def find_natural_loops(func, cfg=None):
"""Return a loop nesting forest for the given function ([Loop])"""
cfg = cfg or cfa.cfg(func)
dominators = cfa.compute_dominators(func, cfg)
loops = []
loop_stack = []
for block in func.blocks:
### Look for incoming back-edge
for pred in cfg.predecessors(block):
if block in dominators[pred]:
# We dominate an incoming block, this means there is a
# back-edge (pred, block)
loop_stack.append(Loop([block]))
### Populate Loop
if loop_stack:
loop = loop_stack[-1]
head = loop.blocks[0]
if head in dominators[block] and head != block:
# Dominated by loop header, add
loop.blocks.append(block)
if head in cfg[block]:
loop_stack.pop()
if loop_stack:
# update outer loop
loop_stack[-1].blocks.extend(loop.blocks)
loop_stack[-1].children.append(loop)
else:
# outermost loop, add to forest
loops.append(loop)
assert not loop_stack
return loops
def find_natural_loops(func, cfg=None):
"""Return a loop nesting forest for the given function ([Loop])"""
cfg = cfg or cfa.cfg(func)
dominators = cfa.compute_dominators(func, cfg)
loops = []
loop_stack = []
for block in func.blocks:
### Look for incoming back-edge
for pred in cfg.predecessors(block):
if block in dominators[pred]:
# We dominate an incoming block, this means there is a
# back-edge (pred, block)
loop_stack.append(Loop([block]))
### Populate Loop
if loop_stack:
loop = loop_stack[-1]
head = loop.blocks[0]
if head in dominators[block] and head != block:
# Dominated by loop header, add
loop.blocks.append(block)
if head in cfg[block]:
loop_stack.pop()
if loop_stack:
# update outer loop
loop_stack[-1].blocks.extend(loop.blocks)
loop_stack[-1].children.append(loop)
else:
# outermost loop, add to forest
loops.append(loop)
assert not loop_stack
return loops
def verify_block_order(func):
"""Verify block order according to dominator tree"""
from pykit.analysis import cfa
flow = cfa.cfg(func)
dominators = cfa.compute_dominators(func, flow)
visited = set()
for block in func.blocks:
visited.add(block.name)
for dominator in dominators[block.name]:
if dominator not in visited:
raise VerifyError("Dominator %s does not precede block %s" % (
dominator, block.name))
def verify_block_order(func):
"""Verify block order according to dominator tree"""
from pykit.analysis import cfa
flow = cfa.cfg(func)
dominators = cfa.compute_dominators(func, flow)
visited = set()
for block in func.blocks:
visited.add(block.name)
for dominator in dominators[block.name]:
if dominator not in visited:
raise VerifyError("Dominator %s does not precede block %s" % (
dominator, block.name))
