optimizer_symbols.c

#ifdef _Py_TIER2

#include "Python.h"

#include "pycore_code.h"
#include "pycore_frame.h"
#include "pycore_long.h"
#include "pycore_optimizer.h"
#include "pycore_stats.h"

#include <stdbool.h>
#include <stdint.h>
#include <stddef.h>

/*

Symbols
=======

https://github.com/faster-cpython/ideas/blob/main/3.13/redundancy_eliminator.md

Logically, all symbols begin as UNKNOWN, and can transition downwards along the
edges of the lattice, but *never* upwards (see the diagram below). The UNKNOWN
state represents no information, and the BOTTOM state represents contradictory
information. Though symbols logically progress through all intermediate nodes,
we often skip in-between states for convenience:

   UNKNOWN-------------------+------------+
   |     |                   |            |
NULL     |                   |            |
|        |                   |            |  <- Anything below this level is an object.
|        NON_NULL-+          |            |
|          |      |          |            |  <- Anything below this level has a known type version.
|    TYPE_VERSION |          |            |
|    |            |          |            |  <- Anything below this level has a known type.
|    KNOWN_CLASS  |          |            |
|    |  |  |   |  |          PREDICATE    DESCR
|    |  | INT* |  |          |            |
|    |  |  |   |  |          |            |  <- Anything below this level has a known truthiness.
|    |  |  |   |  TRUTHINESS |            |
|    |  |  |   |  |          |            |
| TUPLE |  |   |  |          |            |
|    |  |  |   |  |          |            |  <- Anything below this level is a known constant.
|    KNOWN_VALUE--+----------+------------+
|    |                                        <- Anything below this level is unreachable.
BOTTOM

For example, after guarding that the type of an UNKNOWN local is int, we can
narrow the symbol to KNOWN_CLASS (logically progressing though NON_NULL and
TYPE_VERSION to get there). Later, we may learn that it is falsey based on the
result of a truth test, which would allow us to narrow the symbol to KNOWN_VALUE
(with a value of integer zero). If at any point we encounter a float guard on
the same symbol, that would be a contradiction, and the symbol would be set to
BOTTOM (indicating that the code is unreachable).

INT* is a limited range int, currently a "compact" int.

*/

#ifdef Py_DEBUG
static inline int get_lltrace(void) {
    char *uop_debug = Py_GETENV("PYTHON_OPT_DEBUG");
    int lltrace = 0;
    if (uop_debug != NULL && *uop_debug >= '0') {
        lltrace = *uop_debug - '0';  // TODO: Parse an int and all that
    }
    return lltrace;
}
#define DPRINTF(level, ...) \
    if (get_lltrace() >= (level)) { printf(__VA_ARGS__); }

void
_PyUOpSymPrint(JitOptRef ref)
{
    if (PyJitRef_IsNull(ref)) {
        printf("<JitRef NULL>");
        return;
    }
    if (PyJitRef_IsInvalid(ref)) {
        printf("<INVALID frame at %p>", (void *)PyJitRef_Unwrap(ref));
        return;
    }
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    switch (sym->tag) {
        case JIT_SYM_UNKNOWN_TAG:
            printf("<? at %p>", (void *)sym);
            break;
        case JIT_SYM_NULL_TAG:
            printf("<NULL at %p>", (void *)sym);
            break;
        case JIT_SYM_NON_NULL_TAG:
            printf("<!NULL at %p>", (void *)sym);
            break;
        case JIT_SYM_BOTTOM_TAG:
            printf("<BOTTOM at %p>", (void *)sym);
            break;
        case JIT_SYM_TYPE_VERSION_TAG:
            printf("<v%u at %p>", sym->version.version, (void *)sym);
            break;
        case JIT_SYM_KNOWN_CLASS_TAG:
            printf("<%s at %p>", sym->cls.type->tp_name, (void *)sym);
            break;
        case JIT_SYM_KNOWN_VALUE_TAG:
            printf("<%s val=%p at %p>", Py_TYPE(sym->value.value)->tp_name,
                   (void *)sym->value.value, (void *)sym);
            break;
        case JIT_SYM_TUPLE_TAG:
            printf("<tuple[%d] at %p>", sym->tuple.length, (void *)sym);
            break;
        case JIT_SYM_TRUTHINESS_TAG:
            printf("<truthiness%s at %p>", sym->truthiness.invert ? "!" : "", (void *)sym);
            break;
        case JIT_SYM_COMPACT_INT:
            printf("<compact_int at %p>", (void *)sym);
            break;
        case JIT_SYM_PREDICATE_TAG:
            printf("<predicate at %p>", (void *)sym);
            break;
        case JIT_SYM_DESCR_TAG: {
            PyTypeObject *descr_type = _PyType_LookupByVersion(sym->descr.type_version);
            if (descr_type) {
                printf("<%s descr[%d] v%u at %p>", descr_type->tp_name, sym->descr.num_descrs, sym->descr.type_version, (void *)sym);
            } else {
                printf("<descr[%d] v%u at %p>", sym->descr.num_descrs, sym->descr.type_version, (void *)sym);
            }
            break;
        }
        default:
            printf("<tag=%d at %p>", sym->tag, (void *)sym);
            break;
    }
}

#else
#define DPRINTF(level, ...)
#endif


static JitOptSymbol NO_SPACE_SYMBOL = {
    .tag = JIT_SYM_BOTTOM_TAG
};

static JitOptSymbol *
allocation_base(JitOptContext *ctx)
{
    return ctx->t_arena.arena;
}

JitOptSymbol *
out_of_space(JitOptContext *ctx)
{
    ctx->done = true;
    ctx->out_of_space = true;
    return &NO_SPACE_SYMBOL;
}

JitOptRef
out_of_space_ref(JitOptContext *ctx)
{
    return PyJitRef_Wrap(out_of_space(ctx));
}

static JitOptSymbol *
sym_new(JitOptContext *ctx)
{
    JitOptSymbol *self = &ctx->t_arena.arena[ctx->t_arena.ty_curr_number];
    if (ctx->t_arena.ty_curr_number >= ctx->t_arena.ty_max_number) {
        OPT_STAT_INC(optimizer_failure_reason_no_memory);
        DPRINTF(1, "out of space for symbolic expression type\n");
        return NULL;
    }
    ctx->t_arena.ty_curr_number++;
    self->tag = JIT_SYM_UNKNOWN_TAG;;
    return self;
}

static void make_const(JitOptSymbol *sym, PyObject *val)
{
    sym->tag = JIT_SYM_KNOWN_VALUE_TAG;
    sym->value.value = Py_NewRef(val);
}

static inline void
sym_set_bottom(JitOptContext *ctx, JitOptSymbol *sym)
{
    sym->tag = JIT_SYM_BOTTOM_TAG;
    ctx->done = true;
    ctx->contradiction = true;
}

bool
_Py_uop_sym_is_bottom(JitOptRef ref)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    return sym->tag == JIT_SYM_BOTTOM_TAG;
}

bool
_Py_uop_sym_is_not_null(JitOptRef ref) {
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    return sym->tag == JIT_SYM_NON_NULL_TAG || sym->tag > JIT_SYM_BOTTOM_TAG;
}

bool
_Py_uop_sym_is_const(JitOptContext *ctx, JitOptRef ref)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    if (sym->tag == JIT_SYM_KNOWN_VALUE_TAG) {
        return true;
    }
    if (sym->tag == JIT_SYM_TRUTHINESS_TAG) {
        JitOptSymbol *value = allocation_base(ctx) + sym->truthiness.value;
        int truthiness = _Py_uop_sym_truthiness(ctx, PyJitRef_Wrap(value));
        if (truthiness < 0) {
            return false;
        }
        make_const(sym, (truthiness ^ sym->truthiness.invert) ? Py_True : Py_False);
        return true;
    }
    return false;
}

bool
_Py_uop_sym_is_null(JitOptRef ref)
{
    return PyJitRef_Unwrap(ref)->tag == JIT_SYM_NULL_TAG;
}


PyObject *
_Py_uop_sym_get_const(JitOptContext *ctx, JitOptRef ref)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    if (sym->tag == JIT_SYM_KNOWN_VALUE_TAG) {
        return sym->value.value;
    }
    if (sym->tag == JIT_SYM_TRUTHINESS_TAG) {
        JitOptSymbol *value = allocation_base(ctx) + sym->truthiness.value;
        int truthiness = _Py_uop_sym_truthiness(ctx, PyJitRef_Wrap(value));
        if (truthiness < 0) {
            return NULL;
        }
        PyObject *res = (truthiness ^ sym->truthiness.invert) ? Py_True : Py_False;
        make_const(sym, res);
        return res;
    }
    return NULL;
}

