/pypy/jit/metainterp/optimizeopt/test/test_optimizebasic.py

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import py
from pypy.rlib.objectmodel import instantiate
from pypy.jit.metainterp.optimizeopt.test.test_util import (
    LLtypeMixin, BaseTest, FakeMetaInterpStaticData, convert_old_style_to_targets)
from pypy.jit.metainterp.history import TargetToken, JitCellToken
from pypy.jit.metainterp.test.test_compile import FakeLogger
import pypy.jit.metainterp.optimizeopt.optimizer as optimizeopt
import pypy.jit.metainterp.optimizeopt.virtualize as virtualize
from pypy.jit.metainterp.optimize import InvalidLoop
from pypy.jit.metainterp.history import AbstractDescr, ConstInt, BoxInt
from pypy.jit.metainterp import executor, compile, resume, history
from pypy.jit.metainterp.resoperation import rop, opname, ResOperation
from pypy.rlib.rarithmetic import LONG_BIT

def test_store_final_boxes_in_guard():
    from pypy.jit.metainterp.compile import ResumeGuardDescr
    from pypy.jit.metainterp.resume import tag, TAGBOX
    b0 = BoxInt()
    b1 = BoxInt()
    opt = optimizeopt.Optimizer(FakeMetaInterpStaticData(LLtypeMixin.cpu),
                                None)
    fdescr = ResumeGuardDescr()
    op = ResOperation(rop.GUARD_TRUE, ['dummy'], None, descr=fdescr)
    # setup rd data
    fi0 = resume.FrameInfo(None, "code0", 11)
    fdescr.rd_frame_info_list = resume.FrameInfo(fi0, "code1", 33)
    snapshot0 = resume.Snapshot(None, [b0])
    fdescr.rd_snapshot = resume.Snapshot(snapshot0, [b1])
    #
    opt.store_final_boxes_in_guard(op)
    if op.getfailargs() == [b0, b1]:
        assert list(fdescr.rd_numb.nums)      == [tag(1, TAGBOX)]
        assert list(fdescr.rd_numb.prev.nums) == [tag(0, TAGBOX)]
    else:
        assert op.getfailargs() == [b1, b0]
        assert list(fdescr.rd_numb.nums)      == [tag(0, TAGBOX)]
        assert list(fdescr.rd_numb.prev.nums) == [tag(1, TAGBOX)]
    assert fdescr.rd_virtuals is None
    assert fdescr.rd_consts == []

def test_sharing_field_lists_of_virtual():
    class FakeOptimizer(object):
        class optimizer(object):
            class cpu(object):
                pass
    opt = FakeOptimizer()
    virt1 = virtualize.AbstractVirtualStructValue(opt, None)
    lst1 = virt1._get_field_descr_list()
    assert lst1 == []
    lst2 = virt1._get_field_descr_list()
    assert lst1 is lst2
    virt1.setfield(LLtypeMixin.valuedescr, optimizeopt.OptValue(None))
    lst3 = virt1._get_field_descr_list()
    assert lst3 == [LLtypeMixin.valuedescr]
    lst4 = virt1._get_field_descr_list()
    assert lst3 is lst4

    virt2 = virtualize.AbstractVirtualStructValue(opt, None)
    lst5 = virt2._get_field_descr_list()
    assert lst5 is lst1
    virt2.setfield(LLtypeMixin.valuedescr, optimizeopt.OptValue(None))
    lst6 = virt1._get_field_descr_list()
    assert lst6 is lst3

def test_reuse_vinfo():
    class FakeVInfo(object):
        def set_content(self, fieldnums):
            self.fieldnums = fieldnums
        def equals(self, fieldnums):
            return self.fieldnums == fieldnums
    class FakeVirtualValue(virtualize.AbstractVirtualValue):
        def _make_virtual(self, *args):
            return FakeVInfo()
    v1 = FakeVirtualValue(None, None)
    vinfo1 = v1.make_virtual_info(None, [1, 2, 4])
    vinfo2 = v1.make_virtual_info(None, [1, 2, 4])
    assert vinfo1 is vinfo2
    vinfo3 = v1.make_virtual_info(None, [1, 2, 6])
    assert vinfo3 is not vinfo2
    vinfo4 = v1.make_virtual_info(None, [1, 2, 6])
    assert vinfo3 is vinfo4

def test_descrlist_dict():
    from pypy.jit.metainterp.optimizeopt import util as optimizeutil
    h1 = optimizeutil.descrlist_hash([])
    h2 = optimizeutil.descrlist_hash([LLtypeMixin.valuedescr])
    h3 = optimizeutil.descrlist_hash(
            [LLtypeMixin.valuedescr, LLtypeMixin.nextdescr])
    assert h1 != h2
    assert h2 != h3
    assert optimizeutil.descrlist_eq([], [])
    assert not optimizeutil.descrlist_eq([], [LLtypeMixin.valuedescr])
    assert optimizeutil.descrlist_eq([LLtypeMixin.valuedescr],
                                     [LLtypeMixin.valuedescr])
    assert not optimizeutil.descrlist_eq([LLtypeMixin.valuedescr],
                                         [LLtypeMixin.nextdescr])
    assert optimizeutil.descrlist_eq([LLtypeMixin.valuedescr, LLtypeMixin.nextdescr],
                                     [LLtypeMixin.valuedescr, LLtypeMixin.nextdescr])
    assert not optimizeutil.descrlist_eq([LLtypeMixin.nextdescr, LLtypeMixin.valuedescr],
                                         [LLtypeMixin.valuedescr, LLtypeMixin.nextdescr])

    # descrlist_eq should compare by identity of the descrs, not by the result
    # of sort_key
    class FakeDescr(object):
        def sort_key(self):
            return 1

    assert not optimizeutil.descrlist_eq([FakeDescr()], [FakeDescr()])


# ____________________________________________________________


class BaseTestBasic(BaseTest):

    enable_opts = "intbounds:rewrite:virtualize:string:earlyforce:pure:heap"

    def optimize_loop(self, ops, optops, call_pure_results=None):
        loop = self.parse(ops)
        token = JitCellToken()
        loop.operations = [ResOperation(rop.LABEL, loop.inputargs, None, descr=TargetToken(token))] + \
                          loop.operations
        if loop.operations[-1].getopnum() == rop.JUMP:
            loop.operations[-1].setdescr(token)
        expected = convert_old_style_to_targets(self.parse(optops), jump=True)
        self._do_optimize_loop(loop, call_pure_results)
        print '\n'.join([str(o) for o in loop.operations])
        self.assert_equal(loop, expected)

