Add function to decode and show byte code.
diff --git a/py/showbc.c b/py/showbc.c
new file mode 100644
index 0000000..a84d98d
--- /dev/null
+++ b/py/showbc.c
@@ -0,0 +1,371 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+#include "misc.h"
+#include "mpyconfig.h"
+#include "runtime.h"
+#include "bc.h"
+
+#define DECODE_UINT do { unum = *ip++; if (unum > 127) { unum = ((unum & 0x3f) << 8) | (*ip++); } } 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 do { qstr = *ip++; if (qstr > 127) { qstr = ((qstr & 0x3f) << 8) | (*ip++); } } while (0)
+
+void py_show_byte_code(const byte *ip, int len) {
+ const byte *ip_start = ip;
+ machine_uint_t unum;
+ qstr qstr;
+ while (ip - ip_start < len) {
+ printf("%02u ", (uint)(ip - ip_start));
+ int op = *ip++;
+ switch (op) {
+ case PYBC_LOAD_CONST_FALSE:
+ printf("LOAD_CONST_FALSE");
+ break;
+
+ case PYBC_LOAD_CONST_NONE:
+ printf("LOAD_CONST_NONE");
+ break;
+
+ case PYBC_LOAD_CONST_TRUE:
+ printf("LOAD_CONST_TRUE");
+ break;
+
+ case PYBC_LOAD_CONST_SMALL_INT:
+ unum = (ip[0] | (ip[1] << 8) | (ip[2] << 16)) - 0x800000;
+ ip += 3;
+ printf("LOAD_CONST_SMALL_INT %d", (int)unum);
+ break;
+
+ /*
+ case PYBC_LOAD_CONST_DEC:
+ DECODE_QSTR;
+ PUSH(rt_load_const_dec(qstr));
+ break;
+
+ case PYBC_LOAD_CONST_ID:
+ DECODE_QSTR;
+ PUSH(rt_load_const_str(qstr)); // TODO
+ break;
+
+ case PYBC_LOAD_CONST_STRING:
+ DECODE_QSTR;
+ PUSH(rt_load_const_str(qstr));
+ break;
+ */
+
+ case PYBC_LOAD_FAST_0:
+ printf("LOAD_FAST_0");
+ break;
+
+ case PYBC_LOAD_FAST_1:
+ printf("LOAD_FAST_1");
+ break;
+
+ case PYBC_LOAD_FAST_2:
+ printf("LOAD_FAST_2");
+ break;
+
+ /*
+ case PYBC_LOAD_FAST_N:
+ DECODE_UINT;
+ PUSH(fastn[unum]);
+ break;
+ */
+
+ case PYBC_LOAD_NAME:
+ DECODE_QSTR;
+ printf("LOAD_NAME %s", qstr_str(qstr));
+ break;
+
+ case PYBC_LOAD_GLOBAL:
+ DECODE_QSTR;
+ printf("LOAD_GLOBAL %s", qstr_str(qstr));
+ break;
+
+ /*
+ case PYBC_LOAD_ATTR:
+ DECODE_QSTR;
+ *sp = rt_load_attr(*sp, qstr);
+ break;
+ */
+
+ case PYBC_LOAD_METHOD:
+ DECODE_QSTR;
+ printf("LOAD_METHOD %s", qstr_str(qstr));
+ break;
+
+ /*
+ case PYBC_LOAD_BUILD_CLASS:
+ PUSH(rt_load_build_class());
+ break;
+ */
+
+ case PYBC_STORE_FAST_0:
+ printf("STORE_FAST_0");
+ break;
+
+ case PYBC_STORE_FAST_1:
+ printf("STORE_FAST_1");
+ break;
+
+ case PYBC_STORE_FAST_2:
+ printf("STORE_FAST_2");
+ break;
+
+ /*
+ case PYBC_STORE_FAST_N:
+ DECODE_UINT;
+ fastn[unum] = POP();
+ break;
+ */
+
+ case PYBC_STORE_NAME:
+ DECODE_QSTR;
+ printf("STORE_NAME %s", qstr_str(qstr));
+ break;
+
+ /*
+ case PYBC_STORE_GLOBAL:
+ DECODE_QSTR;
+ rt_store_global(qstr, POP());
+ break;
+
+ case PYBC_STORE_ATTR:
+ DECODE_QSTR;
+ rt_store_attr(sp[0], qstr, sp[1]);
+ sp += 2;
+ break;
+
+ case PYBC_STORE_SUBSCR:
+ rt_store_subscr(sp[1], sp[0], sp[2]);
+ sp += 3;
+ break;
+
+ case PYBC_DUP_TOP:
+ obj1 = *sp;
+ PUSH(obj1);
+ break;
+
+ case PYBC_DUP_TOP_TWO:
+ sp -= 2;
+ sp[0] = sp[2];
+ sp[1] = sp[3];
+ break;
+ */
+
+ case PYBC_POP_TOP:
+ printf("POP_TOP");
+ break;
+
+ /*
+ case PYBC_ROT_TWO:
+ obj1 = sp[0];
+ sp[0] = sp[1];
+ sp[1] = obj1;
+ break;
+
+ case PYBC_ROT_THREE:
+ obj1 = sp[0];
+ sp[0] = sp[1];
+ sp[1] = sp[2];
+ sp[2] = obj1;
+ break;
+ */
+
+ case PYBC_JUMP:
+ DECODE_SLABEL;
+ printf("JUMP %lu", ip + unum - ip_start);
+ break;
+
+ case PYBC_POP_JUMP_IF_TRUE:
+ DECODE_SLABEL;
+ printf("POP_JUMP_IF_TRUE %lu", ip + unum - ip_start);
+ break;
+
+ /*
+ case PYBC_POP_JUMP_IF_FALSE:
+ DECODE_SLABEL;
+ if (!rt_is_true(POP())) {
+ ip += unum;
+ }
+ break;
+
+ case PYBC_JUMP_IF_TRUE_OR_POP:
+ DECODE_SLABEL;
+ if (rt_is_true(*sp)) {
+ ip += unum;
+ } else {
+ sp++;
+ }
+ break;
+
+ case PYBC_JUMP_IF_FALSE_OR_POP:
+ DECODE_SLABEL;
+ if (rt_is_true(*sp)) {
+ sp++;
+ } else {
+ ip += unum;
+ }
+ break;
+
+ case PYBC_SETUP_EXCEPT:
+ DECODE_ULABEL; // except labels are always forward
+ *++exc_sp = (machine_uint_t)ip + unum;
+ *++exc_sp = (machine_uint_t)sp;
+ break;
+
+ case PYBC_END_FINALLY:
+ // not implemented
+ // if TOS is an exception, reraises the exception (3 values on TOS)
+ // if TOS is an integer, does something else
+ // if TOS is None, just pops it and continues
+ // else error
+ assert(0);
+ break;
+
+ case PYBC_GET_ITER:
+ *sp = rt_getiter(*sp);
+ break;
+
+ case PYBC_FOR_ITER:
+ DECODE_ULABEL; // the jump offset if iteration finishes; for labels are always forward
+ obj1 = rt_iternext(*sp);
+ if (obj1 == py_const_stop_iteration) {
+ ++sp; // pop the exhausted iterator
+ ip += unum; // jump to after for-block
+ } else {
+ PUSH(obj1); // push the next iteration value
+ }
+ break;
+
+ case PYBC_POP_BLOCK:
+ // pops block and restores the stack
+ assert(0);
+ break;
+
+ case PYBC_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[0]);
+ //sp = (py_obj_t*)(*exc_sp--);
+ //exc_sp--; // discard ip
+ exc_sp -= 2;
+ //sp += 3; // pop 3 exception values
+ break;
+
+ case PYBC_UNARY_OP:
+ unum = *ip++;
+ *sp = rt_unary_op(unum, *sp);
+ break;
+ */
+
+ case PYBC_BINARY_OP:
+ unum = *ip++;
+ printf("BINARY_OP %lu", unum);
+ break;
+
+ case PYBC_COMPARE_OP:
+ unum = *ip++;
+ printf("COMPARE_OP %lu", unum);
+ break;
+
+ /*
+ case PYBC_BUILD_TUPLE:
+ DECODE_UINT;
+ obj1 = rt_build_tuple(unum, sp);
+ sp += unum - 1;
+ *sp = obj1;
+ break;
+
+ case PYBC_BUILD_LIST:
+ DECODE_UINT;
+ obj1 = rt_build_list(unum, sp);
+ sp += unum - 1;
+ *sp = obj1;
+ break;
+
+ case PYBC_LIST_APPEND:
+ DECODE_UINT;
+ // I think it's guaranteed by the compiler that sp[unum] is a list
+ rt_list_append(sp[unum], sp[0]);
+ sp++;
+ break;
+
+ case PYBC_BUILD_MAP:
+ DECODE_UINT;
+ PUSH(rt_build_map(unum));
+ break;
+
+ case PYBC_STORE_MAP:
+ sp += 2;
+ rt_store_map(sp[0], sp[-2], sp[-1]);
+ break;
+
+ case PYBC_MAP_ADD:
+ DECODE_UINT;
+ // I think it's guaranteed by the compiler that sp[unum + 1] is a map
+ rt_store_map(sp[unum + 1], sp[0], sp[1]);
+ sp += 2;
+ break;
+
+ case PYBC_BUILD_SET:
+ DECODE_UINT;
+ obj1 = rt_build_set(unum, sp);
+ sp += unum - 1;
+ *sp = obj1;
+ break;
+
+ case PYBC_SET_ADD:
+ DECODE_UINT;
+ // I think it's guaranteed by the compiler that sp[unum] is a set
+ rt_store_set(sp[unum], sp[0]);
+ sp++;
+ break;
+ */
+
+ case PYBC_MAKE_FUNCTION:
+ DECODE_UINT;
+ printf("MAKE_FUNCTION %lu", unum);
+ break;
+
+ case PYBC_CALL_FUNCTION:
+ DECODE_UINT;
+ assert((unum & 0xff00) == 0); // n_keyword
+ unum &= 0xff; // n_positional
+ printf("CALL_FUNCTION %lu", unum);
+ break;
+
+ case PYBC_CALL_METHOD:
+ DECODE_UINT;
+ assert((unum & 0xff00) == 0); // n_keyword
+ unum &= 0xff;
+ printf("CALL_METHOD %lu", unum);
+ break;
+
+ case PYBC_RETURN_VALUE:
+ printf("RETURN_VALUE");
+ break;
+
+ /*
+ case PYBC_YIELD_VALUE:
+ nlr_pop();
+ *ip_in_out = ip;
+ fastn[0] = fast0;
+ fastn[1] = fast1;
+ fastn[2] = fast2;
+ *sp_in_out = sp;
+ return true;
+ */
+
+ default:
+ printf("code %p, byte code 0x%02x not implemented\n", ip, op);
+ assert(0);
+ return;
+ }
+ printf("\n");
+ }
+}