示例#1
0
文件: vector.py 项目: sota/pypy-old
 def clone(self):
     renamer = Renamer()
     label = copy_resop(self.label)
     prefix = []
     for op in self.prefix:
         newop = copy_resop(op)
         renamer.rename(newop)
         if not newop.returns_void():
             renamer.start_renaming(op, newop)
         prefix.append(newop)
     prefix_label = None
     if self.prefix_label:
         prefix_label = copy_resop(self.prefix_label)
         renamer.rename(prefix_label)
     oplist = []
     for op in self.operations:
         newop = copy_resop(op)
         renamer.rename(newop)
         if not newop.returns_void():
             renamer.start_renaming(op, newop)
         oplist.append(newop)
     jump = copy_resop(self.jump)
     renamer.rename(jump)
     loop = VectorLoop(copy_resop(self.label), oplist, jump)
     loop.prefix = prefix
     loop.prefix_label = prefix_label
     return loop
示例#2
0
class SchedulerState(object):
    def __init__(self, graph):
        self.renamer = Renamer()
        self.graph = graph
        self.oplist = []
        self.worklist = []
        self.invariant_oplist = []
        self.invariant_vector_vars = []
        self.seen = {}

    def post_schedule(self):
        loop = self.graph.loop
        self.renamer.rename(loop.jump)
        self.ensure_args_unpacked(loop.jump)
        loop.operations = self.oplist
        loop.prefix = self.invariant_oplist
        if len(self.invariant_vector_vars) + len(self.invariant_oplist) > 0:
            # label
            args = loop.label.getarglist_copy() + self.invariant_vector_vars
            opnum = loop.label.getopnum()
            op = loop.label.copy_and_change(opnum, args)
            self.renamer.rename(op)
            loop.prefix_label = op
            # jump
            args = loop.jump.getarglist_copy() + self.invariant_vector_vars
            opnum = loop.jump.getopnum()
            op = loop.jump.copy_and_change(opnum, args)
            self.renamer.rename(op)
            loop.jump = op

    def profitable(self):
        return True

    def prepare(self):
        for node in self.graph.nodes:
            if node.depends_count() == 0:
                self.worklist.insert(0, node)

    def emit(self, node, scheduler):
        # implement me in subclass. e.g. as in VecScheduleState
        return False

    def delay(self, node):
        return False

    def has_more(self):
        return len(self.worklist) > 0

    def ensure_args_unpacked(self, op):
        pass

    def post_emit(self, node):
        pass

    def pre_emit(self, node):
        pass
示例#3
0
文件: schedule.py 项目: sota/pypy-old
class SchedulerState(object):
    def __init__(self, graph):
        self.renamer = Renamer()
        self.graph = graph
        self.oplist = []
        self.worklist = []
        self.invariant_oplist = []
        self.invariant_vector_vars = []
        self.seen = {}

    def post_schedule(self):
        loop = self.graph.loop
        self.renamer.rename(loop.jump)
        self.ensure_args_unpacked(loop.jump)
        loop.operations = self.oplist
        loop.prefix = self.invariant_oplist
        if len(self.invariant_vector_vars) + len(self.invariant_oplist) > 0:
            # label
            args = loop.label.getarglist_copy() + self.invariant_vector_vars
            opnum = loop.label.getopnum()
            op = loop.label.copy_and_change(opnum, args)
            self.renamer.rename(op)
            loop.prefix_label = op
            # jump
            args = loop.jump.getarglist_copy() + self.invariant_vector_vars
            opnum = loop.jump.getopnum()
            op = loop.jump.copy_and_change(opnum, args)
            self.renamer.rename(op)
            loop.jump = op

    def profitable(self):
        return True

    def prepare(self):
        for node in self.graph.nodes:
            if node.depends_count() == 0:
                self.worklist.insert(0, node)

    def emit(self, node, scheduler):
        # implement me in subclass. e.g. as in VecScheduleState
        return False

