Exemplo n.º 1
0
def main(argv):
  env.update(EXTRA_ENV)
  ParseArgs(argv, LDPatterns)
  # If the user passed -arch, then they want native output.
  arch_flag_given = GetArch() is not None

  # Both LD_FLAGS_NATIVE and TRANSLATE_FLAGS_USER affect
  # the translation process. If they are non-empty,
  # then --pnacl-allow-native must be given.
  allow_native = env.getbool('ALLOW_NATIVE')
  native_flags = env.get('LD_FLAGS_NATIVE') + env.get('TRANSLATE_FLAGS_USER')
  if len(native_flags) > 0:
    if not allow_native:
      flagstr = ' '.join(native_flags)
      Log.Fatal('"%s" affects translation. '
                'To allow, specify --pnacl-allow-native' % flagstr)

  if allow_native:
    if not arch_flag_given:
      Log.Fatal("--pnacl-allow-native given, but translation "
                "is not happening (missing -arch?)")
    if env.getbool('SHARED'):
      Log.Fatal('Native shared libraries are not supported with pnacl-ld.')

  if env.getbool('SHARED'):
    if env.getbool('RELOCATABLE'):
      Log.Fatal('-r/-relocatable and -shared may not be passed together.')
    env.set('RELOCATABLE', '1')

  # Overriding the lib target uses native-flavored bitcode libs rather than the
  # portable bitcode libs. It is currently only tested/supported for
  # building the IRT.
  if not IsPortable():
    env.set('BASE_USR', "${BASE_USR_ARCH}")
    env.set('BASE_LIB', "${BASE_LIB_ARCH}")

  if env.getbool('RELOCATABLE'):
    env.set('STATIC', '0')

  inputs = env.get('INPUTS')
  output = env.getone('OUTPUT')

  if output == '':
    output = pathtools.normalize('a.out')

  if not arch_flag_given:
    # If -arch is not given, assume X86-32.
    # This is because gold requires an arch (even for bitcode linking).
    SetArch('X8632')
  assert(GetArch() is not None)

  inputs = FixPrivateLibs(inputs)

  # Expand all parameters
  # This resolves -lfoo into actual filenames,
  # and expands linker scripts into command-line arguments.
  inputs = ldtools.ExpandInputs(inputs,
                                env.get('SEARCH_DIRS'),
                                env.getbool('STATIC'),
                                # Once all glibc bitcode link is purely
                                # bitcode (e.g., even libc_nonshared.a)
                                # we may be able to restrict this more.
                                # This is also currently used by
                                # pnacl_generate_pexe=0 with glibc,
                                # for user libraries.
                                ldtools.LibraryTypes.ANY)
  plls, inputs = FilterPlls(inputs)
  plls = [os.path.basename(pll) for pll in plls]

  if not env.getbool('SHARED') and plls != []:
    Log.Fatal('Passing a PLL to the linker requires the "-shared" option.')

  # Make sure the inputs have matching arch.
  CheckInputsArch(inputs)

  regular_inputs, native_objects = SplitLinkLine(inputs)

  if env.getbool('RELOCATABLE'):
    bitcode_type = 'po'
    native_type = 'o'
  else:
    bitcode_type = 'pexe'
    native_type = 'nexe'

  if native_objects and not allow_native:
    argstr = ' '.join(native_objects)
    Log.Fatal("Native objects '%s' detected in the link. "
              "To allow, specify --pnacl-allow-native" % argstr)

  tng = TempNameGen([], output)

  # Do the bitcode link.
  if HasBitcodeInputs(inputs):
    chain = DriverChain(inputs, output, tng)
    chain.add(LinkBC, 'pre_opt.' + bitcode_type)

