/*
 * This file compiles an abstract syntax tree (AST) into Python bytecode.
 *
 * The primary entry point is PyAST_Compile(), which returns a
 * PyCodeObject.  The compiler makes several passes to build the code
 * object:
 *   1. Checks for future statements.  See future.c
 *   2. Builds a symbol table.	See symtable.c.
 *   3. Generate code for basic blocks.  See compiler_mod() in this file.
 *   4. Assemble the basic blocks into final code.  See assemble() in
 *	this file.	 
 *   5. Optimize the byte code (peephole optimizations).  See peephole.c
 *
 * Note that compiler_mod() suggests module, but the module ast type
 * (mod_ty) has cases for expressions and interactive statements.
 *
 * CAUTION: The VISIT_* macros abort the current function when they
 * encounter a problem. So don't invoke them when there is memory
 * which needs to be released. Code blocks are OK, as the compiler
 * structure takes care of releasing those.  Use the arena to manage
 * objects.
 */

#include "Python.h"

#include "Python-ast.h"
#include "node.h"
#include "pyarena.h"
#include "ast.h"
#include "code.h"
#include "compile.h"
#include "symtable.h"
#include "opcode.h"

#define DEFAULT_BLOCK_SIZE 16
#define DEFAULT_BLOCKS 8
#define DEFAULT_CODE_SIZE 128
#define DEFAULT_LNOTAB_SIZE 16

struct instr {
	unsigned i_jabs : 1;
	unsigned i_jrel : 1;
	unsigned i_hasarg : 1;
	unsigned char i_opcode;
	int i_oparg;
	struct basicblock_ *i_target; /* target block (if jump instruction) */
	int i_lineno;
};

typedef struct basicblock_ {
    /* Each basicblock in a compilation unit is linked via b_list in the
       reverse order that the block are allocated.  b_list points to the next
       block, not to be confused with b_next, which is next by control flow. */
	struct basicblock_ *b_list;
	/* number of instructions used */
	int b_iused;
	/* length of instruction array (b_instr) */
	int b_ialloc;
	/* pointer to an array of instructions, initially NULL */
	struct instr *b_instr;
	/* If b_next is non-NULL, it is a pointer to the next
	   block reached by normal control flow. */
	struct basicblock_ *b_next;
	/* b_seen is used to perform a DFS of basicblocks. */
	unsigned b_seen : 1;
	/* b_return is true if a RETURN_VALUE opcode is inserted. */
	unsigned b_return : 1;
	/* depth of stack upon entry of block, computed by stackdepth() */
	int b_startdepth;
	/* instruction offset for block, computed by assemble_jump_offsets() */
	int b_offset;
} basicblock;

/* fblockinfo tracks the current frame block.

A frame block is used to handle loops, try/except, and try/finally.
It's called a frame block to distinguish it from a basic block in the
compiler IR.
*/

enum fblocktype { FOR_LOOP, WHILE_LOOP, EXCEPT, FINALLY_TRY, FINALLY_END };

struct fblockinfo {
	enum fblocktype fb_type;
	basicblock *fb_block;
	basicblock *fb_target;
};

/* The following items change on entry and exit of code blocks.
   They must be saved and restored when returning to a block.
*/
struct compiler_unit {
	PySTEntryObject *u_ste;

	PyObject *u_name;
	/* The following fields are dicts that map objects to
	   the index of them in co_XXX.	 The index is used as
	   the argument for opcodes that refer to those collections.
	*/
	PyObject *u_consts;    /* all constants */
	PyObject *u_names;     /* all names */
	PyObject *u_varnames;  /* local variables */
	PyObject *u_cellvars;  /* cell variables */
	PyObject *u_freevars;  /* free variables */

	PyObject *u_private;	/* for private name mangling */

	int u_argcount;	   /* number of arguments for block */ 
	/* Pointer to the most recently allocated block.  By following b_list
	   members, you can reach all early allocated blocks. */
	basicblock *u_blocks;
	basicblock *u_curblock; /* pointer to current block */
	int u_tmpname;		/* temporary variables for list comps */

	int u_nfblocks;
	struct fblockinfo u_fblock[CO_MAXBLOCKS];

	int u_firstlineno; /* the first lineno of the block */
	int u_lineno;	   /* the lineno for the current stmt */
	bool u_lineno_set; /* boolean to indicate whether instr
			      has been generated with current lineno */
	bool u_uses_exec;  /* Whether this code object uses exec */
};

/* This struct captures the global state of a compilation.  

The u pointer points to the current compilation unit, while units
for enclosing blocks are stored in c_stack.	The u and c_stack are
managed by compiler_enter_scope() and compiler_exit_scope().
*/

struct compiler {
	const char *c_filename;
	struct symtable *c_st;
	PyFutureFeatures *c_future; /* pointer to module's __future__ */
	PyCompilerFlags *c_flags;

	int c_interactive;	 /* true if in interactive mode */
	int c_nestlevel;

	struct compiler_unit *u; /* compiler state for current block */
	PyObject *c_stack;	 /* Python list holding compiler_unit ptrs */
	char *c_encoding;	 /* source encoding (a borrowed reference) */
	PyArena *c_arena;	 /* pointer to memory allocation arena */
};

static int compiler_enter_scope(struct compiler *, identifier, void *, int);
static void compiler_free(struct compiler *);
static basicblock *compiler_new_block(struct compiler *);
static int compiler_next_instr(struct compiler *, basicblock *);
static int compiler_addop(struct compiler *, int);
static int compiler_addop_o(struct compiler *, int, PyObject *, PyObject *);
static int compiler_addop_i(struct compiler *, int, int);
static int compiler_addop_j(struct compiler *, int, basicblock *, int);
static basicblock *compiler_use_new_block(struct compiler *);
static int compiler_error(struct compiler *, const char *);
static int compiler_nameop(struct compiler *, identifier, expr_context_ty);
static int compiler_load_global(struct compiler *, const char *);

static PyCodeObject *compiler_mod(struct compiler *, mod_ty);
static int compiler_visit_stmt(struct compiler *, stmt_ty);
static int compiler_visit_keyword(struct compiler *, keyword_ty);
static int compiler_visit_expr(struct compiler *, expr_ty);
static int compiler_augassign(struct compiler *, stmt_ty);
static int compiler_visit_slice(struct compiler *, slice_ty,
				expr_context_ty);

/* top is the basic block representing the top of the loop or try. target
   is really only relevant for loops, and indicates where a break instruction
   should jump to. */
static int compiler_push_fblock(struct compiler *, enum fblocktype,
				basicblock *top, basicblock *target);
static void compiler_pop_fblock(struct compiler *, enum fblocktype,
				basicblock *top, basicblock *target);
/* Returns true if there is a loop on the fblock stack. */
static int compiler_in_loop(struct compiler *);

static int inplace_binop(struct compiler *, operator_ty);
static int expr_constant(expr_ty e);

static int compiler_with(struct compiler *, stmt_ty);

static PyCodeObject *assemble(struct compiler *, int addNone);
static PyObject *__doc__;

PyObject *
_Py_Mangle(PyObject *privateobj, PyObject *ident)
{
	/* Name mangling: __private becomes _classname__private.
	   This is independent from how the name is used. */
	const char *p, *name = PyString_AsString(ident);
	char *buffer;
	size_t nlen, plen;
	if (privateobj == NULL || !PyString_Check(privateobj) ||
	    name == NULL || name[0] != '_' || name[1] != '_') {
		Py_INCREF(ident);
		return ident;
	}
	p = PyString_AsString(privateobj);
	nlen = strlen(name);
	/* Don't mangle __id__ or names with dots.

	   The only time a name with a dot can occur is when
	   we are compiling an import statement that has a 
	   package name.