    def setup_method(self, meth=None):
        class FailDescr(compile.ResumeGuardDescr):
            oparse = None
            def _oparser_uses_descr_of_guard(self, oparse, fail_args):
                # typically called 3 times: once when parsing 'ops',
                # once when parsing 'preamble', once when parsing 'expected'.
                self.oparse = oparse
                self.rd_frame_info_list, self.rd_snapshot = snapshot(fail_args)
            def _clone_if_mutable(self):
                assert self is fdescr
                return fdescr2
            def __repr__(self):
                if self is fdescr:
                    return 'fdescr'
                if self is fdescr2:
                    return 'fdescr2'
                return compile.ResumeGuardDescr.__repr__(self)
        #
        def snapshot(fail_args, got=[]):
            if not got:    # only the first time, i.e. when parsing 'ops'
                rd_frame_info_list = resume.FrameInfo(None, "code", 11)
                rd_snapshot = resume.Snapshot(None, fail_args)
                got.append(rd_frame_info_list)
                got.append(rd_snapshot)
            return got
        #
        fdescr = instantiate(FailDescr)
        self.namespace['fdescr'] = fdescr
        fdescr2 = instantiate(FailDescr)
        self.namespace['fdescr2'] = fdescr2

    def teardown_method(self, meth):
        self.namespace.pop('fdescr', None)
        self.namespace.pop('fdescr2', None)



class BaseTestOptimizeBasic(BaseTestBasic):

    def test_simple(self):
        ops = """
        [i]
        i0 = int_sub(i, 1)
        guard_value(i0, 0) [i0]
        jump(i)
        """
        expected = """
        [i]
        i0 = int_sub(i, 1)
        guard_value(i0, 0) [i0]
        jump(1)
        """
        self.optimize_loop(ops, expected)

    def test_constant_propagate(self):
        ops = """
        []
        i0 = int_add(2, 3)
        i1 = int_is_true(i0)
        guard_true(i1) []
        i2 = int_is_zero(i1)
        guard_false(i2) []
        guard_value(i0, 5) []
        jump()
        """
        expected = """
        []
        jump()
        """
        self.optimize_loop(ops, expected)

    def test_constant_propagate_ovf(self):
        ops = """
        []
        i0 = int_add_ovf(2, 3)
        guard_no_overflow() []
        i1 = int_is_true(i0)
        guard_true(i1) []
        i2 = int_is_zero(i1)
        guard_false(i2) []
        guard_value(i0, 5) []
        jump()
        """
        expected = """
        []
        jump()
        """
        self.optimize_loop(ops, expected)

    def test_constfold_all(self):
        from pypy.jit.backend.llgraph.llimpl import TYPES     # xxx fish
        from pypy.jit.metainterp.executor import execute_nonspec
        from pypy.jit.metainterp.history import BoxInt
        import random
        for opnum in range(rop.INT_ADD, rop.SAME_AS+1):
            try:
                op = opname[opnum]
            except KeyError:
                continue
            if 'FLOAT' in op:
                continue
            argtypes, restype = TYPES[op.lower()]
            args = []
            for argtype in argtypes:
                assert argtype in ('int', 'bool')
                args.append(random.randrange(1, 20))
            assert restype in ('int', 'bool')
            ops = """
            []
            i1 = %s(%s)
            escape(i1)
            jump()
            """ % (op.lower(), ', '.join(map(str, args)))
            argboxes = [BoxInt(a) for a in args]
            expected_value = execute_nonspec(self.cpu, None, opnum,
                                             argboxes).getint()
            expected = """
            []
            escape(%d)
            jump()
            """ % expected_value
            self.optimize_loop(ops, expected)

    # ----------

    def test_remove_guard_class_1(self):
        ops = """
        [p0]
        guard_class(p0, ConstClass(node_vtable)) []
        guard_class(p0, ConstClass(node_vtable)) []
        jump(p0)
        """
        expected = """
        [p0]
        guard_class(p0, ConstClass(node_vtable)) []
        jump(p0)
        """
        self.optimize_loop(ops, expected)

    def test_remove_guard_class_2(self):
        ops = """
        [i0]
        p0 = new_with_vtable(ConstClass(node_vtable))
        escape(p0)
        guard_class(p0, ConstClass(node_vtable)) []
        jump(i0)
        """
        expected = """
        [i0]
        p0 = new_with_vtable(ConstClass(node_vtable))
        escape(p0)
        jump(i0)
        """
        self.optimize_loop(ops, expected)

    def test_remove_guard_class_constant(self):
        ops = """
        [i0]
        p0 = same_as(ConstPtr(myptr))
        guard_class(p0, ConstClass(node_vtable)) []
        jump(i0)
        """
        expected = """
        [i0]
        jump(i0)
        """
        self.optimize_loop(ops, expected)

    def test_constant_boolrewrite_lt(self):
        ops = """
        [i0]
        i1 = int_lt(i0, 0)
        guard_true(i1) []
        i2 = int_ge(i0, 0)
        guard_false(i2) []
        jump(i0)
        """
        expected = """
        [i0]
        i1 = int_lt(i0, 0)
        guard_true(i1) []
        jump(i0)
        """
        self.optimize_loop(ops, expected)

    def test_constant_boolrewrite_gt(self):
        ops = """
        [i0]
        i1 = int_gt(i0, 0)
        guard_true(i1) []
        i2 = int_le(i0, 0)
        guard_false(i2) []
        jump(i0)
        """
        expected = """
        [i0]
        i1 = int_gt(i0, 0)
        guard_true(i1) []
        jump(i0)
        """
        self.optimize_loop(ops, expected)

    def test_constant_boolrewrite_reflex(self):
        ops = """
        [i0]
        i1 = int_gt(i0, 0)
        guard_true(i1) []
        i2 = int_lt(0, i0)
        guard_true(i2) []
        jump(i0)
        """
        expected = """
        [i0]
        i1 = int_gt(i0, 0)
        guard_true(i1) []
        jump(i0)
        """
        self.optimize_loop(ops, expected)

    def test_constant_boolrewrite_reflex_invers(self):
        ops = """
        [i0]
        i1 = int_gt(i0, 0)
        guard_true(i1) []
        i2 = int_ge(0, i0)
        guard_false(i2) []
        jump(i0)
        """
        expected = """
        [i0]
        i1 = int_gt(i0, 0)
        guard_true(i1) []
        jump(i0)
        """
        self.optimize_loop(ops, expected)

    def test_remove_consecutive_guard_value_constfold(self):
        ops = """
        []
        i0 = escape()
        guard_value(i0, 0) []
        i1 = int_add(i0, 1)
        guard_value(i1, 1) []
        i2 = int_add(i1, 2)
        escape(i2)
        jump()
        """
        expected = """
        []
        i0 = escape()
        guard_value(i0, 0) []
        escape(3)
        jump()
        """
        self.optimize_loop(ops, expected)

    def test_remove_guard_value_if_constant(self):
        ops = """
        [p1]
        guard_value(p1, ConstPtr(myptr)) []
        jump(ConstPtr(myptr))
        """
        expected = """
        []
        jump()
        """
        py.test.skip("XXX")
        self.optimize_loop(ops, 'Constant(myptr)', expected)

