emcc

#!/usr/bin/env python2
# -*- Mode: python -*-

'''
emcc - compiler helper script
=============================

emcc is a drop-in replacement for a compiler like gcc or clang.

Tell your build system to use this instead of the compiler, and similarly
use emar, emranlib etc. instead of the same command without 'em'.

Example uses:

 * For configure, instead of ./configure, cmake, etc., run emconfigure.py
   with that command as an argument, for example

    emconfigure.py ./configure [options]

   emconfigure.py is a tiny script that just sets some environment vars
   as a convenience. The command just shown is equivalent to

    EMMAKEN_JUST_CONFIGURE=1 RANLIB=PATH/emranlib AR=PATH/emar CXX=PATH/em++ CC=PATH/emcc ./configure [options]

   where PATH is the path to this file.

   EMMAKEN_JUST_CONFIGURE tells emcc that it is being run in ./configure,
   so it should relay everything to gcc/g++. You should not define that when
   running make, of course.

After setting that up, run your build system normally.

Note the appearance of em++ instead of emcc
for the C++ compiler. This is needed for cases where we get
a C++ file with a C extension, in which case CMake can be told
to run g++ on it despite the .c extension, see

  https://github.com/kripken/emscripten/issues/6

(If a similar situation occurs with ./configure, you can do the same there too.)

emcc can be influenced by a few environment variables:

  EMMAKEN_NO_SDK - Will tell emcc *not* to use the emscripten headers. Instead
                   your system headers will be used.

  EMMAKEN_COMPILER - The compiler to be used, if you don't want the default clang.
'''

import os, sys, shutil, tempfile, subprocess, shlex, time, re, logging
from subprocess import PIPE
from tools import shared, jsrun, system_libs
from tools.shared import Compression, execute, suffix, unsuffixed, unsuffixed_basename, WINDOWS, safe_move
from tools.response_file import read_response_file

# endings = dot + a suffix, safe to test by  filename.endswith(endings)
C_ENDINGS = ('.c', '.C')
CXX_ENDINGS = ('.cpp', '.cxx', '.cc', '.CPP', '.CXX', '.CC')
OBJC_ENDINGS = ('.m',)
OBJCXX_ENDINGS = ('.mm',)
SOURCE_ENDINGS = C_ENDINGS + CXX_ENDINGS + OBJC_ENDINGS + OBJCXX_ENDINGS
BITCODE_ENDINGS = ('.bc', '.o', '.obj')
DYNAMICLIB_ENDINGS = ('.dylib', '.so') # Windows .dll suffix is not included in this list, since those are never linked to directly on the command line.
STATICLIB_ENDINGS = ('.a',)
ASSEMBLY_ENDINGS = ('.ll',)
HEADER_ENDINGS = ('.h', '.hxx', '.hpp', '.hh', '.H', '.HXX', '.HPP', '.HH')
SUPPORTED_LINKER_FLAGS = ('--start-group', '-(', '--end-group', '-)')

LIB_PREFIXES = ('', 'lib')

JS_CONTAINING_SUFFIXES = ('js', 'html')

# Mapping of emcc opt levels to llvm opt levels. We use llvm opt level 3 in emcc opt
# levels 2 and 3 (emcc 3 is unsafe opts, so unsuitable for the only level to get
# llvm opt level 3, and speed-wise emcc level 2 is already the slowest/most optimizing
# level)
LLVM_OPT_LEVEL = {
  0: 0,
  1: 1,
  2: 3,
  3: 3,
}

DEBUG = os.environ.get('EMCC_DEBUG')
if DEBUG == "0":
  DEBUG = None

TEMP_DIR = os.environ.get('EMCC_TEMP_DIR')
LEAVE_INPUTS_RAW = os.environ.get('EMCC_LEAVE_INPUTS_RAW') # Do not compile .ll files into .bc, just compile them with emscripten directly
                                                           # Not recommended, this is mainly for the test runner, or if you have some other
                                                           # specific need.
                                                           # One major limitation with this mode is that libc and libc++ cannot be
                                                           # added in. Also, LLVM optimizations will not be done, nor dead code elimination
AUTODEBUG = os.environ.get('EMCC_AUTODEBUG') # If set to 1, we will run the autodebugger (the automatic debugging tool, see tools/autodebugger).
                                             # Note that this will disable inclusion of libraries. This is useful because including
                                             # dlmalloc makes it hard to compare native and js builds
EMCC_CFLAGS = os.environ.get('EMCC_CFLAGS') # Additional compiler flags that we treat as if they were passed to us on the commandline