	   TODO(jhylton): Decide whether we want to support
	   mangling of the module name, e.g. __M.X.
	*/
	if ((name[nlen-1] == '_' && name[nlen-2] == '_') 
	    || strchr(name, '.')) {
		Py_INCREF(ident);
		return ident; /* Don't mangle __whatever__ */
	}
	/* Strip leading underscores from class name */
	while (*p == '_')
		p++;
	if (*p == '\0') {
		Py_INCREF(ident);
		return ident; /* Don't mangle if class is just underscores */
	}
	plen = strlen(p);

	assert(1 <= PY_SSIZE_T_MAX - nlen);
	assert(1 + nlen <= PY_SSIZE_T_MAX - plen);

	ident = PyString_FromStringAndSize(NULL, 1 + nlen + plen);
	if (!ident)
		return 0;
	/* ident = "_" + p[:plen] + name # i.e. 1+plen+nlen bytes */
	buffer = PyString_AS_STRING(ident);
	buffer[0] = '_';
	strncpy(buffer+1, p, plen);
	strcpy(buffer+1+plen, name);
	return ident;
}

static int
compiler_init(struct compiler *c)
{
	memset(c, 0, sizeof(struct compiler));

	c->c_stack = PyList_New(0);
	if (!c->c_stack)
		return 0;

	return 1;
}

PyCodeObject *
PyAST_Compile(mod_ty mod, const char *filename, PyCompilerFlags *flags,
	      PyArena *arena)
{
	struct compiler c;
	PyCodeObject *co = NULL;
	PyCompilerFlags local_flags;
	int merged;

	if (!__doc__) {
		__doc__ = PyString_InternFromString("__doc__");
		if (!__doc__)
			return NULL;
	}

	if (!compiler_init(&c))
		return NULL;
	c.c_filename = filename;
	c.c_arena = arena;
	c.c_future = PyFuture_FromAST(mod, filename);
	if (c.c_future == NULL)
		goto finally;
	if (!flags) {
		local_flags.cf_flags = 0;
		flags = &local_flags;
	}
	merged = c.c_future->ff_features | flags->cf_flags;
	c.c_future->ff_features = merged;
	flags->cf_flags = merged;
	c.c_flags = flags;
	c.c_nestlevel = 0;

	c.c_st = PySymtable_Build(mod, filename, c.c_future);
	if (c.c_st == NULL) {
		if (!PyErr_Occurred())
			PyErr_SetString(PyExc_SystemError, "no symtable");
		goto finally;
	}

	/* XXX initialize to NULL for now, need to handle */
	c.c_encoding = NULL;

	co = compiler_mod(&c, mod);

 finally:
	compiler_free(&c);
	assert(co || PyErr_Occurred());
	return co;
}

PyCodeObject *
PyNode_Compile(struct _node *n, const char *filename)
{
	PyCodeObject *co = NULL;
	mod_ty mod;
	PyArena *arena = PyArena_New();
	if (!arena)
		return NULL;
	mod = PyAST_FromNode(n, NULL, filename, arena);
	if (mod)
		co = PyAST_Compile(mod, filename, NULL, arena);
	PyArena_Free(arena);
	return co;
}

static void
compiler_free(struct compiler *c)
{
	if (c->c_st)
		PySymtable_Free(c->c_st);
	if (c->c_future)
		PyObject_Free(c->c_future);
	Py_DECREF(c->c_stack);
}

static PyObject *
list2dict(PyObject *list)
{
	Py_ssize_t i, n;
	PyObject *v, *k;
	PyObject *dict = PyDict_New();
	if (!dict) return NULL;

	n = PyList_Size(list);
	for (i = 0; i < n; i++) {
		v = PyInt_FromLong(i);
		if (!v) {
			Py_DECREF(dict);
			return NULL;
		}
		k = PyList_GET_ITEM(list, i);
		k = PyTuple_Pack(2, k, k->ob_type);
		if (k == NULL || PyDict_SetItem(dict, k, v) < 0) {
			Py_XDECREF(k);
			Py_DECREF(v);
			Py_DECREF(dict);
			return NULL;
		}
		Py_DECREF(k);
		Py_DECREF(v);
	}
	return dict;
}

/* Return new dict containing names from src that match scope(s).

src is a symbol table dictionary.  If the scope of a name matches
either scope_type or flag is set, insert it into the new dict.	The
values are integers, starting at offset and increasing by one for
each key.
*/

static PyObject *
dictbytype(PyObject *src, int scope_type, int flag, int offset)
{
	Py_ssize_t pos = 0, i = offset, scope;
	PyObject *k, *v, *dest = PyDict_New();

	assert(offset >= 0);
	if (dest == NULL)
		return NULL;

	while (PyDict_Next(src, &pos, &k, &v)) {
		/* XXX this should probably be a macro in symtable.h */
		assert(PyInt_Check(v));
		scope = (PyInt_AS_LONG(v) >> SCOPE_OFF) & SCOPE_MASK;

		if (scope == scope_type || PyInt_AS_LONG(v) & flag) {
			PyObject *tuple, *item = PyInt_FromLong(i);
			if (item == NULL) {
				Py_DECREF(dest);
				return NULL;
			}
			i++;
			tuple = PyTuple_Pack(2, k, k->ob_type);
			if (!tuple || PyDict_SetItem(dest, tuple, item) < 0) {
				Py_DECREF(item);
				Py_DECREF(dest);
				Py_XDECREF(tuple);
				return NULL;
			}
			Py_DECREF(item);
			Py_DECREF(tuple);
		}
	}
	return dest;
}

static void
compiler_unit_check(struct compiler_unit *u)
{
	basicblock *block;
	for (block = u->u_blocks; block != NULL; block = block->b_list) {
		assert((void *)block != (void *)0xcbcbcbcb);
		assert((void *)block != (void *)0xfbfbfbfb);
		assert((void *)block != (void *)0xdbdbdbdb);
		if (block->b_instr != NULL) {
			assert(block->b_ialloc > 0);
			assert(block->b_iused > 0);
			assert(block->b_ialloc >= block->b_iused);
		}
		else {
			assert (block->b_iused == 0);
			assert (block->b_ialloc == 0);
		}
	}
}

static void
compiler_unit_free(struct compiler_unit *u)
{
	basicblock *b, *next;

	compiler_unit_check(u);
	b = u->u_blocks;
	while (b != NULL) {
		if (b->b_instr)
			PyObject_Free((void *)b->b_instr);
		next = b->b_list;
		PyObject_Free((void *)b);
		b = next;
	}
	Py_CLEAR(u->u_ste);
	Py_CLEAR(u->u_name);
	Py_CLEAR(u->u_consts);
	Py_CLEAR(u->u_names);
	Py_CLEAR(u->u_varnames);
	Py_CLEAR(u->u_freevars);
	Py_CLEAR(u->u_cellvars);
	Py_CLEAR(u->u_private);
	PyObject_Free(u);
}

static int
compiler_enter_scope(struct compiler *c, identifier name, void *key,
		     int lineno)
{
	struct compiler_unit *u;

	u = (struct compiler_unit *)PyObject_Malloc(sizeof(
						struct compiler_unit));
	if (!u) {
		PyErr_NoMemory();
		return 0;
	}
	memset(u, 0, sizeof(struct compiler_unit));
	u->u_argcount = 0;
	u->u_ste = PySymtable_Lookup(c->c_st, key);
	if (!u->u_ste) {
		compiler_unit_free(u);
		return 0;
	}
	Py_INCREF(name);
	u->u_name = name;
	u->u_varnames = list2dict(u->u_ste->ste_varnames);
	u->u_cellvars = dictbytype(u->u_ste->ste_symbols, CELL, 0, 0);
	if (!u->u_varnames || !u->u_cellvars) {
		compiler_unit_free(u);
		return 0;
	}

	u->u_freevars = dictbytype(u->u_ste->ste_symbols, FREE, DEF_FREE_CLASS,
				   PyDict_Size(u->u_cellvars));
	if (!u->u_freevars) {
		compiler_unit_free(u);
		return 0;
	}

	u->u_blocks = NULL;
	u->u_tmpname = 0;
	u->u_nfblocks = 0;
	u->u_firstlineno = lineno;
	u->u_lineno = 0;
	u->u_lineno_set = false;
	u->u_uses_exec = false;
	u->u_consts = PyDict_New();
	if (!u->u_consts) {
		compiler_unit_free(u);
		return 0;
	}
	u->u_names = PyDict_New();
	if (!u->u_names) {
		compiler_unit_free(u);
		return 0;
	}

	u->u_private = NULL;

