from rpython.rlib.objectmodel import specialize, we_are_translated, compute_hash
from rpython.jit.metainterp.resoperation import AbstractValue, ResOperation,\
     rop, OpHelpers
from rpython.jit.metainterp.history import ConstInt, Const
from rpython.rtyper.lltypesystem import lltype, llmemory
from rpython.jit.metainterp.optimizeopt.rawbuffer import RawBuffer, InvalidRawOperation
from rpython.jit.metainterp.executor import execute
from rpython.jit.metainterp.optimize import InvalidLoop


INFO_NULL = 0
INFO_NONNULL = 1
INFO_UNKNOWN = 2

class AbstractInfo(AbstractValue):
    _attrs_ = ()
    
    is_info_class = True

    def force_box(self, op, optforce):
        return op

    def is_virtual(self):
        return False

    def is_precise(self):
        return False

    def getconst(self):
        raise Exception("not a constant")

    def _is_immutable_and_filled_with_constants(self, optimizer, memo=None):
        return False


class PtrInfo(AbstractInfo):
    _attrs_ = ()

    def is_nonnull(self):
        return False

    def is_about_object(self):
        return False

    def get_descr(self):
        return None

    def is_null(self):
        return False

    def force_at_the_end_of_preamble(self, op, optforce, rec):
        if not self.is_virtual():
            return optforce.get_box_replacement(op)
        return self._force_at_the_end_of_preamble(op, optforce, rec)

    def get_known_class(self, cpu):
        return None

    def getlenbound(self, mode):
        return None

    def getnullness(self):
        if self.is_null():
            return INFO_NULL
        elif self.is_nonnull():
            return INFO_NONNULL
        return INFO_UNKNOWN

    def same_info(self, other):
        return self is other

    def getstrlen(self, op, string_optimizer, mode):
        return None

    def getstrhash(self, op, mode):
        return None

    def copy_fields_to_const(self, constinfo, optheap):
        pass

    def make_guards(self, op, short, optimizer):
        pass

    @specialize.arg(2)
    def get_constant_string_spec(self, string_optimizer, mode):
        return None # can't be constant

class NonNullPtrInfo(PtrInfo):
    _attrs_ = ('last_guard_pos',)
    last_guard_pos = -1
    
    def is_nonnull(self):
        return True

    def get_known_class(self, cpu):
        return None

    def get_last_guard(self, optimizer):
        if self.last_guard_pos == -1:
            return None
        return optimizer._newoperations[self.last_guard_pos]

    def get_last_guard_pos(self):
        return self.last_guard_pos

    def reset_last_guard_pos(self):
        self.last_guard_pos = -1

    def mark_last_guard(self, optimizer):
        if (optimizer.getlastop() is None or
            not optimizer.getlastop().is_guard()):
            # there can be a really emitted operation that's not a guard
            # e.g. a setfield, ignore those
            return
        self.last_guard_pos = len(optimizer._newoperations) - 1
        assert self.get_last_guard(optimizer).is_guard()

    def make_guards(self, op, short, optimizer):
        op = ResOperation(rop.GUARD_NONNULL, [op])
        short.append(op)

class AbstractVirtualPtrInfo(NonNullPtrInfo):
    _attrs_ = ('_cached_vinfo', 'descr', '_is_virtual')
    # XXX merge _cached_vinfo with descr

    _cached_vinfo = None
    descr = None

    def get_descr(self):
        return self.descr

    def is_precise(self):
        return True

    def force_box(self, op, optforce):
        if self.is_virtual():
            #
            if self._is_immutable_and_filled_with_constants(optforce.optimizer):
                constptr = optforce.optimizer.constant_fold(op)
                op.set_forwarded(constptr)
                self._is_virtual = False
                self._force_elements_immutable(self.descr, constptr, optforce)
                return constptr
            #
            op.set_forwarded(None)
            optforce.emit_extra(op)
            newop = optforce.getlastop()
            if newop is not op:
                op.set_forwarded(newop)
            newop.set_forwarded(self)
            descr = self.descr
            self._is_virtual = False
            self._force_elements(newop, optforce, descr)
            return newop
        return op