if DEBUG: logging.warning('invocation: ' + ' '.join(sys.argv) + (' + ' + EMCC_CFLAGS if EMCC_CFLAGS else '') + '  (in ' + os.getcwd() + ')')
if EMCC_CFLAGS: sys.argv.append(EMCC_CFLAGS)

if DEBUG and LEAVE_INPUTS_RAW: logging.warning('leaving inputs raw')

stdout = PIPE if not DEBUG else None # suppress output of child processes
stderr = PIPE if not DEBUG else None # unless we are in DEBUG mode

shared.check_sanity(force=DEBUG)

# Handle some global flags

if len(sys.argv) == 1:
  logging.warning('no input files')
  exit(1)

# read response files very early on
response_file = True
while response_file:
  response_file = None
  for index in range(1, len(sys.argv)):
    if sys.argv[index][0] == '@':
      # found one, loop again next time
      response_file = True
      extra_args = read_response_file(sys.argv[index])
      # slice in extra_args in place of the response file arg
      sys.argv[index:index+1] = extra_args
      break

if len(sys.argv) == 1 or '--help' in sys.argv:
  this = os.path.basename('em++' if os.environ.get('EMMAKEN_CXX') else 'emcc')

  # Documentation for emcc and its options must be updated in: 
  #    site/source/docs/tools_reference/emcc.rst
  # A prebuilt local version of the documentation is available at: 
  #    site/build/text/docs/tools_reference/emcc.txt
  #    (it is read from there and printed out when --help is invoked)
  # You can also build docs locally as HTML or other formats in site/
  # An online HTML version (which may be of a different version of Emscripten)
  #    is up at http://kripken.github.io/emscripten-site/docs/tools_reference/emcc.html

  print '''%s

------------------------------------------------------------------

emcc: supported targets: llvm bitcode, javascript, NOT elf
(autoconf likes to see elf above to enable shared object support)
''' % (open(shared.path_from_root('site', 'build', 'text', 'docs', 'tools_reference', 'emcc.txt')).read())
  exit(0)

elif sys.argv[1] == '--version':
  revision = '(unknown revision)'
  here = os.getcwd()
  os.chdir(shared.path_from_root())
  try:
    revision = execute(['git', 'show'], stdout=PIPE, stderr=PIPE)[0].split('\n')[0]
  except:
    pass
  finally:
    os.chdir(here)
  print '''emcc (Emscripten GCC-like replacement) %s (%s)
Copyright (C) 2014 the Emscripten authors (see AUTHORS.txt)
This is free and open source software under the MIT license.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  ''' % (shared.EMSCRIPTEN_VERSION, revision)
  exit(0)

elif len(sys.argv) == 2 and sys.argv[1] == '-v': # -v with no inputs
  print 'emcc (Emscripten GCC-like replacement + linker emulating GNU ld ) %s' % shared.EMSCRIPTEN_VERSION
  code = subprocess.call([shared.CLANG, '-v'])
  shared.check_sanity(force=True)
  exit(code)

def is_minus_s_for_emcc(newargs, i):
  assert newargs[i] == '-s'
  if i+1 < len(newargs) and '=' in newargs[i+1]: # -s OPT=VALUE is for us, -s by itself is a linker option
    return True
  else:
    logging.warning('treating -s as linker option and not as -s OPT=VALUE for js compilation')
    return False