    # Some ABI simplification passes assume the whole program is
    # available (e.g. -expand-varargs, -nacl-expand-ctors and
    # -nacl-expand-tls).  While we could try running a subset of
    # simplification passes when linking native objects, we don't
    # do this because it complicates testing.  For example,
    # it requires '-expand-constant-expr' to be able to handle
    # 'landingpad' instructions.
    # However, if we aren't using biased bitcode, then at least -expand-byval
    # must be run to work with the PPAPI shim calling convention, and
    # -expand-varargs is needed because after LLVM 3.5 the x86-32 backend does
    # not expand the llvm.va_arg intrinsic correctly.
    # (see https://code.google.com/p/nativeclient/issues/detail?id=3913#c24)
    abi_simplify = (env.getbool('STATIC') and
                    len(native_objects) == 0 and
                    not env.getbool('ALLOW_NEXE_BUILD_ID') and
                    IsPortable())
    still_need_expand_byval = IsPortable() and env.getbool('STATIC')
    still_need_expand_varargs = (still_need_expand_byval and
                                 len(native_objects) == 0)

    # A list of groups of args. Each group should contain a pass to run
    # along with relevant flags that go with that pass.
    opt_args = []
    if env.getbool('SHARED'):
      pre_simplify_shared = [
        # The following is a subset of "-pnacl-abi-simplify-preopt".  We don't
        # want to run the full "-pnacl-abi-simplify-preopt" because it
        # internalizes symbols that we want to export via "-convert-to-pso".
        '-nacl-global-cleanup',
        '-expand-varargs',
        '-rewrite-pnacl-library-calls',
        '-rewrite-llvm-intrinsic-calls',
        '-convert-to-pso',
      ]
      # ConvertToPso takes a list of comma-separated PLL dependencies as an
      # argument.
      if plls != []:
        pre_simplify_shared += ['-convert-to-pso-deps=' + ','.join(plls)]
      opt_args.append(pre_simplify_shared)
      # Post-opt is required, since '-convert-to-pso' adds metadata which must
      # be simplified before finalization. Additionally, all functions must be
      # simplified in the post-opt passes.
      abi_simplify = True
    elif abi_simplify:
      pre_simplify = ['-pnacl-abi-simplify-preopt']
      if env.getone('CXX_EH_MODE') == 'sjlj':
        pre_simplify += ['-enable-pnacl-sjlj-eh']
      else:
        assert env.getone('CXX_EH_MODE') == 'none'
      opt_args.append(pre_simplify)
    else:
      # '-lowerinvoke' prevents use of C++ exception handling, which
      # is not yet supported in the PNaCl ABI.  '-simplifycfg' removes
      # landingpad blocks made unreachable by '-lowerinvoke'.
      #
      # We run this in order to remove 'resume' instructions,
      # otherwise these are translated to calls to _Unwind_Resume(),
      # which will not be available at native link time.
      opt_args.append(['-lowerinvoke', '-simplifycfg'])
      if still_need_expand_varargs:
        opt_args.append(['-expand-varargs'])

    if env.getone('OPT_LEVEL') != '' and env.getone('OPT_LEVEL') != '0':
      opt_args.append(env.get('OPT_FLAGS'))
    if env.getone('STRIP_MODE') != 'none':
      opt_args.append(env.get('STRIP_FLAGS'))

    if abi_simplify:
      post_simplify = ['-pnacl-abi-simplify-postopt']
      if not env.getbool('DISABLE_ABI_CHECK'):
        post_simplify += [
            '-verify-pnaclabi-module',
            '-verify-pnaclabi-functions',
            # A flag for the above -verify-pnaclabi-* passes.
            '-pnaclabi-allow-debug-metadata']
      opt_args.append(post_simplify)
    elif still_need_expand_byval:
      # We may still need -expand-byval to match the PPAPI shim
      # calling convention.
      opt_args.append(['-expand-byval'])
    if len(opt_args) != 0:
      if env.getbool('RUN_PASSES_SEPARATELY'):
        for i, group in enumerate(opt_args):
          chain.add(DoLLVMPasses(group),
                    'simplify_%d.%s' % (i, bitcode_type))
      else:
        flattened_opt_args = [flag for group in opt_args for flag in group]
        chain.add(DoLLVMPasses(flattened_opt_args),
                  'simplify_and_opt.' + bitcode_type)
  else:
    chain = DriverChain('', output, tng)

  if env.getbool('FINALIZE'):
    chain.add(DoFinalize, 'finalize.' + bitcode_type)