    def test_ooisnull_oononnull_1(self):
        ops = """
        [p0]
        guard_class(p0, ConstClass(node_vtable)) []
        guard_nonnull(p0) []
        jump(p0)
        """
        expected = """
        [p0]
        guard_class(p0, ConstClass(node_vtable)) []
        jump(p0)
        """
        self.optimize_loop(ops, expected)

    def test_int_is_true_1(self):
        ops = """
        [i0]
        i1 = int_is_true(i0)
        guard_true(i1) []
        i2 = int_is_true(i0)
        guard_true(i2) []
        jump(i0)
        """
        expected = """
        [i0]
        i1 = int_is_true(i0)
        guard_true(i1) []
        jump(i0)
        """
        self.optimize_loop(ops, expected)

    def test_int_is_true_is_zero(self):
        py.test.skip("XXX implement me")
        ops = """
        [i0]
        i1 = int_is_true(i0)
        guard_true(i1) []
        i2 = int_is_zero(i0)
        guard_false(i2) []
        jump(i0)
        """
        expected = """
        [i0]
        i1 = int_is_true(i0)
        guard_true(i1) []
        jump(i0)
        """
        self.optimize_loop(ops, expected)

    def test_int_is_zero_int_is_true(self):
        ops = """
        [i0]
        i1 = int_is_zero(i0)
        guard_true(i1) []
        i2 = int_is_true(i0)
        guard_false(i2) []
        jump(i0)
        """
        expected = """
        [i0]
        i1 = int_is_zero(i0)
        guard_true(i1) []
        jump(0)
        """
        self.optimize_loop(ops, expected)

    def test_ooisnull_oononnull_2(self):
        ops = """
        [p0]
        guard_nonnull(p0) []
        guard_nonnull(p0) []
        jump(p0)
        """
        expected = """
        [p0]
        guard_nonnull(p0) []
        jump(p0)
        """
        self.optimize_loop(ops, expected)

    def test_ooisnull_on_null_ptr_1(self):
        ops = """
        []
        p0 = escape()
        guard_isnull(p0) []
        guard_isnull(p0) []
        jump()
        """
        expected = """
        []
        p0 = escape()
        guard_isnull(p0) []
        jump()
        """
        self.optimize_loop(ops, expected)

    def test_ooisnull_oononnull_via_virtual(self):
        ops = """
        [p0]
        pv = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(pv, p0, descr=valuedescr)
        guard_nonnull(p0) []
        p1 = getfield_gc(pv, descr=valuedescr)
        guard_nonnull(p1) []
        jump(p0)
        """
        expected = """
        [p0]
        guard_nonnull(p0) []
        jump(p0)
        """
        self.optimize_loop(ops, expected)

    def test_oois_1(self):
        ops = """
        [p0]
        guard_class(p0, ConstClass(node_vtable)) []
        i0 = instance_ptr_ne(p0, NULL)
        guard_true(i0) []
        i1 = instance_ptr_eq(p0, NULL)
        guard_false(i1) []
        i2 = instance_ptr_ne(NULL, p0)
        guard_true(i0) []
        i3 = instance_ptr_eq(NULL, p0)
        guard_false(i1) []
        jump(p0)
        """
        expected = """
        [p0]
        guard_class(p0, ConstClass(node_vtable)) []
        jump(p0)
        """
        self.optimize_loop(ops, expected)

    def test_nonnull_1(self):
        ops = """
        [p0]
        setfield_gc(p0, 5, descr=valuedescr)     # forces p0 != NULL
        i0 = ptr_ne(p0, NULL)
        guard_true(i0) []
        i1 = ptr_eq(p0, NULL)
        guard_false(i1) []
        i2 = ptr_ne(NULL, p0)
        guard_true(i0) []
        i3 = ptr_eq(NULL, p0)
        guard_false(i1) []
        guard_nonnull(p0) []
        jump(p0)
        """
        expected = """
        [p0]
        setfield_gc(p0, 5, descr=valuedescr)
        jump(p0)
        """
        self.optimize_loop(ops, expected)

    def test_const_guard_value(self):
        ops = """
        []
        i = int_add(5, 3)
        guard_value(i, 8) []
        jump()
        """
        expected = """
        []
        jump()
        """
        self.optimize_loop(ops, expected)

    def test_constptr_guard_value(self):
        ops = """
        []
        p1 = escape()
        guard_value(p1, ConstPtr(myptr)) []
        jump()
        """
        self.optimize_loop(ops, ops)

    def test_guard_value_to_guard_true(self):
        ops = """
        [i]
        i1 = int_lt(i, 3)
        guard_value(i1, 1) [i]
        jump(i)
        """
        expected = """
        [i]
        i1 = int_lt(i, 3)
        guard_true(i1) [i]
        jump(i)
        """
        self.optimize_loop(ops, expected)

    def test_guard_value_to_guard_false(self):
        ops = """
        [i]
        i1 = int_is_true(i)
        guard_value(i1, 0) [i]
        jump(i)
        """
        expected = """
        [i]
        i1 = int_is_true(i)
        guard_false(i1) [i]
        jump(i)
        """
        self.optimize_loop(ops, expected)

    def test_guard_value_on_nonbool(self):
        ops = """
        [i]
        i1 = int_add(i, 3)
        guard_value(i1, 0) [i]
        jump(i)
        """
        expected = """
        [i]
        i1 = int_add(i, 3)
        guard_value(i1, 0) [i]
        jump(-3)
        """
        self.optimize_loop(ops, expected)

    def test_int_is_true_of_bool(self):
        ops = """
        [i0, i1]
        i2 = int_gt(i0, i1)
        i3 = int_is_true(i2)
        i4 = int_is_true(i3)
        guard_value(i4, 0) [i0, i1]
        jump(i0, i1)
        """
        expected = """
        [i0, i1]
        i2 = int_gt(i0, i1)
        guard_false(i2) [i0, i1]
        jump(i0, i1)
        """
        self.optimize_loop(ops, expected)




    def test_p123_simple(self):
        ops = """
        [i1, p2, p3]
        i3 = getfield_gc(p3, descr=valuedescr)
        escape(i3)
        p1 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p1, i1, descr=valuedescr)
        jump(i1, p1, p2)
        """
        # We cannot track virtuals that survive for more than two iterations.
        self.optimize_loop(ops, ops)

    def test_p123_nested(self):
        ops = """
        [i1, p2, p3]
        i3 = getfield_gc(p3, descr=valuedescr)
        escape(i3)
        p1 = new_with_vtable(ConstClass(node_vtable))
        p1sub = new_with_vtable(ConstClass(node_vtable2))
        setfield_gc(p1, i1, descr=valuedescr)
        setfield_gc(p1sub, i1, descr=valuedescr)
        setfield_gc(p1, p1sub, descr=nextdescr)
        jump(i1, p1, p2)
        """
        # The same as test_p123_simple, but with a virtual containing another
        # virtual.
        self.optimize_loop(ops, ops)

    def test_p123_anti_nested(self):
        ops = """
        [i1, p2, p3]
        p3sub = getfield_gc(p3, descr=nextdescr)
        i3 = getfield_gc(p3sub, descr=valuedescr)
        escape(i3)
        p1 = new_with_vtable(ConstClass(node_vtable))
        p2sub = new_with_vtable(ConstClass(node_vtable2))
        setfield_gc(p2sub, i1, descr=valuedescr)
        setfield_gc(p2, p2sub, descr=nextdescr)
        jump(i1, p1, p2)
        """
        # The same as test_p123_simple, but in the end the "old" p2 contains
        # a "young" virtual p2sub.  Make sure it is all forced.
        self.optimize_loop(ops, ops)