# If this is a configure-type thing, do not compile to JavaScript, instead use clang
# to compile to a native binary (using our headers, so things make sense later)
CONFIGURE_CONFIG = (os.environ.get('EMMAKEN_JUST_CONFIGURE') or 'conftest.c' in sys.argv) and not os.environ.get('EMMAKEN_JUST_CONFIGURE_RECURSE')
CMAKE_CONFIG = 'CMakeFiles/cmTryCompileExec.dir' in ' '.join(sys.argv)# or 'CMakeCCompilerId' in ' '.join(sys.argv)
if CONFIGURE_CONFIG or CMAKE_CONFIG:
  debug_configure = 0 # XXX use this to debug configure stuff. ./configure's generally hide our normal output including stderr so we write to a file
  use_js = os.environ.get('EMCONFIGURE_JS') # whether we fake configure tests using clang - the local, native compiler - or not. if not we generate JS and use node with a shebang
                   # neither approach is perfect, you can try both, but may need to edit configure scripts in some cases
                   # XXX False is not fully tested yet

  if debug_configure:
    tempout = '/tmp/emscripten_temp/out'
    if not os.path.exists(tempout):
      open(tempout, 'w').write('//\n')

  src = None
  for arg in sys.argv:
    if arg.endswith('.c'):
      try:
        src = open(arg).read()
        if debug_configure: open(tempout, 'a').write('============= ' + arg + '\n' + src + '\n=============\n\n')
      except:
        pass
    elif arg.endswith('.s'):
      if debug_configure: open(tempout, 'a').write('(compiling .s assembly, must use clang\n')
      use_js = 0
    elif arg == '-E':
      use_js = 0

  if src:
    if 'fopen' in src and '"w"' in src:
      use_js = 0 # we cannot write to files from js!
      if debug_configure: open(tempout, 'a').write('Forcing clang since uses fopen to write\n')

  compiler = os.environ.get('CONFIGURE_CC') or (shared.CLANG if not use_js else shared.EMCC) # if CONFIGURE_CC is defined, use that. let's you use local gcc etc. if you need that
  if not ('CXXCompiler' in ' '.join(sys.argv) or os.environ.get('EMMAKEN_CXX')):
    compiler = shared.to_cc(compiler)

  def filter_emscripten_options(argv):
    idx = 0
    skip_next = False
    for el in argv:
      if skip_next:
        skip_next = False
        idx += 1
        continue
      if not use_js and el == '-s' and is_minus_s_for_emcc(argv, idx): # skip -s X=Y if not using js for configure
        skip_next = True
      else:
        yield el
      idx += 1

  if compiler == shared.EMCC: compiler = [shared.PYTHON, shared.EMCC]
  else: compiler = [compiler] 
  cmd = compiler + list(filter_emscripten_options(sys.argv[1:]))
  if not use_js: cmd += shared.EMSDK_OPTS + ['-D__EMSCRIPTEN__', '-DEMSCRIPTEN']
  if use_js: cmd += ['-s', 'ERROR_ON_UNDEFINED_SYMBOLS=1'] # configure tests should fail when an undefined symbol exists

  logging.debug('just configuring: ' + ' '.join(cmd))
  if debug_configure: open(tempout, 'a').write('emcc, just configuring: ' + ' '.join(cmd) + '\n\n')

  if not use_js:
    exit(subprocess.call(cmd))
  else:
    only_object = '-c' in cmd
    target = None
    for i in range(len(cmd)-1):
      if cmd[i] == '-o':
        if not only_object:
          cmd[i+1] += '.js'
        target = cmd[i+1]
        break
    if not target:
      target = 'a.out.js'
    os.environ['EMMAKEN_JUST_CONFIGURE_RECURSE'] = '1'
    ret = subprocess.call(cmd)
    os.environ['EMMAKEN_JUST_CONFIGURE_RECURSE'] = ''
    if not os.path.exists(target): exit(1)
    if target.endswith('.js'):
      shutil.copyfile(target, target[:-3])
      target = target[:-3]
    if not target.endswith(BITCODE_ENDINGS):
      src = open(target).read()
      full_node = ' '.join(shared.NODE_JS)
      if os.path.sep not in full_node:
        full_node = '/usr/bin/' + full_node # TODO: use whereis etc. And how about non-*NIX?
      open(target, 'w').write('#!' + full_node + '\n' + src) # add shebang
      import stat
      os.chmod(target, stat.S_IMODE(os.stat(target).st_mode) | stat.S_IXUSR) # make executable
    exit(ret)

if os.environ.get('EMMAKEN_COMPILER'):
  CXX = os.environ['EMMAKEN_COMPILER']
else:
  CXX = shared.CLANG

CC = shared.to_cc(CXX)

