mirror of
https://github.com/python/cpython.git
synced 2024-12-01 22:04:04 +08:00
2a7f384122
Armin Rigo pointed out that the way the line-# table got built didn't work for lines generating more than 255 bytes of bytecode. Fixed as he suggested, plus corresponding changes to pyassem.py, plus added some long overdue docs about this subtle table to compile.c. Bugfix candidate (line numbers may be off in tracebacks under -O).
779 lines
24 KiB
Python
779 lines
24 KiB
Python
"""A flow graph representation for Python bytecode"""
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import dis
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import new
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import string
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import sys
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import types
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from compiler import misc
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def xxx_sort(l):
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l = l[:]
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def sorter(a, b):
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return cmp(a.bid, b.bid)
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l.sort(sorter)
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return l
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class FlowGraph:
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def __init__(self):
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self.current = self.entry = Block()
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self.exit = Block("exit")
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self.blocks = misc.Set()
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self.blocks.add(self.entry)
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self.blocks.add(self.exit)
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def startBlock(self, block):
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if self._debug:
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if self.current:
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print "end", repr(self.current)
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print " next", self.current.next
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print " ", self.current.get_children()
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print repr(block)
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self.current = block
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def nextBlock(self, block=None):
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# XXX think we need to specify when there is implicit transfer
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# from one block to the next. might be better to represent this
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# with explicit JUMP_ABSOLUTE instructions that are optimized
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# out when they are unnecessary.
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#
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# I think this strategy works: each block has a child
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# designated as "next" which is returned as the last of the
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# children. because the nodes in a graph are emitted in
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# reverse post order, the "next" block will always be emitted
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# immediately after its parent.
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# Worry: maintaining this invariant could be tricky
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if block is None:
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block = self.newBlock()
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# Note: If the current block ends with an unconditional
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# control transfer, then it is incorrect to add an implicit
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# transfer to the block graph. The current code requires
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# these edges to get the blocks emitted in the right order,
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# however. :-( If a client needs to remove these edges, call
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# pruneEdges().
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self.current.addNext(block)
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self.startBlock(block)
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def newBlock(self):
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b = Block()
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self.blocks.add(b)
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return b
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def startExitBlock(self):
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self.startBlock(self.exit)
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_debug = 0
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def _enable_debug(self):
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self._debug = 1
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def _disable_debug(self):
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self._debug = 0
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def emit(self, *inst):
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if self._debug:
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print "\t", inst
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if inst[0] == 'RETURN_VALUE':
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self.current.addOutEdge(self.exit)
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if len(inst) == 2 and isinstance(inst[1], Block):
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self.current.addOutEdge(inst[1])
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self.current.emit(inst)
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def getBlocksInOrder(self):
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"""Return the blocks in reverse postorder
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i.e. each node appears before all of its successors
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"""
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# XXX make sure every node that doesn't have an explicit next
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# is set so that next points to exit
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for b in self.blocks.elements():
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if b is self.exit:
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continue
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if not b.next:
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b.addNext(self.exit)
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order = dfs_postorder(self.entry, {})
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order.reverse()
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self.fixupOrder(order, self.exit)
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# hack alert
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if not self.exit in order:
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order.append(self.exit)
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return order
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def fixupOrder(self, blocks, default_next):
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"""Fixup bad order introduced by DFS."""
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# XXX This is a total mess. There must be a better way to get
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# the code blocks in the right order.
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self.fixupOrderHonorNext(blocks, default_next)
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self.fixupOrderForward(blocks, default_next)
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def fixupOrderHonorNext(self, blocks, default_next):
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"""Fix one problem with DFS.
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The DFS uses child block, but doesn't know about the special
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"next" block. As a result, the DFS can order blocks so that a
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block isn't next to the right block for implicit control
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transfers.
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"""
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index = {}
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for i in range(len(blocks)):
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index[blocks[i]] = i
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for i in range(0, len(blocks) - 1):
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b = blocks[i]
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n = blocks[i + 1]
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if not b.next or b.next[0] == default_next or b.next[0] == n:
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continue
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# The blocks are in the wrong order. Find the chain of
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# blocks to insert where they belong.