_PyStackRef
_Py_uop_sym_get_const_as_stackref(JitOptContext *ctx, JitOptRef sym)
{
    PyObject *const_val = _Py_uop_sym_get_const(ctx, sym);
    if (const_val == NULL) {
        return PyStackRef_NULL;
    }
    return PyStackRef_FromPyObjectBorrow(const_val);
}

/*
 Indicates whether the constant is safe to constant evaluate
 (without side effects).
 */
bool
_Py_uop_sym_is_safe_const(JitOptContext *ctx, JitOptRef sym)
{
    PyObject *const_val = _Py_uop_sym_get_const(ctx, sym);
    if (const_val == NULL) {
        return false;
    }
    if (_PyLong_CheckExactAndCompact(const_val)) {
        return true;
    }
    PyTypeObject *typ = Py_TYPE(const_val);
    return (typ == &PyUnicode_Type) ||
           (typ == &PyFloat_Type) ||
           (typ == &_PyNone_Type) ||
           (typ == &PyBool_Type);
}

void
_Py_uop_sym_set_type(JitOptContext *ctx, JitOptRef ref, PyTypeObject *typ)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    JitSymType tag = sym->tag;
    switch(tag) {
        case JIT_SYM_NULL_TAG:
            sym_set_bottom(ctx, sym);
            return;
        case JIT_SYM_KNOWN_CLASS_TAG:
            if (sym->cls.type != typ) {
                sym_set_bottom(ctx, sym);
            }
            return;
        case JIT_SYM_TYPE_VERSION_TAG:
            if (sym->version.version == typ->tp_version_tag) {
                sym->tag = JIT_SYM_KNOWN_CLASS_TAG;
                sym->cls.type = typ;
                sym->cls.version = typ->tp_version_tag;
            }
            else {
                sym_set_bottom(ctx, sym);
            }
            return;
        case JIT_SYM_KNOWN_VALUE_TAG:
            if (Py_TYPE(sym->value.value) != typ) {
                Py_CLEAR(sym->value.value);
                sym_set_bottom(ctx, sym);
            }
            return;
        case JIT_SYM_TUPLE_TAG:
            if (typ != &PyTuple_Type) {
                sym_set_bottom(ctx, sym);
            }
            return;
        case JIT_SYM_BOTTOM_TAG:
            return;
        case JIT_SYM_NON_NULL_TAG:
        case JIT_SYM_UNKNOWN_TAG:
            sym->tag = JIT_SYM_KNOWN_CLASS_TAG;
            sym->cls.version = 0;
            sym->cls.type = typ;
            return;
        case JIT_SYM_PREDICATE_TAG:
        case JIT_SYM_TRUTHINESS_TAG:
            if (typ != &PyBool_Type) {
                sym_set_bottom(ctx, sym);
            }
            return;
        case JIT_SYM_COMPACT_INT:
            if (typ != &PyLong_Type) {
                sym_set_bottom(ctx, sym);
            }
            return;
        case JIT_SYM_DESCR_TAG:
            if (typ->tp_version_tag != sym->descr.type_version) {
                sym_set_bottom(ctx, sym);
            }
            return;
    }
}

bool
_Py_uop_sym_set_type_version(JitOptContext *ctx, JitOptRef ref, unsigned int version)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    PyTypeObject *type = _PyType_LookupByVersion(version);
    if (type) {
        _Py_uop_sym_set_type(ctx, ref, type);
    }
    JitSymType tag = sym->tag;
    switch(tag) {
        case JIT_SYM_NULL_TAG:
            sym_set_bottom(ctx, sym);
            return false;
        case JIT_SYM_KNOWN_CLASS_TAG:
            if (sym->cls.type->tp_version_tag != version) {
                sym_set_bottom(ctx, sym);
                return false;
            }
            else {
                sym->cls.version = version;
                return true;
            }
        case JIT_SYM_KNOWN_VALUE_TAG:
            if (Py_TYPE(sym->value.value)->tp_version_tag != version) {
                Py_CLEAR(sym->value.value);
                sym_set_bottom(ctx, sym);
                return false;
            };
            return true;
        case JIT_SYM_TUPLE_TAG:
            if (PyTuple_Type.tp_version_tag != version) {
                sym_set_bottom(ctx, sym);
                return false;
            };
            return true;
        case JIT_SYM_TYPE_VERSION_TAG:
            if (sym->version.version != version) {
                sym_set_bottom(ctx, sym);
                return false;
            }
            return true;
        case JIT_SYM_BOTTOM_TAG:
            return false;
        case JIT_SYM_NON_NULL_TAG:
        case JIT_SYM_UNKNOWN_TAG:
            sym->tag = JIT_SYM_TYPE_VERSION_TAG;
            sym->version.version = version;
            return true;
        case JIT_SYM_PREDICATE_TAG:
        case JIT_SYM_TRUTHINESS_TAG:
            if (version != PyBool_Type.tp_version_tag) {
                sym_set_bottom(ctx, sym);
                return false;
            }
            return true;
        case JIT_SYM_COMPACT_INT:
            if (version != PyLong_Type.tp_version_tag) {
                sym_set_bottom(ctx, sym);
                return false;
            }
            return true;
        case JIT_SYM_DESCR_TAG:
            if (version != sym->descr.type_version) {
                sym_set_bottom(ctx, sym);
                return false;
            }
            return true;
    }
    Py_UNREACHABLE();
}

void
_Py_uop_sym_set_const(JitOptContext *ctx, JitOptRef ref, PyObject *const_val)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    JitSymType tag = sym->tag;
    switch(tag) {
        case JIT_SYM_NULL_TAG:
            sym_set_bottom(ctx, sym);
            return;
        case JIT_SYM_KNOWN_CLASS_TAG:
            if (sym->cls.type != Py_TYPE(const_val)) {
                sym_set_bottom(ctx, sym);
                return;
            }
            make_const(sym, const_val);
            return;
        case JIT_SYM_KNOWN_VALUE_TAG:
            if (sym->value.value != const_val) {
                Py_CLEAR(sym->value.value);
                sym_set_bottom(ctx, sym);
            }
            return;
        case JIT_SYM_TUPLE_TAG:
            if (PyTuple_CheckExact(const_val)) {
                Py_ssize_t len = _Py_uop_sym_tuple_length(ref);
                if (len == PyTuple_GET_SIZE(const_val)) {
                    for (Py_ssize_t i = 0; i < len; i++) {
                        JitOptRef sym_item = _Py_uop_sym_tuple_getitem(ctx, ref, i);
                        PyObject *item = PyTuple_GET_ITEM(const_val, i);
                        _Py_uop_sym_set_const(ctx, sym_item, item);
                    }
                    make_const(sym, const_val);
                    return;
                }
            }
            sym_set_bottom(ctx, sym);
            return;
        case JIT_SYM_TYPE_VERSION_TAG:
            if (sym->version.version != Py_TYPE(const_val)->tp_version_tag) {
                sym_set_bottom(ctx, sym);
                return;
            }
            make_const(sym, const_val);
            return;
        case JIT_SYM_BOTTOM_TAG:
            return;
        case JIT_SYM_NON_NULL_TAG:
        case JIT_SYM_UNKNOWN_TAG:
            make_const(sym, const_val);
            return;
        case JIT_SYM_PREDICATE_TAG:
            if (!PyBool_Check(const_val)) {
                sym_set_bottom(ctx, sym);
                return;
            }
            make_const(sym, const_val);
            return;
        case JIT_SYM_TRUTHINESS_TAG:
            if (!PyBool_Check(const_val) ||
                (_Py_uop_sym_is_const(ctx, ref) &&
                 _Py_uop_sym_get_const(ctx, ref) != const_val))
            {
                sym_set_bottom(ctx, sym);
                return;
            }
            JitOptRef value = PyJitRef_Wrap(
                allocation_base(ctx) + sym->truthiness.value);
            PyTypeObject *type = _Py_uop_sym_get_type(value);
            if (const_val == (sym->truthiness.invert ? Py_False : Py_True)) {
                // value is truthy. This is only useful for bool:
                if (type == &PyBool_Type) {
                    _Py_uop_sym_set_const(ctx, value, Py_True);
                }
            }
            // value is falsey:
            else if (type == &PyBool_Type) {
                _Py_uop_sym_set_const(ctx, value, Py_False);
            }
            else if (type == &PyLong_Type) {
                _Py_uop_sym_set_const(ctx, value, Py_GetConstant(Py_CONSTANT_ZERO));
            }
            else if (type == &PyUnicode_Type) {
                _Py_uop_sym_set_const(ctx, value, Py_GetConstant(Py_CONSTANT_EMPTY_STR));
            }
            // TODO: More types (GH-130415)!
            make_const(sym, const_val);
            return;
        case JIT_SYM_COMPACT_INT:
            if (_PyLong_CheckExactAndCompact(const_val)) {
                make_const(sym, const_val);
            }
            else {
                sym_set_bottom(ctx, sym);
            }
            return;
        case JIT_SYM_DESCR_TAG:
            sym_set_bottom(ctx, sym);
            return;
    }
}