    def delay(self, node):
        return False

    def has_more(self):
        return len(self.worklist) > 0

    def ensure_args_unpacked(self, op):
        pass

    def post_emit(self, node):
        pass

    def pre_emit(self, node):
        pass
示例#4
0
class SchedulerState(object):
    def __init__(self, cpu, graph):
        self.cpu = cpu
        self.renamer = Renamer()
        self.graph = graph
        self.oplist = []
        self.worklist = []
        self.invariant_oplist = []
        self.invariant_vector_vars = []
        self.seen = {}
        self.delayed = []

    def resolve_delayed(self, needs_resolving, delayed, op):
        # recursive solving of all delayed objects
        if not delayed:
            return
        args = op.getarglist()
        if op.is_guard():
            args = args[:] + op.getfailargs()
        for arg in args:
            if arg is None or arg.is_constant() or arg.is_inputarg():
                continue
            if arg not in self.seen:
                box = self.renamer.rename_box(arg)
                needs_resolving[box] = None

        indexvars = self.graph.index_vars
        i = len(delayed) - 1
        while i >= 0:
            node = delayed[i]
            op = node.getoperation()
            if op in needs_resolving:
                # either it is a normal operation, or we know that there is a linear combination
                del needs_resolving[op]
                if op in indexvars:
                    opindexvar = indexvars[op]
                    # there might be a variable already, that
                    # calculated the index variable, thus just reuse it
                    for var, indexvar in indexvars.items():
                        if indexvar == opindexvar and var in self.seen:
                            self.renamer.start_renaming(op, var)
                            break
                    else:
                        if opindexvar.calculated_by(op):
                            # just append this operation
                            self.seen[op] = None
                            self.append_to_oplist(op)
                        else:
                            # here is an easier way to calculate just this operation
                            last = op
                            for operation in opindexvar.get_operations():
                                self.append_to_oplist(operation)
                                last = operation
                            indexvars[last] = opindexvar
                            self.renamer.start_renaming(op, last)
                            self.seen[op] = None
                            self.seen[last] = None
                else:
                    self.resolve_delayed(needs_resolving, delayed, op)
                    self.append_to_oplist(op)
                    self.seen[op] = None
                if len(delayed) > i:
                    del delayed[i]
            i -= 1
            # some times the recursive call can remove several items from delayed,
            # thus we correct the index here
            if len(delayed) <= i:
                i = len(delayed) - 1

    def append_to_oplist(self, op):
        self.renamer.rename(op)
        self.oplist.append(op)

    def schedule(self):
        self.prepare()
        Scheduler().walk_and_emit(self)
        self.post_schedule()

    def post_schedule(self):
        loop = self.graph.loop
        jump = loop.jump
        if self.delayed:
            # some operations can be delayed until the jump instruction,
            # handle them here
            self.resolve_delayed({}, self.delayed, jump)
        self.renamer.rename(jump)
        loop.operations = self.oplist

    def profitable(self):
        return True

    def prepare(self):
        for node in self.graph.nodes:
            if node.depends_count() == 0:
                self.worklist.insert(0, node)

    def try_emit_or_delay(self, node):
        if not node.is_imaginary() and node.is_pure():
            # this operation might never be emitted. only if it is really needed
            self.delay_emit(node)
            return
        # emit a now!
        self.pre_emit(node, True)
        self.mark_emitted(node)
        if not node.is_imaginary():
            op = node.getoperation()
            self.seen[op] = None
            self.append_to_oplist(op)

    def delay_emit(self, node):
        """ it has been decided that the operation might be scheduled later """
        delayed = node.delayed or []
        if node not in delayed:
            delayed.append(node)
        node.delayed = None
        provides = node.provides()
        if len(provides) == 0:
            for n in delayed:
                self.delayed.append(n)
        else:
            for to in node.provides():
                tnode = to.target_node()
                self.delegate_delay(tnode, delayed[:])
        self.mark_emitted(node)