# If we got here from a redirection through emmakenxx.py, then force a C++ compiler here
if os.environ.get('EMMAKEN_CXX'):
  CC = CXX

CC_ADDITIONAL_ARGS = shared.COMPILER_OPTS

EMMAKEN_CFLAGS = os.environ.get('EMMAKEN_CFLAGS')
if EMMAKEN_CFLAGS: sys.argv += shlex.split(EMMAKEN_CFLAGS)

# ---------------- Utilities ---------------

seen_names = {}
def uniquename(name):
  if name not in seen_names:
    seen_names[name] = str(len(seen_names))
  return unsuffixed(name) + '_' + seen_names[name] + (('.' + suffix(name)) if suffix(name) else '')

# ---------------- End configs -------------

if len(sys.argv) == 1 or sys.argv[1] in ['x', 't']:
  # noop ar
  logging.debug('just ar')
  sys.exit(0)

use_cxx = True

for i in range(1, len(sys.argv)):
  arg = sys.argv[i]
  if not arg.startswith('-'):
    if arg.endswith(C_ENDINGS + OBJC_ENDINGS):
      use_cxx = False

if '-M' in sys.argv or '-MM' in sys.argv:
  # Just output dependencies, do not compile. Warning: clang and gcc behave differently with -MF! (clang seems to not recognize it)
  cmd = [CC] + shared.COMPILER_OPTS + sys.argv[1:]
  logging.debug('just dependencies: ' + ' '.join(cmd))
  exit(subprocess.call(cmd))

if '-E' in sys.argv:
  # Just run the preprocessor
  cmd = [CC] + shared.COMPILER_OPTS + sys.argv[1:]
  logging.debug('just preprocessor ' + ' '.join(cmd))
  exit(subprocess.call(cmd))

# Check if a target is specified
target = None
for i in range(len(sys.argv)-1):
  if sys.argv[i].startswith('-o='):
    raise Exception('Invalid syntax: do not use -o=X, use -o X')

  if sys.argv[i] == '-o':
    target = sys.argv[i+1]
    sys.argv = sys.argv[:i] + sys.argv[i+2:]
    break

specified_target = target
target = specified_target if specified_target is not None else 'a.out.js' # specified_target is the user-specified one, target is what we will generate
target_basename = unsuffixed_basename(target)

if '.' in target:
  final_suffix = target.split('.')[-1]
else:
  final_suffix = ''

if TEMP_DIR:
  temp_dir = TEMP_DIR
  if os.path.exists(temp_dir):
    shutil.rmtree(temp_dir) # clear it
  os.makedirs(temp_dir)
else:
  temp_root = shared.TEMP_DIR
  if not os.path.exists(temp_root):
    os.makedirs(temp_root)
  temp_dir = tempfile.mkdtemp(dir=temp_root)

def in_temp(name):
  return os.path.join(temp_dir, os.path.basename(name))

def in_directory(root, child):
  # make both path absolute
  root = os.path.realpath(root)
  child = os.path.realpath(child)

  # return true, if the common prefix of both is equal to directory
  # e.g. /a/b/c/d.rst and directory is /a/b, the common prefix is /a/b
  return os.path.commonprefix([root, child]) == root

# Parses the essential suffix of a filename, discarding Unix-style version numbers in the name. For example for 'libz.so.1.2.8' returns '.so'
def filename_type_suffix(filename):
  for i in reversed(filename.split('.')[1:]):
    if not i.isdigit():
      return i
  return ''

def filename_type_ending(filename):
  suffix = filename_type_suffix(filename)
  return '' if not suffix else ('.' + suffix)

# Log out times for emcc stages
log_time_last = time.time()
def log_time(name):
  global log_time_last
  now = time.time()
  logging.debug('emcc step "%s" took %.2f seconds', name, now - log_time_last)
  log_time_last = now

try:
  call = CXX if use_cxx else CC

  ## Parse args

  newargs = sys.argv[1:]