    def _force_at_the_end_of_preamble(self, op, optforce, rec):
        return self.force_box(op, optforce)

    def is_virtual(self):
        return self._is_virtual

    def _visitor_walk_recursive(self, op, visitor, optimizer):
        raise NotImplementedError("abstract")

    def visitor_walk_recursive(self, instbox, visitor, optimizer):
        instbox = instbox.get_box_replacement()
        if visitor.already_seen_virtual(instbox):
            return
        return self._visitor_walk_recursive(instbox, visitor, optimizer)


class AbstractStructPtrInfo(AbstractVirtualPtrInfo):
    _attrs_ = ('_fields',)

    _fields = None

    def init_fields(self, descr, index):
        if self._fields is None:
            self.descr = descr
            self._fields = [None] * len(descr.get_all_fielddescrs())
        if index >= len(self._fields):
            self.descr = descr # a more precise descr
            # we found out a subclass with more fields
            extra_len = len(descr.get_all_fielddescrs()) - len(self._fields)
            self._fields = self._fields + [None] * extra_len

    def clear_cache(self):
        assert not self.is_virtual()
        self._fields = [None] * len(self._fields)

    def copy_fields_to_const(self, constinfo, optheap):
        if self._fields is not None:
            info = constinfo._get_info(self.descr, optheap)
            assert isinstance(info, AbstractStructPtrInfo)
            info._fields = self._fields[:]

    def all_items(self):
        return self._fields

    def setfield(self, fielddescr, struct, op, optheap=None, cf=None):
        self.init_fields(fielddescr.get_parent_descr(), fielddescr.get_index())
        assert isinstance(op, AbstractValue)
        self._fields[fielddescr.get_index()] = op
        if cf is not None:
            assert not self.is_virtual()
            assert struct is not None
            cf.register_info(struct, self)

    def getfield(self, fielddescr, optheap=None):
        self.init_fields(fielddescr.get_parent_descr(), fielddescr.get_index())
        return self._fields[fielddescr.get_index()]

    def _force_elements(self, op, optforce, descr):
        if self._fields is None:
            return
        for i, fielddescr in enumerate(descr.get_all_fielddescrs()):
            fld = self._fields[i]
            if fld is not None:
                subbox = optforce.force_box(fld)
                setfieldop = ResOperation(rop.SETFIELD_GC, [op, subbox],
                                          descr=fielddescr)
                self._fields[i] = None
                optforce.emit_extra(setfieldop)

    def _force_at_the_end_of_preamble(self, op, optforce, rec):
        if self._fields is None:
            return optforce.get_box_replacement(op)
        if self in rec:
            return optforce.get_box_replacement(op)
        rec[self] = None
        for i, fldbox in enumerate(self._fields):
            if fldbox is not None:
                info = optforce.getptrinfo(fldbox)
                if info is not None:
                    fldbox = info.force_at_the_end_of_preamble(fldbox, optforce,
                                                               rec)
                    self._fields[i] = fldbox
        return op

    def _visitor_walk_recursive(self, instbox, visitor, optimizer):
        lst = self.descr.get_all_fielddescrs()
        assert self.is_virtual()
        visitor.register_virtual_fields(instbox,
                                        [optimizer.get_box_replacement(box)
                                         for box in self._fields])
        for i in range(len(lst)):
            op = self._fields[i]
            if op:
                fieldinfo = optimizer.getptrinfo(op)
                if fieldinfo and fieldinfo.is_virtual():
                    fieldinfo.visitor_walk_recursive(op, visitor, optimizer)

    def produce_short_preamble_ops(self, structbox, fielddescr, index, optimizer,
                                   shortboxes):
        if self._fields is None:
            return
        if fielddescr.get_index() >= len(self._fields):
            # we don't know about this item
            return
        op = optimizer.get_box_replacement(self._fields[fielddescr.get_index()])
        if op is None:
            # XXX same bug as in serialize_opt:
            # op should never be None, because that's an invariant violation in
            # AbstractCachedEntry. But it still seems to happen when the info
            # is attached to a Constant. At least we shouldn't crash.
            return
        opnum = OpHelpers.getfield_for_descr(fielddescr)
        getfield_op = ResOperation(opnum, [structbox], descr=fielddescr)
        shortboxes.add_heap_op(op, getfield_op)