    def delegate_delay(self, node, delayed):
        """ Chain up delays, this can reduce many more of the operations """
        if node.delayed is None:
            node.delayed = delayed
        else:
            delayedlist = node.delayed
            for d in delayed:
                if d not in delayedlist:
                    delayedlist.append(d)

    def mark_emitted(state, node, unpack=True):
        """ An operation has been emitted, adds new operations to the worklist
            whenever their dependency count drops to zero.
            Keeps worklist sorted (see priority) """
        worklist = state.worklist
        provides = node.provides()[:]
        for dep in provides:  # COPY
            target = dep.to
            node.remove_edge_to(target)
            if not target.emitted and target.depends_count() == 0:
                # sorts them by priority
                i = len(worklist) - 1
                while i >= 0:
                    cur = worklist[i]
                    c = (cur.priority - target.priority)
                    if c < 0:  # meaning itnode.priority < target.priority:
                        worklist.insert(i + 1, target)
                        break
                    elif c == 0:
                        # if they have the same priority, sort them
                        # using the original position in the trace
                        if target.getindex() < cur.getindex():
                            worklist.insert(i + 1, target)
                            break
                    i -= 1
                else:
                    worklist.insert(0, target)
        node.clear_dependencies()
        node.emitted = True
        if not node.is_imaginary():
            op = node.getoperation()
            state.renamer.rename(op)
            if unpack:
                state.ensure_args_unpacked(op)
            state.post_emit(node)

    def delay(self, node):
        return False

    def has_more(self):
        return len(self.worklist) > 0

    def ensure_args_unpacked(self, op):
        pass

    def post_emit(self, node):
        pass

    def pre_emit(self, orignode, pack_first=True):
        delayed = orignode.delayed
        if delayed:
            # there are some nodes that have been delayed just for this operation
            if pack_first:
                op = orignode.getoperation()
                self.resolve_delayed({}, delayed, op)

            for node in delayed:
                op = node.getoperation()
                if op in self.seen:
                    continue
                if node is not None:
                    provides = node.provides()
                    if len(provides) == 0:
                        # add this node to the final delay list
                        # might be emitted before jump!
                        self.delayed.append(node)
                    else:
                        for to in node.provides():
                            tnode = to.target_node()
                            self.delegate_delay(tnode, [node])
            orignode.delayed = None
示例#5
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    def unroll_loop_iterations(self, loop, unroll_count, align_unroll_once=False):
        """ Unroll the loop `unroll_count` times. There can be an additional unroll step
            if alignment might benefit """
        numops = len(loop.operations)

        renamer = Renamer()
        operations = loop.operations
        orig_jump_args = loop.jump.getarglist()[:]
        prohibit_opnums = (rop.GUARD_FUTURE_CONDITION,
                           rop.GUARD_NOT_INVALIDATED,
                           rop.DEBUG_MERGE_POINT)
        unrolled = []

        if align_unroll_once:
            unroll_count += 1

        # it is assumed that #label_args == #jump_args
        label_arg_count = len(orig_jump_args)
        label = loop.label
        jump = loop.jump
        new_label = loop.label
        for u in range(unroll_count):
            # fill the map with the renaming boxes. keys are boxes from the label
            for i in range(label_arg_count):
                la = label.getarg(i)
                ja = jump.getarg(i)
                ja = renamer.rename_box(ja)
                if la != ja:
                    renamer.start_renaming(la, ja)
            #
            for i, op in enumerate(operations):
                if op.getopnum() in prohibit_opnums:
                    continue # do not unroll this operation twice
                copied_op = copy_resop(op)
                if not copied_op.returns_void():
                    # every result assigns a new box, thus creates an entry
                    # to the rename map.
                    renamer.start_renaming(op, copied_op)
                #
                args = copied_op.getarglist()
                for a, arg in enumerate(args):
                    value = renamer.rename_box(arg)
                    copied_op.setarg(a, value)
                # not only the arguments, but also the fail args need
                # to be adjusted. rd_snapshot stores the live variables
                # that are needed to resume.
                if copied_op.is_guard():
                    self.copy_guard_descr(renamer, copied_op)
                #
                unrolled.append(copied_op)
            #
            if align_unroll_once and u == 0:
                descr = label.getdescr()
                args = label.getarglist()[:]
                new_label = ResOperation(rop.LABEL, args, descr)
                renamer.rename(new_label)
            #