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cur = b
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chain = []
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elt = cur
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while elt.next and elt.next[0] != default_next:
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chain.append(elt.next[0])
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elt = elt.next[0]
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# Now remove the blocks in the chain from the current
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# block list, so that they can be re-inserted.
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l = []
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for b in chain:
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assert index[b] > i
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l.append((index[b], b))
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l.sort()
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l.reverse()
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for j, b in l:
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del blocks[index[b]]
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# Insert the chain in the proper location
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blocks[i:i + 1] = [cur] + chain
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# Finally, re-compute the block indexes
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for i in range(len(blocks)):
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index[blocks[i]] = i
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def fixupOrderForward(self, blocks, default_next):
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"""Make sure all JUMP_FORWARDs jump forward"""
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index = {}
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chains = []
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cur = []
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for b in blocks:
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index[b] = len(chains)
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cur.append(b)
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if b.next and b.next[0] == default_next:
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chains.append(cur)
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cur = []
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chains.append(cur)
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while 1:
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constraints = []
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for i in range(len(chains)):
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l = chains[i]
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for b in l:
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for c in b.get_children():
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if index[c] < i:
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forward_p = 0
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for inst in b.insts:
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if inst[0] == 'JUMP_FORWARD':
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if inst[1] == c:
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forward_p = 1
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if not forward_p:
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continue
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constraints.append((index[c], i))
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if not constraints:
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break
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# XXX just do one for now
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# do swaps to get things in the right order
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goes_before, a_chain = constraints[0]
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assert a_chain > goes_before
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c = chains[a_chain]
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chains.remove(c)
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chains.insert(goes_before, c)
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del blocks[:]
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for c in chains:
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for b in c:
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blocks.append(b)
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def getBlocks(self):
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return self.blocks.elements()
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def getRoot(self):
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"""Return nodes appropriate for use with dominator"""
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return self.entry
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def getContainedGraphs(self):
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l = []
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for b in self.getBlocks():
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l.extend(b.getContainedGraphs())
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return l
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def dfs_postorder(b, seen):
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"""Depth-first search of tree rooted at b, return in postorder"""
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order = []
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seen[b] = b
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for c in b.get_children():
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if seen.has_key(c):
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continue
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order = order + dfs_postorder(c, seen)
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order.append(b)
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return order
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class Block:
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_count = 0
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def __init__(self, label=''):
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self.insts = []
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self.inEdges = misc.Set()
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self.outEdges = misc.Set()
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self.label = label
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self.bid = Block._count
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self.next = []
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Block._count = Block._count + 1
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def __repr__(self):
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if self.label:
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return "<block %s id=%d>" % (self.label, self.bid)
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else:
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return "<block id=%d>" % (self.bid)
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def __str__(self):
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insts = map(str, self.insts)
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return "<block %s %d:\n%s>" % (self.label, self.bid,
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string.join(insts, '\n'))
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def emit(self, inst):
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op = inst[0]
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if op[:4] == 'JUMP':
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self.outEdges.add(inst[1])
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self.insts.append(inst)
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def getInstructions(self):
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return self.insts
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def addInEdge(self, block):
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self.inEdges.add(block)
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def addOutEdge(self, block):
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self.outEdges.add(block)
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def addNext(self, block):
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self.next.append(block)
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assert len(self.next) == 1, map(str, self.next)
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_uncond_transfer = ('RETURN_VALUE', 'RAISE_VARARGS',
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'JUMP_ABSOLUTE', 'JUMP_FORWARD')
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def pruneNext(self):
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"""Remove bogus edge for unconditional transfers
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Each block has a next edge that accounts for implicit control
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transfers, e.g. from a JUMP_IF_FALSE to the block that will be
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executed if the test is true.
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These edges must remain for the current assembler code to
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work. If they are removed, the dfs_postorder gets things in
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weird orders. However, they shouldn't be there for other
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purposes, e.g. conversion to SSA form. This method will
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remove the next edge when it follows an unconditional control
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transfer.
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"""
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try:
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op, arg = self.insts[-1]
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except (IndexError, ValueError):
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return
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if op in self._uncond_transfer:
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self.next = []
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def get_children(self):
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if self.next and self.next[0] in self.outEdges:
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self.outEdges.remove(self.next[0])
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return self.outEdges.elements() + self.next
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def getContainedGraphs(self):
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"""Return all graphs contained within this block.