    # ----------

    def test_keep_guard_no_exception(self):
        ops = """
        [i1]
        i2 = call(i1, descr=nonwritedescr)
        guard_no_exception() [i1, i2]
        jump(i2)
        """
        self.optimize_loop(ops, ops)

    def test_keep_guard_no_exception_with_call_pure_that_is_not_folded(self):
        ops = """
        [i1]
        i2 = call_pure(123456, i1, descr=nonwritedescr)
        guard_no_exception() [i1, i2]
        jump(i2)
        """
        expected = """
        [i1]
        i2 = call(123456, i1, descr=nonwritedescr)
        guard_no_exception() [i1, i2]
        jump(i2)
        """
        self.optimize_loop(ops, expected)

    def test_remove_guard_no_exception_with_call_pure_on_constant_args(self):
        arg_consts = [ConstInt(i) for i in (123456, 81)]
        call_pure_results = {tuple(arg_consts): ConstInt(5)}
        ops = """
        [i1]
        i3 = same_as(81)
        i2 = call_pure(123456, i3, descr=nonwritedescr)
        guard_no_exception() [i1, i2]
        jump(i2)
        """
        expected = """
        [i1]
        jump(5)
        """
        self.optimize_loop(ops, expected, call_pure_results)

    def test_remove_guard_no_exception_with_duplicated_call_pure(self):
        ops = """
        [i1]
        i2 = call_pure(123456, i1, descr=nonwritedescr)
        guard_no_exception() [i1, i2]
        i3 = call_pure(123456, i1, descr=nonwritedescr)
        guard_no_exception() [i1, i2, i3]
        jump(i3)
        """
        expected = """
        [i1]
        i2 = call(123456, i1, descr=nonwritedescr)
        guard_no_exception() [i1, i2]
        jump(i2)
        """
        self.optimize_loop(ops, expected)

    # ----------

    def test_call_loopinvariant(self):
        ops = """
        [i1]
        i2 = call_loopinvariant(1, i1, descr=nonwritedescr)
        guard_no_exception() []
        guard_value(i2, 1) []
        i3 = call_loopinvariant(1, i1, descr=nonwritedescr)
        guard_no_exception() []
        guard_value(i3, 1) []
        i4 = call_loopinvariant(1, i1, descr=nonwritedescr)
        guard_no_exception() []
        guard_value(i4, 1) []
        jump(i1)
        """
        expected = """
        [i1]
        i2 = call(1, i1, descr=nonwritedescr)
        guard_no_exception() []
        guard_value(i2, 1) []
        jump(i1)
        """
        self.optimize_loop(ops, expected)


    # ----------

    def test_virtual_1(self):
        ops = """
        [i, p0]
        i0 = getfield_gc(p0, descr=valuedescr)
        i1 = int_add(i0, i)
        setfield_gc(p0, i1, descr=valuedescr)
        jump(i, p0)
        """
        expected = """
        [i, i2]
        i1 = int_add(i2, i)
        jump(i, i1)
        """
        py.test.skip("XXX")
        self.optimize_loop(ops, 'Not, Virtual(node_vtable, valuedescr=Not)',
                           expected)

    def test_virtual_float(self):
        ops = """
        [f, p0]
        f0 = getfield_gc(p0, descr=floatdescr)
        f1 = float_add(f0, f)
        setfield_gc(p0, f1, descr=floatdescr)
        jump(f, p0)
        """
        expected = """
        [f, f2]
        f1 = float_add(f2, f)
        jump(f, f1)
        """
        py.test.skip("XXX")
        self.optimize_loop(ops, 'Not, Virtual(node_vtable, floatdescr=Not)',
                           expected)

    def test_virtual_2(self):
        ops = """
        [i, p0]
        i0 = getfield_gc(p0, descr=valuedescr)
        i1 = int_add(i0, i)
        p1 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p1, i1, descr=valuedescr)
        jump(i, p1)
        """
        expected = """
        [i, i2]
        i1 = int_add(i2, i)
        jump(i, i1)
        """
        py.test.skip("XXX")
        self.optimize_loop(ops, 'Not, Virtual(node_vtable, valuedescr=Not)',
                           expected)

    def test_virtual_oois(self):
        ops = """
        [p0, p1, p2]
        guard_nonnull(p0) []
        i3 = ptr_ne(p0, NULL)
        guard_true(i3) []
        i4 = ptr_eq(p0, NULL)
        guard_false(i4) []
        i5 = ptr_ne(NULL, p0)
        guard_true(i5) []
        i6 = ptr_eq(NULL, p0)
        guard_false(i6) []
        i7 = ptr_ne(p0, p1)
        guard_true(i7) []
        i8 = ptr_eq(p0, p1)
        guard_false(i8) []
        i9 = ptr_ne(p0, p2)
        guard_true(i9) []
        i10 = ptr_eq(p0, p2)
        guard_false(i10) []
        i11 = ptr_ne(p2, p1)
        guard_true(i11) []
        i12 = ptr_eq(p2, p1)
        guard_false(i12) []
        jump(p0, p1, p2)
        """
        expected = """
        [p2]
        # all constant-folded :-)
        jump(p2)
        """
        py.test.skip("XXX")
        self.optimize_loop(ops, '''Virtual(node_vtable),
                                   Virtual(node_vtable),
                                   Not''',
                           expected)
        #
        # to be complete, we also check the no-opt case where most comparisons
        # are not removed.  The exact set of comparisons removed depends on
        # the details of the algorithm...
        expected2 = """
        [p0, p1, p2]
        guard_nonnull(p0) []
        i7 = ptr_ne(p0, p1)
        guard_true(i7) []
        i9 = ptr_ne(p0, p2)
        guard_true(i9) []
        i11 = ptr_ne(p2, p1)
        guard_true(i11) []
        jump(p0, p1, p2)
        """
        self.optimize_loop(ops, expected2)