  opt_level = 0
  debug_level = 0
  requested_debug = ''
  profiling = False
  tracing = False
  emit_symbol_map = False
  js_opts = None
  llvm_opts = None
  llvm_lto = None
  closure = None
  js_transform = None
  pre_js = ''
  post_js = ''
  split_js_file = None
  preload_files = []
  embed_files = []
  exclude_files = []
  compression = None
  ignore_dynamic_linking = False
  shell_path = shared.path_from_root('src', 'shell.html')
  js_libraries = []
  bind = False
  emrun = False
  jcache = False
  save_bc = False
  memory_init_file = None
  use_preload_cache = False
  no_heap_copy = False
  proxy_to_worker = False
  default_object_extension = '.o'
  valid_abspaths = []

  def is_valid_abspath(path_name):
    # Any path that is underneath the emscripten repository root must be ok.
    if shared.path_from_root().replace('\\', '/') in path_name.replace('\\', '/'):
      return True

    for valid_abspath in valid_abspaths:
      if in_directory(valid_abspath, path_name):
        return True
    return False


  if use_cxx:
    default_cxx_std = '-std=c++03' # Enforce a consistent C++ standard when compiling .cpp files, if user does not specify one on the cmdline.
  else:
    default_cxx_std = '' # Compiling C code with .c files, don't enforce a default C++ std.

  def check_bad_eq(arg):
    assert '=' not in arg, 'Invalid parameter (do not use "=" with "--" options)'

  absolute_warning_shown = False

  # Scan for warning suppression message in advance from other cmdline flags, so that it works even if -I or -L directives are present before this.
  for i in range(len(newargs)):
    if newargs[i] == '-Wno-warn-absolute-paths':
      newargs[i] = ''
      absolute_warning_shown = True

  settings_changes = []

  def validate_arg_level(level_string, max_level, err_msg):
    try:
      level = int(level_string)
      assert 0 <= level <= max_level
    except:
      raise Exception(err_msg)
    return level

