/rpython/translator/c/gcc/trackgcroot.py

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#! /usr/bin/env python
import re, sys, os, random

sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..', '..', '..', '..'))

from rpython.translator.c.gcc.instruction import Insn, Label, InsnCall, InsnRet
from rpython.translator.c.gcc.instruction import InsnFunctionStart, InsnStop
from rpython.translator.c.gcc.instruction import InsnSetLocal, InsnCopyLocal
from rpython.translator.c.gcc.instruction import InsnPrologue, InsnEpilogue
from rpython.translator.c.gcc.instruction import InsnGCROOT, InsnCondJump
from rpython.translator.c.gcc.instruction import InsnStackAdjust
from rpython.translator.c.gcc.instruction import InsnCannotFollowEsp
from rpython.translator.c.gcc.instruction import LocalVar, somenewvalue
from rpython.translator.c.gcc.instruction import frameloc_esp, frameloc_ebp
from rpython.translator.c.gcc.instruction import LOC_REG, LOC_NOWHERE, LOC_MASK
from rpython.translator.c.gcc.instruction import LOC_EBP_PLUS, LOC_EBP_MINUS
from rpython.translator.c.gcc.instruction import LOC_ESP_PLUS

class FunctionGcRootTracker(object):
    skip = 0
    COMMENT = "([#;].*)?"

    @classmethod
    def init_regexp(cls):
        cls.r_label         = re.compile(cls.LABEL+"[:]\s*$")
        cls.r_globl         = re.compile(r"\t[.]globl\t"+cls.LABEL+"\s*$")
        cls.r_globllabel    = re.compile(cls.LABEL+r"=[.][+]%d\s*$"%cls.OFFSET_LABELS)

        cls.r_insn          = re.compile(r"\t([a-z]\w*)\s")
        cls.r_unaryinsn     = re.compile(r"\t[a-z]\w*\s+("+cls.OPERAND+")\s*" + cls.COMMENT + "$")
        cls.r_binaryinsn    = re.compile(r"\t[a-z]\w*\s+(?P<source>"+cls.OPERAND+"),\s*(?P<target>"+cls.OPERAND+")\s*$")

        cls.r_jump          = re.compile(r"\tj\w+\s+"+cls.LABEL+"\s*" + cls.COMMENT + "$")
        cls.r_jmp_switch    = re.compile(r"\tjmp\t[*]"+cls.LABEL+"[(]")
        cls.r_jmp_source    = re.compile(r"\d*[(](%[\w]+)[,)]")

    def __init__(self, funcname, lines, filetag=0):
        self.funcname = funcname
        self.lines = lines
        self.uses_frame_pointer = False
        self.r_localvar = self.r_localvarnofp
        self.filetag = filetag
        # a "stack bottom" function is either pypy_main_function() or a
        # callback from C code.  In both cases they are identified by
        # the presence of pypy_asm_stack_bottom().
        self.is_stack_bottom = False

    def computegcmaptable(self, verbose=0):
        if self.funcname in ['main', '_main']:
            return []     # don't analyze main(), its prologue may contain
                          # strange instructions
        self.findlabels()
        self.parse_instructions()
        try:
            self.trim_unreachable_instructions()
            self.find_noncollecting_calls()
            if not self.list_collecting_call_insns():
                return []
            self.findframesize()
            self.fixlocalvars()
            self.trackgcroots()
            self.extend_calls_with_labels()
        finally:
            if verbose > 2:
                self.dump()
        return self.gettable()

    def replace_symbols(self, operand):
        return operand

    def gettable(self):
        """Returns a list [(label_after_call, callshape_tuple)]
        See format_callshape() for more details about callshape_tuple.
        """
        table = []
        for insn in self.list_collecting_call_insns():
            if not hasattr(insn, 'framesize'):
                continue     # calls that never end up reaching a RET
            if self.is_stack_bottom:
                retaddr = LOC_NOWHERE     # end marker for asmgcroot.py
            elif self.uses_frame_pointer:
                retaddr = frameloc_ebp(self.WORD, self.WORD)
            else:
                retaddr = frameloc_esp(insn.framesize, self.WORD)
            shape = [retaddr]
            # the first gcroots are always the ones corresponding to
            # the callee-saved registers
            for reg in self.CALLEE_SAVE_REGISTERS:
                shape.append(LOC_NOWHERE)
            gcroots = []
            for localvar, tag in insn.gcroots.items():
                if isinstance(localvar, LocalVar):
                    loc = localvar.getlocation(insn.framesize,
                                               self.uses_frame_pointer,
                                               self.WORD)
                elif localvar in self.REG2LOC:
                    loc = self.REG2LOC[localvar]
                else:
                    assert False, "%s: %s" % (self.funcname,
                                              localvar)
                assert isinstance(loc, int)
                if tag is None:
                    gcroots.append(loc)
                else:
                    regindex = self.CALLEE_SAVE_REGISTERS.index(tag)
                    shape[1 + regindex] = loc
            if LOC_NOWHERE in shape and not self.is_stack_bottom:
                reg = self.CALLEE_SAVE_REGISTERS[shape.index(LOC_NOWHERE) - 1]
                raise AssertionError("cannot track where register %s is saved"
                                     % (reg,))
            gcroots.sort()
            shape.extend(gcroots)
            table.append((insn.global_label, tuple(shape)))
        return table

    def findlabels(self):
        self.labels = {}      # {name: Label()}
        for lineno, line in enumerate(self.lines):
            match = self.r_label.match(line)
            label = None
            if match:
                label = match.group(1)
            else:
                # labels used by: j* NNNf
                match = self.r_rel_label.match(line)
                if match:
                    label = "rel %d" % lineno
            if label:
                assert label not in self.labels, "duplicate label: %s" % label
                self.labels[label] = Label(label, lineno)

    def trim_unreachable_instructions(self):
        reached = set([self.insns[0]])
        prevlen = 0
        while len(reached) > prevlen:
            prevlen = len(reached)
            for insn in self.insns:
                if insn not in reached:
                    for previnsn in insn.previous_insns:
                        if previnsn in reached:
                            # this instruction is reachable too
                            reached.add(insn)
                            break
        # now kill all unreachable instructions
        i = 0
        while i < len(self.insns):
            if self.insns[i] in reached:
                i += 1
            else:
                del self.insns[i]