	/* Push the old compiler_unit on the stack. */
	if (c->u) {
		PyObject *wrapper = PyCObject_FromVoidPtr(c->u, NULL);
		if (!wrapper || PyList_Append(c->c_stack, wrapper) < 0) {
			Py_XDECREF(wrapper);
			compiler_unit_free(u);
			return 0;
		}
		Py_DECREF(wrapper);
		u->u_private = c->u->u_private;
		Py_XINCREF(u->u_private);
	}
	c->u = u;

	c->c_nestlevel++;
	if (compiler_use_new_block(c) == NULL)
		return 0;

	return 1;
}

static void
compiler_exit_scope(struct compiler *c)
{
	int n;
	PyObject *wrapper;

	c->c_nestlevel--;
	compiler_unit_free(c->u);
	/* Restore c->u to the parent unit. */
	n = PyList_GET_SIZE(c->c_stack) - 1;
	if (n >= 0) {
		wrapper = PyList_GET_ITEM(c->c_stack, n);
		c->u = (struct compiler_unit *)PyCObject_AsVoidPtr(wrapper);
		assert(c->u);
		/* we are deleting from a list so this really shouldn't fail */
		if (PySequence_DelItem(c->c_stack, n) < 0)
			Py_FatalError("compiler_exit_scope()");
		compiler_unit_check(c->u);
	}
	else
		c->u = NULL;

}

/* Allocate a new "anonymous" local variable.
   Used by list comprehensions and with statements.
*/

static PyObject *
compiler_new_tmpname(struct compiler *c)
{
	char tmpname[256];
	PyOS_snprintf(tmpname, sizeof(tmpname), "_[%d]", ++c->u->u_tmpname);
	return PyString_FromString(tmpname);
}

/* Allocate a new block and return a pointer to it.
   Returns NULL on error.
*/

static basicblock *
compiler_new_block(struct compiler *c)
{
	basicblock *b;
	struct compiler_unit *u;

	u = c->u;
	b = (basicblock *)PyObject_Malloc(sizeof(basicblock));
	if (b == NULL) {
		PyErr_NoMemory();
		return NULL;
	}
	memset((void *)b, 0, sizeof(basicblock));
	/* Extend the singly linked list of blocks with new block. */
	b->b_list = u->u_blocks;
	u->u_blocks = b;
	return b;
}

static basicblock *
compiler_use_new_block(struct compiler *c)
{
	basicblock *block = compiler_new_block(c);
	if (block == NULL)
		return NULL;
	c->u->u_curblock = block;
	return block;
}

static basicblock *
compiler_use_next_block(struct compiler *c, basicblock *block)
{
	assert(block != NULL);

	c->u->u_curblock->b_next = block;
	c->u->u_curblock = block;
	return block;
}

static basicblock *
compiler_next_block(struct compiler *c)
{
	basicblock *block = compiler_new_block(c);
	if (block == NULL)
		return NULL;

        return compiler_use_next_block(c, block);
}
/* Returns the offset of the next instruction in the current block's
   b_instr array.  Resizes the b_instr as necessary.
   Returns -1 on failure.
*/

static int
compiler_next_instr(struct compiler *c, basicblock *b)
{
	assert(b != NULL);
	if (b->b_instr == NULL) {
		b->b_instr = (struct instr *)PyObject_Malloc(
				 sizeof(struct instr) * DEFAULT_BLOCK_SIZE);
		if (b->b_instr == NULL) {
			PyErr_NoMemory();
			return -1;
		}
		b->b_ialloc = DEFAULT_BLOCK_SIZE;
		memset((char *)b->b_instr, 0,
		       sizeof(struct instr) * DEFAULT_BLOCK_SIZE);
	}
	else if (b->b_iused == b->b_ialloc) {
		struct instr *tmp;
		size_t oldsize, newsize;
		oldsize = b->b_ialloc * sizeof(struct instr);
		newsize = oldsize << 1;

		if (oldsize > (PY_SIZE_MAX >> 1)) {
			PyErr_NoMemory();
			return -1;
		}

		if (newsize == 0) {
			PyErr_NoMemory();
			return -1;
		}
		b->b_ialloc <<= 1;
		tmp = (struct instr *)PyObject_Realloc(
						(void *)b->b_instr, newsize);
		if (tmp == NULL) {
			PyErr_NoMemory();
			return -1;
		}
		b->b_instr = tmp;
		memset((char *)b->b_instr + oldsize, 0, newsize - oldsize);
	}
	return b->b_iused++;
}

/* Set the i_lineno member of the instruction at offset off if the
   line number for the current expression/statement has not
   already been set.  If it has been set, the call has no effect.

   The line number is reset in the following cases:
   - when entering a new scope
   - on each statement
   - on each expression that start a new line
   - before the "except" clause
   - before the "for" and "while" expressions
*/

static void
compiler_set_lineno(struct compiler *c, int off)
{
	basicblock *b;
	if (c->u->u_lineno_set)
		return;
	c->u->u_lineno_set = true;
	b = c->u->u_curblock;
	b->b_instr[off].i_lineno = c->u->u_lineno;
}

int
_Py_OpcodeStackEffect(int opcode, int oparg)
{
	switch (opcode) {
		case POP_TOP:
			return -1;
		case ROT_TWO:
		case ROT_THREE:
			return 0;
		case DUP_TOP:
			return 1;
		case ROT_FOUR:
			return 0;

		case UNARY_POSITIVE:
		case UNARY_NEGATIVE:
		case UNARY_NOT:
		case UNARY_CONVERT:
		case UNARY_INVERT:
			return 0;

		case LIST_APPEND:
			return -2;

		case BINARY_POWER:
		case BINARY_MULTIPLY:
		case BINARY_DIVIDE:
		case BINARY_MODULO:
		case BINARY_ADD:
		case BINARY_SUBTRACT:
		case BINARY_SUBSCR:
		case BINARY_FLOOR_DIVIDE:
		case BINARY_TRUE_DIVIDE:
			return -1;
		case INPLACE_FLOOR_DIVIDE:
		case INPLACE_TRUE_DIVIDE:
			return -1;

		case SLICE_NONE:
			return 0;
		case SLICE_LEFT:
			return -1;
		case SLICE_RIGHT:
			return -1;
		case SLICE_BOTH:
			return -2;

		case STORE_SLICE_NONE:
			return -2;
		case STORE_SLICE_LEFT:
			return -3;
		case STORE_SLICE_RIGHT:
			return -3;
		case STORE_SLICE_BOTH:
			return -4;

		case DELETE_SLICE_NONE:
			return -1;
		case DELETE_SLICE_LEFT:
			return -2;
		case DELETE_SLICE_RIGHT:
			return -2;
		case DELETE_SLICE_BOTH:
			return -3;

		case INPLACE_ADD:
		case INPLACE_SUBTRACT:
		case INPLACE_MULTIPLY:
		case INPLACE_DIVIDE:
		case INPLACE_MODULO:
			return -1;
		case STORE_SUBSCR:
			return -3;
		case STORE_MAP:
			return -2;
		case DELETE_SUBSCR:
			return -2;

		case BINARY_LSHIFT:
		case BINARY_RSHIFT:
		case BINARY_AND:
		case BINARY_XOR:
		case BINARY_OR:
			return -1;
		case INPLACE_POWER:
			return -1;
		case GET_ITER:
			return 0;

		case INPLACE_LSHIFT:
		case INPLACE_RSHIFT:
		case INPLACE_AND:
		case INPLACE_XOR:
		case INPLACE_OR:
			return -1;
		case BREAK_LOOP:
			return 0;
		case WITH_CLEANUP:
			return -1;
		case RETURN_VALUE:
			return -1;
		case YIELD_VALUE:
			return 0;

		case POP_BLOCK:
			return 0;
		case END_FINALLY:
			return -3;

		case STORE_NAME:
			return -1;
		case DELETE_NAME:
			return 0;
		case UNPACK_SEQUENCE:
			return oparg-1;
		case FOR_ITER:
			return 1;