    def _is_immutable_and_filled_with_constants(self, optimizer, memo=None):
        # check if it is possible to force the given structure into a
        # compile-time constant: this is allowed only if it is declared
        # immutable, if all fields are already filled, and if each field
        # is either a compile-time constant or (recursively) a structure
        # which also answers True to the same question.
        #
        assert self.is_virtual()
        if not self.descr.is_immutable():
            return False
        if memo is not None and self in memo:
            return True       # recursive case: assume yes
        #
        for op in self._fields:
            if op is None:
                return False     # there is an uninitialized field
            op = op.get_box_replacement()
            if op.is_constant():
                pass            # it is a constant value: ok
            else:
                fieldinfo = optimizer.getptrinfo(op)
                if fieldinfo and fieldinfo.is_virtual():
                    # recursive check
                    if memo is None:
                        memo = {self: None}
                    if not fieldinfo._is_immutable_and_filled_with_constants(
                            optimizer, memo):
                        return False
                else:
                    return False    # not a constant at all
        return True

    def _force_elements_immutable(self, descr, constptr, optforce):
        for i, fielddescr in enumerate(descr.get_all_fielddescrs()):
            fld = self._fields[i]
            subbox = optforce.force_box(fld)
            assert isinstance(subbox, Const)
            execute(optforce.optimizer.cpu, None, rop.SETFIELD_GC,
                    fielddescr, constptr, subbox)

class InstancePtrInfo(AbstractStructPtrInfo):
    _attrs_ = ('_known_class',)
    _fields = None

    def __init__(self, descr=None, known_class=None, is_virtual=False):
        self._known_class = known_class
        # that's a descr of best-known class, can be actually a subclass
        # of the class described in descr
        self.descr = descr
        self._is_virtual = is_virtual

    def get_known_class(self, cpu):
        return self._known_class

    def is_about_object(self):
        return True

    @specialize.argtype(1)
    def visitor_dispatch_virtual_type(self, visitor):
        fielddescrs = self.descr.get_all_fielddescrs()
        assert self.is_virtual()
        return visitor.visit_virtual(self.descr, fielddescrs)

    def make_guards(self, op, short, optimizer):
        if self._known_class is not None:
            if not optimizer.cpu.remove_gctypeptr:
                short.append(ResOperation(rop.GUARD_NONNULL, [op]))
                short.append(ResOperation(rop.GUARD_IS_OBJECT, [op]))
                short.append(ResOperation(rop.GUARD_CLASS,
                                          [op, self._known_class]))
            else:
                short.append(ResOperation(rop.GUARD_NONNULL_CLASS,
                    [op, self._known_class]))
        elif self.descr is not None:
            short.append(ResOperation(rop.GUARD_NONNULL, [op]))
            if not optimizer.cpu.remove_gctypeptr:
                short.append(ResOperation(rop.GUARD_IS_OBJECT, [op]))
            short.append(ResOperation(rop.GUARD_SUBCLASS, [op,
                            ConstInt(self.descr.get_vtable())]))
        else:
            AbstractStructPtrInfo.make_guards(self, op, short, optimizer)

class StructPtrInfo(AbstractStructPtrInfo):
    def __init__(self, descr, is_virtual=False):
        self.descr = descr
        self._is_virtual = is_virtual

    def make_guards(self, op, short, optimizer):
        if self.descr is not None:
            c_typeid = ConstInt(self.descr.get_type_id())
            short.extend([
                ResOperation(rop.GUARD_NONNULL, [op]),
                ResOperation(rop.GUARD_GC_TYPE, [op, c_typeid])
            ])

