Current File : //lib/python3/dist-packages/pythran/analyses/cfg.py
""" Computes the Control Flow Graph of a function. """
from pythran.passmanager import FunctionAnalysis
from pythran.utils import isnum
from pythran.graph import DiGraph
import gast as ast
def is_true_predicate(node):
# FIXME: there may be more patterns here
if isnum(node) and node.value:
return True
if isinstance(node, ast.Attribute) and node.attr == 'True':
return True
if isinstance(node, (ast.List, ast.Tuple, ast.Set)) and node.elts:
return True
if isinstance(node, ast.Dict) and node.keys:
return True
return False
class CFG(FunctionAnalysis):
"""
Computes the Control Flow Graph of a function.
The processing of a node yields a pair containing
* the OUT nodes, to be linked with the IN nodes of the successor
* the RAISE nodes, nodes that stop the control flow (exception/break/...)
"""
#: The sink node in the control flow graph.
#:
#: The predecessors of this node are those AST nodes that terminate
#: control flow without a return statement.
NIL = object()
def __init__(self):
self.result = DiGraph()
super(CFG, self).__init__()
def visit_FunctionDef(self, node):
"""OUT = node, RAISES = ()"""
# the function itself is the entry point
self.result.add_node(node)
currs = (node,)
for n in node.body:
self.result.add_node(n)
for curr in currs:
self.result.add_edge(curr, n)
currs, _ = self.visit(n)
# add an edge to NIL for nodes that end the control flow
# without a return
self.result.add_node(CFG.NIL)
for curr in currs:
self.result.add_edge(curr, CFG.NIL)
return (node,), ()
def visit_Pass(self, node):
"""OUT = node, RAISES = ()"""
return (node,), ()
# All these nodes have the same behavior as pass
visit_Assign = visit_AugAssign = visit_Import = visit_Pass
visit_Expr = visit_Print = visit_ImportFrom = visit_Pass
visit_Yield = visit_Delete = visit_Pass
def visit_Return(self, node):
"""OUT = (), RAISES = ()"""
return (), ()
def visit_For(self, node):
"""
OUT = (node,) + last body statements
RAISES = body's that are not break or continue
"""
currs = (node,)
break_currs = tuple()
raises = ()
# handle body
for n in node.body:
self.result.add_node(n)
for curr in currs:
self.result.add_edge(curr, n)
currs, nraises = self.visit(n)
for nraise in nraises:
if isinstance(nraise, ast.Break):
break_currs += (nraise,)
elif isinstance(nraise, ast.Continue):
self.result.add_edge(nraise, node)
else:
raises += (nraise,)
# add the backward loop
for curr in currs:
self.result.add_edge(curr, node)
# the else statement if needed
if node.orelse:
for n in node.orelse:
self.result.add_node(n)
for curr in currs:
self.result.add_edge(curr, n)
currs, nraises = self.visit(n)
else:
currs = node,
# while only
if isinstance(node, ast.While):
if is_true_predicate(node.test):
return break_currs, raises
else:
return break_currs + currs, raises
# for only
return break_currs + currs, raises
visit_While = visit_For
def visit_If(self, node):
"""
OUT = true branch U false branch
RAISES = true branch U false branch
"""
currs = (node,)
raises = ()
# true branch
for n in node.body:
self.result.add_node(n)
for curr in currs:
self.result.add_edge(curr, n)
currs, nraises = self.visit(n)
raises += nraises
# false branch
tcurrs = currs
traises = raises
currs = (node,)
for n in node.orelse:
self.result.add_node(n)
for curr in currs:
self.result.add_edge(curr, n)
currs, nraises = self.visit(n)
raises = traises + nraises
if is_true_predicate(node.test):
return tcurrs, raises
return tcurrs + currs, raises
def visit_Raise(self, node):
"""OUT = (), RAISES = (node)"""
return (), (node,)
visit_Break = visit_Continue = visit_Raise
def visit_Assert(self, node):
"""OUT = RAISES = (node)"""
return (node,), (node,)
def visit_Try(self, node):
"""
OUT = body's U handler's
RAISES = handler's
this equation is not has good has it could be...
but we need type information to be more accurate
"""
currs = (node,)
raises = ()
for handler in node.handlers:
self.result.add_node(handler)
for n in node.body:
self.result.add_node(n)
for curr in currs:
self.result.add_edge(curr, n)
currs, nraises = self.visit(n)
for nraise in nraises:
if isinstance(nraise, ast.Raise):
for handler in node.handlers:
self.result.add_edge(nraise, handler)
else:
raises += (nraise,)
for handler in node.handlers:
ncurrs, nraises = self.visit(handler)
currs += ncurrs
raises += nraises
return currs, raises
def visit_ExceptHandler(self, node):
"""OUT = body's, RAISES = body's"""
currs = (node,)
raises = ()
for n in node.body:
self.result.add_node(n)
for curr in currs:
self.result.add_edge(curr, n)
currs, nraises = self.visit(n)
raises += nraises
return currs, raises
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