    def find_noncollecting_calls(self):
        cannot_collect = {}
        for line in self.lines:
            match = self.r_gcnocollect_marker.search(line)
            if match:
                name = match.group(1)
                cannot_collect[name] = True
        #
        self.cannot_collect = dict.fromkeys(
            [self.function_names_prefix + name for name in cannot_collect])

    def append_instruction(self, insn):
        # Add the instruction to the list, and link it to the previous one.
        previnsn = self.insns[-1]
        self.insns.append(insn)
        if (isinstance(insn, (InsnSetLocal, InsnCopyLocal)) and
            insn.target == self.tested_for_zero):
            self.tested_for_zero = None

        try:
            lst = insn.previous_insns
        except AttributeError:
            lst = insn.previous_insns = []
        if not isinstance(previnsn, InsnStop):
            lst.append(previnsn)

    def parse_instructions(self):
        self.insns = [InsnFunctionStart(self.CALLEE_SAVE_REGISTERS, self.WORD)]
        self.tested_for_zero = None
        ignore_insns = False
        for lineno, line in enumerate(self.lines):
            if lineno < self.skip:
                continue
            self.currentlineno = lineno
            insn = []
            if line.startswith('\trep;'):
                line = '\t'+line[5:].lstrip()
            match = self.r_insn.match(line)

            if self.r_bottom_marker.match(line):
                self.is_stack_bottom = True
            elif match:
                if not ignore_insns:
                    opname = match.group(1)
                    #
                    try:
                        cf = self.OPS_WITH_PREFIXES_CHANGING_FLAGS[opname]
                    except KeyError:
                        cf = self.find_missing_changing_flags(opname)
                    if cf:
                        self.tested_for_zero = None
                    #
                    try:
                        meth = getattr(self, 'visit_' + opname)
                    except AttributeError:
                        self.find_missing_visit_method(opname)
                        meth = getattr(self, 'visit_' + opname)
                    line = line.rsplit(';', 1)[0]
                    insn = meth(line)
            elif self.r_gcroot_marker.match(line):
                insn = self._visit_gcroot_marker(line)
            elif line == '\t/* ignore_in_trackgcroot */\n':
                ignore_insns = True
            elif line == '\t/* end_ignore_in_trackgcroot */\n':
                ignore_insns = False
            else:
                match = self.r_label.match(line)
                if match:
                    insn = self.labels[match.group(1)]

            if isinstance(insn, list):
                for i in insn:
                    self.append_instruction(i)
            else:
                self.append_instruction(insn)

        del self.currentlineno

    @classmethod
    def find_missing_visit_method(cls, opname):
        # only for operations that are no-ops as far as we are concerned
        prefix = opname
        while prefix not in cls.IGNORE_OPS_WITH_PREFIXES:
            prefix = prefix[:-1]
            if not prefix:
                raise UnrecognizedOperation(opname)
        setattr(cls, 'visit_' + opname, cls.visit_nop)

    @classmethod
    def find_missing_changing_flags(cls, opname):
        prefix = opname
        while prefix and prefix not in cls.OPS_WITH_PREFIXES_CHANGING_FLAGS:
            prefix = prefix[:-1]
        cf = cls.OPS_WITH_PREFIXES_CHANGING_FLAGS.get(prefix, False)
        cls.OPS_WITH_PREFIXES_CHANGING_FLAGS[opname] = cf
        return cf

    def list_collecting_call_insns(self):
        return [insn for insn in self.insns if isinstance(insn, InsnCall)
                     if insn.name not in self.cannot_collect]

    def findframesize(self):
        # the 'framesize' attached to an instruction is the number of bytes
        # in the frame at this point.  This doesn't count the return address
        # which is the word immediately following the frame in memory.
        # The 'framesize' is set to an odd value if it is only an estimate
        # (see InsnCannotFollowEsp).

        def walker(insn, size_delta):
            check = deltas.setdefault(insn, size_delta)
            assert check == size_delta, (
                "inconsistent frame size at instruction %s" % (insn,))
            if isinstance(insn, InsnStackAdjust):
                size_delta -= insn.delta
            if not hasattr(insn, 'framesize'):
                yield size_delta   # continue walking backwards

        for insn in self.insns:
            if isinstance(insn, (InsnRet, InsnEpilogue, InsnGCROOT)):
                deltas = {}
                self.walk_instructions_backwards(walker, insn, 0)
                size_at_insn = []
                for insn1, delta1 in deltas.items():
                    if hasattr(insn1, 'framesize'):
                        size_at_insn.append(insn1.framesize + delta1)
                if not size_at_insn:
                    continue
                size_at_insn = size_at_insn[0]
                for insn1, delta1 in deltas.items():
                    size_at_insn1 = size_at_insn - delta1
                    if hasattr(insn1, 'framesize'):
                        assert insn1.framesize == size_at_insn1, (
                            "inconsistent frame size at instruction %s" %
                            (insn1,))
                    else:
                        insn1.framesize = size_at_insn1

    def fixlocalvars(self):
        def fixvar(localvar):
            if localvar is None:
                return None
            elif isinstance(localvar, (list, tuple)):
                return [fixvar(var) for var in localvar]

            match = self.r_localvar_esp.match(localvar)
            if match:
                if localvar == self.TOP_OF_STACK_MINUS_WORD:
                                                  # for pushl and popl, by
                    hint = None                   # default ebp addressing is
                else:                             # a bit nicer
                    hint = 'esp'
                ofs_from_esp = int(match.group(1) or '0')
                if self.format == 'msvc':
                    ofs_from_esp += int(match.group(2) or '0')
                localvar = ofs_from_esp - insn.framesize
                assert localvar != 0    # that's the return address
                return LocalVar(localvar, hint=hint)
            elif self.uses_frame_pointer:
                match = self.r_localvar_ebp.match(localvar)
                if match:
                    ofs_from_ebp = int(match.group(1) or '0')
                    if self.format == 'msvc':
                        ofs_from_ebp += int(match.group(2) or '0')
                    localvar = ofs_from_ebp - self.WORD
                    assert localvar != 0    # that's the return address
                    return LocalVar(localvar, hint='ebp')
            return localvar