    @specialize.argtype(1)
    def visitor_dispatch_virtual_type(self, visitor):
        fielddescrs = self.descr.get_all_fielddescrs()
        assert self.is_virtual()
        return visitor.visit_vstruct(self.descr, fielddescrs)

class AbstractRawPtrInfo(AbstractVirtualPtrInfo):
    @specialize.argtype(1)
    def visitor_dispatch_virtual_type(self, visitor):
        raise NotImplementedError("abstract")

    def make_guards(self, op, short, optimizer):
        from rpython.jit.metainterp.optimizeopt.optimizer import CONST_0
        op = ResOperation(rop.INT_EQ, [op, CONST_0])
        short.append(op)
        op = ResOperation(rop.GUARD_FALSE, [op])
        short.append(op)

class RawBufferPtrInfo(AbstractRawPtrInfo):
    buffer = None

    def __init__(self, cpu, func, size=-1):
        self.func = func
        self.size = size
        if self.size != -1:
            self.buffer = RawBuffer(cpu, None)

    def _get_buffer(self):
        buffer = self.buffer
        assert buffer is not None
        return buffer

    def all_items(self):
        return []

    def getitem_raw(self, offset, itemsize, descr):
        if not self.is_virtual():
            raise InvalidRawOperation
            # see 'test_virtual_raw_buffer_forced_but_slice_not_forced'
            # for the test above: it's not enough to check is_virtual()
            # on the original object, because it might be a VRawSliceValue
            # instead.  If it is a virtual one, then we'll reach here anway.
        return self._get_buffer().read_value(offset, itemsize, descr)

    def setitem_raw(self, offset, itemsize, descr, itemop):
        if not self.is_virtual():
            raise InvalidRawOperation
        self._get_buffer().write_value(offset, itemsize, descr, itemop)

    def is_virtual(self):
        return self.size != -1

    def _force_elements(self, op, optforce, descr):
        self.size = -1
        # at this point we have just written the
        # 'op = CALL_I(..., OS_RAW_MALLOC_VARSIZE_CHAR)'.
        # Emit now a CHECK_MEMORY_ERROR resop.
        check_op = ResOperation(rop.CHECK_MEMORY_ERROR, [op])
        optforce.emit_extra(check_op)
        #
        buffer = self._get_buffer()
        for i in range(len(buffer.offsets)):
            # write the value
            offset = buffer.offsets[i]
            descr = buffer.descrs[i]
            itembox = buffer.values[i]
            setfield_op = ResOperation(rop.RAW_STORE,
                              [op, ConstInt(offset), itembox], descr=descr)
            optforce.emit_extra(setfield_op)

    def _visitor_walk_recursive(self, op, visitor, optimizer):
        itemboxes = [optimizer.get_box_replacement(box)
                     for box in self._get_buffer().values]
        visitor.register_virtual_fields(op, itemboxes)
        # there can be no virtuals stored in raw buffer

    @specialize.argtype(1)
    def visitor_dispatch_virtual_type(self, visitor):
        buffer = self._get_buffer()
        return visitor.visit_vrawbuffer(self.func,
                                        self.size,
                                        buffer.offsets[:],
                                        buffer.descrs[:])

class RawStructPtrInfo(AbstractRawPtrInfo):
    def __init__(self):
        pass

    def is_virtual(self):
        return False

class RawSlicePtrInfo(AbstractRawPtrInfo):
    def __init__(self, offset, parent):
        self.offset = offset
        self.parent = parent

    def is_virtual(self):
        return self.parent is not None

    def getitem_raw(self, offset, itemsize, descr):
        return self.parent.getitem_raw(self.offset+offset, itemsize, descr)

    def setitem_raw(self, offset, itemsize, descr, itemop):
        self.parent.setitem_raw(self.offset+offset, itemsize, descr, itemop)
    
    def _force_elements(self, op, optforce, descr):
        if self.parent.is_virtual():
            self.parent._force_elements(op, optforce, descr)
        self.parent = None

    def _visitor_walk_recursive(self, op, visitor, optimizer):
        source_op = optimizer.get_box_replacement(op.getarg(0))
        visitor.register_virtual_fields(op, [source_op])
        if self.parent.is_virtual():
            self.parent.visitor_walk_recursive(source_op, visitor, optimizer)