void
_Py_uop_sym_set_null(JitOptContext *ctx, JitOptRef ref)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    if (sym->tag == JIT_SYM_UNKNOWN_TAG) {
        sym->tag = JIT_SYM_NULL_TAG;
    }
    else if (sym->tag > JIT_SYM_NULL_TAG) {
        sym_set_bottom(ctx, sym);
    }
}

void
_Py_uop_sym_set_non_null(JitOptContext *ctx, JitOptRef ref)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    if (sym->tag == JIT_SYM_UNKNOWN_TAG) {
        sym->tag = JIT_SYM_NON_NULL_TAG;
    }
    else if (sym->tag == JIT_SYM_NULL_TAG) {
        sym_set_bottom(ctx, sym);
    }
}

JitOptRef
_Py_uop_sym_new_unknown(JitOptContext *ctx)
{
    JitOptSymbol *res = sym_new(ctx);
    if (res == NULL) {
        return out_of_space_ref(ctx);
    }
    return PyJitRef_Wrap(res);
}

JitOptRef
_Py_uop_sym_new_not_null(JitOptContext *ctx)
{
    JitOptSymbol *res = sym_new(ctx);
    if (res == NULL) {
        return out_of_space_ref(ctx);
    }
    res->tag = JIT_SYM_NON_NULL_TAG;
    return PyJitRef_Wrap(res);
}

JitOptRef
_Py_uop_sym_new_type(JitOptContext *ctx, PyTypeObject *typ)
{
    JitOptSymbol *res = sym_new(ctx);
    if (res == NULL) {
        return out_of_space_ref(ctx);
    }
    JitOptRef ref = PyJitRef_Wrap(res);
    _Py_uop_sym_set_type(ctx, ref, typ);
    return ref;
}

// Adds a new reference to const_val, owned by the symbol.
JitOptRef
_Py_uop_sym_new_const(JitOptContext *ctx, PyObject *const_val)
{
    assert(const_val != NULL);
    JitOptSymbol *res = sym_new(ctx);
    if (res == NULL) {
        return out_of_space_ref(ctx);
    }
    JitOptRef ref = PyJitRef_Wrap(res);
    _Py_uop_sym_set_const(ctx, ref, const_val);
    return ref;
}

JitOptRef
_Py_uop_sym_new_const_steal(JitOptContext *ctx, PyObject *const_val)
{
    assert(const_val != NULL);
    JitOptRef res = _Py_uop_sym_new_const(ctx, const_val);
    // Decref once because sym_new_const increfs it.
    Py_DECREF(const_val);
    return res;
}

JitOptRef
_Py_uop_sym_new_null(JitOptContext *ctx)
{
    JitOptSymbol *null_sym = sym_new(ctx);
    if (null_sym == NULL) {
        return out_of_space_ref(ctx);
    }
    JitOptRef ref = PyJitRef_Wrap(null_sym);
    _Py_uop_sym_set_null(ctx, ref);
    return ref;
}

PyTypeObject *
_Py_uop_sym_get_type(JitOptRef ref)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    JitSymType tag = sym->tag;
    switch(tag) {
        case JIT_SYM_NULL_TAG:
        case JIT_SYM_BOTTOM_TAG:
        case JIT_SYM_NON_NULL_TAG:
        case JIT_SYM_UNKNOWN_TAG:
            return NULL;
        case JIT_SYM_KNOWN_CLASS_TAG:
            return sym->cls.type;
        case JIT_SYM_KNOWN_VALUE_TAG:
            return Py_TYPE(sym->value.value);
        case JIT_SYM_TYPE_VERSION_TAG:
            return _PyType_LookupByVersion(sym->version.version);
        case JIT_SYM_TUPLE_TAG:
            return &PyTuple_Type;
        case JIT_SYM_PREDICATE_TAG:
        case JIT_SYM_TRUTHINESS_TAG:
            return &PyBool_Type;
        case JIT_SYM_COMPACT_INT:
            return &PyLong_Type;
        case JIT_SYM_DESCR_TAG:
            return _PyType_LookupByVersion(sym->descr.type_version);
    }
    Py_UNREACHABLE();
}

unsigned int
_Py_uop_sym_get_type_version(JitOptRef ref)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    JitSymType tag = sym->tag;
    switch(tag) {
        case JIT_SYM_NULL_TAG:
        case JIT_SYM_BOTTOM_TAG:
        case JIT_SYM_NON_NULL_TAG:
        case JIT_SYM_UNKNOWN_TAG:
            return 0;
        case JIT_SYM_TYPE_VERSION_TAG:
            return sym->version.version;
        case JIT_SYM_KNOWN_CLASS_TAG:
            return sym->cls.version;
        case JIT_SYM_KNOWN_VALUE_TAG:
            return Py_TYPE(sym->value.value)->tp_version_tag;
        case JIT_SYM_TUPLE_TAG:
            return PyTuple_Type.tp_version_tag;
        case JIT_SYM_PREDICATE_TAG:
        case JIT_SYM_TRUTHINESS_TAG:
            return PyBool_Type.tp_version_tag;
        case JIT_SYM_COMPACT_INT:
            return PyLong_Type.tp_version_tag;
        case JIT_SYM_DESCR_TAG:
            return sym->descr.type_version;
    }
    Py_UNREACHABLE();
}

bool
_Py_uop_sym_has_type(JitOptRef sym)
{
    return _Py_uop_sym_get_type(sym) != NULL;
}

bool
_Py_uop_sym_matches_type(JitOptRef sym, PyTypeObject *typ)
{
    assert(typ != NULL && PyType_Check(typ));
    return _Py_uop_sym_get_type(sym) == typ;
}

bool
_Py_uop_sym_matches_type_version(JitOptRef sym, unsigned int version)
{
    return _Py_uop_sym_get_type_version(sym) == version;
}

int
_Py_uop_sym_truthiness(JitOptContext *ctx, JitOptRef ref)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    switch(sym->tag) {
        case JIT_SYM_NULL_TAG:
        case JIT_SYM_TYPE_VERSION_TAG:
        case JIT_SYM_BOTTOM_TAG:
        case JIT_SYM_NON_NULL_TAG:
        case JIT_SYM_UNKNOWN_TAG:
        case JIT_SYM_COMPACT_INT:
        case JIT_SYM_PREDICATE_TAG:
        case JIT_SYM_DESCR_TAG:
            return -1;
        case JIT_SYM_KNOWN_CLASS_TAG:
            /* TODO :
             * Instances of some classes are always
             * true. We should return 1 in those cases */
            return -1;
        case JIT_SYM_KNOWN_VALUE_TAG:
            break;
        case JIT_SYM_TUPLE_TAG:
            return sym->tuple.length != 0;
        case JIT_SYM_TRUTHINESS_TAG:
            ;
            JitOptSymbol *value = allocation_base(ctx) + sym->truthiness.value;
            int truthiness = _Py_uop_sym_truthiness(ctx,
                                                    PyJitRef_Wrap(value));
            if (truthiness < 0) {
                return truthiness;
            }
            truthiness ^= sym->truthiness.invert;
            make_const(sym, truthiness ? Py_True : Py_False);
            return truthiness;
    }
    PyObject *value = sym->value.value;
    /* Only handle a few known safe types */
    if (value == Py_None) {
        return 0;
    }
    PyTypeObject *tp = Py_TYPE(value);
    if (tp == &PyLong_Type) {
        return !_PyLong_IsZero((PyLongObject *)value);
    }
    if (tp == &PyUnicode_Type) {
        return value != &_Py_STR(empty);
    }
    if (tp == &PyBool_Type) {
        return value == Py_True;
    }
    return -1;
}

