cpython/Python/ast_opt.c

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/* AST Optimizer */
#include "Python.h"
#include "Python-ast.h"
/* TODO: is_const and get_const_value are copied from Python/compile.c.
It should be deduped in the future. Maybe, we can include this file
from compile.c?
*/
static int
is_const(expr_ty e)
{
switch (e->kind) {
case Constant_kind:
case Num_kind:
case Str_kind:
case Bytes_kind:
case Ellipsis_kind:
case NameConstant_kind:
return 1;
default:
return 0;
}
}
static PyObject *
get_const_value(expr_ty e)
{
switch (e->kind) {
case Constant_kind:
return e->v.Constant.value;
case Num_kind:
return e->v.Num.n;
case Str_kind:
return e->v.Str.s;
case Bytes_kind:
return e->v.Bytes.s;
case Ellipsis_kind:
return Py_Ellipsis;
case NameConstant_kind:
return e->v.NameConstant.value;
default:
Py_UNREACHABLE();
}
}
static int
make_const(expr_ty node, PyObject *val, PyArena *arena)
{
if (val == NULL) {
if (PyErr_ExceptionMatches(PyExc_KeyboardInterrupt)) {
return 0;
}
PyErr_Clear();
return 1;
}
if (PyArena_AddPyObject(arena, val) < 0) {
Py_DECREF(val);
return 0;
}
node->kind = Constant_kind;
node->v.Constant.value = val;
return 1;
}
#define COPY_NODE(TO, FROM) (memcpy((TO), (FROM), sizeof(struct _expr)))
static PyObject*
unary_not(PyObject *v)
{
int r = PyObject_IsTrue(v);
if (r < 0)
return NULL;
return PyBool_FromLong(!r);
}
static int
fold_unaryop(expr_ty node, PyArena *arena)
{
expr_ty arg = node->v.UnaryOp.operand;
if (!is_const(arg)) {
/* Fold not into comparison */
if (node->v.UnaryOp.op == Not && arg->kind == Compare_kind &&
asdl_seq_LEN(arg->v.Compare.ops) == 1) {
/* Eq and NotEq are often implemented in terms of one another, so
folding not (self == other) into self != other breaks implementation
of !=. Detecting such cases doesn't seem worthwhile.
Python uses </> for 'is subset'/'is superset' operations on sets.
They don't satisfy not folding laws. */
int op = asdl_seq_GET(arg->v.Compare.ops, 0);
switch (op) {
case Is:
op = IsNot;
break;
case IsNot:
op = Is;
break;
case In:
op = NotIn;
break;
case NotIn:
op = In;
break;
default:
op = 0;
}
if (op) {
asdl_seq_SET(arg->v.Compare.ops, 0, op);
COPY_NODE(node, arg);
return 1;
}
}
return 1;
}
typedef PyObject *(*unary_op)(PyObject*);
static const unary_op ops[] = {
[Invert] = PyNumber_Invert,
[Not] = unary_not,
[UAdd] = PyNumber_Positive,
[USub] = PyNumber_Negative,
};
PyObject *newval = ops[node->v.UnaryOp.op](get_const_value(arg));
return make_const(node, newval, arena);
}
static int
fold_binop(expr_ty node, PyArena *arena)
{
expr_ty lhs, rhs;
lhs = node->v.BinOp.left;
rhs = node->v.BinOp.right;
if (!is_const(lhs) || !is_const(rhs)) {
return 1;
}
PyObject *lv = get_const_value(lhs);
PyObject *rv = get_const_value(rhs);
PyObject *newval;
switch (node->v.BinOp.op) {
case Add:
newval = PyNumber_Add(lv, rv);
break;
case Sub:
newval = PyNumber_Subtract(lv, rv);
break;
case Mult:
newval = PyNumber_Multiply(lv, rv);
break;
case Div:
newval = PyNumber_TrueDivide(lv, rv);
break;
case FloorDiv:
newval = PyNumber_FloorDivide(lv, rv);
break;
case Mod:
newval = PyNumber_Remainder(lv, rv);
break;
case Pow:
newval = PyNumber_Power(lv, rv, Py_None);
break;
case LShift:
newval = PyNumber_Lshift(lv, rv);
break;
case RShift:
newval = PyNumber_Rshift(lv, rv);
break;
case BitOr:
newval = PyNumber_Or(lv, rv);
break;
case BitXor:
newval = PyNumber_Xor(lv, rv);
break;
case BitAnd:
newval = PyNumber_And(lv, rv);
break;
default: // Unknown operator
return 1;
}
if (newval == NULL) {
if (PyErr_ExceptionMatches(PyExc_KeyboardInterrupt)) {
return 0;
}
PyErr_Clear();
return 1;
}
/* Avoid creating large constants. */
Py_ssize_t size = PyObject_Size(newval);
if (size == -1) {
if (PyErr_ExceptionMatches(PyExc_KeyboardInterrupt)) {
Py_DECREF(newval);
return 0;
}
PyErr_Clear();
}
else if (size > 20) {
Py_DECREF(newval);
return 1;
}
return make_const(node, newval, arena);
}
static PyObject*
make_const_tuple(asdl_seq *elts, int make_set)
{
for (int i = 0; i < asdl_seq_LEN(elts); i++) {
expr_ty e = (expr_ty)asdl_seq_GET(elts, i);
if (!is_const(e)) {
return NULL;
}
}
PyObject *newval = PyTuple_New(asdl_seq_LEN(elts));
if (newval == NULL) {
return NULL;
}
for (int i = 0; i < asdl_seq_LEN(elts); i++) {
expr_ty e = (expr_ty)asdl_seq_GET(elts, i);
PyObject *v = get_const_value(e);
Py_INCREF(v);
PyTuple_SET_ITEM(newval, i, v);
}
/* Need to create frozen_set instead. */
if (make_set) {
Py_SETREF(newval, PyFrozenSet_New(newval));
}
return newval;
}
static int
fold_tuple(expr_ty node, PyArena *arena)
{
PyObject *newval;
if (node->v.Tuple.ctx != Load)
return 1;
newval = make_const_tuple(node->v.Tuple.elts, 0);
return make_const(node, newval, arena);
}
static int
fold_subscr(expr_ty node, PyArena *arena)
{
PyObject *newval;
expr_ty arg, idx;
slice_ty slice;
arg = node->v.Subscript.value;
slice = node->v.Subscript.slice;
if (node->v.Subscript.ctx != Load ||
!is_const(arg) ||
/* TODO: handle other types of slices */
slice->kind != Index_kind ||
!is_const(slice->v.Index.value))
{
return 1;
}
idx = slice->v.Index.value;
newval = PyObject_GetItem(get_const_value(arg), get_const_value(idx));
return make_const(node, newval, arena);
}
static int
fold_compare(expr_ty node, PyArena *arena)
{
asdl_int_seq *ops;
asdl_seq *args;
PyObject *newval;
int i;
ops = node->v.Compare.ops;
args = node->v.Compare.comparators;
/* TODO: optimize cases with literal arguments. */
for (i = 0; i < asdl_seq_LEN(ops); i++) {
int op;
expr_ty arg;
asdl_seq *elts;
op = asdl_seq_GET(ops, i);
arg = (expr_ty)asdl_seq_GET(args, i);
/* Change literal list or set in 'in' or 'not in' into
tuple or frozenset respectively. */
/* TODO: do the same when list or set is used as iterable
in for loop and comprehensions? */
if (op != In && op != NotIn)
continue;
if (arg->kind == List_kind)
elts = arg->v.List.elts;
else if (arg->kind == Set_kind)
elts = arg->v.Set.elts;
else continue;
newval = make_const_tuple(elts, arg->kind == Set_kind);
make_const(arg, newval, arena);
}
return 1;
}
static int astfold_mod(mod_ty node_, PyArena* ctx_);
static int astfold_stmt(stmt_ty node_, PyArena* ctx_);
static int astfold_expr(expr_ty node_, PyArena* ctx_);
static int astfold_arguments(arguments_ty node_, PyArena* ctx_);
static int astfold_comprehension(comprehension_ty node_, PyArena* ctx_);
static int astfold_keyword(keyword_ty node_, PyArena* ctx_);
static int astfold_slice(slice_ty node_, PyArena* ctx_);
static int astfold_arg(arg_ty node_, PyArena* ctx_);
static int astfold_withitem(withitem_ty node_, PyArena* ctx_);