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For example, a MAKE_FUNCTION block will contain a reference to
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the graph for the function body.
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"""
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contained = []
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for inst in self.insts:
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if len(inst) == 1:
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continue
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op = inst[1]
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if hasattr(op, 'graph'):
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contained.append(op.graph)
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return contained
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# flags for code objects
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CO_OPTIMIZED = 0x0001
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CO_NEWLOCALS = 0x0002
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CO_VARARGS = 0x0004
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CO_VARKEYWORDS = 0x0008
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CO_NESTED = 0x0010
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# the FlowGraph is transformed in place; it exists in one of these states
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RAW = "RAW"
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FLAT = "FLAT"
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CONV = "CONV"
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DONE = "DONE"
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class PyFlowGraph(FlowGraph):
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super_init = FlowGraph.__init__
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def __init__(self, name, filename, args=(), optimized=0):
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self.super_init()
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self.name = name
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self.filename = filename
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self.docstring = None
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self.args = args # XXX
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self.argcount = getArgCount(args)
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if optimized:
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self.flags = CO_OPTIMIZED | CO_NEWLOCALS
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else:
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self.flags = 0
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self.consts = []
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self.names = []
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# Free variables found by the symbol table scan, including
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# variables used only in nested scopes, are included here.
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self.freevars = []
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self.cellvars = []
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# The closure list is used to track the order of cell
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# variables and free variables in the resulting code object.
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# The offsets used by LOAD_CLOSURE/LOAD_DEREF refer to both
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# kinds of variables.
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self.closure = []
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self.varnames = list(args) or []
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for i in range(len(self.varnames)):
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var = self.varnames[i]
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if isinstance(var, TupleArg):
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self.varnames[i] = var.getName()
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self.stage = RAW
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def setDocstring(self, doc):
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self.docstring = doc
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def setFlag(self, flag):
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self.flags = self.flags | flag
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if flag == CO_VARARGS:
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self.argcount = self.argcount - 1
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def setFreeVars(self, names):
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self.freevars = list(names)
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def setCellVars(self, names):
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self.cellvars = names
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def getCode(self):
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"""Get a Python code object"""
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if self.stage == RAW:
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self.flattenGraph()
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if self.stage == FLAT:
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self.convertArgs()
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if self.stage == CONV:
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self.makeByteCode()
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if self.stage == DONE:
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return self.newCodeObject()
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raise RuntimeError, "inconsistent PyFlowGraph state"
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def dump(self, io=None):
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if io:
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save = sys.stdout
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sys.stdout = io
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pc = 0
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for t in self.insts:
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opname = t[0]
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if opname == "SET_LINENO":
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print
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if len(t) == 1:
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print "\t", "%3d" % pc, opname
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pc = pc + 1
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else:
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print "\t", "%3d" % pc, opname, t[1]
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pc = pc + 3
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if io:
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sys.stdout = save
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def flattenGraph(self):
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"""Arrange the blocks in order and resolve jumps"""
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assert self.stage == RAW
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self.insts = insts = []
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pc = 0
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begin = {}
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end = {}
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for b in self.getBlocksInOrder():
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begin[b] = pc
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for inst in b.getInstructions():
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insts.append(inst)
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if len(inst) == 1:
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pc = pc + 1
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else:
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# arg takes 2 bytes
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pc = pc + 3
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end[b] = pc
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pc = 0
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for i in range(len(insts)):
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inst = insts[i]
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if len(inst) == 1:
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pc = pc + 1
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else:
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pc = pc + 3
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opname = inst[0]
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if self.hasjrel.has_elt(opname):
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oparg = inst[1]
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offset = begin[oparg] - pc
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insts[i] = opname, offset
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elif self.hasjabs.has_elt(opname):
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insts[i] = opname, begin[inst[1]]
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self.stacksize = findDepth(self.insts)
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self.stage = FLAT
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hasjrel = misc.Set()
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for i in dis.hasjrel:
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hasjrel.add(dis.opname[i])
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hasjabs = misc.Set()
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for i in dis.hasjabs:
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hasjabs.add(dis.opname[i])
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def convertArgs(self):
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"""Convert arguments from symbolic to concrete form"""
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assert self.stage == FLAT
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self.consts.insert(0, self.docstring)
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self.sort_cellvars()
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for i in range(len(self.insts)):
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t = self.insts[i]
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if len(t) == 2:
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opname = t[0]
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oparg = t[1]
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conv = self._converters.get(opname, None)
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if conv:
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self.insts[i] = opname, conv(self, oparg)
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self.stage = CONV
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def sort_cellvars(self):
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"""Sort cellvars in the order of varnames and prune from freevars.