JitOptRef
_Py_uop_sym_new_tuple(JitOptContext *ctx, int size, JitOptRef *args)
{
    JitOptSymbol *res = sym_new(ctx);
    if (res == NULL) {
        return out_of_space_ref(ctx);
    }
    if (size > MAX_SYMBOLIC_TUPLE_SIZE) {
        res->tag = JIT_SYM_KNOWN_CLASS_TAG;
        res->cls.type = &PyTuple_Type;
    }
    else {
        res->tag = JIT_SYM_TUPLE_TAG;
        res->tuple.length = size;
        for (int i = 0; i < size; i++) {
            res->tuple.items[i] = (uint16_t)(PyJitRef_Unwrap(args[i]) - allocation_base(ctx));
        }
    }
    return PyJitRef_Wrap(res);
}

JitOptRef
_Py_uop_sym_tuple_getitem(JitOptContext *ctx, JitOptRef ref, Py_ssize_t item)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    assert(item >= 0);
    if (sym->tag == JIT_SYM_KNOWN_VALUE_TAG) {
        PyObject *tuple = sym->value.value;
        if (PyTuple_CheckExact(tuple) && item < PyTuple_GET_SIZE(tuple)) {
            return _Py_uop_sym_new_const(ctx, PyTuple_GET_ITEM(tuple, item));
        }
    }
    else if (sym->tag == JIT_SYM_TUPLE_TAG && item < sym->tuple.length) {
        return PyJitRef_Wrap(allocation_base(ctx) + sym->tuple.items[item]);
    }
    return _Py_uop_sym_new_not_null(ctx);
}

Py_ssize_t
_Py_uop_sym_tuple_length(JitOptRef ref)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    if (sym->tag == JIT_SYM_KNOWN_VALUE_TAG) {
        PyObject *tuple = sym->value.value;
        if (PyTuple_CheckExact(tuple)) {
            return PyTuple_GET_SIZE(tuple);
        }
    }
    else if (sym->tag == JIT_SYM_TUPLE_TAG) {
        return sym->tuple.length;
    }
    return -1;
}

// Return true if known to be immortal.
bool
_Py_uop_symbol_is_immortal(JitOptSymbol *sym)
{
    if (sym->tag == JIT_SYM_KNOWN_VALUE_TAG) {
        return _Py_IsImmortal(sym->value.value);
    }
    if (sym->tag == JIT_SYM_KNOWN_CLASS_TAG) {
        return sym->cls.type == &PyBool_Type;
    }
    return false;
}

bool
_Py_uop_sym_is_compact_int(JitOptRef ref)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    if (sym->tag == JIT_SYM_KNOWN_VALUE_TAG) {
        return (bool)_PyLong_CheckExactAndCompact(sym->value.value);
    }
    return sym->tag == JIT_SYM_COMPACT_INT;
}

bool
_Py_uop_sym_is_immortal(JitOptRef ref)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    return _Py_uop_symbol_is_immortal(sym);
}

void
_Py_uop_sym_set_compact_int(JitOptContext *ctx, JitOptRef ref)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    JitSymType tag = sym->tag;
    switch(tag) {
        case JIT_SYM_NULL_TAG:
            sym_set_bottom(ctx, sym);
            return;
        case JIT_SYM_KNOWN_CLASS_TAG:
            if (sym->cls.type == &PyLong_Type) {
                sym->tag = JIT_SYM_COMPACT_INT;
            } else {
                sym_set_bottom(ctx, sym);
            }
            return;
        case JIT_SYM_TYPE_VERSION_TAG:
            if (sym->version.version == PyLong_Type.tp_version_tag) {
                sym->tag = JIT_SYM_COMPACT_INT;
            }
            else {
                sym_set_bottom(ctx, sym);
            }
            return;
        case JIT_SYM_KNOWN_VALUE_TAG:
            if (!_PyLong_CheckExactAndCompact(sym->value.value)) {
                Py_CLEAR(sym->value.value);
                sym_set_bottom(ctx, sym);
            }
            return;
        case JIT_SYM_TUPLE_TAG:
        case JIT_SYM_PREDICATE_TAG:
        case JIT_SYM_TRUTHINESS_TAG:
        case JIT_SYM_DESCR_TAG:
            sym_set_bottom(ctx, sym);
            return;
        case JIT_SYM_BOTTOM_TAG:
        case JIT_SYM_COMPACT_INT:
            return;
        case JIT_SYM_NON_NULL_TAG:
        case JIT_SYM_UNKNOWN_TAG:
            sym->tag = JIT_SYM_COMPACT_INT;
            return;
    }
}

JitOptRef
_Py_uop_sym_new_predicate(JitOptContext *ctx, JitOptRef lhs_ref, JitOptRef rhs_ref, JitOptPredicateKind kind)
{
    JitOptSymbol *lhs = PyJitRef_Unwrap(lhs_ref);
    JitOptSymbol *rhs = PyJitRef_Unwrap(rhs_ref);

    JitOptSymbol *res = sym_new(ctx);
    if (res == NULL) {
        return out_of_space_ref(ctx);
    }

    res->tag = JIT_SYM_PREDICATE_TAG;
    res->predicate.kind = kind;
    res->predicate.lhs = (uint16_t)(lhs - allocation_base(ctx));
    res->predicate.rhs = (uint16_t)(rhs - allocation_base(ctx));

    return PyJitRef_Wrap(res);
}

void
_Py_uop_sym_apply_predicate_narrowing(JitOptContext *ctx, JitOptRef ref, bool branch_is_true)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    if (sym->tag != JIT_SYM_PREDICATE_TAG) {
        return;
    }

    JitOptPredicate pred = sym->predicate;

    JitOptRef lhs_ref = PyJitRef_Wrap(allocation_base(ctx) + pred.lhs);
    JitOptRef rhs_ref = PyJitRef_Wrap(allocation_base(ctx) + pred.rhs);

    bool lhs_is_const = _Py_uop_sym_is_const(ctx, lhs_ref);
    bool rhs_is_const = _Py_uop_sym_is_const(ctx, rhs_ref);
    if (!lhs_is_const && !rhs_is_const) {
        return;
    }

    bool narrow = false;
    switch(pred.kind) {
        case JIT_PRED_EQ:
        case JIT_PRED_IS:
            narrow = branch_is_true;
            break;
        case JIT_PRED_NE:
        case JIT_PRED_IS_NOT:
            narrow = !branch_is_true;
            break;
        default:
            return;
    }
    if (!narrow) {
        return;
    }

    JitOptRef subject_ref = lhs_is_const ? rhs_ref : lhs_ref;
    JitOptRef const_ref = lhs_is_const ? lhs_ref : rhs_ref;

    PyObject *const_val = _Py_uop_sym_get_const(ctx, const_ref);
    if (const_val == NULL) {
        return;
    }
    _Py_uop_sym_set_const(ctx, subject_ref, const_val);
    assert(_Py_uop_sym_is_const(ctx, subject_ref));
}

JitOptRef
_Py_uop_sym_new_truthiness(JitOptContext *ctx, JitOptRef ref, bool truthy)
{
    JitOptSymbol *value = PyJitRef_Unwrap(ref);
    // It's clearer to invert this in the signature:
    bool invert = !truthy;
    if (value->tag == JIT_SYM_TRUTHINESS_TAG && value->truthiness.invert == invert) {
        return ref;
    }
    JitOptSymbol *res = sym_new(ctx);
    if (res == NULL) {
        return out_of_space_ref(ctx);
    }
    int truthiness = _Py_uop_sym_truthiness(ctx, ref);
    if (truthiness < 0) {
        res->tag = JIT_SYM_TRUTHINESS_TAG;
        res->truthiness.invert = invert;
        res->truthiness.value = (uint16_t)(value - allocation_base(ctx));
    }
    else {
        make_const(res, (truthiness ^ invert) ? Py_True : Py_False);
    }
    return PyJitRef_Wrap(res);
}

JitOptRef
_Py_uop_sym_new_compact_int(JitOptContext *ctx)
{
    JitOptSymbol *sym = sym_new(ctx);
    if (sym == NULL) {
        return out_of_space_ref(ctx);
    }
    sym->tag = JIT_SYM_COMPACT_INT;
    return PyJitRef_Wrap(sym);
}