static int astfold_excepthandler(excepthandler_ty node_, PyArena* ctx_);
#define CALL(FUNC, TYPE, ARG) \
if (!FUNC((ARG), ctx_)) \
return 0;
#define CALL_OPT(FUNC, TYPE, ARG) \
if ((ARG) != NULL && !FUNC((ARG), ctx_)) \
return 0;
#define CALL_SEQ(FUNC, TYPE, ARG) { \
int i; \
asdl_seq *seq = (ARG); /* avoid variable capture */ \
for (i = 0; i < asdl_seq_LEN(seq); i++) { \
TYPE elt = (TYPE)asdl_seq_GET(seq, i); \
if (elt != NULL && !FUNC(elt, ctx_)) \
return 0; \
} \
}
#define CALL_INT_SEQ(FUNC, TYPE, ARG) { \
int i; \
asdl_int_seq *seq = (ARG); /* avoid variable capture */ \
for (i = 0; i < asdl_seq_LEN(seq); i++) { \
TYPE elt = (TYPE)asdl_seq_GET(seq, i); \
if (!FUNC(elt, ctx_)) \
return 0; \
} \
}
static int
astfold_mod(mod_ty node_, PyArena* ctx_)
{
switch (node_->kind) {
case Module_kind:
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.Module.body);
break;
case Interactive_kind:
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.Interactive.body);
break;
case Expression_kind:
CALL(astfold_expr, expr_ty, node_->v.Expression.body);
break;
case Suite_kind:
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.Suite.body);
break;
default:
break;
}
return 1;
}
static int
astfold_expr(expr_ty node_, PyArena* ctx_)
{
switch (node_->kind) {
case BoolOp_kind:
CALL_SEQ(astfold_expr, expr_ty, node_->v.BoolOp.values);
break;
case BinOp_kind:
CALL(astfold_expr, expr_ty, node_->v.BinOp.left);
CALL(astfold_expr, expr_ty, node_->v.BinOp.right);
CALL(fold_binop, expr_ty, node_);
break;
case UnaryOp_kind:
CALL(astfold_expr, expr_ty, node_->v.UnaryOp.operand);
CALL(fold_unaryop, expr_ty, node_);
break;
case Lambda_kind:
CALL(astfold_arguments, arguments_ty, node_->v.Lambda.args);
CALL(astfold_expr, expr_ty, node_->v.Lambda.body);
break;
case IfExp_kind:
CALL(astfold_expr, expr_ty, node_->v.IfExp.test);
CALL(astfold_expr, expr_ty, node_->v.IfExp.body);
CALL(astfold_expr, expr_ty, node_->v.IfExp.orelse);
break;
case Dict_kind:
CALL_SEQ(astfold_expr, expr_ty, node_->v.Dict.keys);
CALL_SEQ(astfold_expr, expr_ty, node_->v.Dict.values);
break;
case Set_kind:
CALL_SEQ(astfold_expr, expr_ty, node_->v.Set.elts);
break;
case ListComp_kind:
CALL(astfold_expr, expr_ty, node_->v.ListComp.elt);
CALL_SEQ(astfold_comprehension, comprehension_ty, node_->v.ListComp.generators);
break;
case SetComp_kind:
CALL(astfold_expr, expr_ty, node_->v.SetComp.elt);
CALL_SEQ(astfold_comprehension, comprehension_ty, node_->v.SetComp.generators);
break;
case DictComp_kind:
CALL(astfold_expr, expr_ty, node_->v.DictComp.key);
CALL(astfold_expr, expr_ty, node_->v.DictComp.value);
CALL_SEQ(astfold_comprehension, comprehension_ty, node_->v.DictComp.generators);
break;
case GeneratorExp_kind:
CALL(astfold_expr, expr_ty, node_->v.GeneratorExp.elt);
CALL_SEQ(astfold_comprehension, comprehension_ty, node_->v.GeneratorExp.generators);
break;
case Await_kind:
CALL(astfold_expr, expr_ty, node_->v.Await.value);
break;
case Yield_kind:
CALL_OPT(astfold_expr, expr_ty, node_->v.Yield.value);
break;
case YieldFrom_kind:
CALL(astfold_expr, expr_ty, node_->v.YieldFrom.value);
break;
case Compare_kind:
CALL(astfold_expr, expr_ty, node_->v.Compare.left);
CALL_SEQ(astfold_expr, expr_ty, node_->v.Compare.comparators);
CALL(fold_compare, expr_ty, node_);
