pyt/analysis/fixed_point.py
"""This module implements the fixed point algorithm."""
from .constraint_table import constraint_table
from .reaching_definitions_taint import ReachingDefinitionsTaintAnalysis
class FixedPointAnalysis():
"""Run the fix point analysis."""
def __init__(self, cfg):
"""Fixed point analysis.
Analysis must be a dataflow analysis containing a 'fixpointmethod'
method that analyses one CFG."""
self.analysis = ReachingDefinitionsTaintAnalysis(cfg)
self.cfg = cfg
def fixpoint_runner(self):
"""Work list algorithm that runs the fixpoint algorithm."""
q = self.cfg.nodes
while q != []:
x_i = constraint_table[q[0]] # x_i = q[0].old_constraint
self.analysis.fixpointmethod(q[0]) # y = F_i(x_1, ..., x_n);
y = constraint_table[q[0]] # y = q[0].new_constraint
if y != x_i:
for node in self.analysis.dep(q[0]): # for (v in dep(v_i))
q.append(node) # q.append(v):
constraint_table[q[0]] = y # q[0].old_constraint = q[0].new_constraint # x_i = y
q = q[1:] # q = q.tail() # The list minus the head
def analyse(cfg_list):
"""Analyse a list of control flow graphs with a given analysis type."""
for cfg in cfg_list:
analysis = FixedPointAnalysis(cfg)
analysis.fixpoint_runner()