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bpo-29469: Optimize literal lists and sets iterating on the AST level. #4866

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serhiy-storchaka merged 2 commits into from
Dec 14, 2017
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bpo-29469: Optimize literal lists and sets iterating on the AST level. #4866

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bpo-29469: Optimize literal lists and sets iterating on the AST level.
serhiy-storchaka Dec 14, 2017
8ad2f96
Add comments and fix the optimization of chained 'in' and 'not in'.
serhiy-storchaka Dec 14, 2017
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67 changes: 38 additions & 29 deletions Python/ast_opt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -205,7 +205,7 @@ fold_binop(expr_ty node, PyArena *arena)
}

static PyObject*
make_const_tuple(asdl_seq *elts, int make_set)
make_const_tuple(asdl_seq *elts)
{
for (int i = 0; i < asdl_seq_LEN(elts); i++) {
expr_ty e = (expr_ty)asdl_seq_GET(elts, i);
Expand All @@ -225,11 +225,6 @@ make_const_tuple(asdl_seq *elts, int make_set)
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;
}

Expand All @@ -241,7 +236,7 @@ fold_tuple(expr_ty node, PyArena *arena)
if (node->v.Tuple.ctx != Load)
return 1;

newval = make_const_tuple(node->v.Tuple.elts, 0);
newval = make_const_tuple(node->v.Tuple.elts);
return make_const(node, newval, arena);
}

Expand All @@ -268,38 +263,48 @@ fold_subscr(expr_ty node, PyArena *arena)
return make_const(node, newval, arena);
}

/* Change literal list or set of constants into constant
tuple or frozenset respectively.
Used for right operand of "in" and "not in" tests and for iterable
in "for" loop and comprehensions.
*/
static int
fold_iter(expr_ty arg, PyArena *arena)
{
PyObject *newval;
if (arg->kind == List_kind) {
newval = make_const_tuple(arg->v.List.elts);
}
else if (arg->kind == Set_kind) {
newval = make_const_tuple(arg->v.Set.elts);
if (newval) {
Py_SETREF(newval, PyFrozenSet_New(newval));
}
}
else {
return 1;
}
return make_const(arg, newval, arena);
}

static int
fold_compare(expr_ty node, PyArena *arena)
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@pitrou pitrou Dec 14, 2017

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Ditto here.

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@serhiy-storchaka serhiy-storchaka Dec 14, 2017

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This already is documented inside the function. In future the optimization for literal operands (like 1 < 2) can be added here, but currently it optimizes only the particular case of 'in' and 'not in' operators.

{
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);
/* Change literal list or set in 'in' or 'not in' into
tuple or frozenset respectively. */
i = asdl_seq_LEN(ops) - 1;
int op = asdl_seq_GET(ops, i);
if (op == In || op == NotIn) {
if (!fold_iter((expr_ty)asdl_seq_GET(args, i), arena)) {
return 0;
}
}
return 1;
}
Expand Down Expand Up @@ -497,6 +502,8 @@ 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);

CALL(fold_iter, expr_ty, node_->iter);
return 1;
}

Expand Down Expand Up @@ -565,6 +572,8 @@ astfold_stmt(stmt_ty node_, PyArena* ctx_)
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);

CALL(fold_iter, expr_ty, node_->v.For.iter);
break;
case AsyncFor_kind:
CALL(astfold_expr, expr_ty, node_->v.AsyncFor.target);
Expand Down
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