		case STORE_ATTR:
			return -2;
		case DELETE_ATTR:
			return -1;
		case STORE_GLOBAL:
			return -1;
		case DELETE_GLOBAL:
			return 0;
		case DUP_TOP_TWO:
			return 2;
		case DUP_TOP_THREE:
			return 3;
		case LOAD_CONST:
			return 1;
		case LOAD_NAME:
			return 1;
		case BUILD_TUPLE:
		case BUILD_LIST:
			return 1-oparg;
		case BUILD_MAP:
			return 1;
		case LOAD_ATTR:
			return 0;
		case LOAD_METHOD:
			return 1;  /* Maybe set top, push one. */
		case COMPARE_OP:
			return -1;
		case IMPORT_NAME:
			return -2;  /* Pop three, push one. */

		case JUMP_FORWARD:
		case JUMP_IF_TRUE_OR_POP:  /* -1 if jump not taken */
		case JUMP_IF_FALSE_OR_POP:  /*  "" */
		case JUMP_ABSOLUTE:
			return 0;

		case POP_JUMP_IF_FALSE:
		case POP_JUMP_IF_TRUE:
			return -1;

		case LOAD_GLOBAL:
			return 1;

		case CONTINUE_LOOP:
			return 0;
		case SETUP_LOOP:
			return 0;
		case SETUP_EXCEPT:
		case SETUP_FINALLY:
			return 3; /* actually pushed by an exception */

		case LOAD_FAST:
			return 1;
		case STORE_FAST:
			return -1;
		case DELETE_FAST:
			return 0;

		case RAISE_VARARGS_ZERO:
			return 0;
		case RAISE_VARARGS_ONE:
			return -1;
		case RAISE_VARARGS_TWO:
			return -2;
		case RAISE_VARARGS_THREE:
			return -3;
#define NARGS(o) (((o) % 256) + 2*((o) / 256))
		case CALL_FUNCTION:
			return -NARGS(oparg);
		case CALL_METHOD:
			return -NARGS(oparg)-1;
		case CALL_FUNCTION_VAR:
		case CALL_FUNCTION_KW:
			return -NARGS(oparg)-1;
		case CALL_FUNCTION_VAR_KW:
			return -NARGS(oparg)-2;
#undef NARGS			
		case BUILD_SLICE_TWO:
			return -1;
		case BUILD_SLICE_THREE:
			return -2;
		case MAKE_CLOSURE:
			return -(oparg + 1);
		case LOAD_CLOSURE:
			return 1;
		case LOAD_DEREF:
			return 1;
		case STORE_DEREF:
			return -1;
		default:
			fprintf(stderr, "opcode = %d\n", opcode);
			Py_FatalError("_Py_OpcodeStackEffect()");

	}
	return 0; /* not reachable */
}

/* Add an opcode with no argument.
   Returns 0 on failure, 1 on success.
*/

static int
compiler_addop(struct compiler *c, int opcode)
{
	basicblock *b;
	struct instr *i;
	int off;
	off = compiler_next_instr(c, c->u->u_curblock);
	if (off < 0)
		return 0;
	b = c->u->u_curblock;
	i = &b->b_instr[off];
	i->i_opcode = opcode;
	i->i_hasarg = 0;
	if (opcode == RETURN_VALUE)
		b->b_return = 1;
	compiler_set_lineno(c, off);
	return 1;
}

/* Adds 'o' to the mapping stored in 'dict' (if it wasn't already
 * there) so it can be looked up by opcodes like LOAD_CONST and
 * LOAD_NAME.  This function derives a tuple from o to avoid pairs of
 * values like 0.0 and -0.0 or 0 and 0.0 that compare equal but need
 * to be kept separate.  'o' is mapped to a small integer, and its
 * mapping is returned. */
static int
compiler_add_o(struct compiler *c, PyObject *dict, PyObject *o)
{
	PyObject *t, *v;
	Py_ssize_t arg;
	unsigned char *p, *q;
	Py_complex z;
	double d;
	int real_part_zero, imag_part_zero;

	/* necessary to make sure types aren't coerced (e.g., int and long) */
        /* _and_ to distinguish 0.0 from -0.0 e.g. on IEEE platforms */
        if (PyFloat_Check(o)) {
		d = PyFloat_AS_DOUBLE(o);
		p = (unsigned char*) &d;
		/* all we need is to make the tuple different in either the 0.0
		 * or -0.0 case from all others, just to avoid the "coercion".
		 */
		if (*p==0 && p[sizeof(double)-1]==0)
			t = PyTuple_Pack(3, o, o->ob_type, Py_None);
		else
			t = PyTuple_Pack(2, o, o->ob_type);
	}
	else if (PyComplex_Check(o)) {
		/* complex case is even messier: we need to make complex(x,
		   0.) different from complex(x, -0.) and complex(0., y)
		   different from complex(-0., y), for any x and y.  In
		   particular, all four complex zeros should be
		   distinguished.*/
		z = PyComplex_AsCComplex(o);
		p = (unsigned char*) &(z.real);
		q = (unsigned char*) &(z.imag);
		/* all that matters here is that on IEEE platforms
		   real_part_zero will be true if z.real == 0., and false if
		   z.real == -0.  In fact, real_part_zero will also be true
		   for some other rarely occurring nonzero floats, but this
		   doesn't matter. Similar comments apply to
		   imag_part_zero. */
		real_part_zero = *p==0 && p[sizeof(double)-1]==0;
		imag_part_zero = *q==0 && q[sizeof(double)-1]==0;
		if (real_part_zero && imag_part_zero) {
			t = PyTuple_Pack(4, o, o->ob_type, Py_True, Py_True);
		}
		else if (real_part_zero && !imag_part_zero) {
			t = PyTuple_Pack(4, o, o->ob_type, Py_True, Py_False);
		}
		else if (!real_part_zero && imag_part_zero) {
			t = PyTuple_Pack(4, o, o->ob_type, Py_False, Py_True);
		}
		else {
			t = PyTuple_Pack(2, o, o->ob_type);
		}
        }
	else {
		t = PyTuple_Pack(2, o, o->ob_type);
        }
	if (t == NULL)
		return -1;

	v = PyDict_GetItem(dict, t);
	if (!v) {
		arg = PyDict_Size(dict);
		v = PyInt_FromLong(arg);
		if (!v) {
			Py_DECREF(t);
			return -1;
		}
		if (PyDict_SetItem(dict, t, v) < 0) {
			Py_DECREF(t);
			Py_DECREF(v);
			return -1;
		}
		Py_DECREF(v);
	}
	else
		arg = PyInt_AsLong(v);
	Py_DECREF(t);
	return arg;
}

/* Adds opcode(o) as the next instruction in the current basic block.
   Because opcodes only take integer arguments, we give 'o' a number
   unique within 'dict' and store the mapping in 'dict'.  'dict' is one
   of c->u->u_{consts,names,varnames} and must match the code::co_list
   that 'opcode' looks in.
*/
static int
compiler_addop_o(struct compiler *c, int opcode, PyObject *dict,
		 PyObject *o)
{
    int arg = compiler_add_o(c, dict, o);
    if (arg < 0)
	return 0;
    return compiler_addop_i(c, opcode, arg);
}

/* Like compiler_addop_o, but name-mangles 'o' if appropriate. */
static int
compiler_addop_name(struct compiler *c, int opcode, PyObject *dict,
		    PyObject *o)
{
    int arg;
    PyObject *mangled = _Py_Mangle(c->u->u_private, o);
    if (!mangled)
	return 0;
    arg = compiler_add_o(c, dict, mangled);
    Py_DECREF(mangled);
    if (arg < 0)
	return 0;
    return compiler_addop_i(c, opcode, arg);
}

/* Add an opcode with an integer argument.
   Returns 0 on failure, 1 on success.
*/

static int
compiler_addop_i(struct compiler *c, int opcode, int oparg)
{
	struct instr *i;
	int off;
	off = compiler_next_instr(c, c->u->u_curblock);
	if (off < 0)
		return 0;
	i = &c->u->u_curblock->b_instr[off];
	i->i_opcode = opcode;
	i->i_oparg = oparg;
	i->i_hasarg = 1;
	compiler_set_lineno(c, off);
	return 1;
}