JitOptRef
_Py_uop_sym_new_descr_object(JitOptContext *ctx, unsigned int type_version)
{
    JitOptSymbol *res = sym_new(ctx);
    if (res == NULL) {
        return out_of_space_ref(ctx);
    }
    res->tag = JIT_SYM_DESCR_TAG;
    res->descr.num_descrs = 0;
    res->descr.descrs = NULL;
    res->descr.type_version = type_version;
    res->descr.last_escape_index = uop_buffer_length(&ctx->out_buffer);
    return PyJitRef_Wrap(res);
}

JitOptRef
_Py_uop_sym_get_attr(JitOptContext *ctx, JitOptRef ref, uint16_t slot_index)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);

    switch (sym->tag) {
        case JIT_SYM_DESCR_TAG:
            // Only return tracked slot values if:
            // 1. Symbol has mappings allocated
            // 2. No escape has occurred since last modification (state is fresh)
            if (sym->descr.descrs != NULL &&
                sym->descr.last_escape_index >= ctx->last_escape_index)
            {
                for (int i = 0; i < sym->descr.num_descrs; i++) {
                    if (sym->descr.descrs[i].slot_index == slot_index) {
                        return PyJitRef_Wrap(allocation_base(ctx) + sym->descr.descrs[i].symbol);
                    }
                }
            }
            break;
        default:
            break;
    }

    return _Py_uop_sym_new_not_null(ctx);
}

static JitOptDescrMapping *
descr_arena_alloc(JitOptContext *ctx)
{
    if (ctx->d_arena.descr_curr_number + MAX_SYMBOLIC_DESCR_SIZE > ctx->d_arena.descr_max_number) {
        return NULL;
    }
    JitOptDescrMapping *descrs = &ctx->d_arena.arena[ctx->d_arena.descr_curr_number];
    ctx->d_arena.descr_curr_number += MAX_SYMBOLIC_DESCR_SIZE;
    return descrs;
}

JitOptRef
_Py_uop_sym_set_attr(JitOptContext *ctx, JitOptRef ref, uint16_t slot_index, JitOptRef value)
{
    JitOptSymbol *sym = PyJitRef_Unwrap(ref);
    switch (sym->tag) {
        case JIT_SYM_DESCR_TAG: {
            // Check escape
            if (sym->descr.last_escape_index < ctx->last_escape_index) {
                sym->descr.num_descrs = 0;
                sym->descr.last_escape_index = uop_buffer_length(&ctx->out_buffer);
                return _Py_uop_sym_new_unknown(ctx);
            }

            // Get old value before updating
            JitOptRef old_value = _Py_uop_sym_new_unknown(ctx);
            if (sym->descr.descrs != NULL) {
                for (int i = 0; i < sym->descr.num_descrs; i++) {
                    if (sym->descr.descrs[i].slot_index == slot_index) {
                        old_value = PyJitRef_Wrap(allocation_base(ctx) + sym->descr.descrs[i].symbol);
                        break;
                    }
                }
            }

            // Check if have arena space allocated
            if (sym->descr.descrs == NULL) {
                sym->descr.descrs = descr_arena_alloc(ctx);
                if (sym->descr.descrs == NULL) {
                    ctx->done = true;
                    ctx->out_of_space = true;
                    return _Py_uop_sym_new_null(ctx);
                }
            }
            // Check if the slot already exists
            for (int i = 0; i < sym->descr.num_descrs; i++) {
                if (sym->descr.descrs[i].slot_index == slot_index) {
                    sym->descr.descrs[i].symbol = (uint16_t)(PyJitRef_Unwrap(value) - allocation_base(ctx));
                    assert(!_Py_uop_sym_is_null(old_value));
                    return old_value;
                }
            }
            // Add new mapping if there's space
            if (sym->descr.num_descrs < MAX_SYMBOLIC_DESCR_SIZE) {
                int idx = sym->descr.num_descrs++;
                sym->descr.descrs[idx].slot_index = slot_index;
                sym->descr.descrs[idx].symbol = (uint16_t)(PyJitRef_Unwrap(value) - allocation_base(ctx));
            }

            // No value there. Objects are initialized to NULL, so it's safe.
            return _Py_uop_sym_new_null(ctx);
        }
        default:
            return _Py_uop_sym_new_unknown(ctx);
    }
}

// 0 on success, -1 on error.
_Py_UOpsAbstractFrame *
_Py_uop_frame_new(
    JitOptContext *ctx,
    PyCodeObject *co,
    int curr_stackentries,
    JitOptRef *args,
    int arg_len)
{
    if (ctx->curr_frame_depth >= MAX_ABSTRACT_FRAME_DEPTH) {
        ctx->done = true;
        ctx->out_of_space = true;
        OPT_STAT_INC(optimizer_frame_overflow);
        return NULL;
    }
    _Py_UOpsAbstractFrame *frame = &ctx->frames[ctx->curr_frame_depth];
    frame->code = co;
    frame->stack_len = co->co_stacksize;
    frame->locals_len = co->co_nlocalsplus;

    frame->locals = ctx->n_consumed;
    frame->stack = frame->locals + co->co_nlocalsplus;
    frame->stack_pointer = frame->stack + curr_stackentries;
    frame->globals_checked_version = 0;
    frame->globals_watched = false;
    frame->func = NULL;
    ctx->n_consumed = ctx->n_consumed + (co->co_nlocalsplus + co->co_stacksize);
    if (ctx->n_consumed >= ctx->limit) {
        ctx->done = true;
        ctx->out_of_space = true;
        return NULL;
    }

    // Initialize with the initial state of all local variables
    for (int i = 0; i < arg_len; i++) {
        frame->locals[i] = args[i];
    }

    // If the args are known, then it's safe to just initialize
    // every other non-set local to null symbol.
    bool default_null = args != NULL;

    for (int i = arg_len; i < co->co_nlocalsplus; i++) {
        JitOptRef local = default_null ? _Py_uop_sym_new_null(ctx) : _Py_uop_sym_new_unknown(ctx);
        frame->locals[i] = local;
    }


    // Initialize the stack as well
    for (int i = 0; i < curr_stackentries; i++) {
        JitOptRef stackvar = _Py_uop_sym_new_unknown(ctx);
        frame->stack[i] = stackvar;
    }

    return frame;
}

void
_Py_uop_abstractcontext_fini(JitOptContext *ctx)
{
    if (ctx == NULL) {
        return;
    }
    ctx->curr_frame_depth = 0;
    int tys = ctx->t_arena.ty_curr_number;
    for (int i = 0; i < tys; i++) {
        JitOptSymbol *sym = &ctx->t_arena.arena[i];
        if (sym->tag == JIT_SYM_KNOWN_VALUE_TAG) {
            Py_CLEAR(sym->value.value);
        }
    }
}

void
_Py_uop_abstractcontext_init(JitOptContext *ctx)
{
    static_assert(sizeof(JitOptSymbol) <= 3 * sizeof(uint64_t), "JitOptSymbol has grown");
    ctx->limit = ctx->locals_and_stack + MAX_ABSTRACT_INTERP_SIZE;
    ctx->n_consumed = ctx->locals_and_stack;
#ifdef Py_DEBUG // Aids debugging a little. There should never be NULL in the abstract interpreter.
    for (int i = 0 ; i < MAX_ABSTRACT_INTERP_SIZE; i++) {
        ctx->locals_and_stack[i] = PyJitRef_NULL;
    }
#endif

    // Setup the arena for sym expressions.
    ctx->t_arena.ty_curr_number = 0;
    ctx->t_arena.ty_max_number = TY_ARENA_SIZE;

    // Setup the arena for descriptor mappings.
    ctx->d_arena.descr_curr_number = 0;
    ctx->d_arena.descr_max_number = DESCR_ARENA_SIZE;

    // Frame setup
    ctx->curr_frame_depth = 0;

    // Ctx signals.
    // Note: this must happen before frame_new, as it might override
    // the result should frame_new set things to bottom.
    ctx->done = false;
    ctx->out_of_space = false;
    ctx->contradiction = false;
    ctx->builtins_watched = false;
    ctx->last_escape_index = 0;
}

int
_Py_uop_frame_pop(JitOptContext *ctx, PyCodeObject *co, int curr_stackentries)
{
    _Py_UOpsAbstractFrame *frame = ctx->frame;
    ctx->n_consumed = frame->locals;

    ctx->curr_frame_depth--;

    if (ctx->curr_frame_depth >= 1) {
        ctx->frame = &ctx->frames[ctx->curr_frame_depth - 1];

        // We returned to the correct code. Nothing to do here.
        if (co == ctx->frame->code) {
            return 0;
        }
        // Else: the code we recorded doesn't match the code we *think* we're
        // returning to. We could trace anything, we can't just return to the
        // old frame. We have to restore what the tracer recorded
        // as the traced next frame.
        // Remove the current frame, and later swap it out with the right one.
        else {
            ctx->curr_frame_depth--;
        }
    }
    // Else: trace stack underflow.