    def test_virtual_default_field(self):
        ops = """
        [p0]
        i0 = getfield_gc(p0, descr=valuedescr)
        guard_value(i0, 0) []
        p1 = new_with_vtable(ConstClass(node_vtable))
        # the field 'value' has its default value of 0
        jump(p1)
        """
        expected = """
        [i]
        guard_value(i, 0) []
        jump(0)
        """
        # the 'expected' is sub-optimal, but it should be done by another later
        # optimization step.  See test_find_nodes_default_field() for why.
        py.test.skip("XXX")
        self.optimize_loop(ops, 'Virtual(node_vtable, valuedescr=Not)',
                           expected)

    def test_virtual_3(self):
        ops = """
        [i]
        p1 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p1, i, descr=valuedescr)
        i0 = getfield_gc(p1, descr=valuedescr)
        i1 = int_add(i0, 1)
        jump(i1)
        """
        expected = """
        [i]
        i1 = int_add(i, 1)
        jump(i1)
        """
        self.optimize_loop(ops, expected)

    def test_virtual_4(self):
        ops = """
        [i0, p0]
        guard_class(p0, ConstClass(node_vtable)) []
        i1 = getfield_gc(p0, descr=valuedescr)
        i2 = int_sub(i1, 1)
        i3 = int_add(i0, i1)
        p1 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p1, i2, descr=valuedescr)
        jump(i3, p1)
        """
        expected = """
        [i0, i1]
        i2 = int_sub(i1, 1)
        i3 = int_add(i0, i1)
        jump(i3, i2)
        """
        py.test.skip("XXX")
        self.optimize_loop(ops, 'Not, Virtual(node_vtable, valuedescr=Not)',
                           expected)

    def test_virtual_5(self):
        ops = """
        [i0, p0]
        guard_class(p0, ConstClass(node_vtable)) []
        i1 = getfield_gc(p0, descr=valuedescr)
        i2 = int_sub(i1, 1)
        i3 = int_add(i0, i1)
        p2 = new_with_vtable(ConstClass(node_vtable2))
        setfield_gc(p2, i1, descr=valuedescr)
        p1 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p1, i2, descr=valuedescr)
        setfield_gc(p1, p2, descr=nextdescr)
        jump(i3, p1)
        """
        expected = """
        [i0, i1, i1bis]
        i2 = int_sub(i1, 1)
        i3 = int_add(i0, i1)
        jump(i3, i2, i1)
        """
        py.test.skip("XXX")
        self.optimize_loop(ops,
            '''Not, Virtual(node_vtable,
                            valuedescr=Not,
                            nextdescr=Virtual(node_vtable2,
                                              valuedescr=Not))''',
                           expected)

    def test_virtual_constant_isnull(self):
        ops = """
        [i0]
        p0 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p0, NULL, descr=nextdescr)
        p2 = getfield_gc(p0, descr=nextdescr)
        i1 = ptr_eq(p2, NULL)
        jump(i1)
        """
        expected = """
        [i0]
        jump(1)
        """
        self.optimize_loop(ops, expected)

    def test_virtual_constant_isnonnull(self):
        ops = """
        [i0]
        p0 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p0, ConstPtr(myptr), descr=nextdescr)
        p2 = getfield_gc(p0, descr=nextdescr)
        i1 = ptr_eq(p2, NULL)
        jump(i1)
        """
        expected = """
        [i0]
        jump(0)
        """
        self.optimize_loop(ops, expected)

    def test_virtual_array_of_struct(self):
        ops = """
        [f0, f1, f2, f3]
        p0 = new_array(2, descr=complexarraydescr)
        setinteriorfield_gc(p0, 0, f0, descr=complexrealdescr)
        setinteriorfield_gc(p0, 0, f1, descr=compleximagdescr)
        setinteriorfield_gc(p0, 1, f2, descr=complexrealdescr)
        setinteriorfield_gc(p0, 1, f3, descr=compleximagdescr)
        f4 = getinteriorfield_gc(p0, 0, descr=complexrealdescr)
        f5 = getinteriorfield_gc(p0, 1, descr=complexrealdescr)
        f6 = float_mul(f4, f5)
        f7 = getinteriorfield_gc(p0, 0, descr=compleximagdescr)
        f8 = getinteriorfield_gc(p0, 1, descr=compleximagdescr)
        f9 = float_mul(f7, f8)
        f10 = float_add(f6, f9)
        finish(f10)
        """
        expected = """
        [f0, f1, f2, f3]
        f4 = float_mul(f0, f2)
        f5 = float_mul(f1, f3)
        f6 = float_add(f4, f5)
        finish(f6)
        """
        self.optimize_loop(ops, expected)

    def test_virtual_array_of_struct_forced(self):
        ops = """
        [f0, f1]
        p0 = new_array(1, descr=complexarraydescr)
        setinteriorfield_gc(p0, 0, f0, descr=complexrealdescr)
        setinteriorfield_gc(p0, 0, f1, descr=compleximagdescr)
        f2 = getinteriorfield_gc(p0, 0, descr=complexrealdescr)
        f3 = getinteriorfield_gc(p0, 0, descr=compleximagdescr)
        f4 = float_mul(f2, f3)
        i0 = escape(f4, p0)
        finish(i0)
        """
        expected = """
        [f0, f1]
        f2 = float_mul(f0, f1)
        p0 = new_array(1, descr=complexarraydescr)
        setinteriorfield_gc(p0, 0, f0, descr=complexrealdescr)
        setinteriorfield_gc(p0, 0, f1, descr=compleximagdescr)
        i0 = escape(f2, p0)
        finish(i0)
        """
        self.optimize_loop(ops, expected)

    def test_nonvirtual_1(self):
        ops = """
        [i]
        p1 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p1, i, descr=valuedescr)
        i0 = getfield_gc(p1, descr=valuedescr)
        i1 = int_add(i0, 1)
        escape(p1)
        escape(p1)
        jump(i1)
        """
        expected = """
        [i]
        i1 = int_add(i, 1)
        p1 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p1, i, descr=valuedescr)
        escape(p1)
        escape(p1)
        jump(i1)
        """
        self.optimize_loop(ops, expected)

    def test_nonvirtual_2(self):
        ops = """
        [i, p0]
        i0 = getfield_gc(p0, descr=valuedescr)
        escape(p0)
        i1 = int_add(i0, i)
        p1 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p1, i1, descr=valuedescr)
        jump(i, p1)
        """
        expected = ops
        self.optimize_loop(ops, expected)

    def test_nonvirtual_later(self):
        ops = """
        [i]
        p1 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p1, i, descr=valuedescr)
        i1 = getfield_gc(p1, descr=valuedescr)
        escape(p1)
        i2 = getfield_gc(p1, descr=valuedescr)
        i3 = int_add(i1, i2)
        jump(i3)
        """
        expected = """
        [i]
        p1 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p1, i, descr=valuedescr)
        escape(p1)
        i2 = getfield_gc(p1, descr=valuedescr)
        i3 = int_add(i, i2)
        jump(i3)
        """
        self.optimize_loop(ops, expected)