  should_exit = False

  for i in range(len(newargs)):
    newargs[i] = newargs[i].strip() # On Windows Vista (and possibly others), excessive spaces in the command line leak into the items in this array, so trim e.g. 'foo.cpp ' -> 'foo.cpp'
    if newargs[i].startswith('-O'):
      # Let -O default to -O2, which is what gcc does.
      requested_level = newargs[i][2:] or '2'
      if requested_level == 's':
        llvm_opts = ['-Os']
        requested_level = 2
        settings_changes.append('INLINING_LIMIT=50')
      elif requested_level == 'z':
        llvm_opts = ['-Oz']
        requested_level = 2
        settings_changes.append('INLINING_LIMIT=25')
      opt_level = validate_arg_level(requested_level, 3, 'Invalid optimization level: ' + newargs[i])
      # We leave the -O option in place so that the clang front-end runs in that
      # optimization mode, but we disable the actual optimization passes, as we'll
      # run them separately.
      newargs.append('-mllvm')
      newargs.append('-disable-llvm-optzns')
    elif newargs[i].startswith('--js-opts'):
      check_bad_eq(newargs[i])
      js_opts = eval(newargs[i+1])
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith('--llvm-opts'):
      check_bad_eq(newargs[i])
      llvm_opts = eval(newargs[i+1])
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith('--llvm-lto'):
      check_bad_eq(newargs[i])
      llvm_lto = eval(newargs[i+1])
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith('--closure'):
      check_bad_eq(newargs[i])
      closure = int(newargs[i+1])
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith('--js-transform'):
      check_bad_eq(newargs[i])
      js_transform = newargs[i+1]
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith('--pre-js'):
      check_bad_eq(newargs[i])
      pre_js += open(newargs[i+1]).read() + '\n'
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith('--post-js'):
      check_bad_eq(newargs[i])
      post_js += open(newargs[i+1]).read() + '\n'
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith('--minify'):
      check_bad_eq(newargs[i])
      assert newargs[i+1] == '0', '0 is the only supported option for --minify; 1 has been deprecated'
      debug_level = max(1, debug_level)
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith('--split'):
      check_bad_eq(newargs[i])
      split_js_file = int(newargs[i+1])
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith('-g'):
      requested_level = newargs[i][2:] or '3'
      debug_level = validate_arg_level(requested_level, 4, 'Invalid debug level: ' + newargs[i])
      requested_debug = newargs[i]
      newargs[i] = ''
    elif newargs[i] == '-profiling' or newargs[i] == '--profiling':
      debug_level = 2
      profiling = True
      newargs[i] = ''
    elif newargs[i] == '--tracing':
      tracing = True
      newargs[i] = ''
      newargs.append('-D__EMSCRIPTEN_TRACING__=1')
      settings_changes.append("EMSCRIPTEN_TRACING=1")
      js_libraries.append(shared.path_from_root('src', 'library_trace.js'))
    elif newargs[i] == '--emit-symbol-map':
      emit_symbol_map = True
      newargs[i] = ''
    elif newargs[i] == '--bind':
      bind = True
      newargs[i] = ''
      js_libraries.append(shared.path_from_root('src', 'embind', 'emval.js'))
      js_libraries.append(shared.path_from_root('src', 'embind', 'embind.js'))
      if default_cxx_std:
        default_cxx_std = '-std=c++11' # Force C++11 for embind code, but only if user has not explicitly overridden a standard.
    elif newargs[i].startswith('-std='):
      default_cxx_std = '' # User specified a standard to use, clear Emscripten from specifying it.
    elif newargs[i].startswith('--embed-file'):
      check_bad_eq(newargs[i])
      embed_files.append(newargs[i+1])
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith('--preload-file'):
      check_bad_eq(newargs[i])
      preload_files.append(newargs[i+1])
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith('--exclude-file'):
      check_bad_eq(newargs[i])
      exclude_files.append(newargs[i+1])
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith('--compression'):
      logging.warning('--compression is deprecated. Instead, it is recommended you use native gzip compression in your webserver')
      check_bad_eq(newargs[i])
      parts = newargs[i+1].split(',')
      assert len(parts) == 3, '--compression requires specifying    native_encoder,js_decoder,js_name  - see emcc --help. got: %s' % newargs[i+1]
      def locate(tool):
        if WINDOWS:
          if os.path.exists(tool+'.exe'):
            return tool+'.exe'
          if os.path.exists(tool+'.bat'):
            return tool+'.bat'
          if os.path.exists(tool+'.cmd'):
            return tool+'.cmd'
        return tool
      Compression.encoder = locate(parts[0])
      Compression.decoder = locate(parts[1])
      Compression.js_name = parts[2]
      assert os.path.exists(Compression.encoder), 'native encoder %s does not exist' % Compression.encoder
      assert os.path.exists(Compression.decoder), 'js decoder %s does not exist' % Compression.decoder
      Compression.on = True
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith('--use-preload-cache'):
      use_preload_cache = True
      newargs[i] = ''
    elif newargs[i].startswith('--no-heap-copy'):
      no_heap_copy = True
      newargs[i] = ''
    elif newargs[i] == '--ignore-dynamic-linking':
      ignore_dynamic_linking = True
      newargs[i] = ''
    elif newargs[i] == '-v':
      shared.COMPILER_OPTS += ['-v']
      #shared.LINK_CMD += ['-v'] # Enable verbose output from llvm-link, since it can take a long time and this gives some indication of progress.
      shared.check_sanity(force=True)
      newargs[i] = ''
    elif newargs[i].startswith('--shell-file'):
      check_bad_eq(newargs[i])
      shell_path = newargs[i+1]
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith('--js-library'):
      check_bad_eq(newargs[i])
      js_libraries.append(newargs[i+1])
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i] == '--remove-duplicates':
      logging.warning('--remove-duplicates is deprecated as it is no longer needed. If you cannot link without it, file a bug with a testcase')
      newargs[i] = ''
    elif newargs[i] == '--jcache':
      logging.warning('jcache is deprecated')
      jcache = True
      newargs[i] = ''
    elif newargs[i] == '--cache':
      check_bad_eq(newargs[i])
      os.environ['EM_CACHE'] = newargs[i+1]
      shared.reconfigure_cache()
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i] == '--clear-cache':
      logging.warning('clearing cache')
      shared.Cache.erase()
      shared.check_sanity(force=True) # this is a good time for a sanity check
      should_exit = True
    elif newargs[i] == '--clear-ports':
      logging.warning('clearing ports')
      system_libs.Ports.erase()
      should_exit = True
    elif newargs[i] == '--show-ports':
      system_libs.show_ports()
      should_exit = True
    elif newargs[i] == '--save-bc':
      check_bad_eq(newargs[i])
      save_bc = newargs[i+1]
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i] == '--memory-init-file':
      check_bad_eq(newargs[i])
      memory_init_file = int(newargs[i+1])
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i] == '--proxy-to-worker':
      proxy_to_worker = True
      newargs[i] = ''
    elif newargs[i] == '--valid-abspath':
      valid_abspaths.append(newargs[i+1])
      newargs[i] = ''
      newargs[i+1] = ''
    elif newargs[i].startswith(('-I', '-L')):
      path_name = newargs[i][2:]
      if not absolute_warning_shown and os.path.isabs(path_name) and not is_valid_abspath(path_name):
        logging.warning('-I or -L of an absolute path "' + newargs[i] + '" encountered. If this is to a local system header/library, it may cause problems (local system files make sense for compiling natively on your system, but not necessarily to JavaScript). Pass \'-Wno-warn-absolute-paths\' to emcc to hide this warning.') # Of course an absolute path to a non-system-specific library or header is fine, and you can ignore this warning. The danger are system headers that are e.g. x86 specific and nonportable. The emscripten bundled headers are modified to be portable, local system ones are generally not
        absolute_warning_shown = True
    elif newargs[i] == '--emrun':
      emrun = True
      newargs[i] = ''
    elif newargs[i] == '--default-obj-ext':
      newargs[i] = ''
      default_object_extension = newargs[i+1]
      if not default_object_extension.startswith('.'):
        default_object_extension = '.' + default_object_extension
      newargs[i+1] = ''