    // This handles swapping out frames.
    assert(curr_stackentries >= 1);
    // -1 to stackentries as we push to the stack our return value after this.
    _Py_UOpsAbstractFrame *new_frame = _Py_uop_frame_new(ctx, co, curr_stackentries - 1, NULL, 0);
    if (new_frame == NULL) {
        ctx->done = true;
        return 1;
    }

    ctx->curr_frame_depth++;
    ctx->frame = new_frame;

    return 0;
}

#define TEST_PREDICATE(PRED, MSG) \
do { \
    if (!(PRED)) { \
        PyErr_SetString( \
            PyExc_AssertionError, \
            (MSG)); \
        goto fail; \
    } \
} while (0)

static JitOptSymbol *
make_bottom(JitOptContext *ctx)
{
    JitOptSymbol *sym = sym_new(ctx);
    sym->tag = JIT_SYM_BOTTOM_TAG;
    return sym;
}

PyObject *
_Py_uop_symbols_test(PyObject *Py_UNUSED(self), PyObject *Py_UNUSED(ignored))
{
    JitOptContext context;
    JitOptContext *ctx = &context;
    _Py_uop_abstractcontext_init(ctx);
    PyObject *val_42 = NULL;
    PyObject *val_43 = NULL;
    PyObject *val_big = NULL;
    PyObject *tuple = NULL;

    // Use a single 'sym' variable so copy-pasting tests is easier.
    JitOptRef ref = _Py_uop_sym_new_unknown(ctx);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    TEST_PREDICATE(!_Py_uop_sym_is_null(ref), "top is NULL");
    TEST_PREDICATE(!_Py_uop_sym_is_not_null(ref), "top is not NULL");
    TEST_PREDICATE(!_Py_uop_sym_matches_type(ref, &PyLong_Type), "top matches a type");
    TEST_PREDICATE(!_Py_uop_sym_is_const(ctx, ref), "top is a constant");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, ref) == NULL, "top as constant is not NULL");
    TEST_PREDICATE(!_Py_uop_sym_is_bottom(ref), "top is bottom");

    ref = PyJitRef_Wrap(make_bottom(ctx));
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    TEST_PREDICATE(!_Py_uop_sym_is_null(ref), "bottom is NULL is not false");
    TEST_PREDICATE(!_Py_uop_sym_is_not_null(ref), "bottom is not NULL is not false");
    TEST_PREDICATE(!_Py_uop_sym_matches_type(ref, &PyLong_Type), "bottom matches a type");
    TEST_PREDICATE(!_Py_uop_sym_is_const(ctx, ref), "bottom is a constant is not false");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, ref) == NULL, "bottom as constant is not NULL");
    TEST_PREDICATE(_Py_uop_sym_is_bottom(ref), "bottom isn't bottom");

    ref = _Py_uop_sym_new_type(ctx, &PyLong_Type);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    TEST_PREDICATE(!_Py_uop_sym_is_null(ref), "int is NULL");
    TEST_PREDICATE(_Py_uop_sym_is_not_null(ref), "int isn't not NULL");
    TEST_PREDICATE(_Py_uop_sym_matches_type(ref, &PyLong_Type), "int isn't int");
    TEST_PREDICATE(!_Py_uop_sym_matches_type(ref, &PyFloat_Type), "int matches float");
    TEST_PREDICATE(!_Py_uop_sym_is_const(ctx, ref), "int is a constant");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, ref) == NULL, "int as constant is not NULL");

    _Py_uop_sym_set_type(ctx, ref, &PyLong_Type);  // Should be a no-op
    TEST_PREDICATE(_Py_uop_sym_matches_type(ref, &PyLong_Type), "(int and int) isn't int");

    _Py_uop_sym_set_type(ctx, ref, &PyFloat_Type);  // Should make it bottom
    TEST_PREDICATE(_Py_uop_sym_is_bottom(ref), "(int and float) isn't bottom");

    val_42 = PyLong_FromLong(42);
    assert(val_42 != NULL);
    assert(_Py_IsImmortal(val_42));

    val_43 = PyLong_FromLong(43);
    assert(val_43 != NULL);
    assert(_Py_IsImmortal(val_43));

    ref = _Py_uop_sym_new_type(ctx, &PyLong_Type);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_set_const(ctx, ref, val_42);
    TEST_PREDICATE(_Py_uop_sym_truthiness(ctx, ref) == 1, "bool(42) is not True");
    TEST_PREDICATE(!_Py_uop_sym_is_null(ref), "42 is NULL");
    TEST_PREDICATE(_Py_uop_sym_is_not_null(ref), "42 isn't not NULL");
    TEST_PREDICATE(_Py_uop_sym_matches_type(ref, &PyLong_Type), "42 isn't an int");
    TEST_PREDICATE(!_Py_uop_sym_matches_type(ref, &PyFloat_Type), "42 matches float");
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, ref), "42 is not a constant");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, ref) != NULL, "42 as constant is NULL");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, ref) == val_42, "42 as constant isn't 42");
    TEST_PREDICATE(_Py_uop_sym_is_immortal(ref), "42 is not immortal");

    _Py_uop_sym_set_type(ctx, ref, &PyLong_Type);  // Should be a no-op
    TEST_PREDICATE(_Py_uop_sym_matches_type(ref, &PyLong_Type), "(42 and 42) isn't an int");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, ref) == val_42, "(42 and 42) as constant isn't 42");

    _Py_uop_sym_set_type(ctx, ref, &PyFloat_Type);  // Should make it bottom
    TEST_PREDICATE(_Py_uop_sym_is_bottom(ref), "(42 and float) isn't bottom");

    ref = _Py_uop_sym_new_type(ctx, &PyBool_Type);
    TEST_PREDICATE(_Py_uop_sym_is_immortal(ref), "a bool is not immortal");

    ref = _Py_uop_sym_new_type(ctx, &PyLong_Type);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_set_const(ctx, ref, val_42);
    _Py_uop_sym_set_const(ctx, ref, val_43);  // Should make it bottom
    TEST_PREDICATE(_Py_uop_sym_is_bottom(ref), "(42 and 43) isn't bottom");


    ref = _Py_uop_sym_new_const(ctx, Py_None);
    TEST_PREDICATE(_Py_uop_sym_truthiness(ctx, ref) == 0, "bool(None) is not False");
    ref = _Py_uop_sym_new_const(ctx, Py_False);
    TEST_PREDICATE(_Py_uop_sym_truthiness(ctx, ref) == 0, "bool(False) is not False");
    ref = _Py_uop_sym_new_const(ctx, PyLong_FromLong(0));
    TEST_PREDICATE(_Py_uop_sym_truthiness(ctx, ref) == 0, "bool(0) is not False");

    JitOptRef i1 = _Py_uop_sym_new_type(ctx, &PyFloat_Type);
    JitOptRef i2 = _Py_uop_sym_new_const(ctx, val_43);
    JitOptRef array[2] = { i1, i2 };
    ref = _Py_uop_sym_new_tuple(ctx, 2, array);
    TEST_PREDICATE(
        _Py_uop_sym_matches_type(_Py_uop_sym_tuple_getitem(ctx, ref, 0), &PyFloat_Type),
        "tuple item does not match value used to create tuple"
    );
    TEST_PREDICATE(
        _Py_uop_sym_get_const(ctx, _Py_uop_sym_tuple_getitem(ctx, ref, 1)) == val_43,
        "tuple item does not match value used to create tuple"
    );
    PyObject *pair[2] = { val_42, val_43 };
    tuple = PyTuple_FromArray(pair, 2);
    ref = _Py_uop_sym_new_const(ctx, tuple);
    TEST_PREDICATE(
        _Py_uop_sym_get_const(ctx, _Py_uop_sym_tuple_getitem(ctx, ref, 1)) == val_43,
        "tuple item does not match value used to create tuple"
    );
    ref = _Py_uop_sym_new_type(ctx, &PyTuple_Type);
    TEST_PREDICATE(
        _Py_uop_sym_is_not_null(_Py_uop_sym_tuple_getitem(ctx, ref, 42)),
        "Unknown tuple item is not narrowed to non-NULL"
    );
    JitOptRef value = _Py_uop_sym_new_type(ctx, &PyBool_Type);
    ref = _Py_uop_sym_new_truthiness(ctx, value, false);
    TEST_PREDICATE(_Py_uop_sym_matches_type(ref, &PyBool_Type), "truthiness is not boolean");
    TEST_PREDICATE(_Py_uop_sym_truthiness(ctx, ref) == -1, "truthiness is not unknown");
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, ref) == false, "truthiness is constant");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, ref) == NULL, "truthiness is not NULL");
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, value) == false, "value is constant");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, value) == NULL, "value is not NULL");
    _Py_uop_sym_set_const(ctx, ref, Py_False);
    TEST_PREDICATE(_Py_uop_sym_matches_type(ref, &PyBool_Type), "truthiness is not boolean");
    TEST_PREDICATE(_Py_uop_sym_truthiness(ctx, ref) == 0, "truthiness is not True");
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, ref) == true, "truthiness is not constant");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, ref) == Py_False, "truthiness is not False");
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, value) == true, "value is not constant");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, value) == Py_True, "value is not True");