break;
case Call_kind:
CALL(astfold_expr, expr_ty, node_->v.Call.func);
CALL_SEQ(astfold_expr, expr_ty, node_->v.Call.args);
CALL_SEQ(astfold_keyword, keyword_ty, node_->v.Call.keywords);
break;
case FormattedValue_kind:
CALL(astfold_expr, expr_ty, node_->v.FormattedValue.value);
CALL_OPT(astfold_expr, expr_ty, node_->v.FormattedValue.format_spec);
break;
case JoinedStr_kind:
CALL_SEQ(astfold_expr, expr_ty, node_->v.JoinedStr.values);
break;
case Attribute_kind:
CALL(astfold_expr, expr_ty, node_->v.Attribute.value);
break;
case Subscript_kind:
CALL(astfold_expr, expr_ty, node_->v.Subscript.value);
CALL(astfold_slice, slice_ty, node_->v.Subscript.slice);
CALL(fold_subscr, expr_ty, node_);
break;
case Starred_kind:
CALL(astfold_expr, expr_ty, node_->v.Starred.value);
break;
case List_kind:
CALL_SEQ(astfold_expr, expr_ty, node_->v.List.elts);
break;
case Tuple_kind:
CALL_SEQ(astfold_expr, expr_ty, node_->v.Tuple.elts);
CALL(fold_tuple, expr_ty, node_);
break;
default:
break;
}
return 1;
}
static int
astfold_slice(slice_ty node_, PyArena* ctx_)
{
switch (node_->kind) {
case Slice_kind:
CALL_OPT(astfold_expr, expr_ty, node_->v.Slice.lower);
CALL_OPT(astfold_expr, expr_ty, node_->v.Slice.upper);
CALL_OPT(astfold_expr, expr_ty, node_->v.Slice.step);
break;
case ExtSlice_kind:
CALL_SEQ(astfold_slice, slice_ty, node_->v.ExtSlice.dims);
break;
case Index_kind:
CALL(astfold_expr, expr_ty, node_->v.Index.value);
break;
default:
break;
}
return 1;
}
static int
astfold_keyword(keyword_ty node_, PyArena* ctx_)
{
CALL(astfold_expr, expr_ty, node_->value);
return 1;
}
static int
astfold_comprehension(comprehension_ty node_, PyArena* ctx_)
{
CALL(astfold_expr, expr_ty, node_->target);
CALL(astfold_expr, expr_ty, node_->iter);
CALL_SEQ(astfold_expr, expr_ty, node_->ifs);
return 1;
}
static int
astfold_arguments(arguments_ty node_, PyArena* ctx_)
{
CALL_SEQ(astfold_arg, arg_ty, node_->args);
CALL_OPT(astfold_arg, arg_ty, node_->vararg);
CALL_SEQ(astfold_arg, arg_ty, node_->kwonlyargs);
CALL_SEQ(astfold_expr, expr_ty, node_->kw_defaults);
CALL_OPT(astfold_arg, arg_ty, node_->kwarg);
CALL_SEQ(astfold_expr, expr_ty, node_->defaults);
return 1;
}
static int
astfold_arg(arg_ty node_, PyArena* ctx_)
{
CALL_OPT(astfold_expr, expr_ty, node_->annotation);
return 1;
}
static int
astfold_stmt(stmt_ty node_, PyArena* ctx_)
{
switch (node_->kind) {
case FunctionDef_kind:
CALL(astfold_arguments, arguments_ty, node_->v.FunctionDef.args);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.FunctionDef.body);
CALL_SEQ(astfold_expr, expr_ty, node_->v.FunctionDef.decorator_list);
CALL_OPT(astfold_expr, expr_ty, node_->v.FunctionDef.returns);
break;
case AsyncFunctionDef_kind:
CALL(astfold_arguments, arguments_ty, node_->v.AsyncFunctionDef.args);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.AsyncFunctionDef.body);
CALL_SEQ(astfold_expr, expr_ty, node_->v.AsyncFunctionDef.decorator_list);
CALL_OPT(astfold_expr, expr_ty, node_->v.AsyncFunctionDef.returns);
break;
case ClassDef_kind:
CALL_SEQ(astfold_expr, expr_ty, node_->v.ClassDef.bases);
CALL_SEQ(astfold_keyword, keyword_ty, node_->v.ClassDef.keywords);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.ClassDef.body);