        # the jump arguments have been changed
        # if label(iX) ... jump(i(X+1)) is called, at the next unrolled loop
        # must look like this: label(i(X+1)) ... jump(i(X+2))
        args = loop.jump.getarglist()
        for i, arg in enumerate(args):
            value = renamer.rename_box(arg)
            loop.jump.setarg(i, value)
        #
        loop.label = new_label
        if align_unroll_once:
            loop.align_operations = operations
            loop.operations = unrolled
        else:
            loop.operations = operations + unrolled
示例#6
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文件: guard.py 项目: cimarieta/usp
class GuardStrengthenOpt(object):
    """ Note that this optimization is only used in the vector optimizer (yet) """
    def __init__(self, index_vars):
        self.index_vars = index_vars
        self._newoperations = []
        self.strength_reduced = 0 # how many guards could be removed?
        self.strongest_guards = {}
        self.guards = {}
        self.delayed = {}

    def collect_guard_information(self, loop):
        operations = loop.operations
        last_guard = None
        for i,op in enumerate(operations):
            op = operations[i]
            if not op.is_guard():
                continue
            if op.getopnum() in (rop.GUARD_TRUE, rop.GUARD_FALSE):
                guard = Guard.of(op.getarg(0), operations, i, self.index_vars)
                if guard is None:
                    continue
                self.record_guard(guard.getleftkey(), guard)
                self.record_guard(guard.getrightkey(), guard)

    def record_guard(self, key, guard):
        if key is None:
            return
        # the operations are processed from 1..n (forward),
        # thus if the key is not present (1), the guard is saved
        # (2) guard(s) with this key is/are already present,
        # thus each of is seen as possible candidate to strengthen
        # or imply the current. in both cases the current guard is
        # not emitted and the original is replaced with the current
        others = self.strongest_guards.setdefault(key, [])
        if len(others) > 0: # (2)
            replaced = False
            for i,other in enumerate(others):
                assert guard is not other
                if guard.implies(other, self):
                    # strengthend
                    others[i] = guard
                    self.guards[guard.index] = None # mark as 'do not emit'
                    guard.inhert_attributes(other)
                    self.guards[other.index] = guard
                    replaced = True
                    continue
                elif other.implies(guard, self):
                    # implied
                    self.guards[guard.index] = None # mark as 'do not emit'
                    replaced = True
                    continue
            if not replaced:
                others.append(guard)
        else: # (2)
            others.append(guard)

    def eliminate_guards(self, loop):
        self.renamer = Renamer()
        for i,op in enumerate(loop.operations):
            op = loop.operations[i]
            if op.is_guard():
                if i in self.guards:
                    # either a stronger guard has been saved
                    # or it should not be emitted
                    guard = self.guards[i]
                    # this guard is implied or marked as not emitted (= None)
                    self.strength_reduced += 1
                    if guard is None:
                        continue
                    guard.emit_operations(self)
                    continue
                else:
                    self.emit_operation(op)
                    continue
            if not op.returns_void():
                index_var = self.index_vars.get(op, None)
                if index_var:
                    if not index_var.is_identity():
                        var = index_var.emit_operations(self, op)
                        self.renamer.start_renaming(op, var)
                        continue
            self.emit_operation(op)
        self.renamer.rename(loop.jump)
        #
        loop.operations = self._newoperations[:]

    def propagate_all_forward(self, info, loop, user_code=False):
        """ strengthens the guards that protect an integral value """
        # the guards are ordered. guards[i] is before guards[j] iff i < j
        self.collect_guard_information(loop)
        self.eliminate_guards(loop)
        #
        assert len(info.versions) == 1
        version = info.versions[0]