  if should_exit:
    sys.exit(0)

  newargs = [arg for arg in newargs if arg is not '']

  # If user did not specify a default -std for C++ code, specify the emscripten default.
  if default_cxx_std:
    newargs = newargs + [default_cxx_std]

  if emrun:
    pre_js += open(shared.path_from_root('src', 'emrun_prejs.js')).read() + '\n'
    post_js += open(shared.path_from_root('src', 'emrun_postjs.js')).read() + '\n'

  if js_opts is None: js_opts = opt_level >= 2
  if llvm_opts is None: llvm_opts = LLVM_OPT_LEVEL[opt_level]
  if opt_level == 0: debug_level = max(3, debug_level)
  if memory_init_file is None: memory_init_file = opt_level >= 2

  if llvm_lto is None and bind:
    logging.debug('running lto for embind') # XXX this is a workaround for a pointer issue
    llvm_lto = 1

  # TODO: support source maps with js_transform
  if js_transform and debug_level >= 4:
    logging.warning('disabling source maps because a js transform is being done')
    debug_level = 3

  if DEBUG: start_time = time.time() # done after parsing arguments, which might affect debug state

  for i in range(len(newargs)):
    if newargs[i] == '-s':
      if is_minus_s_for_emcc(newargs, i):
        settings_changes.append(newargs[i+1])
        newargs[i] = newargs[i+1] = ''
    elif newargs[i].startswith('--typed-arrays'):
      assert '=' not in newargs[i], 'Invalid typed arrays parameter (do not use "=")'
      settings_changes.append('USE_TYPED_ARRAYS=' + newargs[i+1])
      newargs[i] = ''
      newargs[i+1] = ''
  newargs = [arg for arg in newargs if arg is not '']

  if split_js_file:
    settings_changes.append("PRINT_SPLIT_FILE_MARKER=1")

  # Find input files

  # These three arrays are used to store arguments of different types for
  # type-specific processing. In order to shuffle the arguments back together
  # after processing, all of these arrays hold tuples (original_index, value).
  # Note that the index part of the tuple can have a fractional part for input
  # arguments that expand into multiple processed arguments, as in -Wl,-f1,-f2.
  input_files = []
  libs = []
  link_flags = []