    def test_nonvirtual_dont_write_null_fields_on_force(self):
        ops = """
        [i]
        p1 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p1, i, descr=valuedescr)
        i1 = getfield_gc(p1, descr=valuedescr)
        setfield_gc(p1, 0, descr=valuedescr)
        escape(p1)
        i2 = getfield_gc(p1, descr=valuedescr)
        jump(i2)
        """
        expected = """
        [i]
        p1 = new_with_vtable(ConstClass(node_vtable))
        escape(p1)
        i2 = getfield_gc(p1, descr=valuedescr)
        jump(i2)
        """
        self.optimize_loop(ops, expected)

    def test_getfield_gc_pure_1(self):
        ops = """
        [i]
        p1 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p1, i, descr=valuedescr)
        i1 = getfield_gc_pure(p1, descr=valuedescr)
        jump(i1)
        """
        expected = """
        [i]
        jump(i)
        """
        self.optimize_loop(ops, expected)

    def test_getfield_gc_pure_2(self):
        ops = """
        [i]
        i1 = getfield_gc_pure(ConstPtr(myptr), descr=valuedescr)
        jump(i1)
        """
        expected = """
        [i]
        jump(5)
        """
        self.node.value = 5
        self.optimize_loop(ops, expected)

    def test_getfield_gc_nonpure_2(self):
        ops = """
        [i]
        i1 = getfield_gc(ConstPtr(myptr), descr=valuedescr)
        jump(i1)
        """
        expected = ops
        self.optimize_loop(ops, expected)

    def test_varray_1(self):
        ops = """
        [i1]
        p1 = new_array(3, descr=arraydescr)
        i3 = arraylen_gc(p1, descr=arraydescr)
        guard_value(i3, 3) []
        setarrayitem_gc(p1, 1, i1, descr=arraydescr)
        setarrayitem_gc(p1, 0, 25, descr=arraydescr)
        i2 = getarrayitem_gc(p1, 1, descr=arraydescr)
        jump(i2)
        """
        expected = """
        [i1]
        jump(i1)
        """
        self.optimize_loop(ops, expected)

    def test_varray_alloc_and_set(self):
        ops = """
        [i1]
        p1 = new_array(2, descr=arraydescr)
        setarrayitem_gc(p1, 0, 25, descr=arraydescr)
        i2 = getarrayitem_gc(p1, 1, descr=arraydescr)
        jump(i2)
        """
        expected = """
        [i1]
        jump(0)
        """
        self.optimize_loop(ops, expected)

    def test_varray_float(self):
        ops = """
        [f1]
        p1 = new_array(3, descr=floatarraydescr)
        i3 = arraylen_gc(p1, descr=floatarraydescr)
        guard_value(i3, 3) []
        setarrayitem_gc(p1, 1, f1, descr=floatarraydescr)
        setarrayitem_gc(p1, 0, 3.5, descr=floatarraydescr)
        f2 = getarrayitem_gc(p1, 1, descr=floatarraydescr)
        jump(f2)
        """
        expected = """
        [f1]
        jump(f1)
        """
        self.optimize_loop(ops, expected)

    def test_array_non_optimized(self):
        ops = """
        [i1, p0]
        setarrayitem_gc(p0, 0, i1, descr=arraydescr)
        guard_nonnull(p0) []
        p1 = new_array(i1, descr=arraydescr)
        jump(i1, p1)
        """
        expected = """
        [i1, p0]
        p1 = new_array(i1, descr=arraydescr)
        setarrayitem_gc(p0, 0, i1, descr=arraydescr)
        jump(i1, p1)
        """
        self.optimize_loop(ops, expected)

    def test_nonvirtual_array_dont_write_null_fields_on_force(self):
        ops = """
        [i1]
        p1 = new_array(5, descr=arraydescr)
        setarrayitem_gc(p1, 0, i1, descr=arraydescr)
        setarrayitem_gc(p1, 1, 0, descr=arraydescr)
        escape(p1)
        jump(i1)
        """
        expected = """
        [i1]
        p1 = new_array(5, descr=arraydescr)
        setarrayitem_gc(p1, 0, i1, descr=arraydescr)
        escape(p1)
        jump(i1)
        """
        self.optimize_loop(ops, expected)

    def test_varray_2(self):
        ops = """
        [i0, p1]
        i1 = getarrayitem_gc(p1, 0, descr=arraydescr)
        i2 = getarrayitem_gc(p1, 1, descr=arraydescr)
        i3 = int_sub(i1, i2)
        guard_value(i3, 15) []
        p2 = new_array(2, descr=arraydescr)
        setarrayitem_gc(p2, 1, i0, descr=arraydescr)
        setarrayitem_gc(p2, 0, 20, descr=arraydescr)
        jump(i0, p2)
        """
        expected = """
        [i0, i1, i2]
        i3 = int_sub(i1, i2)
        guard_value(i3, 15) []
        jump(i0, 20, i0)
        """
        py.test.skip("XXX")
        self.optimize_loop(ops, 'Not, VArray(arraydescr, Not, Not)', expected)

    def test_p123_array(self):
        ops = """
        [i1, p2, p3]
        i3 = getarrayitem_gc(p3, 0, descr=arraydescr)
        escape(i3)
        p1 = new_array(1, descr=arraydescr)
        setarrayitem_gc(p1, 0, i1, descr=arraydescr)
        jump(i1, p1, p2)
        """
        # We cannot track virtuals that survive for more than two iterations.
        self.optimize_loop(ops, ops)

    def test_varray_forced_1(self):
        ops = """
        []
        p2 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p2, 3, descr=valuedescr)
        i1 = getfield_gc(p2, descr=valuedescr)    # i1 = const 3
        p1 = new_array(i1, descr=arraydescr)
        escape(p1)
        i2 = arraylen_gc(p1)
        escape(i2)
        jump()
        """
        expected = """
        []
        p1 = new_array(3, descr=arraydescr)
        escape(p1)
        i2 = arraylen_gc(p1)
        escape(i2)
        jump()
        """
        self.optimize_loop(ops, expected)

    def test_vstruct_1(self):
        ops = """
        [i1, p2]
        i2 = getfield_gc(p2, descr=adescr)
        escape(i2)
        p3 = new(descr=ssize)
        setfield_gc(p3, i1, descr=adescr)
        jump(i1, p3)
        """
        expected = """
        [i1, i2]
        escape(i2)
        jump(i1, i1)
        """
        py.test.skip("XXX")
        self.optimize_loop(ops, 'Not, VStruct(ssize, adescr=Not)', expected)

