
                    //printf("find %lu %d %d\n", bc, code_info[12], code_info[13]);
                    const byte* ci = code_info + 12;
                    if (*ci) {
                        source_line = 1;
                        for (; *ci && bc >= ((*ci) & 31); ci++) {
                            bc -= *ci & 31;
                            source_line += *ci >> 5;
                        }
                    }
                    mp_obj_exception_add_traceback(nlr.ret_val, source_file, source_line, block_name);
                }
    
                while (currently_in_except_block) {
                    // nested exception
    
                    assert(exc_sp >= exc_stack);
    
                    // TODO make a proper message for nested exception
                    // at the moment we are just raising the very last exception (the one that caused the nested exception)
    
                    // move up to previous exception handler
                    POP_EXC_BLOCK();
                }
    
                if (exc_sp >= exc_stack) {
                    // set flag to indicate that we are now handling an exception
                    currently_in_except_block = 1;
    
                    // catch exception and pass to byte code
                    code_state->ip = exc_sp->handler;
                    mp_obj_t *sp = MP_TAGPTR_PTR(exc_sp->val_sp);
                    // save this exception in the stack so it can be used in a reraise, if needed
                    exc_sp->prev_exc = nlr.ret_val;
                    // push(traceback, exc-val, exc-type)
                    PUSH(mp_const_none);
                    PUSH(nlr.ret_val);
                    PUSH(mp_obj_get_type(nlr.ret_val));
                    code_state->sp = sp;
    
                } else {
                    // propagate exception to higher level
                    // TODO what to do about ip and sp? they don't really make sense at this point
                    fastn[0] = nlr.ret_val; // must put exception here because sp is invalid
                    return MP_VM_RETURN_EXCEPTION;
                }
            }
        }
    }