/* Adds a jump opcode whose target is 'b'. This works for both
   conditional and unconditional jumps.
*/
static int
compiler_addop_j(struct compiler *c, int opcode, basicblock *b, int absolute)
{
	struct instr *i;
	int off;

	assert(b != NULL);
	off = compiler_next_instr(c, c->u->u_curblock);
	if (off < 0)
		return 0;
	i = &c->u->u_curblock->b_instr[off];
	i->i_opcode = opcode;
	i->i_target = b;
	i->i_hasarg = 1;
	if (absolute)
		i->i_jabs = 1;
	else
		i->i_jrel = 1;
	compiler_set_lineno(c, off);
	return 1;
}

/* NEXT_BLOCK() creates a new block, creates an implicit jump from the
   current block to the new block, and sets the new block as the
   current block.
*/

/* The returns inside these macros make it impossible to decref objects
   created in the local function.  Local objects should use the arena.
*/


#define NEXT_BLOCK(C) { \
	if (compiler_next_block((C)) == NULL) \
		return 0; \
}

#define ADDOP(C, OP) { \
	if (!compiler_addop((C), (OP))) \
		return 0; \
}

#define ADDOP_IN_SCOPE(C, OP) { \
	if (!compiler_addop((C), (OP))) { \
		compiler_exit_scope(c); \
		return 0; \
	} \
}

#define ADDOP_O(C, OP, O, TYPE) { \
	if (!compiler_addop_o((C), (OP), (C)->u->u_ ## TYPE, (O))) \
		return 0; \
}

#define ADDOP_NAME(C, OP, O, TYPE) { \
	if (!compiler_addop_name((C), (OP), (C)->u->u_ ## TYPE, (O))) \
		return 0; \
}

#define ADDOP_I(C, OP, O) { \
	if (!compiler_addop_i((C), (OP), (O))) \
		return 0; \
}

#define ADDOP_JABS(C, OP, O) { \
	if (!compiler_addop_j((C), (OP), (O), 1)) \
		return 0; \
}

#define ADDOP_JREL(C, OP, O) { \
	if (!compiler_addop_j((C), (OP), (O), 0)) \
		return 0; \
}

/* VISIT and VISIT_SEQ takes an ASDL type as their second argument.  They use
   the ASDL name to synthesize the name of the C type and the visit function.
*/

#define VISIT(C, TYPE, V) {\
	if (!compiler_visit_ ## TYPE((C), (V))) \
		return 0; \
}

#define VISIT_IN_SCOPE(C, TYPE, V) {\
	if (!compiler_visit_ ## TYPE((C), (V))) { \
		compiler_exit_scope(c); \
		return 0; \
	} \
}

#define VISIT_SLICE(C, V, CTX) {\
	if (!compiler_visit_slice((C), (V), (CTX))) \
		return 0; \
}

#define VISIT_SEQ(C, TYPE, SEQ) { \
	int _i; \
	asdl_seq *seq = (SEQ); /* avoid variable capture */ \
	for (_i = 0; _i < asdl_seq_LEN(seq); _i++) { \
		TYPE ## _ty elt = (TYPE ## _ty)asdl_seq_GET(seq, _i); \
		if (!compiler_visit_ ## TYPE((C), elt)) \
			return 0; \
	} \
}

#define VISIT_SEQ_IN_SCOPE(C, TYPE, SEQ) { \
	int _i; \
	asdl_seq *seq = (SEQ); /* avoid variable capture */ \
	for (_i = 0; _i < asdl_seq_LEN(seq); _i++) { \
		TYPE ## _ty elt = (TYPE ## _ty)asdl_seq_GET(seq, _i); \
		if (!compiler_visit_ ## TYPE((C), elt)) { \
			compiler_exit_scope(c); \
			return 0; \
		} \
	} \
}

static int
compiler_isdocstring(stmt_ty s)
{
    if (s->kind != Expr_kind)
	return 0;
    return s->v.Expr.value->kind == Str_kind;
}

/* Compile a sequence of statements, checking for a docstring. */

static int
compiler_body(struct compiler *c, asdl_seq *stmts)
{
	int i = 0;
	stmt_ty st;

	if (!asdl_seq_LEN(stmts))
		return 1;
	st = (stmt_ty)asdl_seq_GET(stmts, 0);
	if (compiler_isdocstring(st) && Py_OptimizeFlag < 2) {
		/* don't generate docstrings if -OO */
		i = 1;
		VISIT(c, expr, st->v.Expr.value);
		if (!compiler_nameop(c, __doc__, Store))
			return 0;
	}
	for (; i < asdl_seq_LEN(stmts); i++)
	    VISIT(c, stmt, (stmt_ty)asdl_seq_GET(stmts, i));
	return 1;
}

static PyCodeObject *
compiler_mod(struct compiler *c, mod_ty mod)
{
	PyCodeObject *co;
	int addNone = 1;
	static PyObject *module;
	if (!module) {
		module = PyString_InternFromString("<module>");
		if (!module)
			return NULL;
	}
	/* Use 0 for firstlineno initially, will fixup in assemble(). */
	if (!compiler_enter_scope(c, module, mod, 0))
		return NULL;
	switch (mod->kind) {
	case Module_kind: 
		if (!compiler_body(c, mod->v.Module.body)) {
			compiler_exit_scope(c);
			return 0;
		}
		break;
	case Interactive_kind:
		c->c_interactive = 1;
		VISIT_SEQ_IN_SCOPE(c, stmt, 
					mod->v.Interactive.body);
		break;
	case Expression_kind:
		VISIT_IN_SCOPE(c, expr, mod->v.Expression.body);
		addNone = 0;
		break;
	case Suite_kind:
		PyErr_SetString(PyExc_SystemError,
				"suite should not be possible");
		return 0;
	default:
		PyErr_Format(PyExc_SystemError,
			     "module kind %d should not be possible",
			     mod->kind);
		return 0;
	}
	co = assemble(c, addNone);
	compiler_exit_scope(c);
	return co;
}

/* The test for LOCAL must come before the test for FREE in order to
   handle classes where name is both local and free.  The local var is
   a method and the free var is a free var referenced within a method.
*/

static int
get_ref_type(struct compiler *c, PyObject *name)
{
	int scope = PyST_GetScope(c->u->u_ste, name);
	if (scope == 0) {
	    char buf[350];
	    PyOS_snprintf(buf, sizeof(buf),
			  "unknown scope for %.100s in %.100s(%s) in %s\n"
			  "symbols: %s\nlocals: %s\nglobals: %s\n",
			  PyString_AS_STRING(name), 
			  PyString_AS_STRING(c->u->u_name), 
			  PyObject_REPR(c->u->u_ste->ste_id),
			  c->c_filename,
			  PyObject_REPR(c->u->u_ste->ste_symbols),
			  PyObject_REPR(c->u->u_varnames),
			  PyObject_REPR(c->u->u_names)
		);
	    Py_FatalError(buf);
	}

	return scope;
}

static int
compiler_lookup_arg(PyObject *dict, PyObject *name)
{
    PyObject *k, *v;
    k = PyTuple_Pack(2, name, name->ob_type);
    if (k == NULL)
	return -1;
    v = PyDict_GetItem(dict, k);
    Py_DECREF(k);
    if (v == NULL)
	return -1;
    return PyInt_AS_LONG(v);
}

static int
compiler_make_closure(struct compiler *c, PyCodeObject *co, asdl_seq *defaults)
{
	int i, free = PyCode_GetNumFree(co), ndefaults = 0;
	if (free == 0) {
		if (!compiler_load_global(c, "#@make_function"))
			return 0;
		ADDOP_O(c, LOAD_CONST, (PyObject*)co, consts);
		if (defaults)
			VISIT_SEQ(c, expr, defaults);
		ADDOP_I(c, CALL_FUNCTION, asdl_seq_LEN(defaults) + 1);
		return 1;
	}
	if (defaults) {
		ndefaults = asdl_seq_LEN(defaults);
		VISIT_SEQ(c, expr, defaults);
	}
	for (i = 0; i < free; ++i) {
		/* Bypass com_addop_varname because it will generate
		   LOAD_DEREF but LOAD_CLOSURE is needed. 
		*/
		PyObject *name = PyTuple_GET_ITEM(co->co_freevars, i);
		int arg, reftype;