  # If -arch is also specified, invoke pnacl-translate afterwards.
  if arch_flag_given:
    env.set('NATIVE_OBJECTS', *native_objects)
    chain.add(DoTranslate, native_type)

  chain.run()

  if bitcode_type == 'pexe' and not arch_flag_given:
    # Mark .pexe files as executable.
    # Some versions of 'configure' expect this.
    SetExecutableMode(output)
  return 0
Exemplo n.º 2
0
def main(argv):
    env.update(EXTRA_ENV)
    CheckSetup()
    ParseArgs(argv, CustomPatterns + GCCPatterns)

    # "configure", especially when run as part of a toolchain bootstrap
    # process, will invoke gcc with various diagnostic options and
    # parse the output. In these cases we do not alter the incoming
    # commandline. It is also important to not emit spurious messages.
    if env.getbool('DIAGNOSTIC'):
        if env.getbool('SHOW_VERSION'):
            code, stdout, stderr = Run(env.get('CC') + env.get('CC_FLAGS'),
                                       redirect_stdout=subprocess.PIPE)
            out = stdout.split('\n')
            nacl_version = ReadDriverRevision()
            out[0] += ' nacl-version=%s' % nacl_version
            stdout = '\n'.join(out)
            print stdout,
        else:
            Run(env.get('CC') + env.get('CC_FLAGS'))
        return 0

    unmatched = env.get('UNMATCHED')
    if len(unmatched) > 0:
        UnrecognizedOption(*unmatched)

    # If -arch was given, we are compiling directly to native code
    compiling_to_native = GetArch() is not None

    if env.getbool('ALLOW_NATIVE'):
        if not compiling_to_native:
            Log.Fatal("--pnacl-allow-native without -arch is not meaningful.")
        # For native/mixed links, also bring in the native libgcc and
        # libcrt_platform to avoid link failure if pre-translated native
        # code needs functions from it.
        env.append('LD_FLAGS', env.eval('-L${LIBS_NATIVE_ARCH}'))
        env.append('STDLIBS', '-lgcc')
        env.append('STDLIBS', '-lcrt_platform')

    flags_and_inputs = env.get('INPUTS')
    output = env.getone('OUTPUT')

    if len(flags_and_inputs) == 0:
        if env.getbool('VERBOSE'):
            # -v can be invoked without any inputs. Runs the original
            # command without modifying the commandline for this case.
            Run(env.get('CC') + env.get('CC_FLAGS'))
            return 0
        else:
            Log.Fatal('No input files')

    gcc_mode = env.getone('GCC_MODE')
    output_type = DriverOutputTypes(gcc_mode, compiling_to_native)

    # '-shared' modifies the output from the linker and should be considered when
    # determining the final output type.
    if env.getbool('SHARED'):
        if compiling_to_native:
            Log.Fatal('Building native shared libraries not supported')
        if gcc_mode != '':
            Log.Fatal('-c, -S, and -E are disallowed with -shared')
        output_type = 'pll'

    # INPUTS consists of actual input files and a subset of flags like -Wl,<foo>.
    # Create a version with just the files.
    inputs = [f for f in flags_and_inputs if not IsFlag(f)]
    header_inputs = [
        f for f in inputs if filetype.IsHeaderType(filetype.FileType(f))
    ]
    # Handle PCH case specially (but only for a limited sense...)
    if header_inputs and gcc_mode != '-E':
        # We only handle doing pre-compiled headers for all inputs or not at
        # all at the moment. This is because DriverOutputTypes only assumes
        # one type of output, depending on the "gcc_mode" flag. When mixing
        # header inputs w/ non-header inputs, some of the outputs will be
        # pch while others will be output_type. We would also need to modify
        # the input->output chaining for the needs_linking case.
        if len(header_inputs) != len(inputs):
            Log.Fatal('mixed compiling of headers and source not supported')
        CompileHeaders(header_inputs, output)
        return 0

    needs_linking = (gcc_mode == '')

    if env.getbool('NEED_DASH_E') and gcc_mode != '-E':
        Log.Fatal("-E or -x required when input is from stdin")