    @specialize.argtype(1)
    def visitor_dispatch_virtual_type(self, visitor):
        return visitor.visit_vrawslice(self.offset)


class ArrayPtrInfo(AbstractVirtualPtrInfo):
    _attrs_ = ('length', '_items', 'lenbound', '_clear', 'descr',
               '_is_virtual')

    _items = None
    lenbound = None
    length = -1

    def __init__(self, descr, const=None, size=0, clear=False,
                 is_virtual=False):
        from rpython.jit.metainterp.optimizeopt import intutils
        assert descr is not None
        self.descr = descr
        self._is_virtual = is_virtual
        if is_virtual:
            self._init_items(const, size, clear)
            self.lenbound = intutils.ConstIntBound(size)
        self._clear = clear

    def getlenbound(self, mode):
        from rpython.jit.metainterp.optimizeopt import intutils

        assert mode is None
        if self.lenbound is None:
            assert self.length == -1
            self.lenbound = intutils.IntLowerBound(0)
        return self.lenbound

    def _init_items(self, const, size, clear):
        self.length = size
        if clear:
            self._items = [const] * size
        else:
            self._items = [None] * size

    def all_items(self):
        return self._items

    def copy_fields_to_const(self, constinfo, optheap):
        descr = self.descr
        if self._items is not None:
            info = constinfo._get_array_info(descr, optheap)
            assert isinstance(info, ArrayPtrInfo)
            info._items = self._items[:]

    def _force_elements(self, op, optforce, descr):
        # XXX
        descr = op.getdescr()
        const = optforce.new_const_item(self.descr)
        for i in range(self.length):
            item = self._items[i]
            if item is None:
                continue
            if self._clear and const.same_constant(item):
                # clear the item so we don't know what's there
                self._items[i] = None
                continue
            subbox = optforce.force_box(item)
            setop = ResOperation(rop.SETARRAYITEM_GC,
                                 [op, ConstInt(i), subbox],
                                  descr=descr)
            self._items[i] = None
            optforce.emit_extra(setop)
        optforce.pure_from_args(rop.ARRAYLEN_GC, [op], ConstInt(len(self._items)))

    def setitem(self, descr, index, struct, op, optheap=None, cf=None):
        if self._items is None:
            self._items = [None] * (index + 1)
        if index >= len(self._items):
            assert not self.is_virtual()
            self._items = self._items + [None] * (index - len(self._items) + 1)
        self._items[index] = op
        if cf is not None:
            assert not self.is_virtual()
            cf.register_info(struct, self)

    def getitem(self, descr, index, optheap=None):
        if self._items is None or index >= len(self._items):
            return None
        return self._items[index]

    def getlength(self):
        return self.length

    def _visitor_walk_recursive(self, instbox, visitor, optimizer):
        itemops = [optimizer.get_box_replacement(item)
                   for item in self._items]
        visitor.register_virtual_fields(instbox, itemops)
        for i in range(self.getlength()):
            itemop = self._items[i]
            if (itemop is not None and
                not isinstance(itemop, Const)):
                ptrinfo = optimizer.getptrinfo(itemop)
                if ptrinfo and ptrinfo.is_virtual():
                    ptrinfo.visitor_walk_recursive(itemop, visitor, optimizer)

    @specialize.argtype(1)
    def visitor_dispatch_virtual_type(self, visitor):
        return visitor.visit_varray(self.descr, self._clear)

    def produce_short_preamble_ops(self, structbox, descr, index, optimizer,
                                   shortboxes):
        if self._items is None:
            return
        if index >= len(self._items):
            # we don't know about this item
            return
        item = self._items[index]
        if item is not None:
            # see comment in AbstractStructPtrInfo.produce_short_preamble_ops
            op = optimizer.get_box_replacement(item)
            opnum = OpHelpers.getarrayitem_for_descr(descr)
            getarrayitem_op = ResOperation(opnum, [structbox, ConstInt(index)],
                                           descr=descr)
            shortboxes.add_heap_op(op, getarrayitem_op)