        for i,op in enumerate(loop.operations):
            if not op.is_guard():
                continue
            descr = op.getdescr()
            if descr and descr.loop_version():
                assert isinstance(descr, AbstractFailDescr)
                info.track(op, descr, version)

        if user_code:
            self.eliminate_array_bound_checks(info, loop)

    def emit_operation(self, op):
        self.renamer.rename(op)
        self._newoperations.append(op)

    def operation_position(self):
        return len(self._newoperations)

    def eliminate_array_bound_checks(self, info, loop):
        info.mark()
        version = None
        self._newoperations = []
        for key, guards in self.strongest_guards.items():
            if len(guards) <= 1:
                continue
            # there is more than one guard for that key,
            # that is why we could imply the guards 2..n
            # iff we add invariant guards
            one = guards[0]
            for other in guards[1:]:
                transitive_guard = one.transitive_imply(other, self, loop)
                if transitive_guard:
                    if version is None:
                        version = info.snapshot(loop)
                    info.remove(other.op.getdescr())
                    other.set_to_none(info, loop)
                    descr = transitive_guard.getdescr()
                    assert isinstance(descr, AbstractFailDescr)
                    info.track(transitive_guard, descr, version)
        info.clear()

        loop.prefix = self._newoperations + loop.prefix
        loop.operations = [op for op in loop.operations if op]
示例#7
0
class GuardStrengthenOpt(object):
    """ Note that this optimization is only used in the vector optimizer (yet) """
    def __init__(self, index_vars):
        self.index_vars = index_vars
        self._newoperations = []
        self.strength_reduced = 0  # how many guards could be removed?
        self.strongest_guards = {}
        self.guards = {}
        self.delayed = {}

    def collect_guard_information(self, loop):
        operations = loop.operations
        last_guard = None
        for i, op in enumerate(operations):
            op = operations[i]
            if not op.is_guard():
                continue
            if op.getopnum() in (rop.GUARD_TRUE, rop.GUARD_FALSE):
                guard = Guard.of(op.getarg(0), operations, i, self.index_vars)
                if guard is None:
                    continue
                self.record_guard(guard.getleftkey(), guard)
                self.record_guard(guard.getrightkey(), guard)

    def record_guard(self, key, guard):
        if key is None:
            return
        # the operations are processed from 1..n (forward),
        # thus if the key is not present (1), the guard is saved
        # (2) guard(s) with this key is/are already present,
        # thus each of is seen as possible candidate to strengthen
        # or imply the current. in both cases the current guard is
        # not emitted and the original is replaced with the current
        others = self.strongest_guards.setdefault(key, [])
        if len(others) > 0:  # (2)
            replaced = False
            for i, other in enumerate(others):
                assert guard is not other
                if guard.implies(other, self):
                    # strengthend
                    others[i] = guard
                    self.guards[guard.index] = None  # mark as 'do not emit'
                    guard.inhert_attributes(other)
                    self.guards[other.index] = guard
                    replaced = True
                    continue
                elif other.implies(guard, self):
                    # implied
                    self.guards[guard.index] = None  # mark as 'do not emit'
                    replaced = True
                    continue
            if not replaced:
                others.append(guard)
        else:  # (2)
            others.append(guard)

    def eliminate_guards(self, loop):
        self.renamer = Renamer()
        for i, op in enumerate(loop.operations):
            op = loop.operations[i]
            if op.is_guard():
                if i in self.guards:
                    # either a stronger guard has been saved
                    # or it should not be emitted
                    guard = self.guards[i]
                    # this guard is implied or marked as not emitted (= None)
                    self.strength_reduced += 1
                    if guard is None:
                        continue
                    guard.emit_operations(self)
                    continue
                else:
                    self.emit_operation(op)
                    continue
            if not op.returns_void():
                index_var = self.index_vars.get(op, None)
                if index_var:
                    if not index_var.is_identity():
                        var = index_var.emit_operations(self, op)
                        self.renamer.start_renaming(op, var)
                        continue
            self.emit_operation(op)
        self.renamer.rename(loop.jump)
        #
        loop.operations = self._newoperations[:]