    def test_p123_vstruct(self):
        ops = """
        [i1, p2, p3]
        i3 = getfield_gc(p3, descr=adescr)
        escape(i3)
        p1 = new(descr=ssize)
        setfield_gc(p1, i1, descr=adescr)
        jump(i1, p1, p2)
        """
        # We cannot track virtuals that survive for more than two iterations.
        self.optimize_loop(ops, ops)

    def test_duplicate_getfield_1(self):
        ops = """
        [p1, p2]
        i1 = getfield_gc(p1, descr=valuedescr)
        i2 = getfield_gc(p2, descr=valuedescr)
        i3 = getfield_gc(p1, descr=valuedescr)
        i4 = getfield_gc(p2, descr=valuedescr)
        escape(i1)
        escape(i2)
        escape(i3)
        escape(i4)
        jump(p1, p2)
        """
        expected = """
        [p1, p2]
        i1 = getfield_gc(p1, descr=valuedescr)
        i2 = getfield_gc(p2, descr=valuedescr)
        escape(i1)
        escape(i2)
        escape(i1)
        escape(i2)
        jump(p1, p2)
        """
        self.optimize_loop(ops, expected)

    def test_getfield_after_setfield(self):
        ops = """
        [p1, i1]
        setfield_gc(p1, i1, descr=valuedescr)
        i2 = getfield_gc(p1, descr=valuedescr)
        escape(i2)
        jump(p1, i1)
        """
        expected = """
        [p1, i1]
        setfield_gc(p1, i1, descr=valuedescr)
        escape(i1)
        jump(p1, i1)
        """
        self.optimize_loop(ops, expected)

    def test_setfield_of_different_type_does_not_clear(self):
        ops = """
        [p1, p2, i1]
        setfield_gc(p1, i1, descr=valuedescr)
        setfield_gc(p2, p1, descr=nextdescr)
        i2 = getfield_gc(p1, descr=valuedescr)
        escape(i2)
        jump(p1, p2, i1)
        """
        expected = """
        [p1, p2, i1]
        setfield_gc(p1, i1, descr=valuedescr)
        setfield_gc(p2, p1, descr=nextdescr)
        escape(i1)
        jump(p1, p2, i1)
        """
        self.optimize_loop(ops, expected)

    def test_setfield_of_same_type_clears(self):
        ops = """
        [p1, p2, i1, i2]
        setfield_gc(p1, i1, descr=valuedescr)
        setfield_gc(p2, i2, descr=valuedescr)
        i3 = getfield_gc(p1, descr=valuedescr)
        escape(i3)
        jump(p1, p2, i1, i3)
        """
        self.optimize_loop(ops, ops)

    def test_duplicate_getfield_mergepoint_has_no_side_effects(self):
        ops = """
        [p1]
        i1 = getfield_gc(p1, descr=valuedescr)
        debug_merge_point(15, 0)
        i2 = getfield_gc(p1, descr=valuedescr)
        escape(i1)
        escape(i2)
        jump(p1)
        """
        expected = """
        [p1]
        i1 = getfield_gc(p1, descr=valuedescr)
        debug_merge_point(15, 0)
        escape(i1)
        escape(i1)
        jump(p1)
        """
        self.optimize_loop(ops, expected)

    def test_duplicate_getfield_ovf_op_does_not_clear(self):
        ops = """
        [p1]
        i1 = getfield_gc(p1, descr=valuedescr)
        i2 = int_add_ovf(i1, 14)
        guard_no_overflow() []
        i3 = getfield_gc(p1, descr=valuedescr)
        escape(i2)
        escape(i3)
        jump(p1)
        """
        expected = """
        [p1]
        i1 = getfield_gc(p1, descr=valuedescr)
        i2 = int_add_ovf(i1, 14)
        guard_no_overflow() []
        escape(i2)
        escape(i1)
        jump(p1)
        """
        self.optimize_loop(ops, expected)

    def test_duplicate_getfield_setarrayitem_does_not_clear(self):
        ops = """
        [p1, p2]
        i1 = getfield_gc(p1, descr=valuedescr)
        setarrayitem_gc(p2, 0, p1, descr=arraydescr2)
        i3 = getfield_gc(p1, descr=valuedescr)
        escape(i1)
        escape(i3)
        jump(p1, p2)
        """
        expected = """
        [p1, p2]
        i1 = getfield_gc(p1, descr=valuedescr)
        setarrayitem_gc(p2, 0, p1, descr=arraydescr2)
        escape(i1)
        escape(i1)
        jump(p1, p2)
        """
        self.optimize_loop(ops, expected)

    def test_duplicate_getfield_constant(self):
        ops = """
        []
        i1 = getfield_gc(ConstPtr(myptr), descr=valuedescr)
        i2 = getfield_gc(ConstPtr(myptr), descr=valuedescr)
        escape(i1)
        escape(i2)
        jump()
        """
        expected = """
        []
        i1 = getfield_gc(ConstPtr(myptr), descr=valuedescr)
        escape(i1)
        escape(i1)
        jump()
        """
        self.optimize_loop(ops, expected)

    def test_duplicate_getfield_guard_value_const(self):
        ops = """
        [p1]
        guard_value(p1, ConstPtr(myptr)) []
        i1 = getfield_gc(p1, descr=valuedescr)
        i2 = getfield_gc(ConstPtr(myptr), descr=valuedescr)
        escape(i1)
        escape(i2)
        jump(p1)
        """
        expected = """
        []
        i1 = getfield_gc(ConstPtr(myptr), descr=valuedescr)
        escape(i1)
        escape(i1)
        jump()
        """
        py.test.skip("XXX")
        self.optimize_loop(ops, 'Constant(myptr)', expected)

    def test_duplicate_getfield_sideeffects_1(self):
        ops = """
        [p1]
        i1 = getfield_gc(p1, descr=valuedescr)
        escape()
        i2 = getfield_gc(p1, descr=valuedescr)
        escape(i1)
        escape(i2)
        jump(p1)
        """
        self.optimize_loop(ops, ops)

    def test_duplicate_getfield_sideeffects_2(self):
        ops = """
        [p1, i1]
        setfield_gc(p1, i1, descr=valuedescr)
        escape()
        i2 = getfield_gc(p1, descr=valuedescr)
        escape(i2)
        jump(p1, i1)
        """
        self.optimize_loop(ops, ops)

    def test_duplicate_setfield_1(self):
        ops = """
        [p1, i1, i2]
        setfield_gc(p1, i1, descr=valuedescr)
        setfield_gc(p1, i2, descr=valuedescr)
        jump(p1, i1, i2)
        """
        expected = """
        [p1, i1, i2]
        setfield_gc(p1, i2, descr=valuedescr)
        jump(p1, i1, i2)
        """
        self.optimize_loop(ops, expected)