		/* Special case: If a class contains a method with a
		   free variable that has the same name as a method,
		   the name will be considered free *and* local in the
		   class.  It should be handled by the closure, as
		   well as by the normal name loookup logic.
		*/
		reftype = get_ref_type(c, name);
		if (reftype == CELL)
			arg = compiler_lookup_arg(c->u->u_cellvars, name);
		else /* (reftype == FREE) */
			arg = compiler_lookup_arg(c->u->u_freevars, name);
		if (arg == -1) {
			printf("lookup %s in %s %d %d\n"
				"freevars of %s: %s\n",
				PyObject_REPR(name),
				PyString_AS_STRING(c->u->u_name),
				reftype, arg,
				PyString_AS_STRING(co->co_name),
				PyObject_REPR(co->co_freevars));
			Py_FatalError("compiler_make_closure()");
		}
		ADDOP_I(c, LOAD_CLOSURE, arg);
	}
	ADDOP_I(c, BUILD_TUPLE, free);
	ADDOP_O(c, LOAD_CONST, (PyObject*)co, consts);
	ADDOP_I(c, MAKE_CLOSURE, ndefaults);
	return 1;
}

static int
compiler_decorators(struct compiler *c, asdl_seq* decos)
{
	int i;

	if (!decos)
		return 1;

	for (i = 0; i < asdl_seq_LEN(decos); i++) {
		VISIT(c, expr, (expr_ty)asdl_seq_GET(decos, i));
	}
	return 1;
}

static int
compiler_arguments(struct compiler *c, arguments_ty args)
{
	int i;
	int n = asdl_seq_LEN(args->args);
	/* Correctly handle nested argument lists */
	for (i = 0; i < n; i++) {
		expr_ty arg = (expr_ty)asdl_seq_GET(args->args, i);
		if (arg->kind == Tuple_kind) {
			PyObject *id = PyString_FromFormat(".%d", i);
			if (id == NULL) {
				return 0;
			}
			if (!compiler_nameop(c, id, Load)) {
				Py_DECREF(id);
				return 0;
			}
			Py_DECREF(id);
			VISIT(c, expr, arg);
		}
	}
	return 1;
}

static int
compiler_function(struct compiler *c, stmt_ty s)
{
	PyCodeObject *co;
	PyObject *first_const = Py_None;
	arguments_ty args = s->v.FunctionDef.args;
	asdl_seq* decos = s->v.FunctionDef.decorator_list;
	stmt_ty st;
	int i, n, docstring;

	assert(s->kind == FunctionDef_kind);

	if (!compiler_decorators(c, decos))
		return 0;
	if (!compiler_enter_scope(c, s->v.FunctionDef.name, (void *)s,
				  s->lineno))
		return 0;

	st = (stmt_ty)asdl_seq_GET(s->v.FunctionDef.body, 0);
	docstring = compiler_isdocstring(st);
	if (docstring && Py_OptimizeFlag < 2)
		first_const = st->v.Expr.value->v.Str.s;
	if (compiler_add_o(c, c->u->u_consts, first_const) < 0) {
		compiler_exit_scope(c);
		return 0;
	}

	/* unpack nested arguments */
	compiler_arguments(c, args);

	c->u->u_argcount = asdl_seq_LEN(args->args);
	n = asdl_seq_LEN(s->v.FunctionDef.body);
	/* if there was a docstring, we need to skip the first statement */
	for (i = docstring; i < n; i++) {
		st = (stmt_ty)asdl_seq_GET(s->v.FunctionDef.body, i);
		VISIT_IN_SCOPE(c, stmt, st);
	}
	co = assemble(c, 1);
	compiler_exit_scope(c);
	if (co == NULL)
		return 0;

	compiler_make_closure(c, co, args->defaults);
	Py_DECREF(co);

	for (i = 0; i < asdl_seq_LEN(decos); i++) {
		ADDOP_I(c, CALL_FUNCTION, 1);
	}

	return compiler_nameop(c, s->v.FunctionDef.name, Store);
}

static int
compiler_class(struct compiler *c, stmt_ty s)
{
	int n, i;
	PyCodeObject *co;
	PyObject *str;
	asdl_seq* decos = s->v.ClassDef.decorator_list;

	if (!compiler_decorators(c, decos))
		return 0;

	if (!compiler_load_global(c, "#@buildclass"))
		return 0;

	/* push class name on stack, needed by #@buildclass */
	ADDOP_O(c, LOAD_CONST, s->v.ClassDef.name, consts);
	/* push the tuple of base classes on the stack */
	n = asdl_seq_LEN(s->v.ClassDef.bases);
	if (n > 0)
		VISIT_SEQ(c, expr, s->v.ClassDef.bases);
	ADDOP_I(c, BUILD_TUPLE, n);
	if (!compiler_enter_scope(c, s->v.ClassDef.name, (void *)s,
				  s->lineno))
		return 0;
	Py_XDECREF(c->u->u_private);
	c->u->u_private = s->v.ClassDef.name;
	Py_INCREF(c->u->u_private);
	str = PyString_InternFromString("__name__");
	if (!str || !compiler_nameop(c, str, Load)) {
		Py_XDECREF(str);
		compiler_exit_scope(c);
		return 0;
	}

	Py_DECREF(str);
	str = PyString_InternFromString("__module__");
	if (!str || !compiler_nameop(c, str, Store)) {
		Py_XDECREF(str);
		compiler_exit_scope(c);
		return 0;
	}
	Py_DECREF(str);

	if (!compiler_body(c, s->v.ClassDef.body)) {
		compiler_exit_scope(c);
		return 0;
	}

	if (!compiler_load_global(c, "#@locals"))
		return 0;
	ADDOP_I(c, CALL_FUNCTION, 0);

	ADDOP_IN_SCOPE(c, RETURN_VALUE);
	co = assemble(c, 1);
	compiler_exit_scope(c);
	if (co == NULL)
		return 0;

	compiler_make_closure(c, co, NULL);
	Py_DECREF(co);

	ADDOP_I(c, CALL_FUNCTION, 0);

	/* Call #@buildclass */
	ADDOP_I(c, CALL_FUNCTION, 3);

	/* apply decorators */
	for (i = 0; i < asdl_seq_LEN(decos); i++) {
		ADDOP_I(c, CALL_FUNCTION, 1);
	}
	if (!compiler_nameop(c, s->v.ClassDef.name, Store))
		return 0;
	return 1;
}

static int
compiler_exec(struct compiler *c, stmt_ty s)
{
	if (!compiler_load_global(c, "#@exec"))
		return 0;

	VISIT(c, expr, s->v.Exec.body);
	if (s->v.Exec.globals) {
		VISIT(c, expr, s->v.Exec.globals);
		if (s->v.Exec.locals) {
			VISIT(c, expr, s->v.Exec.locals);
		} else {
			ADDOP(c, DUP_TOP);
		}
	} else {
		ADDOP_O(c, LOAD_CONST, Py_None, consts);
		ADDOP(c, DUP_TOP);
	}
	ADDOP_I(c, CALL_FUNCTION, 3);
	ADDOP(c, POP_TOP);
	c->u->u_uses_exec = true;
	return 1;
}

static int
compiler_ifexp(struct compiler *c, expr_ty e)
{
	basicblock *end, *next;

	assert(e->kind == IfExp_kind);
	end = compiler_new_block(c);
	if (end == NULL)
		return 0;
	next = compiler_new_block(c);
	if (next == NULL)
		return 0;
	VISIT(c, expr, e->v.IfExp.test);
	ADDOP_JABS(c, POP_JUMP_IF_FALSE, next);
	VISIT(c, expr, e->v.IfExp.body);
	ADDOP_JREL(c, JUMP_FORWARD, end);
	compiler_use_next_block(c, next);
	VISIT(c, expr, e->v.IfExp.orelse);
	compiler_use_next_block(c, end);
	return 1;
}

static int
compiler_lambda(struct compiler *c, expr_ty e)
{
	PyCodeObject *co;
	static identifier name;
	arguments_ty args = e->v.Lambda.args;
	assert(e->kind == Lambda_kind);

	if (!name) {
		name = PyString_InternFromString("<lambda>");
		if (!name)
			return 0;
	}

	if (!compiler_enter_scope(c, name, (void *)e, e->lineno))
		return 0;