        for insn in self.insns:
            if not hasattr(insn, 'framesize'):
                continue
            for name in insn._locals_:
                localvar = getattr(insn, name)
                setattr(insn, name, fixvar(localvar))

    def trackgcroots(self):

        def walker(insn, loc):
            source = insn.source_of(loc, tag)
            if source is somenewvalue:
                pass   # done
            else:
                yield source

        for insn in self.insns:
            for loc, tag in insn.requestgcroots(self).items():
                self.walk_instructions_backwards(walker, insn, loc)

    def dump(self):
        for insn in self.insns:
            size = getattr(insn, 'framesize', '?')
            print >> sys.stderr, '%4s  %s' % (size, insn)

    def walk_instructions_backwards(self, walker, initial_insn, initial_state):
        pending = []
        seen = set()
        def schedule(insn, state):
            for previnsn in insn.previous_insns:
                key = previnsn, state
                if key not in seen:
                    seen.add(key)
                    pending.append(key)
        schedule(initial_insn, initial_state)
        while pending:
            insn, state = pending.pop()
            for prevstate in walker(insn, state):
                schedule(insn, prevstate)

    def extend_calls_with_labels(self):
        # walk backwards, because inserting the global labels in self.lines
        # is going to invalidate the lineno of all the InsnCall objects
        # after the current one.
        for call in self.list_collecting_call_insns()[::-1]:
            if hasattr(call, 'framesize'):
                self.create_global_label(call)

    def create_global_label(self, call):
        # we need a globally-declared label just after the call.
        # Reuse one if it is already there (e.g. from a previous run of this
        # script); otherwise invent a name and add the label to tracker.lines.
        label = None
        # this checks for a ".globl NAME" followed by "NAME:"
        match = self.r_globl.match(self.lines[call.lineno+1])
        if match:
            label1 = match.group(1)
            match = self.r_globllabel.match(self.lines[call.lineno+2])
            if match:
                label2 = match.group(1)
                if label1 == label2:
                    label = label2
        if label is None:
            k = call.lineno
            if self.format == 'msvc':
                # Some header files (ws2tcpip.h) define STDCALL functions
                funcname = self.funcname.split('@')[0]
            else:
                funcname = self.funcname
            while 1:
                label = '__gcmap_%s__%s_%d' % (self.filetag, funcname, k)
                if label not in self.labels:
                    break
                k += 1
            self.labels[label] = None
            if self.format == 'msvc':
                self.lines.insert(call.lineno+1, '%s::\n' % (label,))
                self.lines.insert(call.lineno+1, 'PUBLIC\t%s\n' % (label,))
            else:
                # These global symbols are not directly labels pointing to the
                # code location because such global labels in the middle of
                # functions confuse gdb.  Instead, we add to the global symbol's
                # value a big constant, which is subtracted again when we need
                # the original value for gcmaptable.s.  That's a hack.
                self.lines.insert(call.lineno+1, '%s=.+%d\n' % (label,
                                                                self.OFFSET_LABELS))
                self.lines.insert(call.lineno+1, '\t.globl\t%s\n' % (label,))
        call.global_label = label

    @classmethod
    def compress_callshape(cls, shape):
        # For a single shape, this turns the list of integers into a list of
        # bytes and reverses the order of the entries.  The length is
        # encoded by inserting a 0 marker after the gc roots coming from
        # shape[N:] and before the N values coming from shape[N-1] to
        # shape[0] (for N == 5 on 32-bit or 7 on 64-bit platforms).
        # In practice it seems that shapes contain many integers
        # whose value is up to a few thousands, which the algorithm below
        # compresses down to 2 bytes.  Very small values compress down to a
        # single byte.

        # Callee-save regs plus ret addr
        min_size = len(cls.CALLEE_SAVE_REGISTERS) + 1

        assert len(shape) >= min_size
        shape = list(shape)
        assert 0 not in shape[min_size:]
        shape.insert(min_size, 0)
        result = []
        for loc in shape:
            assert loc >= 0
            flag = 0
            while loc >= 0x80:
                result.append(int(loc & 0x7F) | flag)
                flag = 0x80
                loc >>= 7
            result.append(int(loc) | flag)
        result.reverse()
        return result

    @classmethod
    def decompress_callshape(cls, bytes):
        # For tests.  This logic is copied in asmgcroot.py.
        result = []
        n = 0
        while n < len(bytes):
            value = 0
            while True:
                b = bytes[n]
                n += 1
                value += b
                if b < 0x80:
                    break
                value = (value - 0x80) << 7
            result.append(value)
        result.reverse()
        assert result[5] == 0
        del result[5]
        return result
    # ____________________________________________________________

    BASE_FUNCTIONS_NOT_RETURNING = {
        'abort': None,
        'pypy_debug_catch_fatal_exception': None,
        'RPyAbort': None,
        'RPyAssertFailed': None,
        }

    def _visit_gcroot_marker(self, line):
        match = self.r_gcroot_marker.match(line)
        loc = match.group(1)
        return InsnGCROOT(self.replace_symbols(loc))

    def visit_nop(self, line):
        return []