    def _force_at_the_end_of_preamble(self, op, optforce, rec):
        if self._items is None:
            return optforce.get_box_replacement(op)
        if self in rec:
            return optforce.get_box_replacement(op)
        rec[self] = None
        for i, fldbox in enumerate(self._items):
            if fldbox is not None:
                info = optforce.getptrinfo(fldbox)
                if info is not None:
                    fldbox = info.force_at_the_end_of_preamble(fldbox, optforce,
                                                               rec)
                    self._items[i] = fldbox
        return op

    def make_guards(self, op, short, optimizer):
        AbstractVirtualPtrInfo.make_guards(self, op, short, optimizer)
        c_type_id = ConstInt(self.descr.get_type_id())
        short.append(ResOperation(rop.GUARD_GC_TYPE, [op, c_type_id]))
        if self.lenbound is not None:
            lenop = ResOperation(rop.ARRAYLEN_GC, [op], descr=self.descr)
            short.append(lenop)
            self.lenbound.make_guards(lenop, short, optimizer)

class ArrayStructInfo(ArrayPtrInfo):
    def __init__(self, descr, size, is_virtual=False):
        from rpython.jit.metainterp.optimizeopt import intutils

        self.length = size
        lgt = len(descr.get_all_fielddescrs())
        self.lenbound = intutils.ConstIntBound(size)
        self.descr = descr
        self._items = [None] * (size * lgt)
        self._is_virtual = is_virtual

    def _compute_index(self, index, fielddescr):
        all_fdescrs = fielddescr.get_arraydescr().get_all_fielddescrs()
        if all_fdescrs is None:
            return 0 # annotation hack
        one_size = len(all_fdescrs)
        return index * one_size + fielddescr.get_field_descr().get_index()
        
    def setinteriorfield_virtual(self, index, fielddescr, fld):
        index = self._compute_index(index, fielddescr)
        self._items[index] = fld

    def getinteriorfield_virtual(self, index, fielddescr):
        index = self._compute_index(index, fielddescr)
        return self._items[index]

    def _force_elements(self, op, optforce, descr):
        i = 0
        fielddescrs = op.getdescr().get_all_fielddescrs()
        for index in range(self.length):
            for fielddescr in fielddescrs:
                fld = self._items[i]
                if fld is not None:
                    subbox = optforce.force_box(fld)
                    setfieldop = ResOperation(rop.SETINTERIORFIELD_GC,
                                              [op, ConstInt(index), subbox],
                                              descr=fielddescr)
                    optforce.emit_extra(setfieldop)
                    # heapcache does not work for interiorfields
                    # if it does, we would need a fix here
                i += 1

    def _visitor_walk_recursive(self, instbox, visitor, optimizer):
        itemops = [optimizer.get_box_replacement(item)
                   for item in self._items]
        visitor.register_virtual_fields(instbox, itemops)
        fielddescrs = self.descr.get_all_fielddescrs()
        i = 0
        for index in range(self.getlength()):
            for fielddescr in fielddescrs:
                itemop = self._items[i]
                if (itemop is not None and
                    not isinstance(itemop, Const)):
                    ptrinfo = optimizer.getptrinfo(itemop)
                    if ptrinfo and ptrinfo.is_virtual():
                        ptrinfo.visitor_walk_recursive(itemop, visitor,
                                                       optimizer)
                i += 1

    @specialize.argtype(1)
    def visitor_dispatch_virtual_type(self, visitor):
        flddescrs = self.descr.get_all_fielddescrs()
        return visitor.visit_varraystruct(self.descr, self.getlength(),
                                          flddescrs)

class ConstPtrInfo(PtrInfo):
    _attrs_ = ('_const',)
    
    def __init__(self, const):
        self._const = const

    def getconst(self):
        return self._const

    def make_guards(self, op, short, optimizer):
        short.append(ResOperation(rop.GUARD_VALUE, [op, self._const]))

    def _get_info(self, descr, optheap):
        ref = self._const.getref_base()
        if not ref: raise InvalidLoop   # null protection
        info = optheap.const_infos.get(ref, None)
        if info is None:
            info = StructPtrInfo(descr)
            optheap.const_infos[ref] = info
        return info