    # There are multiple input files and no linking is being done.
    # There will be multiple outputs. Handle this case separately.
    if not needs_linking:
        if output != '' and len(inputs) > 1:
            Log.Fatal(
                'Cannot have -o with -c, -S, or -E and multiple inputs: %s',
                repr(inputs))

        for f in inputs:
            intype = filetype.FileType(f)
            if not (filetype.IsSourceType(intype)
                    or filetype.IsHeaderType(intype)):
                if ((output_type == 'pp' and intype != 'S')
                        or (output_type == 'll')
                        or (output_type == 'po' and intype != 'll') or
                    (output_type == 's' and intype not in ('ll', 'po', 'S'))
                        or (output_type == 'o'
                            and intype not in ('ll', 'po', 'S', 's'))):
                    Log.Fatal("%s: Unexpected type of file for '%s'",
                              pathtools.touser(f), gcc_mode)

            if output == '':
                f_output = DefaultOutputName(f, output_type)
            else:
                f_output = output

            namegen = TempNameGen([f], f_output)
            CompileOne(f, output_type, namegen, f_output)
        return 0

    # Linking case
    assert (needs_linking)
    assert (output_type in ('pll', 'pexe', 'nexe'))

    if output == '':
        output = pathtools.normalize('a.out')
    namegen = TempNameGen(flags_and_inputs, output)

    # Compile all source files (c/c++/ll) to .po
    for i in xrange(0, len(flags_and_inputs)):
        if IsFlag(flags_and_inputs[i]):
            continue
        intype = filetype.FileType(flags_and_inputs[i])
        if filetype.IsSourceType(intype) or intype == 'll':
            flags_and_inputs[i] = CompileOne(flags_and_inputs[i], 'po',
                                             namegen)

    # Compile all .s/.S to .o
    if env.getbool('ALLOW_NATIVE'):
        for i in xrange(0, len(flags_and_inputs)):
            if IsFlag(flags_and_inputs[i]):
                continue
            intype = filetype.FileType(flags_and_inputs[i])
            if intype in ('s', 'S'):
                flags_and_inputs[i] = CompileOne(flags_and_inputs[i], 'o',
                                                 namegen)

    # We should only be left with .po and .o and libraries
    for f in flags_and_inputs:
        if IsFlag(f):
            continue
        intype = filetype.FileType(f)
        if intype in ('o', 's', 'S') or filetype.IsNativeArchive(f):
            if not env.getbool('ALLOW_NATIVE'):
                Log.Fatal(
                    '%s: Native object files not allowed in link. '
                    'Use --pnacl-allow-native to override.',
                    pathtools.touser(f))
        assert (intype in ('po', 'o', 'so', 'ldscript')
                or filetype.IsArchive(f))

    # Fix the user-specified linker arguments
    ld_inputs = []
    for f in flags_and_inputs:
        if f.startswith('-Xlinker='):
            ld_inputs.append(f[len('-Xlinker='):])
        elif f.startswith('-Wl,'):
            ld_inputs += f[len('-Wl,'):].split(',')
        else:
            ld_inputs.append(f)

    if env.getbool('ALLOW_NATIVE'):
        ld_inputs.append('--pnacl-allow-native')

    # Invoke the linker
    env.set('ld_inputs', *ld_inputs)

    ld_args = env.get('LD_ARGS')
    ld_flags = env.get('LD_FLAGS')

    RunDriver('pnacl-ld', ld_flags + ld_args + ['-o', output])
    return 0
Exemplo n.º 3
0
def main(argv):
  env.update(EXTRA_ENV)
  CheckSetup()
  ParseArgs(argv, CustomPatterns + GCCPatterns)