    IGNORE_OPS_WITH_PREFIXES = dict.fromkeys([
        'cmp', 'test', 'set', 'sahf', 'lahf', 'cld', 'std',
        'rep', 'movs', 'movhp', 'lods', 'stos', 'scas', 'cwde', 'prefetch',
        # floating-point operations cannot produce GC pointers
        'f',
        'cvt', 'ucomi', 'comi', 'subs', 'subp', 'adds', 'addp', 'xorp',
        'movap', 'movd', 'movlp', 'movup', 'sqrt', 'rsqrt', 'movhlp', 'movlhp',
        'mins', 'minp', 'maxs', 'maxp', 'unpck', 'pxor', 'por', # sse2
        'shufps', 'shufpd',
        # arithmetic operations should not produce GC pointers
        'inc', 'dec', 'not', 'neg', 'or', 'and', 'sbb', 'adc',
        'shl', 'shr', 'sal', 'sar', 'rol', 'ror', 'mul', 'imul', 'div', 'idiv',
        'bswap', 'bt', 'rdtsc', 'rounds',
        'pabs', 'pack', 'padd', 'palign', 'pand', 'pavg', 'pcmp', 'pextr',
        'phadd', 'phsub', 'pinsr', 'pmadd', 'pmax', 'pmin', 'pmovmsk',
        'pmul', 'por', 'psadb', 'pshuf', 'psign', 'psll', 'psra', 'psrl',
        'psub', 'punpck', 'pxor',
        # all vectors don't produce pointers
        'v',
        # sign-extending moves should not produce GC pointers
        'cbtw', 'cwtl', 'cwtd', 'cltd', 'cltq', 'cqto',
        # zero-extending moves should not produce GC pointers
        'movz',
        # locked operations should not move GC pointers, at least so far
        'lock', 'pause',
        # non-temporal moves should be reserved for areas containing
        # raw data, not GC pointers
        'movnt', 'mfence', 'lfence', 'sfence',
        # bit manipulations
        'bextr',
    ])

    # a partial list is hopefully good enough for now; it's all to support
    # only one corner case, tested in elf64/track_zero.s
    OPS_WITH_PREFIXES_CHANGING_FLAGS = dict.fromkeys([
        'cmp', 'test', 'lahf', 'cld', 'std', 'rep',
        'ucomi', 'comi',
        'add', 'sub', 'xor',
        'inc', 'dec', 'not', 'neg', 'or', 'and', 'sbb', 'adc',
        'shl', 'shr', 'sal', 'sar', 'rol', 'ror', 'mul', 'imul', 'div', 'idiv',
        'bt', 'call', 'int',
        'jmp',     # not really changing flags, but we shouldn't assume
                   # anything about the operations on the following lines
        ], True)

    visit_movb = visit_nop
    visit_movw = visit_nop
    visit_addb = visit_nop
    visit_addw = visit_nop
    visit_subb = visit_nop
    visit_subw = visit_nop
    visit_xorb = visit_nop
    visit_xorw = visit_nop

    def _visit_add(self, line, sign=+1):
        match = self.r_binaryinsn.match(line)
        source = match.group("source")
        target = match.group("target")
        if target == self.ESP:
            count = self.extract_immediate(source)
            if count is None:
                # strange instruction - I've seen 'subl %eax, %esp'
                return InsnCannotFollowEsp()
            return InsnStackAdjust(sign * count)
        elif self.r_localvar.match(target):
            return InsnSetLocal(target, [source, target])
        else:
            return []

    def _visit_sub(self, line):
        return self._visit_add(line, sign=-1)

    def unary_insn(self, line):
        match = self.r_unaryinsn.match(line)
        target = match.group(1)
        if self.r_localvar.match(target):
            return InsnSetLocal(target)
        else:
            return []

    def binary_insn(self, line):
        match = self.r_binaryinsn.match(line)
        if not match:
            raise UnrecognizedOperation(line)
        source = match.group("source")
        target = match.group("target")
        if self.r_localvar.match(target):
            return InsnSetLocal(target, [source])
        elif target == self.ESP:
            raise UnrecognizedOperation(line)
        else:
            return []

    # The various cmov* operations
    for name in '''
        e ne g ge l le a ae b be p np s ns o no
        '''.split():
        locals()['visit_cmov' + name] = binary_insn
        locals()['visit_cmov' + name + 'l'] = binary_insn

    def _visit_and(self, line):
        match = self.r_binaryinsn.match(line)
        target = match.group("target")
        if target == self.ESP:
            # only for  andl $-16, %esp  used to align the stack in main().
            # main() should not be seen at all.  But on e.g. MSVC we see
            # the instruction somewhere else too...
            return InsnCannotFollowEsp()
        else:
            return self.binary_insn(line)

    def _visit_lea(self, line):
        match = self.r_binaryinsn.match(line)
        target = match.group("target")
        if target == self.ESP:
            # only for  leal -12(%ebp), %esp  in function epilogues
            source = match.group("source")
            match = self.r_localvar_ebp.match(source)
            if match:
                if not self.uses_frame_pointer:
                    raise UnrecognizedOperation('epilogue without prologue')
                ofs_from_ebp = int(match.group(1) or '0')
                assert ofs_from_ebp <= 0
                framesize = self.WORD - ofs_from_ebp
            else:
                match = self.r_localvar_esp.match(source)
                # leal 12(%esp), %esp
                if match:
                    return InsnStackAdjust(int(match.group(1)))

                framesize = None    # strange instruction
            return InsnEpilogue(framesize)
        else:
            return self.binary_insn(line)

    def insns_for_copy(self, source, target):
        source = self.replace_symbols(source)
        target = self.replace_symbols(target)
        if target == self.ESP:
            raise UnrecognizedOperation('%s -> %s' % (source, target))
        elif self.r_localvar.match(target):
            if self.r_localvar.match(source):
                # eg, movl %eax, %ecx: possibly copies a GC root
                return [InsnCopyLocal(source, target)]
            else:
                # eg, movl (%eax), %edi or mov %esp, %edi: load a register
                # from "outside".  If it contains a pointer to a GC root,
                # it will be announced later with the GCROOT macro.
                return [InsnSetLocal(target, [source])]
        else:
            # eg, movl %ebx, (%edx) or mov %ebp, %esp: does not write into
            # a general register
            return []

    def _visit_mov(self, line):
        match = self.r_binaryinsn.match(line)
        source = match.group("source")
        target = match.group("target")
        if source == self.ESP and target == self.EBP:
            return self._visit_prologue()
        elif source == self.EBP and target == self.ESP:
            return self._visit_epilogue()
        if source == self.ESP and self.funcname.startswith('VALGRIND_'):
            return []     # in VALGRIND_XXX functions, there is a dummy-looking
                          # mov %esp, %eax.  Shows up only when compiling with
                          # gcc -fno-unit-at-a-time.
        return self.insns_for_copy(source, target)