    def propagate_all_forward(self, info, loop, user_code=False):
        """ strengthens the guards that protect an integral value """
        # the guards are ordered. guards[i] is before guards[j] iff i < j
        self.collect_guard_information(loop)
        self.eliminate_guards(loop)
        #
        assert len(info.versions) == 1
        version = info.versions[0]

        for i, op in enumerate(loop.operations):
            if not op.is_guard():
                continue
            descr = op.getdescr()
            if descr and descr.loop_version():
                assert isinstance(descr, AbstractFailDescr)
                info.track(op, descr, version)

        if user_code:
            self.eliminate_array_bound_checks(info, loop)

    def emit_operation(self, op):
        self.renamer.rename(op)
        self._newoperations.append(op)

    def operation_position(self):
        return len(self._newoperations)

    def eliminate_array_bound_checks(self, info, loop):
        info.mark()
        version = None
        self._newoperations = []
        for key, guards in self.strongest_guards.items():
            if len(guards) <= 1:
                continue
            # there is more than one guard for that key,
            # that is why we could imply the guards 2..n
            # iff we add invariant guards
            one = guards[0]
            for other in guards[1:]:
                transitive_guard = one.transitive_imply(other, self, loop)
                if transitive_guard:
                    if version is None:
                        version = info.snapshot(loop)
                    info.remove(other.op.getdescr())
                    other.set_to_none(info, loop)
                    descr = transitive_guard.getdescr()
                    assert isinstance(descr, AbstractFailDescr)
                    info.track(transitive_guard, descr, version)
        info.clear()

        loop.prefix = self._newoperations + loop.prefix
        loop.operations = [op for op in loop.operations if op]
示例#8
0
class SchedulerState(object):
    def __init__(self, cpu, graph):
        self.cpu = cpu
        self.renamer = Renamer()
        self.graph = graph
        self.oplist = []
        self.worklist = []
        self.invariant_oplist = []
        self.invariant_vector_vars = []
        self.seen = {}
        self.delayed = []

    def resolve_delayed(self, needs_resolving, delayed, op):
        # recursive solving of all delayed objects
        if not delayed:
            return
        args = op.getarglist()
        if op.is_guard():
            args = args[:] + op.getfailargs()
        for arg in args:
            if arg is None or arg.is_constant() or arg.is_inputarg():
                continue
            if arg not in self.seen:
                box = self.renamer.rename_box(arg)
                needs_resolving[box] = None

        indexvars = self.graph.index_vars
        i = len(delayed)-1
        while i >= 0:
            node = delayed[i]
            op = node.getoperation()
            if op in needs_resolving:
                # either it is a normal operation, or we know that there is a linear combination
                del needs_resolving[op]
                if op in indexvars:
                    opindexvar = indexvars[op]
                    # there might be a variable already, that
                    # calculated the index variable, thus just reuse it
                    for var, indexvar in indexvars.items(): 
                        if indexvar == opindexvar and var in self.seen:
                            self.renamer.start_renaming(op, var)
                            break
                    else:
                        if opindexvar.calculated_by(op):
                            # just append this operation
                            self.seen[op] = None
                            self.append_to_oplist(op)
                        else:
                            # here is an easier way to calculate just this operation
                            last = op
                            for operation in opindexvar.get_operations():
                                self.append_to_oplist(operation)
                                last = operation
                            indexvars[last] = opindexvar
                            self.renamer.start_renaming(op, last)
                            self.seen[op] = None
                            self.seen[last] = None
                else: 
                    self.resolve_delayed(needs_resolving, delayed, op)
                    self.append_to_oplist(op)
                    self.seen[op] = None
                if len(delayed) > i:
                    del delayed[i]
            i -= 1
            # some times the recursive call can remove several items from delayed,
            # thus we correct the index here
            if len(delayed) <= i:
                i = len(delayed)-1