	/* unpack nested arguments */
	compiler_arguments(c, args);

	c->u->u_argcount = asdl_seq_LEN(args->args);
	VISIT_IN_SCOPE(c, expr, e->v.Lambda.body);
	ADDOP_IN_SCOPE(c, RETURN_VALUE);
	co = assemble(c, 1);
	compiler_exit_scope(c);
	if (co == NULL)
		return 0;

	compiler_make_closure(c, co, args->defaults);
	Py_DECREF(co);

	return 1;
}

static int
compiler_print(struct compiler *c, stmt_ty s)
{
	int i, n, kwargs = 0;
	PyObject *str;

	assert(s->kind == Print_kind);
	n = asdl_seq_LEN(s->v.Print.values);

	if (!compiler_load_global(c, "#@print_stmt"))
		return 0;

	for (i = 0; i < n; i++) {
		expr_ty e = (expr_ty)asdl_seq_GET(s->v.Print.values, i);
		VISIT(c, expr, e);
	}
	if (!s->v.Print.nl) {
		str = PyString_InternFromString("end");
		if (!str)
			return 0;
		ADDOP_O(c, LOAD_CONST, str, consts);
		Py_DECREF(str);
		str = PyString_FromString("");
		if (!str)
			return 0;
		ADDOP_O(c, LOAD_CONST, str, consts);
		Py_DECREF(str);
		kwargs++;
	}
	if (s->v.Print.dest) {
		str = PyString_InternFromString("file");
		if (!str)
			return 0;
		ADDOP_O(c, LOAD_CONST, str, consts);
		Py_DECREF(str);
		VISIT(c, expr, s->v.Print.dest);
		kwargs++;
	}
	ADDOP_I(c, CALL_FUNCTION, n | (kwargs << 8));
	ADDOP(c, POP_TOP);
	return 1;
}

static int
compiler_if(struct compiler *c, stmt_ty s)
{
	basicblock *end, *next;
	int constant;
	assert(s->kind == If_kind);
	end = compiler_new_block(c);
	if (end == NULL)
		return 0;

	constant = expr_constant(s->v.If.test);
	/* constant = 0: "if 0"
	 * constant = 1: "if 1", "if 2", ...
	 * constant = -1: rest */
	if (constant == 0) {
		if (s->v.If.orelse)
			VISIT_SEQ(c, stmt, s->v.If.orelse);
	} else if (constant == 1) {
		VISIT_SEQ(c, stmt, s->v.If.body);
	} else {
		if (s->v.If.orelse) {
			next = compiler_new_block(c);
			if (next == NULL)
			    return 0;
		}
		else
			next = end;
		VISIT(c, expr, s->v.If.test);
		ADDOP_JABS(c, POP_JUMP_IF_FALSE, next);
		VISIT_SEQ(c, stmt, s->v.If.body);
		ADDOP_JREL(c, JUMP_FORWARD, end);
		if (s->v.If.orelse) {
			compiler_use_next_block(c, next);
			VISIT_SEQ(c, stmt, s->v.If.orelse);
		}
	}
	compiler_use_next_block(c, end);
	return 1;
}

static int
compiler_for(struct compiler *c, stmt_ty s)
{
	basicblock *start, *cleanup, *end;

	start = compiler_new_block(c);
	cleanup = compiler_new_block(c);
	end = compiler_new_block(c);
	if (start == NULL || end == NULL || cleanup == NULL)
		return 0;
	if (c->u->u_ste->ste_blockstack)
		ADDOP_JREL(c, SETUP_LOOP, end);
	if (!compiler_push_fblock(c, FOR_LOOP, start, end))
		return 0;
	VISIT(c, expr, s->v.For.iter);
	ADDOP(c, GET_ITER);
	compiler_use_next_block(c, start);
	ADDOP_JREL(c, FOR_ITER, cleanup);
	VISIT(c, expr, s->v.For.target);
	VISIT_SEQ(c, stmt, s->v.For.body);
	ADDOP_JABS(c, JUMP_ABSOLUTE, start);
	compiler_use_next_block(c, cleanup);
	if (c->u->u_ste->ste_blockstack)
		ADDOP(c, POP_BLOCK);
	compiler_pop_fblock(c, FOR_LOOP, start, end);
	VISIT_SEQ(c, stmt, s->v.For.orelse);
	compiler_use_next_block(c, end);
	return 1;
}

static int
compiler_while(struct compiler *c, stmt_ty s)
{
	basicblock *loop, *orelse, *end, *anchor = NULL;
	int constant = expr_constant(s->v.While.test);

	if (constant == 0) {
		if (s->v.While.orelse)
			VISIT_SEQ(c, stmt, s->v.While.orelse);
		return 1;
	}
	loop = compiler_new_block(c);
	end = compiler_new_block(c);
	if (constant == -1) {
		anchor = compiler_new_block(c);
		if (anchor == NULL)
			return 0;
	}
	if (loop == NULL || end == NULL)
		return 0;
	if (s->v.While.orelse) {
		orelse = compiler_new_block(c);
		if (orelse == NULL)
			return 0;
	}
	else
		orelse = NULL;

	if (c->u->u_ste->ste_blockstack)
		ADDOP_JREL(c, SETUP_LOOP, end);
	compiler_use_next_block(c, loop);
	if (!compiler_push_fblock(c, WHILE_LOOP, loop, end))
		return 0;
	if (constant == -1) {
		VISIT(c, expr, s->v.While.test);
		ADDOP_JABS(c, POP_JUMP_IF_FALSE, anchor);
	}
	VISIT_SEQ(c, stmt, s->v.While.body);
	ADDOP_JABS(c, JUMP_ABSOLUTE, loop);

	/* XXX should the two POP instructions be in a separate block
	   if there is no else clause ?
	*/

	if (constant == -1) {
		compiler_use_next_block(c, anchor);
		if (c->u->u_ste->ste_blockstack)
			ADDOP(c, POP_BLOCK);
	}
	compiler_pop_fblock(c, WHILE_LOOP, loop, end);
	if (orelse != NULL) { /* what if orelse is just pass? */
		compiler_use_next_block(c, orelse);
		VISIT_SEQ(c, stmt, s->v.While.orelse);
	}
	compiler_use_next_block(c, end);

	return 1;
}

static int
compiler_break(struct compiler *c)
{
	if (!compiler_in_loop(c))
		return compiler_error(c, "'break' outside loop");
	if (c->u->u_ste->ste_blockstack) {
		ADDOP(c, BREAK_LOOP);
	} else {
		int top = c->u->u_nfblocks - 1;
		assert(c->u->u_fblock[top].fb_target);
		if (c->u->u_fblock[top].fb_type == FOR_LOOP) {
			ADDOP(c, POP_TOP);
		} else {
			assert(c->u->u_fblock[top].fb_type == WHILE_LOOP);
		}
		ADDOP_JABS(c, JUMP_ABSOLUTE, c->u->u_fblock[top].fb_target);
	}
	return 1;
}

static int
compiler_continue(struct compiler *c)
{
	static const char LOOP_ERROR_MSG[] = "'continue' not properly in loop";
	static const char IN_FINALLY_ERROR_MSG[] =
			"'continue' not supported inside 'finally' clause";
	int i;

	if (!c->u->u_nfblocks)
		return compiler_error(c, LOOP_ERROR_MSG);
	i = c->u->u_nfblocks - 1;
	switch (c->u->u_fblock[i].fb_type) {
	case FOR_LOOP:
	case WHILE_LOOP:
		ADDOP_JABS(c, JUMP_ABSOLUTE, c->u->u_fblock[i].fb_block);
		break;
	case EXCEPT:
	case FINALLY_TRY:
		while (--i >= 0 && !(c->u->u_fblock[i].fb_type == FOR_LOOP ||
		                     c->u->u_fblock[i].fb_type == WHILE_LOOP)) {
			/* Prevent continue anywhere under a finally
			      even if hidden in a sub-try or except. */
			if (c->u->u_fblock[i].fb_type == FINALLY_END)
				return compiler_error(c, IN_FINALLY_ERROR_MSG);
		}
		if (i == -1)
			return compiler_error(c, LOOP_ERROR_MSG);
		ADDOP_JABS(c, CONTINUE_LOOP, c->u->u_fblock[i].fb_block);
		break;
	case FINALLY_END:
		return compiler_error(c, IN_FINALLY_ERROR_MSG);
	}

	return 1;
}

/* Code generated for "try: <body> finally: <finalbody>" is as follows:
   