    def _visit_push(self, line):
        match = self.r_unaryinsn.match(line)
        source = match.group(1)
        return self.insns_for_copy(source, self.TOP_OF_STACK_MINUS_WORD) + \
               [InsnStackAdjust(-self.WORD)]

    def _visit_pop(self, target):
        return [InsnStackAdjust(+self.WORD)] + \
               self.insns_for_copy(self.TOP_OF_STACK_MINUS_WORD, target)

    def _visit_prologue(self):
        # for the prologue of functions that use %ebp as frame pointer
        self.uses_frame_pointer = True
        self.r_localvar = self.r_localvarfp
        return [InsnPrologue(self.WORD)]

    def _visit_epilogue(self):
        if not self.uses_frame_pointer:
            raise UnrecognizedOperation('epilogue without prologue')
        return [InsnEpilogue(self.WORD)]

    def visit_leave(self, line):
        return self._visit_epilogue() + self._visit_pop(self.EBP)

    def visit_ret(self, line):
        return InsnRet(self.CALLEE_SAVE_REGISTERS)

    def visit_rep(self, line):
        # 'rep ret' or 'rep; ret': bad reasons for this bogus 'rep' here
        if line.split()[:2] == ['rep', 'ret']:
            return self.visit_ret(line)
        return []

    def visit_jmp(self, line):
        tablelabels = []
        match = self.r_jmp_switch.match(line)
        if match:
            # this is a jmp *Label(%index), used for table-based switches.
            # Assume that the table is just a list of lines looking like
            # .long LABEL or .long 0, ending in a .text or .section .text.hot.
            tablelabels.append(match.group(1))
        elif self.r_unaryinsn_star.match(line):
            # maybe a jmp similar to the above, but stored in a
            # registry:
            #     movl L9341(%eax), %eax
            #     jmp *%eax
            operand = self.r_unaryinsn_star.match(line).group(1)
            def walker(insn, locs):
                sources = []
                for loc in locs:
                    for s in insn.all_sources_of(loc):
                        # if the source looks like 8(%eax,%edx,4)
                        # %eax is the real source, %edx is an offset.
                        match = self.r_jmp_source.match(s)
                        if match and not self.r_localvar_esp.match(s):
                            sources.append(match.group(1))
                        else:
                            sources.append(s)
                for source in sources:
                    label_match = re.compile(self.LABEL).match(source)
                    if label_match:
                        tablelabels.append(label_match.group(0))
                        return
                yield tuple(sources)
            insn = InsnStop()
            insn.previous_insns = [self.insns[-1]]
            self.walk_instructions_backwards(walker, insn, (operand,))

            # Remove probable tail-calls
            tablelabels = [label for label in tablelabels
                           if label in self.labels]
        assert len(tablelabels) <= 1
        if tablelabels:
            tablelin = self.labels[tablelabels[0]].lineno + 1
            while not self.r_jmptable_end.match(self.lines[tablelin]):
                # skip empty lines
                if (not self.lines[tablelin].strip()
                    or self.lines[tablelin].startswith(';')):
                    tablelin += 1
                    continue
                match = self.r_jmptable_item.match(self.lines[tablelin])
                if not match:
                    raise NoPatternMatch(repr(self.lines[tablelin]))
                label = match.group(1)
                if label != '0':
                    self.register_jump_to(label)
                tablelin += 1
            return InsnStop("jump table")
        if self.r_unaryinsn_star.match(line):
            # that looks like an indirect tail-call.
            # tail-calls are equivalent to RET for us
            return InsnRet(self.CALLEE_SAVE_REGISTERS)
        try:
            self.conditional_jump(line)
        except KeyError:
            # label not found: check if it's a tail-call turned into a jump
            match = self.r_unaryinsn.match(line)
            target = match.group(1)
            assert not target.startswith('.')
            # tail-calls are equivalent to RET for us
            return InsnRet(self.CALLEE_SAVE_REGISTERS)
        return InsnStop("jump")

    def register_jump_to(self, label, lastinsn=None):
        if lastinsn is None:
            lastinsn = self.insns[-1]
        if not isinstance(lastinsn, InsnStop):
            self.labels[label].previous_insns.append(lastinsn)

    def conditional_jump(self, line, je=False, jne=False):
        match = self.r_jump.match(line)
        if not match:
            match = self.r_jump_rel_label.match(line)
            if not match:
                raise UnrecognizedOperation(line)
            # j* NNNf
            label = match.group(1)
            label += ":"
            i = self.currentlineno + 1
            while True:
                if self.lines[i].startswith(label):
                    label = "rel %d" % i
                    break
                i += 1
        else:
            label = match.group(1)
        prefix = []
        lastinsn = None
        postfix = []
        if self.tested_for_zero is not None:
            if je:
                # generate pseudo-code...
                prefix = [InsnCopyLocal(self.tested_for_zero, '%tmp'),
                          InsnSetLocal(self.tested_for_zero)]
                postfix = [InsnCopyLocal('%tmp', self.tested_for_zero)]
                lastinsn = prefix[-1]
            elif jne:
                postfix = [InsnSetLocal(self.tested_for_zero)]
        self.register_jump_to(label, lastinsn)
        return prefix + [InsnCondJump(label)] + postfix

    visit_jmpl = visit_jmp
    visit_jg = conditional_jump
    visit_jge = conditional_jump
    visit_jl = conditional_jump
    visit_jle = conditional_jump
    visit_ja = conditional_jump
    visit_jae = conditional_jump
    visit_jb = conditional_jump
    visit_jbe = conditional_jump
    visit_jp = conditional_jump
    visit_jnp = conditional_jump
    visit_js = conditional_jump
    visit_jns = conditional_jump
    visit_jo = conditional_jump
    visit_jno = conditional_jump
    visit_jc = conditional_jump
    visit_jnc = conditional_jump

    def visit_je(self, line):
        return self.conditional_jump(line, je=True)

    def visit_jne(self, line):
        return self.conditional_jump(line, jne=True)

    def _visit_test(self, line):
        match = self.r_binaryinsn.match(line)
        source = match.group("source")
        target = match.group("target")
        if source == target:
            self.tested_for_zero = source
        return []