    // Resolving predicate result to True should narrow subject to True
    JitOptRef subject = _Py_uop_sym_new_unknown(ctx);
    JitOptRef const_true = _Py_uop_sym_new_const(ctx, Py_True);
    if (PyJitRef_IsNull(subject) || PyJitRef_IsNull(const_true)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_true, JIT_PRED_IS);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, true);
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, subject), "predicate narrowing did not const-narrow subject");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, subject) == Py_True, "predicate narrowing did not narrow subject to True");

    // Resolving predicate result to False should not narrow subject
    subject = _Py_uop_sym_new_unknown(ctx);
    if (PyJitRef_IsNull(subject)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_true, JIT_PRED_IS);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, false);
    TEST_PREDICATE(!_Py_uop_sym_is_const(ctx, subject), "predicate narrowing incorrectly narrowed subject");

    // Resolving inverted predicate to False should narrow subject to True
    subject = _Py_uop_sym_new_unknown(ctx);
    if (PyJitRef_IsNull(subject)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_true, JIT_PRED_IS_NOT);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, false);
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, subject), "predicate narrowing (inverted) did not const-narrow subject");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, subject) == Py_True, "predicate narrowing (inverted) did not narrow subject to True");

    // Resolving inverted predicate to True should not narrow subject
    subject = _Py_uop_sym_new_unknown(ctx);
    if (PyJitRef_IsNull(subject)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_true, JIT_PRED_IS_NOT);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, true);
    TEST_PREDICATE(!_Py_uop_sym_is_const(ctx, subject), "predicate narrowing incorrectly narrowed subject (inverted/true)");

    // Test narrowing subject to None
    subject = _Py_uop_sym_new_unknown(ctx);
    JitOptRef const_none = _Py_uop_sym_new_const(ctx, Py_None);
    if (PyJitRef_IsNull(subject) || PyJitRef_IsNull(const_none)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_none, JIT_PRED_IS);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, true);
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, subject), "predicate narrowing did not const-narrow subject (None)");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, subject) == Py_None, "predicate narrowing did not narrow subject to None");

    // Test narrowing subject to numerical constant from is comparison
    subject = _Py_uop_sym_new_unknown(ctx);
    PyObject *one_obj = PyLong_FromLong(1);
    JitOptRef const_one = _Py_uop_sym_new_const(ctx, one_obj);
    if (PyJitRef_IsNull(subject) || one_obj == NULL || PyJitRef_IsNull(const_one)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_one, JIT_PRED_IS);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, true);
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, subject), "predicate narrowing did not const-narrow subject (1)");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, subject) == one_obj, "predicate narrowing did not narrow subject to 1");

    // Test narrowing subject to constant from EQ predicate for int
    subject = _Py_uop_sym_new_unknown(ctx);
    if (PyJitRef_IsNull(subject)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_one, JIT_PRED_EQ);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, true);
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, subject), "predicate narrowing did not const-narrow subject (1)");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, subject) == one_obj, "predicate narrowing did not narrow subject to 1");

    // Resolving EQ predicate to False should not narrow subject for int
    subject = _Py_uop_sym_new_unknown(ctx);
    if (PyJitRef_IsNull(subject)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_one, JIT_PRED_EQ);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, false);
    TEST_PREDICATE(!_Py_uop_sym_is_const(ctx, subject), "predicate narrowing incorrectly narrowed subject (inverted/true)");

    // Test narrowing subject to constant from NE predicate for int
    subject = _Py_uop_sym_new_unknown(ctx);
    if (PyJitRef_IsNull(subject)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_one, JIT_PRED_NE);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, false);
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, subject), "predicate narrowing did not const-narrow subject (1)");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, subject) == one_obj, "predicate narrowing did not narrow subject to 1");

    // Resolving NE predicate to true should not narrow subject for int
    subject = _Py_uop_sym_new_unknown(ctx);
    if (PyJitRef_IsNull(subject)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_one, JIT_PRED_NE);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, true);
    TEST_PREDICATE(!_Py_uop_sym_is_const(ctx, subject), "predicate narrowing incorrectly narrowed subject (inverted/true)");

    // Test narrowing subject to constant from EQ predicate for float
    subject = _Py_uop_sym_new_unknown(ctx);
    PyObject *float_tenth_obj = PyFloat_FromDouble(0.1);
    JitOptRef const_float_tenth = _Py_uop_sym_new_const(ctx, float_tenth_obj);
    if (PyJitRef_IsNull(subject) || float_tenth_obj == NULL || PyJitRef_IsNull(const_float_tenth)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_float_tenth, JIT_PRED_EQ);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, true);
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, subject), "predicate narrowing did not const-narrow subject (float)");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, subject) == float_tenth_obj, "predicate narrowing did not narrow subject to 0.1");

    // Resolving EQ predicate to False should not narrow subject for float
    subject = _Py_uop_sym_new_unknown(ctx);
    if (PyJitRef_IsNull(subject)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_float_tenth, JIT_PRED_EQ);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, false);
    TEST_PREDICATE(!_Py_uop_sym_is_const(ctx, subject), "predicate narrowing incorrectly narrowed subject (inverted/true)");

    // Test narrowing subject to constant from NE predicate for float
    subject = _Py_uop_sym_new_unknown(ctx);
    if (PyJitRef_IsNull(subject)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_float_tenth, JIT_PRED_NE);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, false);
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, subject), "predicate narrowing did not const-narrow subject (float)");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, subject) == float_tenth_obj, "predicate narrowing did not narrow subject to 0.1");

    // Resolving NE predicate to true should not narrow subject for float
    subject = _Py_uop_sym_new_unknown(ctx);
    if (PyJitRef_IsNull(subject)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_float_tenth, JIT_PRED_NE);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, true);
    TEST_PREDICATE(!_Py_uop_sym_is_const(ctx, subject), "predicate narrowing incorrectly narrowed subject (inverted/true)");

    // Test narrowing subject to constant from EQ predicate for str
    subject = _Py_uop_sym_new_unknown(ctx);
    PyObject *str_hello_obj = PyUnicode_FromString("hello");
    JitOptRef const_str_hello = _Py_uop_sym_new_const(ctx, str_hello_obj);
    if (PyJitRef_IsNull(subject) || str_hello_obj == NULL || PyJitRef_IsNull(const_str_hello)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_str_hello, JIT_PRED_EQ);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, true);
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, subject), "predicate narrowing did not const-narrow subject (str)");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, subject) == str_hello_obj, "predicate narrowing did not narrow subject to hello");

    // Resolving EQ predicate to False should not narrow subject for str
    subject = _Py_uop_sym_new_unknown(ctx);
    if (PyJitRef_IsNull(subject)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_str_hello, JIT_PRED_EQ);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, false);
    TEST_PREDICATE(!_Py_uop_sym_is_const(ctx, subject), "predicate narrowing incorrectly narrowed subject (inverted/true)");

    // Test narrowing subject to constant from NE predicate for str
    subject = _Py_uop_sym_new_unknown(ctx);
    if (PyJitRef_IsNull(subject)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_str_hello, JIT_PRED_NE);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, false);
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, subject), "predicate narrowing did not const-narrow subject (str)");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, subject) == str_hello_obj, "predicate narrowing did not narrow subject to hello");