  # "configure", especially when run as part of a toolchain bootstrap
  # process, will invoke gcc with various diagnostic options and
  # parse the output. In these cases we do not alter the incoming
  # commandline. It is also important to not emit spurious messages.
  if env.getbool('DIAGNOSTIC'):
    if env.getbool('SHOW_VERSION'):
      code, stdout, stderr = Run(env.get('CC') + env.get('CC_FLAGS'),
                                 redirect_stdout=subprocess.PIPE)
      out = stdout.split('\n')
      nacl_version = ReadDriverRevision()
      out[0] += ' nacl-version=%s' % nacl_version
      stdout = '\n'.join(out)
      print stdout,
    else:
      Run(env.get('CC') + env.get('CC_FLAGS'))
    return 0

  unmatched = env.get('UNMATCHED')
  if len(unmatched) > 0:
    UnrecognizedOption(*unmatched)

  # If -arch was given, we are compiling directly to native code
  compiling_to_native = GetArch() is not None

  if env.getbool('ALLOW_NATIVE') and not compiling_to_native:
    Log.Fatal("--pnacl-allow-native without -arch is not meaningful.")

  if not env.get('STDLIB'):
    # Default C++ Standard Library.
    SetStdLib('libc++')

  inputs = env.get('INPUTS')
  output = env.getone('OUTPUT')

  if len(inputs) == 0:
    if env.getbool('VERBOSE'):
      # -v can be invoked without any inputs. Runs the original
      # command without modifying the commandline for this case.
      Run(env.get('CC') + env.get('CC_FLAGS'))
      return 0
    else:
      Log.Fatal('No input files')

  gcc_mode = env.getone('GCC_MODE')
  output_type = DriverOutputTypes(gcc_mode, compiling_to_native)
  needs_linking = (gcc_mode == '')

  if env.getbool('NEED_DASH_E') and gcc_mode != '-E':
    Log.Fatal("-E or -x required when input is from stdin")

  # There are multiple input files and no linking is being done.
  # There will be multiple outputs. Handle this case separately.
  if not needs_linking:
    # Filter out flags
    inputs = [f for f in inputs if not IsFlag(f)]
    if output != '' and len(inputs) > 1:
      Log.Fatal('Cannot have -o with -c, -S, or -E and multiple inputs: %s',
                repr(inputs))

    for f in inputs:
      if IsFlag(f):
        continue
      intype = filetype.FileType(f)
      if not filetype.IsSourceType(intype):
        if ((output_type == 'pp' and intype != 'S') or
            (output_type == 'll') or
            (output_type == 'po' and intype != 'll') or
            (output_type == 's' and intype not in ('ll','po','S')) or
            (output_type == 'o' and intype not in ('ll','po','S','s'))):
          Log.Fatal("%s: Unexpected type of file for '%s'",
                    pathtools.touser(f), gcc_mode)

      if output == '':
        f_output = DefaultOutputName(f, output_type)
      else:
        f_output = output

      namegen = TempNameGen([f], f_output)
      CompileOne(f, output_type, namegen, f_output)
    return 0

  # Linking case
  assert(needs_linking)
  assert(output_type in ('pso','so','pexe','nexe'))

  if output == '':
    output = pathtools.normalize('a.out')
  namegen = TempNameGen(inputs, output)

  # Compile all source files (c/c++/ll) to .po
  for i in xrange(0, len(inputs)):
    if IsFlag(inputs[i]):
      continue
    intype = filetype.FileType(inputs[i])
    if filetype.IsSourceType(intype) or intype == 'll':
      inputs[i] = CompileOne(inputs[i], 'po', namegen)

  # Compile all .s/.S to .o
  if env.getbool('ALLOW_NATIVE'):
    for i in xrange(0, len(inputs)):
      if IsFlag(inputs[i]):
        continue
      intype = filetype.FileType(inputs[i])
      if intype in ('s','S'):
        inputs[i] = CompileOne(inputs[i], 'o', namegen)