    def test_duplicate_setfield_2(self):
        ops = """
        [p1, i1, i3]
        setfield_gc(p1, i1, descr=valuedescr)
        i2 = getfield_gc(p1, descr=valuedescr)
        setfield_gc(p1, i3, descr=valuedescr)
        escape(i2)
        jump(p1, i1, i3)
        """
        expected = """
        [p1, i1, i3]
        setfield_gc(p1, i3, descr=valuedescr)
        escape(i1)
        jump(p1, i1, i3)
        """
        self.optimize_loop(ops, expected)

    def test_duplicate_setfield_3(self):
        ops = """
        [p1, p2, i1, i3]
        setfield_gc(p1, i1, descr=valuedescr)
        i2 = getfield_gc(p2, descr=valuedescr)
        setfield_gc(p1, i3, descr=valuedescr)
        escape(i2)
        jump(p1, p2, i1, i3)
        """
        # potential aliasing of p1 and p2 means that we cannot kill the
        # the setfield_gc
        self.optimize_loop(ops, ops)

    def test_duplicate_setfield_4(self):
        ops = """
        [p1, i1, i2, p3]
        setfield_gc(p1, i1, descr=valuedescr)
        #
        # some operations on which the above setfield_gc cannot have effect
        i3 = getarrayitem_gc_pure(p3, 1, descr=arraydescr)
        i4 = getarrayitem_gc(p3, i3, descr=arraydescr)
        i5 = int_add(i3, i4)
        setarrayitem_gc(p3, 0, i5, descr=arraydescr)
        setfield_gc(p1, i4, descr=nextdescr)
        #
        setfield_gc(p1, i2, descr=valuedescr)
        jump(p1, i1, i2, p3)
        """
        expected = """
        [p1, i1, i2, p3]
        #
        i3 = getarrayitem_gc_pure(p3, 1, descr=arraydescr)
        i4 = getarrayitem_gc(p3, i3, descr=arraydescr)
        i5 = int_add(i3, i4)
        #
        setfield_gc(p1, i2, descr=valuedescr)
        setarrayitem_gc(p3, 0, i5, descr=arraydescr)
        setfield_gc(p1, i4, descr=nextdescr)
        jump(p1, i1, i2, p3)
        """
        self.optimize_loop(ops, expected)

    def test_duplicate_setfield_5(self):
        ops = """
        [p0, i1]
        p1 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p1, i1, descr=valuedescr)
        setfield_gc(p0, p1, descr=nextdescr)
        setfield_raw(i1, i1, descr=valuedescr)    # random op with side-effects
        p2 = getfield_gc(p0, descr=nextdescr)
        i2 = getfield_gc(p2, descr=valuedescr)
        setfield_gc(p0, NULL, descr=nextdescr)
        escape(i2)
        jump(p0, i1)
        """
        expected = """
        [p0, i1]
        setfield_raw(i1, i1, descr=valuedescr)
        setfield_gc(p0, NULL, descr=nextdescr)
        escape(i1)
        jump(p0, i1)
        """
        self.optimize_loop(ops, expected)

    def test_duplicate_setfield_sideeffects_1(self):
        ops = """
        [p1, i1, i2]
        setfield_gc(p1, i1, descr=valuedescr)
        escape()
        setfield_gc(p1, i2, descr=valuedescr)
        jump(p1, i1, i2)
        """
        self.optimize_loop(ops, ops)

    def test_duplicate_setfield_residual_guard_1(self):
        ops = """
        [p1, i1, i2, i3]
        setfield_gc(p1, i1, descr=valuedescr)
        guard_true(i3) []
        i4 = int_neg(i2)
        setfield_gc(p1, i2, descr=valuedescr)
        jump(p1, i1, i2, i4)
        """
        self.optimize_loop(ops, ops)

    def test_duplicate_setfield_residual_guard_2(self):
        # the difference with the previous test is that the field value is
        # a virtual, which we try hard to keep virtual
        ops = """
        [p1, i2, i3]
        p2 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p1, p2, descr=nextdescr)
        guard_true(i3) []
        i4 = int_neg(i2)
        setfield_gc(p1, NULL, descr=nextdescr)
        jump(p1, i2, i4)
        """
        expected = """
        [p1, i2, i3]
        guard_true(i3) [p1]
        i4 = int_neg(i2)
        setfield_gc(p1, NULL, descr=nextdescr)
        jump(p1, i2, i4)
        """
        self.optimize_loop(ops, expected)

    def test_duplicate_setfield_residual_guard_3(self):
        ops = """
        [p1, i2, i3]
        p2 = new_with_vtable(ConstClass(node_vtable))
        setfield_gc(p2, i2, descr=valuedescr)
        setfield_gc(p1, p2, descr=nextdescr)
        guard_true(i3) []
        i4 = int_neg(i2)
        setfield_gc(p1, NULL, descr=nextdescr)
        jump(p1, i2, i4)
        """
        expected = """
        [p1, i2, i3]
        guard_true(i3) [i2, p1]
        i4 = int_neg(i2)
        setfield_gc(p1, NULL, descr=nextdescr)
        jump(p1, i2, i4)
        """
        self.optimize_loop(ops, expected)

    def test_duplicate_setfield_residual_guard_4(self):
        # test that the setfield_gc does not end up between int_eq and
        # the following guard_true
        ops = """
        [p1, i1, i2, i3]
        setfield_gc(p1, i1, descr=valuedescr)
        i5 = int_eq(i3, 5)
        guard_true(i5) []
        i4 = int_neg(i2)
        setfield_gc(p1, i2, descr=valuedescr)
        jump(p1, i1, i2, i4)
        """
        self.optimize_loop(ops, ops)

    def test_duplicate_setfield_aliasing(self):
        # a case where aliasing issues (and not enough cleverness) mean
        # that we fail to remove any setfield_gc
        ops = """
        [p1, p2, i1, i2, i3]
        setfield_gc(p1, i1, descr=valuedescr)
        setfield_gc(p2, i2, descr=valuedescr)
        setfield_gc(p1, i3, descr=valuedescr)
        jump(p1, p2, i1, i2, i3)
        """
        self.optimize_loop(ops, ops)

    def test_duplicate_setfield_guard_value_const(self):
        ops = """
        [p1, i1, i2]
        guard_value(p1, ConstPtr(myptr)) []
        setfield_gc(p1, i1, descr=valuedescr)
        setfield_gc(ConstPtr(myptr), i2, descr=valuedescr)
        jump(p1, i1, i2)
        """
        expected = """
        [i1, i2]
        setfield_gc(ConstPtr(myptr), i2, descr=valuedescr)
        jump(i1, i2)
        """
        py.test.skip("XXX")
        self.optimize_loop(ops, 'Constant(myptr), Not, Not', expected)

    def test_duplicate_getarrayitem_1(self):
        ops = """
        [p1]
        p2 = getarrayitem_gc(p1, 0, descr=arraydescr2)
        p3 = getarrayitem_gc(p1, 1, descr=arraydescr2)
        p4 = getarrayitem_gc(p1, 0, descr=arraydescr2)
        p5…