    def append_to_oplist(self, op):
        self.renamer.rename(op)
        self.oplist.append(op)

    def schedule(self):
        self.prepare()
        Scheduler().walk_and_emit(self)
        self.post_schedule()

    def post_schedule(self):
        loop = self.graph.loop
        jump = loop.jump
        if self.delayed:
            # some operations can be delayed until the jump instruction,
            # handle them here
            self.resolve_delayed({}, self.delayed, jump)
        self.renamer.rename(jump)
        loop.operations = self.oplist

    def profitable(self):
        return True

    def prepare(self):
        for node in self.graph.nodes:
            if node.depends_count() == 0:
                self.worklist.insert(0, node)

    def try_emit_or_delay(self, node):
        if not node.is_imaginary() and node.is_pure():
            # this operation might never be emitted. only if it is really needed
            self.delay_emit(node)
            return
        # emit a now!
        self.pre_emit(node, True)
        self.mark_emitted(node)
        if not node.is_imaginary():
            op = node.getoperation()
            self.seen[op] = None
            self.append_to_oplist(op)

    def delay_emit(self, node):
        """ it has been decided that the operation might be scheduled later """
        delayed = node.delayed or []
        if node not in delayed:
            delayed.append(node)
        node.delayed = None
        provides = node.provides()
        if len(provides) == 0:
            for n in delayed:
                self.delayed.append(n)
        else:
            for to in node.provides():
                tnode = to.target_node()
                self.delegate_delay(tnode, delayed[:])
        self.mark_emitted(node)

    def delegate_delay(self, node, delayed):
        """ Chain up delays, this can reduce many more of the operations """
        if node.delayed is None:
            node.delayed = delayed
        else:
            delayedlist = node.delayed
            for d in delayed:
                if d not in delayedlist:
                    delayedlist.append(d)


    def mark_emitted(state, node, unpack=True):
        """ An operation has been emitted, adds new operations to the worklist
            whenever their dependency count drops to zero.
            Keeps worklist sorted (see priority) """
        worklist = state.worklist
        provides = node.provides()[:]
        for dep in provides: # COPY
            target = dep.to
            node.remove_edge_to(target)
            if not target.emitted and target.depends_count() == 0:
                # sorts them by priority
                i = len(worklist)-1
                while i >= 0:
                    cur = worklist[i]
                    c = (cur.priority - target.priority)
                    if c < 0: # meaning itnode.priority < target.priority:
                        worklist.insert(i+1, target)
                        break
                    elif c == 0:
                        # if they have the same priority, sort them
                        # using the original position in the trace
                        if target.getindex() < cur.getindex():
                            worklist.insert(i+1, target)
                            break
                    i -= 1
                else:
                    worklist.insert(0, target)
        node.clear_dependencies()
        node.emitted = True
        if not node.is_imaginary():
            op = node.getoperation()
            state.renamer.rename(op)
            if unpack:
                state.ensure_args_unpacked(op)
            state.post_emit(node)


    def delay(self, node):
        return False

    def has_more(self):
        return len(self.worklist) > 0

    def ensure_args_unpacked(self, op):
        pass

    def post_emit(self, node):
        pass

    def pre_emit(self, orignode, pack_first=True):
        delayed = orignode.delayed
        if delayed:
            # there are some nodes that have been delayed just for this operation
            if pack_first:
                op = orignode.getoperation()
                self.resolve_delayed({}, delayed, op)

            for node in delayed:
                op = node.getoperation()
                if op in self.seen:
                    continue
                if node is not None:
                    provides = node.provides()
                    if len(provides) == 0:
                        # add this node to the final delay list
                        # might be emitted before jump!
                        self.delayed.append(node)
                    else:
                        for to in node.provides():
                            tnode = to.target_node()
                            self.delegate_delay(tnode, [node])
            orignode.delayed = None