		SETUP_FINALLY	L
		<code for body>
		POP_BLOCK
		LOAD_CONST	<None>
	L:	<code for finalbody>
		END_FINALLY
   
   The special instructions use the block stack.  Each block
   stack entry contains the instruction that created it (here
   SETUP_FINALLY), the level of the value stack at the time the
   block stack entry was created, and a label (here L).
   
   SETUP_FINALLY:
	Pushes the current value stack level and the label
	onto the block stack.
   POP_BLOCK:
	Pops en entry from the block stack, and pops the value
	stack until its level is the same as indicated on the
	block stack.  (The label is ignored.)
   END_FINALLY:
	Pops a variable number of entries from the *value* stack
	and re-raises the exception they specify.  The number of
	entries popped depends on the (pseudo) exception type.
   
   The block stack is unwound when an exception is raised:
   when a SETUP_FINALLY entry is found, the exception is pushed
   onto the value stack (and the exception condition is cleared),
   and the interpreter jumps to the label gotten from the block
   stack.
*/

static int
compiler_try_finally(struct compiler *c, stmt_ty s)
{
	basicblock *body, *end;
	body = compiler_new_block(c);
	end = compiler_new_block(c);
	if (body == NULL || end == NULL)
		return 0;

	ADDOP_JREL(c, SETUP_FINALLY, end);
	compiler_use_next_block(c, body);
	if (!compiler_push_fblock(c, FINALLY_TRY, body, end))
		return 0;
	VISIT_SEQ(c, stmt, s->v.TryFinally.body);
	ADDOP(c, POP_BLOCK);
	compiler_pop_fblock(c, FINALLY_TRY, body, end);

	ADDOP_O(c, LOAD_CONST, Py_None, consts);
	ADDOP(c, DUP_TOP);
	ADDOP(c, DUP_TOP);
	compiler_use_next_block(c, end);
	if (!compiler_push_fblock(c, FINALLY_END, end, NULL))
		return 0;
	VISIT_SEQ(c, stmt, s->v.TryFinally.finalbody);
	ADDOP(c, END_FINALLY);
	compiler_pop_fblock(c, FINALLY_END, end, NULL);

	return 1;
}

/*
   Code generated for "try: S except E1, V1: S1 except E2, V2: S2 ...":
   (The contents of the value stack is shown in [], with the top
   at the right; 'tb' is trace-back info, 'val' the exception's
   associated value, and 'exc' the exception.)
   
   Value stack		Label	Instruction	Argument
   []				SETUP_EXCEPT	L1
   []				<code for S>
   []				POP_BLOCK
   []				JUMP_FORWARD	L0
   
   [tb, val, exc]	L1:	DUP				)
   [tb, val, exc, exc]		<evaluate E1>			)
   [tb, val, exc, exc, E1]	COMPARE_OP	EXC_MATCH	) only if E1
   [tb, val, exc, 1-or-0]	POP_JUMP_IF_FALSE	L2	)
   [tb, val, exc]		POP
   [tb, val]			<assign to V1>	(or POP if no V1)
   [tb]				POP
   []				<code for S1>
				JUMP_FORWARD	L0
   
   [tb, val, exc]	L2:	DUP
   .............................etc.......................

   [tb, val, exc]	Ln+1:	END_FINALLY	# re-raise exception
   
   []			L0:	<next statement>
   
   Of course, parts are not generated if Vi or Ei is not present.
*/
static int
compiler_try_except(struct compiler *c, stmt_ty s)
{
	basicblock *body, *orelse, *except, *end;
	int i, n;

	body = compiler_new_block(c);
	except = compiler_new_block(c);
	orelse = compiler_new_block(c);
	end = compiler_new_block(c);
	if (body == NULL || except == NULL || orelse == NULL || end == NULL)
		return 0;
	ADDOP_JREL(c, SETUP_EXCEPT, except);
	compiler_use_next_block(c, body);
	if (!compiler_push_fblock(c, EXCEPT, body, except))
		return 0;
	VISIT_SEQ(c, stmt, s->v.TryExcept.body);
	ADDOP(c, POP_BLOCK);
	compiler_pop_fblock(c, EXCEPT, body, except);
	ADDOP_JREL(c, JUMP_FORWARD, orelse);
	n = asdl_seq_LEN(s->v.TryExcept.handlers);
	compiler_use_next_block(c, except);
	for (i = 0; i < n; i++) {
		excepthandler_ty handler = (excepthandler_ty)asdl_seq_GET(
						s->v.TryExcept.handlers, i);
		if (!handler->v.ExceptHandler.type && i < n-1)
		    return compiler_error(c, "default 'except:' must be last");
		c->u->u_lineno_set = false;
		c->u->u_lineno = handler->lineno;
		except = compiler_new_block(c);
		if (except == NULL)
			return 0;
		if (handler->v.ExceptHandler.type) {
			ADDOP(c, DUP_TOP);
			VISIT(c, expr, handler->v.ExceptHandler.type);
			ADDOP_I(c, COMPARE_OP, PyCmp_EXC_MATCH);
			ADDOP_JABS(c, POP_JUMP_IF_FALSE, except);
		}
		ADDOP(c, POP_TOP);
		if (handler->v.ExceptHandler.name) {
			VISIT(c, expr, handler->v.ExceptHandler.name);
		}
		else {
			ADDOP(c, POP_TOP);
		}
		ADDOP(c, POP_TOP);
		VISIT_SEQ(c, stmt, handler->v.ExceptHandler.body);
		ADDOP_JREL(c, JUMP_FORWARD, end);
		compiler_use_next_block(c, except);
	}
	ADDOP(c, END_FINALLY);
	compiler_use_next_block(c, orelse);
	VISIT_SEQ(c, stmt, s->v.TryExcept.orelse);
	compiler_use_next_block(c, end);
	return 1;
}

static int
compiler_import_as(struct compiler *c, identifier name, identifier asname)
{
	/* The IMPORT_NAME opcode was already generated.  This function
	   merely needs to bind the result to a name.

	   If there is a dot in name, we need to split it and emit a 
	   LOAD_ATTR for each name.
	*/
	const char *src = PyString_AS_STRING(name);
	const char *dot = strchr(src, '.');
	if (dot) {
		/* Consume the base module name to get the first attribute */
		src = dot + 1;
		while (dot) {
			/* NB src is only defined when dot != NULL */
			PyObject *attr;
			dot = strchr(src, '.');
			attr = PyString_FromStringAndSize(src,
					    dot ? dot - src : strlen(src));
			if (!attr)
				return -1;
			ADDOP_O(c, LOAD_ATTR, attr, names);
			Py_DECREF(attr);
			src = dot + 1;
		}
	}
	return compiler_nameop(c, asname, Store);
}

static int
compiler_import(struct compiler *c, stmt_ty s)
{
	/* The Import node stores a module name like a.b.c as a single
	   string.  This is convenient for all cases except
	     import a.b.c as d
	   where we need to parse that string to extract the individual
	   module names.  
	   XXX…