    // Resolving NE predicate to true should not narrow subject for str
    subject = _Py_uop_sym_new_unknown(ctx);
    if (PyJitRef_IsNull(subject)) {
        goto fail;
    }
    ref = _Py_uop_sym_new_predicate(ctx, subject, const_str_hello, JIT_PRED_NE);
    if (PyJitRef_IsNull(ref)) {
        goto fail;
    }
    _Py_uop_sym_apply_predicate_narrowing(ctx, ref, true);
    TEST_PREDICATE(!_Py_uop_sym_is_const(ctx, subject), "predicate narrowing incorrectly narrowed subject (inverted/true)");

    subject = _Py_uop_sym_new_unknown(ctx);
    value = _Py_uop_sym_new_const(ctx, one_obj);
    ref = _Py_uop_sym_new_predicate(ctx, subject, value, JIT_PRED_IS);
    if (PyJitRef_IsNull(subject) || PyJitRef_IsNull(value) || PyJitRef_IsNull(ref)) {
        goto fail;
    }
    TEST_PREDICATE(_Py_uop_sym_matches_type(ref, &PyBool_Type), "predicate is not boolean");
    TEST_PREDICATE(_Py_uop_sym_truthiness(ctx, ref) == -1, "predicate is not unknown");
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, ref) == false, "predicate is constant");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, ref) == NULL, "predicate is not NULL");
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, value) == true, "value is not constant");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, value) == one_obj, "value is not 1");
    _Py_uop_sym_set_const(ctx, ref, Py_False);
    TEST_PREDICATE(_Py_uop_sym_matches_type(ref, &PyBool_Type), "predicate is not boolean");
    TEST_PREDICATE(_Py_uop_sym_truthiness(ctx, ref) == 0, "predicate is not False");
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, ref) == true, "predicate is not constant");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, ref) == Py_False, "predicate is not False");
    TEST_PREDICATE(_Py_uop_sym_is_const(ctx, value) == true, "value is not constant");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, value) == one_obj, "value is not 1");

    val_big = PyNumber_Lshift(_PyLong_GetOne(), PyLong_FromLong(66));
    if (val_big == NULL) {
        goto fail;
    }

    JitOptRef ref_42 = _Py_uop_sym_new_const(ctx, val_42);
    JitOptRef ref_big = _Py_uop_sym_new_const(ctx, val_big);
    JitOptRef ref_int = _Py_uop_sym_new_compact_int(ctx);
    TEST_PREDICATE(_Py_uop_sym_is_compact_int(ref_42), "42 is not a compact int");
    TEST_PREDICATE(!_Py_uop_sym_is_compact_int(ref_big), "(1 << 66) is a compact int");
    TEST_PREDICATE(_Py_uop_sym_is_compact_int(ref_int), "compact int is not a compact int");
    TEST_PREDICATE(_Py_uop_sym_matches_type(ref_int, &PyLong_Type), "compact int is not an int");

    _Py_uop_sym_set_type(ctx, ref_int, &PyLong_Type);  // Should have no effect
    TEST_PREDICATE(_Py_uop_sym_is_compact_int(ref_int), "compact int is not a compact int after cast");
    TEST_PREDICATE(_Py_uop_sym_matches_type(ref_int, &PyLong_Type), "compact int is not an int after cast");

    _Py_uop_sym_set_type(ctx, ref_int, &PyFloat_Type);  // Should make it bottom
    TEST_PREDICATE(_Py_uop_sym_is_bottom(ref_int), "compact int cast to float isn't bottom");

    ref_int = _Py_uop_sym_new_compact_int(ctx);
    _Py_uop_sym_set_const(ctx, ref_int, val_43);
    TEST_PREDICATE(_Py_uop_sym_is_compact_int(ref_int), "43 is not a compact int");
    TEST_PREDICATE(_Py_uop_sym_matches_type(ref_int, &PyLong_Type), "43 is not an int");
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, ref_int) == val_43, "43 isn't 43");

    JitOptRef descr_obj = _Py_uop_sym_new_descr_object(ctx, 42);
    TEST_PREDICATE(!_Py_uop_sym_is_null(descr_obj), "descr object is NULL");
    TEST_PREDICATE(_Py_uop_sym_is_not_null(descr_obj), "descr object is not not-null");
    TEST_PREDICATE(_Py_uop_sym_get_type_version(descr_obj) == 42,
                   "descr object has wrong type version");

    JitOptRef slot_val = _Py_uop_sym_new_const(ctx, val_42);
    JitOptRef old_val = _Py_uop_sym_set_attr(ctx, descr_obj, 0, slot_val);
    TEST_PREDICATE(_Py_uop_sym_is_null(old_val), "set_attr on new slot should return NULL");
    JitOptRef retrieved = _Py_uop_sym_get_attr(ctx, descr_obj, 0);
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, retrieved) == val_42,
                   "descr getattr(0) didn't return val_42");

    JitOptRef missing = _Py_uop_sym_get_attr(ctx, descr_obj, 99);
    TEST_PREDICATE(_Py_uop_sym_is_not_null(missing), "missing slot is not not-null");
    TEST_PREDICATE(!_Py_uop_sym_is_const(ctx, missing), "missing slot is const");

    JitOptRef slot_val2 = _Py_uop_sym_new_const(ctx, val_43);
    old_val = _Py_uop_sym_set_attr(ctx, descr_obj, 0, slot_val2);
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, old_val) == val_42,
                   "set_attr should return old value (val_42)");
    retrieved = _Py_uop_sym_get_attr(ctx, descr_obj, 0);
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, retrieved) == val_43,
                   "descr getattr(0) didn't return val_43 after update");

    // Test multiple slots
    JitOptRef slot_val3 = _Py_uop_sym_new_const(ctx, val_42);
    _Py_uop_sym_set_attr(ctx, descr_obj, 1, slot_val3);
    retrieved = _Py_uop_sym_get_attr(ctx, descr_obj, 1);
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, retrieved) == val_42,
                   "descr getattr(1) didn't return val_42");
    retrieved = _Py_uop_sym_get_attr(ctx, descr_obj, 0);
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, retrieved) == val_43,
                   "descr getattr(0) changed unexpectedly");
    // Test setattr with escape
    ctx->last_escape_index = INT_MAX;
    retrieved = _Py_uop_sym_set_attr(ctx, descr_obj, 1, slot_val3);
    TEST_PREDICATE(PyJitRef_Unwrap(retrieved)->tag == JIT_SYM_UNKNOWN_TAG,
                   "descr setattr should be unknown after escaping");
    ctx->last_escape_index = 0;

    // Test escape invalidation
    JitOptRef descr_obj3 = _Py_uop_sym_new_descr_object(ctx, 100);
    JitOptRef escape_val = _Py_uop_sym_new_const(ctx, val_42);
    _Py_uop_sym_set_attr(ctx, descr_obj3, 0, escape_val);
    retrieved = _Py_uop_sym_get_attr(ctx, descr_obj3, 0);
    TEST_PREDICATE(_Py_uop_sym_get_const(ctx, retrieved) == val_42,
                   "descr getattr before escape didn't return val_42");
    // Simulate escape by setting last_escape_index higher
    ctx->last_escape_index = INT_MAX;
    retrieved = _Py_uop_sym_get_attr(ctx, descr_obj3, 0);
    TEST_PREDICATE(!_Py_uop_sym_is_const(ctx, retrieved),
                   "descr getattr after escape should not return const");
    TEST_PREDICATE(_Py_uop_sym_is_not_null(retrieved),
                   "descr getattr after escape should return not-null");
    ctx->last_escape_index = 0;

    JitOptRef descr_obj2 = _Py_uop_sym_new_descr_object(ctx, 42);
    _Py_uop_sym_set_type_version(ctx, descr_obj2, 43);
    TEST_PREDICATE(_Py_uop_sym_is_bottom(descr_obj2),
                   "descr object with wrong type version isn't bottom");
    _Py_uop_abstractcontext_fini(ctx);
    Py_DECREF(val_42);
    Py_DECREF(val_43);
    Py_DECREF(val_big);
    Py_DECREF(tuple);
    Py_RETURN_NONE;

fail:
    _Py_uop_abstractcontext_fini(ctx);
    Py_XDECREF(val_42);
    Py_XDECREF(val_43);
    Py_XDECREF(val_big);
    Py_DECREF(tuple);
    return NULL;
}

#endif /* _Py_TIER2 */