  # We should only be left with .po and .o and libraries
  for f in inputs:
    if IsFlag(f):
      continue
    intype = filetype.FileType(f)
    if intype in ('o','s','S') or filetype.IsNativeArchive(f):
      if not env.getbool('ALLOW_NATIVE'):
        Log.Fatal('%s: Native object files not allowed in link. '
                  'Use --pnacl-allow-native to override.', pathtools.touser(f))
    assert(intype in ('po','o','so','ldscript') or filetype.IsArchive(f))

  # Fix the user-specified linker arguments
  ld_inputs = []
  for f in inputs:
    if f.startswith('-Xlinker='):
      ld_inputs.append(f[len('-Xlinker='):])
    elif f.startswith('-Wl,'):
      ld_inputs += f[len('-Wl,'):].split(',')
    else:
      ld_inputs.append(f)

  if env.getbool('ALLOW_NATIVE'):
    ld_inputs.append('--pnacl-allow-native')

  # Invoke the linker
  env.set('ld_inputs', *ld_inputs)

  ld_args = env.get('LD_ARGS')
  ld_flags = env.get('LD_FLAGS')

  RunDriver('ld', ld_flags + ld_args + ['-o', output])
  return 0
Exemplo n.º 4
0
def main(argv):
  env.update(EXTRA_ENV)
  ParseArgs(argv, LDPatterns)
  # If the user passed -arch, then they want native output.
  arch_flag_given = GetArch() is not None

  # Both LD_FLAGS_NATIVE and TRANSLATE_FLAGS_USER affect
  # the translation process. If they are non-empty,
  # then --pnacl-allow-native must be given.
  allow_native = env.getbool('ALLOW_NATIVE')
  native_flags = env.get('LD_FLAGS_NATIVE') + env.get('TRANSLATE_FLAGS_USER')
  if len(native_flags) > 0:
    if not allow_native:
      flagstr = ' '.join(native_flags)
      Log.Fatal('"%s" affects translation. '
                'To allow, specify --pnacl-allow-native' % flagstr)

  if env.getbool('ALLOW_NATIVE') and not arch_flag_given:
      Log.Fatal("--pnacl-allow-native given, but translation "
                "is not happening (missing -arch?)")

  # Overriding the lib target uses native-flavored bitcode libs rather than the
  # portable bitcode libs. It is currently only tested/supported for
  # building the IRT.
  if not IsPortable():
    env.set('BASE_USR', "${BASE_USR_ARCH}")
    env.set('BASE_LIB', "${BASE_LIB_ARCH}")

  if env.getbool('RELOCATABLE'):
    env.set('STATIC', '0')

  inputs = env.get('INPUTS')
  output = env.getone('OUTPUT')

  if output == '':
    output = pathtools.normalize('a.out')

  if not arch_flag_given:
    # If -arch is not given, assume X86-32.
    # This is because gold requires an arch (even for bitcode linking).
    SetArch('X8632')
  assert(GetArch() is not None)

  inputs = FixPrivateLibs(inputs)

  # Expand all parameters
  # This resolves -lfoo into actual filenames,
  # and expands linker scripts into command-line arguments.
  inputs = ldtools.ExpandInputs(inputs,
                                env.get('SEARCH_DIRS'),
                                env.getbool('STATIC'),
                                # Once all glibc bitcode link is purely
                                # bitcode (e.g., even libc_nonshared.a)
                                # we may be able to restrict this more.
                                # This is also currently used by
                                # pnacl_generate_pexe=0 with glibc,
                                # for user libraries.
                                ldtools.LibraryTypes.ANY)

  # Make sure the inputs have matching arch.
  CheckInputsArch(inputs)

  regular_inputs, native_objects = SplitLinkLine(inputs)

  if env.getbool('RELOCATABLE'):
    bitcode_type = 'po'
    native_type = 'o'
  else:
    bitcode_type = 'pexe'
    native_type = 'nexe'

  if native_objects and not allow_native:
    argstr = ' '.join(native_objects)
    Log.Fatal("Native objects '%s' detected in the link. "
              "To allow, specify --pnacl-allow-native" % argstr)

  tng = TempNameGen([], output)

