def leave_Return(self, original_node: cst.Return,
updated_node: cst.Return) -> cst.RemovalSentinel:
assert self.return_format is not None
assert self.attr_format is not None
assignments = []
cond = self.get_metadata(IncrementalConditionProvider, original_node)
for name, attr in self.names_to_attr.items():
assert isinstance(attr.value, cst.Name)
state = self.attr_states.setdefault(name, [])
attr_name = cst.Name(value=self.attr_format.format(
attr.value.value, attr.attr.value, len(state)))
self.added_names.add(attr_name.value)
state.append((cond, attr_name))
assignments.append(make_assign(attr_name, cst.Name(name)))
r_name = cst.Name(value=self.return_format.format(len(self.returns)))
self.added_names.add(r_name.value)
self.returns.append((cond, r_name))
if updated_node.value is None:
r_val = cst.Name(value='None')
else:
r_val = updated_node.value
assignments.append(make_assign(r_name, r_val))
return cst.FlattenSentinel(assignments)
def _mux_name(name, t_name, f_name):
new_name = self._make_name(name)
assign = make_assign(
cst.Name(new_name),
cst.IfExp(
test=new_test,
body=cst.Name(t_name),
orelse=cst.Name(f_name),
),
)
self.name_assignments[new_name] = assign
stmt = to_stmt(assign)
assert isinstance(original_node, cst.If)
assert isinstance(self.name_assignments[t_name],
(cst.Assign, cst.Param))
assert isinstance(self.name_assignments[f_name],
(cst.Assign, cst.Param))
self.track_with_children((
self.name_assignments[t_name],
self.name_assignments[f_name],
original_node,
), stmt)
assert assign in self.node_tracking_table.i
return stmt
def leave_FunctionDef(self, original_node: cst.FunctionDef,
updated_node: cst.FunctionDef) -> cst.FunctionDef:
final_node = updated_node
if original_node is self.scope:
suite = updated_node.body
tail = self.tail
for name, attr in self.names_to_attr.items():
state = self.attr_states.get(name, [])
# default writeback initial value
state.append(([], cst.Name(name)))
attr_val = _fold_conditions(_simplify_gaurds(state),
self.strict)
write = to_stmt(make_assign(attr, attr_val))
tail.append(write)
if self.returns:
strict = self.strict
try:
return_val = _fold_conditions(
_simplify_gaurds(self.returns), strict)
except IncompleteGaurdError:
raise SyntaxError(
'Cannot prove function always returns') from None
return_stmt = cst.SimpleStatementLine(
[cst.Return(value=return_val)])
tail.append(return_stmt)
return final_node
def leave_If(
self,
original_node: cst.If,
updated_node: cst.If,
) -> cst.If:
c_name = cst.Name(value=self.format.format(len(self.added_names)))
self.added_names.add(c_name.value)
assign = to_stmt(make_assign(c_name, updated_node.test))
final_node = updated_node.with_changes(test=c_name)
return cst.FlattenSentinel([assign, final_node])
def rewrite(self, original_tree: cst.FunctionDef, env: SymbolTable,
metadata: tp.MutableMapping) -> PASS_ARGS_T:
if not isinstance(original_tree, cst.FunctionDef):
raise TypeError('ssa must be run on a FunctionDef')
# resolve position information necessary for generating symbol table
wrapper = _wrap(to_module(original_tree))
pos_info = wrapper.resolve(PositionProvider)
# convert `elif cond:` to `else: if cond:`
# (simplifies ssa logic)
transformer = with_tracking(ElifToElse)()
tree = original_tree.visit(transformer)
# original node -> generated nodes
node_tracking_table = transformer.node_tracking_table
# node_tracking_table.i
# generated node -> original nodes
wrapper = _wrap(to_module(tree))
writter_attr_visitor = WrittenAttrs()
wrapper.visit(writter_attr_visitor)
replacer = with_tracking(AttrReplacer)()
attr_format = gen_free_prefix(tree, env, '_attr') + '_{}_{}'
init_reads = []
names_to_attr = {}
seen = set()
for written_attr in writter_attr_visitor.written_attrs:
d_attr = DeepNode(written_attr)
if d_attr in seen:
continue
if not isinstance(written_attr.value, cst.Name):
raise NotImplementedError(
'writing non name nodes is not supported')
seen.add(d_attr)
attr_name = attr_format.format(
written_attr.value.value,
written_attr.attr.value,
)
# using normal node instead of original node
# is safe as parenthesis don't matter:
# (name).attr == (name.attr) == name.attr
norm = d_attr.normal_node
names_to_attr[attr_name] = norm
name = cst.Name(attr_name)
replacer.add_replacement(written_attr, name)
read = to_stmt(make_assign(name, norm))
init_reads.append(read)
# Replace references to attr with the name generated above
tree = tree.visit(replacer)
node_tracking_table = replacer.trace_origins(node_tracking_table)
# Rewrite conditions to be ssa
cond_prefix = gen_free_prefix(tree, env, '_cond')
wrapper = _wrap(tree)
name_tests = NameTests(cond_prefix)
tree = wrapper.visit(name_tests)
node_tracking_table = name_tests.trace_origins(node_tracking_table)
# Transform to single return format
wrapper = _wrap(tree)
single_return = SingleReturn(env, names_to_attr, self.strict)
tree = wrapper.visit(single_return)
node_tracking_table = single_return.trace_origins(node_tracking_table)
# insert the initial reads / final writes / return
body = tree.body
body = body.with_changes(body=(*init_reads, *body.body,
*single_return.tail))
tree = tree.with_changes(body=body)
# perform ssa
wrapper = _wrap(to_module(tree))
ctxs = wrapper.resolve(ExpressionContextProvider)
# These names were constructed in such a way that they are
# guaranteed to be ssa and shouldn't be touched by the
# transformer
final_names = single_return.added_names | name_tests.added_names
ssa_transformer = SSATransformer(env,
ctxs,
final_names,
single_return.returning_blocks,
strict=self.strict)
tree = tree.visit(ssa_transformer)
node_tracking_table = ssa_transformer.trace_origins(
node_tracking_table)
tree.validate_types_deep()
# generate symbol table
start_ln = pos_info[original_tree].start.line
end_ln = pos_info[original_tree].end.line
visitor = GenerateSymbolTable(
node_tracking_table,
ssa_transformer.original_names,
pos_info,
start_ln,
end_ln,
)
tree.visit(visitor)
metadata.setdefault('SYMBOL-TABLE', list()).append(
(type(self), visitor.symbol_table))
return tree, env, metadata