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656 lines
20 KiB
Python
656 lines
20 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 " ", 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, force=0):
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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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# hack alert
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if not self.exit in order:
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order.append(self.exit)
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## for b in order:
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## print repr(b)
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## print "\t", b.get_children()
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## print b
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## print
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return order
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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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# 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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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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self.consts.insert(0, 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 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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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 _lookupName(self, name, list):
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"""Return index of name in list, appending if necessary"""
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found = None
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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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found = 1
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break
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if found:
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# this is cheap, but incorrect in some cases, e.g 2 vs. 2L
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if type(name) == type(list[i]):
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return i
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for i in range(len(list)):
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elt = list[i]
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if type(elt) == type(name) and elt == 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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_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])
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else:
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oparg = t[1]
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if opname == "SET_LINENO":
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lnotab.nextLine(oparg)
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hi, lo = twobyte(oparg)
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try:
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lnotab.addCode(self.opnum[opname], lo, hi)
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except ValueError:
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print opname, oparg
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print self.opnum[opname], lo, hi
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raise
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self.stage = DONE
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opnum = {}
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for num in range(len(dis.opname)):
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opnum[dis.opname[num]] = num
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del num
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def newCodeObject(self):
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assert self.stage == DONE
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if self.flags == 0:
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nlocals = 0
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else:
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nlocals = len(self.varnames)
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argcount = self.argcount
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if self.flags & CO_VARKEYWORDS:
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argcount = argcount - 1
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return new.code(argcount, nlocals, self.stacksize, self.flags,
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self.lnotab.getCode(), self.getConsts(),
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tuple(self.names), tuple(self.varnames),
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self.filename, self.name, self.lnotab.firstline,
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self.lnotab.getTable())
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def getConsts(self):
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"""Return a tuple for the const slot of the code object
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Must convert references to code (MAKE_FUNCTION) to code
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objects recursively.
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"""
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l = []
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for elt in self.consts:
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if isinstance(elt, PyFlowGraph):
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elt = elt.getCode()
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l.append(elt)
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return tuple(l)
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def isJump(opname):
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if opname[:4] == 'JUMP':
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return 1
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class TupleArg:
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"""Helper for marking func defs with nested tuples in arglist"""
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def __init__(self, count, names):
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self.count = count
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self.names = names
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def __repr__(self):
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return "TupleArg(%s, %s)" % (self.count, self.names)
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def getName(self):
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return ".nested%d" % self.count
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def getArgCount(args):
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argcount = len(args)
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if args:
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for arg in args:
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if isinstance(arg, TupleArg):
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numNames = len(misc.flatten(arg.names))
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argcount = argcount - numNames
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return argcount
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def twobyte(val):
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"""Convert an int argument into high and low bytes"""
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assert type(val) == types.IntType
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return divmod(val, 256)
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class LineAddrTable:
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"""lnotab
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This class builds the lnotab, which is undocumented but described
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by com_set_lineno in compile.c. Here's an attempt at explanation:
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For each SET_LINENO instruction after the first one, two bytes are
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added to lnotab. (In some cases, multiple two-byte entries are
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added.) The first byte is the distance in bytes between the
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instruction for the last SET_LINENO and the current SET_LINENO.
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The second byte is offset in line numbers. If either offset is
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greater than 255, multiple two-byte entries are added -- one entry
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for each factor of 255.
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"""
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def __init__(self):
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self.code = []
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self.codeOffset = 0
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self.firstline = 0
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self.lastline = 0
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self.lastoff = 0
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self.lnotab = []
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def addCode(self, *args):
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for arg in args:
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self.code.append(chr(arg))
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self.codeOffset = self.codeOffset + len(args)
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def nextLine(self, lineno):
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if self.firstline == 0:
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self.firstline = lineno
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self.lastline = lineno
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else:
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# compute deltas
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addr = self.codeOffset - self.lastoff
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line = lineno - self.lastline
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# Python assumes that lineno always increases with
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# increasing bytecode address (lnotab is unsigned char).
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# Depending on when SET_LINENO instructions are emitted
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# this is not always true. Consider the code:
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# a = (1,
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# b)
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# In the bytecode stream, the assignment to "a" occurs
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# after the loading of "b". This works with the C Python
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# compiler because it only generates a SET_LINENO instruction
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# for the assignment.
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if line > 0:
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while addr > 0 or line > 0:
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# write the values in 1-byte chunks that sum
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# to desired value
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trunc_addr = addr
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trunc_line = line
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if trunc_addr > 255:
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trunc_addr = 255
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if trunc_line > 255:
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trunc_line = 255
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self.lnotab.append(trunc_addr)
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self.lnotab.append(trunc_line)
|
|
addr = addr - trunc_addr
|
|
line = line - trunc_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
|