    def _visit_xchg(self, line):
        # only support the format used in VALGRIND_DISCARD_TRANSLATIONS
        # which is to use a marker no-op "xchgl %ebx, %ebx"
        match = self.r_binaryinsn.match(line)
        source = match.group("source")
        target = match.group("target")
        if source == target:
            return []
        raise UnrecognizedOperation(line)

    def visit_call(self, line):
        match = self.r_unaryinsn.match(line)

        if match is None:
            assert self.r_unaryinsn_star.match(line)   # indirect call
            return [InsnCall('<indirect>', self.currentlineno),
                    InsnSetLocal(self.EAX)]      # the result is there

        target = match.group(1)

        if self.format in ('msvc',):
            # On win32, the address of a foreign function must be
            # computed, the optimizer may store it in a register.  We
            # could ignore this, except when the function need special
            # processing (not returning, __stdcall...)
            def find_register(target):
                reg = []
                def walker(insn, locs):
                    sources = []
                    for loc in locs:
                        for s in insn.all_sources_of(loc):
                            sources.append(s)
                    for source in sources:
                        m = re.match("DWORD PTR " + self.LABEL, source)
                        if m:
                            reg.append(m.group(1))
                    if reg:
                        return
                    yield tuple(sources)
                insn = InsnStop()
                insn.previous_insns = [self.insns[-1]]
                self.walk_instructions_backwards(walker, insn, (target,))
                return reg

            if match and self.r_localvarfp.match(target):
                sources = find_register(target)
                if sources:
                    target, = sources

        if target.endswith('@PLT'):
            # In -fPIC mode, all functions calls have this suffix
            target = target[:-4]

        if target in self.FUNCTIONS_NOT_RETURNING:
            return [InsnStop(target)]
        if self.format == 'mingw32' and target == '__alloca':
            # in functions with large stack requirements, windows
            # needs a call to _alloca(), to turn reserved pages
            # into committed memory.
            # With mingw32 gcc at least, %esp is not used before
            # this call.  So we don't bother to compute the exact
            # stack effect.
            return [InsnCannotFollowEsp()]
        if target in self.labels:
            lineoffset = self.labels[target].lineno - self.currentlineno
            if lineoffset >= 0:
                assert  lineoffset in (1,2)
                return [InsnStackAdjust(-4)]

        insns = [InsnCall(target, self.currentlineno),
                 InsnSetLocal(self.EAX)]      # the result is there
        if self.format in ('mingw32', 'msvc'):
            # handle __stdcall calling convention:
            # Stack cleanup is performed by the called function,
            # Function name is decorated with "@N" where N is the stack size
            if '@' in target and not target.startswith('@'):
                insns.append(InsnStackAdjust(int(target.rsplit('@', 1)[1])))
            # Some (intrinsic?) functions use the "fastcall" calling convention
            # XXX without any declaration, how can we guess the stack effect?
            if target in ['__alldiv', '__allrem', '__allmul', '__alldvrm',
                          '__aulldiv', '__aullrem', '__aullmul', '__aulldvrm']:
                insns.append(InsnStackAdjust(16))
        return insns

    # __________ debugging output __________

    @classmethod
    def format_location(cls, loc):
        # A 'location' is a single number describing where a value is stored
        # across a call.  It can be in one of the CALLEE_SAVE_REGISTERS, or
        # in the stack frame at an address relative to either %esp or %ebp.
        # The last two bits of the location number are used to tell the cases
        # apart; see format_location().
        assert loc >= 0
        kind = loc & LOC_MASK
        if kind == LOC_REG:
            if loc == LOC_NOWHERE:
                return '?'
            reg = (loc >> 2) - 1
            return '%' + cls.CALLEE_SAVE_REGISTERS[reg].replace("%", "")
        else:
            offset = loc & ~ LOC_MASK
            if cls.WORD == 8:
                offset <<= 1
            if kind == LOC_EBP_PLUS:
                result = '(%' + cls.EBP.replace("%", "") + ')'
            elif kind == LOC_EBP_MINUS:
                result = '(%' + cls.EBP.replace("%", "") + ')'
                offset = -offset
            elif kind == LOC_ESP_PLUS:
                result = '(%' + cls.ESP.replace("%", "") + ')'
            else:
                assert 0, kind
            if offset != 0:
                result = str(offset) + result
            return result

    @classmethod
    def format_callshape(cls, shape):
        # A 'call shape' is a tuple of locations in the sense of
        # format_location().  They describe where in a function frame
        # interesting values are stored, when this function executes a 'call'
        # instruction.
        #
        #   shape[0]    is the location that stores the fn's own return
        #               address (not the return address for the currently
        #               executing 'call')
        #
        #   shape[1..N] is where the fn saved its own caller's value of a
        #               certain callee save register. (where N is the number
        #               of callee save registers.)
        #
        #   shape[>N]   are GC roots: where the fn has put its local GCPTR
        #               vars
        #
        num_callee_save_regs = len(cls.CALLEE_SAVE_REGISTERS)
        assert isinstance(shape, tuple)
        # + 1 for the return address
        assert len(shape) >= (num_callee_save_regs + 1)
        result = [cls.format_location(loc) for loc in shape]
        return '{%s | %s | %s}' % (result[0],
                                   ', '.join(result[1:(num_callee_save_regs+1)]),
                                   ', '.join(result[(num_callee_save_regs+1):]))


class FunctionGcRootTracker32(FunctionGcRootTracker):
    WORD = 4

    visit_mov = FunctionGcRootTracker._visit_mov
    visit_movl = FunctionGcRootTracker._visit_mov
    visit_pushl = FunctionGcRootTracker._visit_push
    visit_leal = FunctionGcRootTracker._visit_lea

    visit_addl = FunctionGcRootTracker._visit_add
    visit_subl = FunctionGcRootTracker._visit_sub
    visit_andl = FunctionGcRootTracker._visit_and
    visit_and = FunctionGcRootTracker._visit_and

    visit_xchgl = FunctionGcRootTracker._visit_xchg
    visit_testl = FunctionGcRootTracker._visit_test

    # used in "xor reg, reg" to create a NULL GC ptr
    visit_xorl = FunctionGcRootTracker.binary_insn
    visit_orl = FunctionGcRootTracker.binary_insn     # unsure about this one