CALL_SEQ(astfold_expr, expr_ty, node_->v.ClassDef.decorator_list);
break;
case Return_kind:
CALL_OPT(astfold_expr, expr_ty, node_->v.Return.value);
break;
case Delete_kind:
CALL_SEQ(astfold_expr, expr_ty, node_->v.Delete.targets);
break;
case Assign_kind:
CALL_SEQ(astfold_expr, expr_ty, node_->v.Assign.targets);
CALL(astfold_expr, expr_ty, node_->v.Assign.value);
break;
case AugAssign_kind:
CALL(astfold_expr, expr_ty, node_->v.AugAssign.target);
CALL(astfold_expr, expr_ty, node_->v.AugAssign.value);
break;
case AnnAssign_kind:
CALL(astfold_expr, expr_ty, node_->v.AnnAssign.target);
CALL(astfold_expr, expr_ty, node_->v.AnnAssign.annotation);
CALL_OPT(astfold_expr, expr_ty, node_->v.AnnAssign.value);
break;
case For_kind:
CALL(astfold_expr, expr_ty, node_->v.For.target);
CALL(astfold_expr, expr_ty, node_->v.For.iter);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.For.body);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.For.orelse);
break;
case AsyncFor_kind:
CALL(astfold_expr, expr_ty, node_->v.AsyncFor.target);
CALL(astfold_expr, expr_ty, node_->v.AsyncFor.iter);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.AsyncFor.body);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.AsyncFor.orelse);
break;
case While_kind:
CALL(astfold_expr, expr_ty, node_->v.While.test);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.While.body);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.While.orelse);
break;
case If_kind:
CALL(astfold_expr, expr_ty, node_->v.If.test);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.If.body);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.If.orelse);
break;
case With_kind:
CALL_SEQ(astfold_withitem, withitem_ty, node_->v.With.items);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.With.body);
break;
case AsyncWith_kind:
CALL_SEQ(astfold_withitem, withitem_ty, node_->v.AsyncWith.items);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.AsyncWith.body);
break;
case Raise_kind:
CALL_OPT(astfold_expr, expr_ty, node_->v.Raise.exc);
CALL_OPT(astfold_expr, expr_ty, node_->v.Raise.cause);
break;
case Try_kind:
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.Try.body);
CALL_SEQ(astfold_excepthandler, excepthandler_ty, node_->v.Try.handlers);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.Try.orelse);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.Try.finalbody);
break;
case Assert_kind:
CALL(astfold_expr, expr_ty, node_->v.Assert.test);
CALL_OPT(astfold_expr, expr_ty, node_->v.Assert.msg);
break;
case Expr_kind:
CALL(astfold_expr, expr_ty, node_->v.Expr.value);
break;
default:
break;
}
return 1;
}
static int
astfold_excepthandler(excepthandler_ty node_, PyArena* ctx_)
{
switch (node_->kind) {
case ExceptHandler_kind:
CALL_OPT(astfold_expr, expr_ty, node_->v.ExceptHandler.type);
CALL_SEQ(astfold_stmt, stmt_ty, node_->v.ExceptHandler.body);
break;
default:
break;
}
return 1;
}
static int
astfold_withitem(withitem_ty node_, PyArena* ctx_)
{
CALL(astfold_expr, expr_ty, node_->context_expr);
CALL_OPT(astfold_expr, expr_ty, node_->optional_vars);
return 1;
}
#undef CALL
#undef CALL_OPT
#undef CALL_SEQ
#undef CALL_INT_SEQ
int
_PyAST_Optimize(mod_ty mod, PyArena *arena)
{
int ret = astfold_mod(mod, arena);
assert(ret || PyErr_Occurred());
return ret;
}