  # Do the bitcode link.
  if HasBitcodeInputs(inputs):
    chain = DriverChain(inputs, output, tng)
    chain.add(LinkBC, 'pre_opt.' + bitcode_type)

    # Some ABI simplification passes assume the whole program is
    # available (e.g. -expand-varargs, -nacl-expand-ctors and
    # -nacl-expand-tls).  While we could try running a subset of
    # simplification passes when linking native objects, we don't
    # do this because it complicates testing.  For example,
    # it requires '-expand-constant-expr' to be able to handle
    # 'landingpad' instructions.
    # However, if we aren't using biased bitcode, then at least -expand-byval
    # must be run to work with the PPAPI shim calling convention.
    # This assumes that PPAPI does not use var-args, so passes like
    # -expand-varargs and other calling-convention-changing passes are
    # not needed.
    abi_simplify = (env.getbool('STATIC') and
                    len(native_objects) == 0 and
                    env.getone('CXX_EH_MODE') != 'zerocost' and
                    not env.getbool('ALLOW_NEXE_BUILD_ID') and
                    IsPortable())
    still_need_expand_byval = IsPortable()

    abi_simplify_opts = []
    if env.getone('CXX_EH_MODE') == 'sjlj':
      abi_simplify_opts += ['-enable-pnacl-sjlj-eh']

    preopt_passes = []
    if abi_simplify:
      preopt_passes += ['-pnacl-abi-simplify-preopt'] + abi_simplify_opts
    elif env.getone('CXX_EH_MODE') != 'zerocost':
      # '-lowerinvoke' prevents use of C++ exception handling, which
      # is not yet supported in the PNaCl ABI.  '-simplifycfg' removes
      # landingpad blocks made unreachable by '-lowerinvoke'.
      #
      # We run this in order to remove 'resume' instructions,
      # otherwise these are translated to calls to _Unwind_Resume(),
      # which will not be available at native link time.
      preopt_passes += ['-lowerinvoke', '-simplifycfg']
    if len(preopt_passes) != 0:
      chain.add(DoLLVMPasses(preopt_passes), 'simplify_preopt.' + bitcode_type)

    if env.getone('OPT_LEVEL') != '' and env.getone('OPT_LEVEL') != '0':
      chain.add(DoLTO, 'opt.' + bitcode_type)
    elif env.getone('STRIP_MODE') != 'none':
      chain.add(DoStrip, 'stripped.' + bitcode_type)

    postopt_passes = []
    if abi_simplify:
      postopt_passes = ['-pnacl-abi-simplify-postopt'] + abi_simplify_opts
      if not env.getbool('DISABLE_ABI_CHECK'):
        postopt_passes += [
            '-verify-pnaclabi-module',
            '-verify-pnaclabi-functions',
            # A flag for the above -verify-pnaclabi-* passes.
            '-pnaclabi-allow-debug-metadata']
        if env.getbool('ALLOW_DEV_INTRINSICS'):
          # A flag for the above -verify-pnaclabi-* passes.
          postopt_passes += ['-pnaclabi-allow-dev-intrinsics']
    elif still_need_expand_byval:
      # We may still need -expand-byval to match the PPAPI shim
      # calling convention.
      postopt_passes = ['-expand-byval']
    if len(postopt_passes) != 0:
      chain.add(DoLLVMPasses(postopt_passes),
                'simplify_postopt.' + bitcode_type)
  else:
    chain = DriverChain('', output, tng)

  # If -arch is also specified, invoke pnacl-translate afterwards.
  if arch_flag_given:
    env.set('NATIVE_OBJECTS', *native_objects)
    chain.add(DoTranslate, native_type)

  chain.run()

  if bitcode_type == 'pexe' and not arch_flag_given:
    # Mark .pexe files as executable.
    # Some versions of 'configure' expect this.
    SetExecutableMode(output)
  return 0