    # occasionally used on 32-bits to move floats around
    visit_movq = FunctionGcRootTracker.visit_nop

    def visit_pushw(self, line):
        return [InsnStackAdjust(-2)]   # rare but not impossible

    def visit_popl(self, line):
        match = self.r_unaryinsn.match(line)
        target = match.group(1)
        return self._visit_pop(target)

class FunctionGcRootTracker64(FunctionGcRootTracker):
    WORD = 8

    # Regex ignores destination
    r_save_xmm_register = re.compile(r"\tmovaps\s+%xmm(\d+)")

    def _maybe_32bit_dest(func):
        def wrapper(self, line):
            # Using a 32-bit reg as a destination in 64-bit mode zero-extends
            # to 64-bits, so sometimes gcc uses a 32-bit operation to copy a
            # statically known pointer to a register

            # %eax -> %rax
            new_line = re.sub(r"%e(ax|bx|cx|dx|di|si|bp)$", r"%r\1", line)
            # %r10d -> %r10
            new_line = re.sub(r"%r(\d+)d$", r"%r\1", new_line)
            return func(self, new_line)
        return wrapper

    visit_addl = FunctionGcRootTracker.visit_nop
    visit_subl = FunctionGcRootTracker.visit_nop
    visit_leal = FunctionGcRootTracker.visit_nop

    visit_cltq = FunctionGcRootTracker.visit_nop

    visit_movq = FunctionGcRootTracker._visit_mov
    # just a special assembler mnemonic for mov
    visit_movabsq = FunctionGcRootTracker._visit_mov
    visit_mov = _maybe_32bit_dest(FunctionGcRootTracker._visit_mov)
    visit_movl = visit_mov

    visit_xorl = _maybe_32bit_dest(FunctionGcRootTracker.binary_insn)

    visit_pushq = FunctionGcRootTracker._visit_push

    visit_addq = FunctionGcRootTracker._visit_add
    visit_subq = FunctionGcRootTracker._visit_sub

    visit_leaq = FunctionGcRootTracker._visit_lea

    visit_xorq = FunctionGcRootTracker.binary_insn
    visit_xchgq = FunctionGcRootTracker._visit_xchg
    visit_testq = FunctionGcRootTracker._visit_test

    # FIXME: similar to visit_popl for 32-bit
    def visit_popq(self, line):
        match = self.r_unaryinsn.match(line)
        target = match.group(1)
        return self._visit_pop(target)

    def visit_jmp(self, line):
        # On 64-bit, %al is used when calling varargs functions to specify an
        # upper-bound on the number of xmm registers used in the call. gcc
        # uses %al to compute an indirect jump that looks like:
        #
        #     jmp *[some register]
        #     movaps %xmm7, [stack location]
        #     movaps %xmm6, [stack location]
        #     movaps %xmm5, [stack location]
        #     movaps %xmm4, [stack location]
        #     movaps %xmm3, [stack location]
        #     movaps %xmm2, [stack location]
        #     movaps %xmm1, [stack location]
        #     movaps %xmm0, [stack location]
        #
        # The jmp is always to somewhere in the block of "movaps"
        # instructions, according to how many xmm registers need to be saved
        # to the stack. The point of all this is that we can safely ignore
        # jmp instructions of that form.
        if (self.currentlineno + 8) < len(self.lines) and self.r_unaryinsn_star.match(line):
            matches = [self.r_save_xmm_register.match(self.lines[self.currentlineno + 1 + i]) for i in range(8)]
            if all(m and int(m.group(1)) == (7 - i) for i, m in enumerate(matches)):
                return []

        return FunctionGcRootTracker.visit_jmp(self, line)



class ElfFunctionGcRootTracker32(FunctionGcRootTracker32):
    format = 'elf'
    function_names_prefix = ''

    ESP     = '%esp'
    EBP     = '%ebp'
    EAX     = '%eax'
    CALLEE_SAVE_REGISTERS = ['%ebx', '%esi', '%edi', '%ebp']
    REG2LOC = dict((_reg, LOC_REG | ((_i+1)<<2))
                   for _i, _reg in enumerate(CALLEE_SAVE_REGISTERS))
    OPERAND = r'(?:[-\w$%+.:@"]+(?:[(][\w%,]+[)])?|[(][\w%,]+[)])'
    LABEL   = r'([a-zA-Z_$.][a-zA-Z0-9_$@.]*)'
    OFFSET_LABELS   = 2**30
    TOP_OF_STACK_MINUS_WORD = '-4(%esp)'

    r_functionstart = re.compile(r"\t.type\s+"+LABEL+",\s*[@]function\s*$")
    r_functionend   = re.compile(r"\t.size\s+"+LABEL+",\s*[.]-"+LABEL+"\s*$")
    LOCALVAR        = r"%eax|%edx|%ecx|%ebx|%esi|%edi|%ebp|-?\d*[(]%esp[)]"
    LOCALVARFP      = LOCALVAR + r"|-?\d*[(]%ebp[)]"
    r_localvarnofp  = re.compile(LOCALVAR)
    r_localvarfp    = re.compile(LOCALVARFP)
    r_localvar_esp  = re.compile(r"(-?\d*)[(]%esp[)]")
    r_localvar_ebp  = re.compile(r"(-?\d*)[(]%ebp[)]")

    r_rel_label      = re.compile(r"(\d+):\s*$")
    r_jump_rel_label = re.compile(r"\tj\w+\s+"+"(\d+)f"+"\s*$")

    r_unaryinsn_star= re.compile(r"\t[a-z]\w*\s+[*]("+OPERAND+")\s*$")
    r_jmptable_item = re.compile(r"\t.long\t"+LABEL+"(-\"[A-Za-z0-9$]+\")?\s*$")
    r_jmptable_end  = re.compile(r"\t.text|\t.section\s+.text|\t\.align|"+LABEL)

    r_gcroot_marker = re.compile(r"\t/[*] GCROOT ("+LOCALVARFP+") [*]/")
    r_gcnocollect_marker = re.compile(r"\t/[*] GC_NOCOLLECT ("+OPERAND+") [*]/")
    r_bottom_marker = re.compile(r"\t/[*] GC_STACK_BOTTOM [*]/")