    def _get_array_info(self, descr, optheap):
        ref = self._const.getref_base()
        if not ref: raise InvalidLoop   # null protection
        info = optheap.const_infos.get(ref, None)
        if info is None:
            info = ArrayPtrInfo(descr)
            optheap.const_infos[ref] = info
        return info        

    def getfield(self, fielddescr, optheap=None):
        info = self._get_info(fielddescr.get_parent_descr(), optheap)
        return info.getfield(fielddescr)

    def getitem(self, descr, index, optheap=None):
        info = self._get_array_info(descr, optheap)
        return info.getitem(descr, index)

    def setitem(self, descr, index, struct, op, optheap=None, cf=None):
        info = self._get_array_info(descr, optheap)
        info.setitem(descr, index, struct, op, optheap=optheap, cf=cf)

    def setfield(self, fielddescr, struct, op, optheap=None, cf=None):
        info = self._get_info(fielddescr.get_parent_descr(), optheap)
        info.setfield(fielddescr, struct, op, optheap=optheap, cf=cf)

    def is_null(self):
        return not bool(self._const.getref_base())

    def is_nonnull(self):
        return bool(self._const.getref_base())

    def is_virtual(self):
        return False

    def get_known_class(self, cpu):
        if not self._const.nonnull():
            return None
        if cpu.supports_guard_gc_type:
            # we should only be called on an unknown box here from
            # virtualstate.py, which is only when the cpu supports
            # guard_gc_type
            if not cpu.check_is_object(self._const.getref_base()):
                return None
        return cpu.ts.cls_of_box(self._const)

    def same_info(self, other):
        if not isinstance(other, ConstPtrInfo):
            return False
        return self._const.same_constant(other._const)

    def get_last_guard(self, optimizer):
        return None

    def is_constant(self):
        return True

    # --------------------- vstring -------------------

    @specialize.arg(1)
    def _unpack_str(self, mode):
        return mode.hlstr(lltype.cast_opaque_ptr(
            lltype.Ptr(mode.LLTYPE), self._const.getref_base()))

    @specialize.arg(2)
    def get_constant_string_spec(self, optforce, mode):
        return self._unpack_str(mode)

    def getlenbound(self, mode):
        from rpython.jit.metainterp.optimizeopt.intutils import ConstIntBound,\
                IntLowerBound

        length = self.getstrlen1(mode)
        if length < 0:
            # XXX we can do better if we know it's an array
            return IntLowerBound(0)
        return ConstIntBound(length)

    def getstrlen(self, op, string_optimizer, mode):
        length = self.getstrlen1(mode)
        if length < 0:
            return None
        return ConstInt(length)

    def getstrlen1(self, mode):
        from rpython.jit.metainterp.optimizeopt import vstring

        if mode is vstring.mode_string:
            s = self._unpack_str(vstring.mode_string)
            if s is None:
                return -1
            return len(s)
        elif mode is vstring.mode_unicode:
            s = self._unpack_str(vstring.mode_unicode)            
            if s is None:
                return -1
            return len(s)
        else:
            return -1

    def getstrhash(self, op, mode):
        from rpython.jit.metainterp.optimizeopt import vstring

        if mode is vstring.mode_string:
            s = self._unpack_str(vstring.mode_string)
            if s is None:
                return None
            return ConstInt(compute_hash(s))
        else:
            s = self._unpack_str(vstring.mode_unicode)
            if s is None:
                return None
            return ConstInt(compute_hash(s))

    def string_copy_parts(self, op, string_optimizer, targetbox, offsetbox,
                          mode):
        from rpython.jit.metainterp.optimizeopt import vstring
        from rpython.jit.metainterp.optimizeopt.optimizer import CONST_0

        lgt = self.getstrlen(op, string_optimizer, mode)
        return vstring.copy_str_content(string_optimizer, self._const,
                                        targetbox, CONST_0, offsetbox,
                                        lgt, mode)

    
class FloatConstInfo(AbstractInfo):
    def __init__(self, const):
        self._const = const

    def is_constant(self):
        return True

    def getconst(self):
        return self._const

    def make_guards(self, op, short, optimizer):
        short.append(ResOperation(rop.GUARD_VALUE, [op, self._const]))