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"""
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cells = {}
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for name in self.cellvars:
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cells[name] = 1
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self.cellvars = [name for name in self.varnames
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if cells.has_key(name)]
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for name in self.cellvars:
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del cells[name]
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self.cellvars = self.cellvars + cells.keys()
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self.closure = self.cellvars + self.freevars
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def _lookupName(self, name, list):
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"""Return index of name in list, appending if necessary"""
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t = type(name)
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for i in range(len(list)):
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# must do a comparison on type first to prevent UnicodeErrors
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if t == type(list[i]) and list[i] == name:
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return i
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end = len(list)
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list.append(name)
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return end
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_converters = {}
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def _convert_LOAD_CONST(self, arg):
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if hasattr(arg, 'getCode'):
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arg = arg.getCode()
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return self._lookupName(arg, self.consts)
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def _convert_LOAD_FAST(self, arg):
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self._lookupName(arg, self.names)
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return self._lookupName(arg, self.varnames)
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_convert_STORE_FAST = _convert_LOAD_FAST
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_convert_DELETE_FAST = _convert_LOAD_FAST
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def _convert_NAME(self, arg):
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return self._lookupName(arg, self.names)
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_convert_LOAD_NAME = _convert_NAME
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_convert_STORE_NAME = _convert_NAME
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_convert_DELETE_NAME = _convert_NAME
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_convert_IMPORT_NAME = _convert_NAME
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_convert_IMPORT_FROM = _convert_NAME
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_convert_STORE_ATTR = _convert_NAME
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_convert_LOAD_ATTR = _convert_NAME
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_convert_DELETE_ATTR = _convert_NAME
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_convert_LOAD_GLOBAL = _convert_NAME
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_convert_STORE_GLOBAL = _convert_NAME
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_convert_DELETE_GLOBAL = _convert_NAME
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def _convert_DEREF(self, arg):
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self._lookupName(arg, self.names)
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self._lookupName(arg, self.varnames)
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return self._lookupName(arg, self.closure)
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_convert_LOAD_DEREF = _convert_DEREF
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_convert_STORE_DEREF = _convert_DEREF
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def _convert_LOAD_CLOSURE(self, arg):
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self._lookupName(arg, self.varnames)
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return self._lookupName(arg, self.closure)
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_cmp = list(dis.cmp_op)
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def _convert_COMPARE_OP(self, arg):
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return self._cmp.index(arg)
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# similarly for other opcodes...
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for name, obj in locals().items():
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if name[:9] == "_convert_":
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opname = name[9:]
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_converters[opname] = obj
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del name, obj, opname
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def makeByteCode(self):
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assert self.stage == CONV
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self.lnotab = lnotab = LineAddrTable()
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for t in self.insts:
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opname = t[0]
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if len(t) == 1:
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lnotab.addCode(self.opnum[opname])
|
|
else:
|
|
oparg = t[1]
|
|
if opname == "SET_LINENO":
|
|
lnotab.nextLine(oparg)
|
|
hi, lo = twobyte(oparg)
|
|
try:
|
|
lnotab.addCode(self.opnum[opname], lo, hi)
|
|
except ValueError:
|
|
print opname, oparg
|
|
print self.opnum[opname], lo, hi
|
|
raise
|
|
self.stage = DONE
|
|
|
|
opnum = {}
|
|
for num in range(len(dis.opname)):
|
|
opnum[dis.opname[num]] = num
|
|
del num
|
|
|
|
def newCodeObject(self):
|
|
assert self.stage == DONE
|
|
if self.flags == 0:
|
|
nlocals = 0
|
|
else:
|
|
nlocals = len(self.varnames)
|
|
argcount = self.argcount
|
|
if self.flags & CO_VARKEYWORDS:
|
|
argcount = argcount - 1
|
|
return new.code(argcount, nlocals, self.stacksize, self.flags,
|
|
self.lnotab.getCode(), self.getConsts(),
|
|
tuple(self.names), tuple(self.varnames),
|
|
self.filename, self.name, self.lnotab.firstline,
|
|
self.lnotab.getTable(), tuple(self.freevars),
|
|
tuple(self.cellvars))
|
|
|
|
def getConsts(self):
|
|
"""Return a tuple for the const slot of the code object
|
|
|
|
Must convert references to code (MAKE_FUNCTION) to code
|
|
objects recursively.