    FUNCTIONS_NOT_RETURNING = {
        '_exit': None,
        '__assert_fail': None,
        '___assert_rtn': None,
        'L___assert_rtn$stub': None,
        'L___eprintf$stub': None,
        '__stack_chk_fail': None,
        }
    for _name in FunctionGcRootTracker.BASE_FUNCTIONS_NOT_RETURNING:
        FUNCTIONS_NOT_RETURNING[_name] = None

    def __init__(self, lines, filetag=0):
        match = self.r_functionstart.match(lines[0])
        funcname = match.group(1)
        match = self.r_functionend.match(lines[-1])
        assert funcname == match.group(1)
        assert funcname == match.group(2)
        super(ElfFunctionGcRootTracker32, self).__init__(
            funcname, lines, filetag)

    def extract_immediate(self, value):
        if not value.startswith('$'):
            return None
        return int(value[1:])

ElfFunctionGcRootTracker32.init_regexp()

class ElfFunctionGcRootTracker64(FunctionGcRootTracker64):
    format = 'elf64'
    function_names_prefix = ''

    ESP = '%rsp'
    EBP = '%rbp'
    EAX = '%rax'
    CALLEE_SAVE_REGISTERS = ['%rbx', '%r12', '%r13', '%r14', '%r15', '%rbp']
    REG2LOC = dict((_reg, LOC_REG | ((_i+1)<<2))
                   for _i, _reg in enumerate(CALLEE_SAVE_REGISTERS))
    OPERAND = r'(?:[-\w$%+.:@"]+(?:[(][\w%,]+[)])?|[(][\w%,]+[)])'
    LABEL   = r'([a-zA-Z_$.][a-zA-Z0-9_$@.]*)'
    OFFSET_LABELS   = 2**30
    TOP_OF_STACK_MINUS_WORD = '-8(%rsp)'

    r_functionstart = re.compile(r"\t.type\s+"+LABEL+",\s*[@]function\s*$")
    r_functionend   = re.compile(r"\t.size\s+"+LABEL+",\s*[.]-"+LABEL+"\s*$")
    LOCALVAR = r"%rax|%rbx|%rcx|%rdx|%rdi|%rsi|%rbp|%r8|%r9|%r10|%r11|%r12|%r13|%r14|%r15|-?\d*[(]%rsp[)]"
    LOCALVARFP = LOCALVAR + r"|-?\d*[(]%rbp[)]"
    r_localvarnofp  = re.compile(LOCALVAR)
    r_localvarfp    = re.compile(LOCALVARFP)
    r_localvar_esp  = re.compile(r"(-?\d*)[(]%rsp[)]")
    r_localvar_ebp  = re.compile(r"(-?\d*)[(]%rbp[)]")

    r_rel_label      = re.compile(r"(\d+):\s*$")
    r_jump_rel_label = re.compile(r"\tj\w+\s+"+"(\d+)f"+"\s*$")

    r_unaryinsn_star= re.compile(r"\t[a-z]\w*\s+[*]("+OPERAND+")\s*$")
    r_jmptable_item = re.compile(r"\t.(?:quad|long)\t"+LABEL+"(-\"[A-Za-z0-9$]+\"|-"+LABEL+")?\s*$")
    r_jmptable_end  = re.compile(r"\t.text|\t.section\s+.text|\t\.align|"+LABEL)

    r_gcroot_marker = re.compile(r"\t/[*] GCROOT ("+LOCALVARFP+") [*]/")
    r_gcnocollect_marker = re.compile(r"\t/[*] GC_NOCOLLECT ("+OPERAND+") [*]/")
    r_bottom_marker = re.compile(r"\t/[*] GC_STACK_BOTTOM [*]/")

    FUNCTIONS_NOT_RETURNING = {
        '_exit': None,
        '__assert_fail': None,
        '___assert_rtn': None,
        'L___assert_rtn$stub': None,
        'L___eprintf$stub': None,
        '__stack_chk_fail': None,
        }
    for _name in FunctionGcRootTracker.BASE_FUNCTIONS_NOT_RETURNING:
        FUNCTIONS_NOT_RETURNING[_name] = None

    def __init__(self, lines, filetag=0):
        match = self.r_functionstart.match(lines[0])
        funcname = match.group(1)
        match = self.r_functionend.match(lines[-1])
        assert funcname == match.group(1)
        assert funcname == match.group(2)
        super(ElfFunctionGcRootTracker64, self).__init__(
            funcname, lines, filetag)

    def extract_immediate(self, value):
        if not value.startswith('$'):
            return None
        return int(value[1:])

ElfFunctionGcRootTracker64.init_regexp()

class DarwinFunctionGcRootTracker32(ElfFunctionGcRootTracker32):
    format = 'darwin'
    function_names_prefix = '_'

    r_functionstart = re.compile(r"_(\w+):\s*$")
    OFFSET_LABELS   = 0

    def __init__(self, lines, filetag=0):
        match = self.r_functionstart.match(lines[0])
        funcname = '_' + match.group(1)
        FunctionGcRootTracker32.__init__(self, funcname, lines, filetag)

class DarwinFunctionGcRootTracker64(ElfFunctionGcRootTracker64):
    format = 'darwin64'
    function_names_prefix = '_'

    LABEL = ElfFunctionGcRootTracker64.LABEL
    r_jmptable_item = re.compile(r"\t.(?:long|quad)\t"+LABEL+"(-\"?[A-Za-z0-9$]+\"?)?\s*$")

    r_functionstart = re.compile(r"_(\w+):\s*$")
    OFFSET_LABELS   = 0

    def __init__(self, lines, filetag=0):
        match = self.r_functionstart.match(lines[0])
        funcname = '_' + match.group(1)
        FunctionGcRootTracker64.__init__(self, funcname, lines, filetag)

class Mingw32FunctionGcRootTracker(DarwinFunctionGcRootTracker32):
    format = 'mingw32'
    function_names_prefix = '_'

    FUNCTIONS_NOT_RETURNING = {
        '_exit': None,
        '__assert': None,
       …