|
|
"""
|
|
l = []
|
|
for elt in self.consts:
|
|
if isinstance(elt, PyFlowGraph):
|
|
elt = elt.getCode()
|
|
l.append(elt)
|
|
return tuple(l)
|
|
|
|
def isJump(opname):
|
|
if opname[:4] == 'JUMP':
|
|
return 1
|
|
|
|
class TupleArg:
|
|
"""Helper for marking func defs with nested tuples in arglist"""
|
|
def __init__(self, count, names):
|
|
self.count = count
|
|
self.names = names
|
|
def __repr__(self):
|
|
return "TupleArg(%s, %s)" % (self.count, self.names)
|
|
def getName(self):
|
|
return ".%d" % self.count
|
|
|
|
def getArgCount(args):
|
|
argcount = len(args)
|
|
if args:
|
|
for arg in args:
|
|
if isinstance(arg, TupleArg):
|
|
numNames = len(misc.flatten(arg.names))
|
|
argcount = argcount - numNames
|
|
return argcount
|
|
|
|
def twobyte(val):
|
|
"""Convert an int argument into high and low bytes"""
|
|
assert type(val) == types.IntType
|
|
return divmod(val, 256)
|
|
|
|
class LineAddrTable:
|
|
"""lnotab
|
|
|
|
This class builds the lnotab, which is documented in compile.c.
|
|
Here's a brief recap:
|
|
|
|
For each SET_LINENO instruction after the first one, two bytes are
|
|
added to lnotab. (In some cases, multiple two-byte entries are
|
|
added.) The first byte is the distance in bytes between the
|
|
instruction for the last SET_LINENO and the current SET_LINENO.
|
|
The second byte is offset in line numbers. If either offset is
|
|
greater than 255, multiple two-byte entries are added -- see
|
|
compile.c for the delicate details.
|
|
"""
|
|
|
|
def __init__(self):
|
|
self.code = []
|
|
self.codeOffset = 0
|
|
self.firstline = 0
|
|
self.lastline = 0
|
|
self.lastoff = 0
|
|
self.lnotab = []
|
|
|
|
def addCode(self, *args):
|
|
for arg in args:
|
|
self.code.append(chr(arg))
|
|
self.codeOffset = self.codeOffset + len(args)
|
|
|
|
def nextLine(self, lineno):
|
|
if self.firstline == 0:
|
|
self.firstline = lineno
|
|
self.lastline = lineno
|
|
else:
|
|
# compute deltas
|
|
addr = self.codeOffset - self.lastoff
|
|
line = lineno - self.lastline
|
|
# Python assumes that lineno always increases with
|
|
# increasing bytecode address (lnotab is unsigned char).
|
|
# Depending on when SET_LINENO instructions are emitted
|
|
# this is not always true. Consider the code:
|
|
# a = (1,
|
|
# b)
|
|
# In the bytecode stream, the assignment to "a" occurs
|
|
# after the loading of "b". This works with the C Python
|
|
# compiler because it only generates a SET_LINENO instruction
|
|
# for the assignment.
|
|
if line > 0:
|
|
push = self.lnotab.append
|
|
while addr > 255:
|
|
push(255); push(0)
|
|
addr -= 255
|
|
while line > 255:
|
|
push(addr); push(255)
|
|
line -= 255
|
|
addr = 0
|
|
if addr > 0 or line > 0:
|
|
push(addr); push(line)
|
|
self.lastline = lineno
|
|
self.lastoff = self.codeOffset
|
|
|
|
def getCode(self):
|
|
return string.join(self.code, '')
|
|
|
|
def getTable(self):
|
|
return string.join(map(chr, self.lnotab), '')
|
|
|
|
class StackDepthTracker:
|
|
# XXX 1. need to keep track of stack depth on jumps
|
|
# XXX 2. at least partly as a result, this code is broken
|
|
|
|
def findDepth(self, insts):
|
|
depth = 0
|
|
maxDepth = 0
|
|
for i in insts:
|
|
opname = i[0]
|
|
delta = self.effect.get(opname, 0)
|
|
if delta > 1:
|
|
depth = depth + delta
|
|
elif delta < 0:
|
|
if depth > maxDepth:
|
|
maxDepth = depth
|
|
depth = depth + delta
|
|
else:
|
|
if depth > maxDepth:
|
|
maxDepth = depth
|
|
# now check patterns
|
|
for pat, pat_delta in self.patterns:
|
|
if opname[:len(pat)] == pat:
|
|
delta = pat_delta
|
|
depth = depth + delta
|
|
break
|
|
# if we still haven't found a match
|
|
if delta == 0:
|
|
meth = getattr(self, opname, None)
|
|
if meth is not None:
|
|
depth = depth + meth(i[1])
|
|
if depth < 0:
|
|
depth = 0
|
|
return maxDepth
|
|
|
|
effect = {
|
|
'POP_TOP': -1,
|
|
'DUP_TOP': 1,
|
|
'SLICE+1': -1,
|
|
'SLICE+2': -1,
|
|
'SLICE+3': -2,
|
|
'STORE_SLICE+0': -1,
|
|
'STORE_SLICE+1': -2,
|
|
'STORE_SLICE+2': -2,
|
|
'STORE_SLICE+3': -3,
|
|
'DELETE_SLICE+0': -1,
|
|
'DELETE_SLICE+1': -2,
|
|
'DELETE_SLICE+2': -2,
|
|
'DELETE_SLICE+3': -3,
|
|
'STORE_SUBSCR': -3,
|
|
'DELETE_SUBSCR': -2,
|
|
# PRINT_EXPR?
|
|
'PRINT_ITEM': -1,
|
|
'LOAD_LOCALS': 1,
|
|
'RETURN_VALUE': -1,
|
|
'EXEC_STMT': -2,
|
|
'BUILD_CLASS': -2,
|
|
'STORE_NAME': -1,
|
|
'STORE_ATTR': -2,
|
|
'DELETE_ATTR': -1,
|
|
'STORE_GLOBAL': -1,
|
|
'BUILD_MAP': 1,
|
|
'COMPARE_OP': -1,
|
|
'STORE_FAST': -1,
|
|
'IMPORT_STAR': -1,
|
|
'IMPORT_NAME': 0,
|
|
'IMPORT_FROM': 1,
|
|
}
|
|
# use pattern match
|
|
patterns = [
|
|
('BINARY_', -1),
|
|
('LOAD_', 1),
|
|
]
|
|
|
|
# special cases:
|
|
# UNPACK_SEQUENCE, BUILD_TUPLE,
|
|
# BUILD_LIST, CALL_FUNCTION, MAKE_FUNCTION, BUILD_SLICE
|
|
def UNPACK_SEQUENCE(self, count):
|
|
return count
|
|
def BUILD_TUPLE(self, count):
|
|
return -count
|
|
def BUILD_LIST(self, count):
|
|
return -count
|
|
def CALL_FUNCTION(self, argc):
|
|
hi, lo = divmod(argc, 256)
|
|
return lo + hi * 2
|
|
def CALL_FUNCTION_VAR(self, argc):
|
|
return self.CALL_FUNCTION(argc)+1
|
|
def CALL_FUNCTION_KW(self, argc):
|
|
return self.CALL_FUNCTION(argc)+1
|
|
def CALL_FUNCTION_VAR_KW(self, argc):
|
|
return self.CALL_FUNCTION(argc)+2
|
|
def MAKE_FUNCTION(self, argc):
|
|
return -argc
|
|
def BUILD_SLICE(self, argc):
|
|
if argc == 2:
|
|
return -1
|
|
elif argc == 3:
|
|
return -2
|
|
|
|
findDepth = StackDepthTracker().findDepth
|