  # All of the above arg lists entries contain indexes into the full argument
  # list. In order to add extra implicit args (embind.cc, etc) below, we keep a
  # counter for the next index that should be used.
  next_arg_index = len(newargs)

  has_source_inputs = False
  has_header_inputs = False
  lib_dirs = [shared.path_from_root('system', 'local', 'lib'),
              shared.path_from_root('system', 'lib')]
  for i in range(len(newargs)): # find input files XXX this a simple heuristic. we should really analyze based on a full understanding of gcc params,
                                # right now we just assume that what is left contains no more |-x OPT| things
    arg = newargs[i]

    if i > 0:
      prev = newargs[i-1]
      if prev in ['-MT', '-MF', '-MQ', '-D', '-U', '-o', '-x', '-Xpreprocessor', '-include', '-imacros', '-idirafter', '-iprefix', '-iwithprefix', '-iwithprefixbefore', '-isysroot', '-imultilib', '-A', '-isystem', '-iquote', '-install_name', '-compatibility_version', '-current_version', '-I', '-L']: continue # ignore this gcc-style argument

    if os.path.islink(arg) and os.path.realpath(arg).endswith(SOURCE_ENDINGS + BITCODE_ENDINGS + DYNAMICLIB_ENDINGS + ASSEMBLY_ENDINGS + HEADER_ENDINGS):
      arg = os.path.realpath(arg)

    if not arg.startswith('-'):
      if not os.path.exists(arg):
        logging.error('%s: No such file or directory ("%s" was expected to be an input file, based on the commandline arguments provided)', arg, arg)
        exit(1)

      arg_ending = filename_type_ending(arg)
      if arg_ending.endswith(SOURCE_ENDINGS + BITCODE_ENDINGS + DYNAMICLIB_ENDINGS + ASSEMBLY_ENDINGS + HEADER_ENDINGS) or shared.Building.is_ar(arg): # we already removed -o <target>, so all these should be inputs
        newargs[i] = ''
        if arg_ending.endswith(SOURCE_ENDINGS):
          input_files.append((i, arg))
          has_source_inputs = True
        elif arg_ending.endswith(HEADER_ENDINGS):
          input_files.append((i, arg))
          has_header_inputs = True
        elif arg_ending.endswith(ASSEMBLY_ENDINGS) or shared.Building.is_bitcode(arg): # this should be bitcode, make sure it is valid
          input_files.append((i, arg))
        elif arg_ending.endswith(STATICLIB_ENDINGS + DYNAMICLIB_ENDINGS):
          # if it's not, and it's a library, just add it to libs to find later
          l = unsuffixed_basename(arg)
          for prefix in LIB_PREFIXES:
            if not prefix: continue
            if l.startswith(prefix):
              l = l[len(prefix):]
              break
          libs.append((i, l))
          newargs[i] = ''
        else:
          logging.warning(arg + ' is not valid LLVM bitcode')
      elif arg_ending.endswith(STATICLIB_ENDINGS):
        if not shared.Building.is_ar(arg):
          if shared.Building.is_bitcode(arg):
            logging.error(arg + ': File has a suffix of a static library ' + str(STATICLIB_ENDINGS) + ', but instead is an LLVM bitcode file! When linking LLVM bitcode files, use one of the suffixes ' + str(BITCODE_ENDINGS))
          else:
            logging.error(arg + ': Unknown format, not a static library!')
          exit(1)
      else:
        logging.error(arg + ": Input file has an unknown suffix, don't know what to do with it!")
        exit(1)
    elif arg.startswith('-L'):
      lib_dirs.append(arg[2:])
      newargs[i] = ''
    elif arg.startswith('-l'):
      libs.append((i, arg[2:]))
      newargs[i] = ''
    elif arg.startswith('-Wl,'):
      # Multiple comma separated link flags can be specified. Create fake
      # fractional indices for these: -Wl,a,b,c,d at index 4 becomes:
      # (4, a), (4.25, b), (4.5, c), (4.75, d)
      link_flags_to_add = arg.split(',')[1:]
      for flag_index, flag in enumerate(link_flags_to_add):
        # Only keep flags that shared.Building.link knows how to deal with.
        # We currently can't handle flags with options (like
        # -Wl,-rpath,/bin:/lib, where /bin:/lib is an option for the -rpath
        # flag).
        if flag in SUPPORTED_LINKER_FLAGS:
          link_flags.append((i + float(flag_index) / len(link_flags_to_add), flag))
      newargs[i] = ''

  original_input_files = input_files[:]

  newargs = [arg for arg in newargs if arg is not '']

  # -c means do not link in gcc, and for us, the parallel is to not go all the way to JS, but stop at bitcode
  has_dash_c = '-c' in newargs
  if has_dash_c:
    assert has_source_inputs or has_header_inputs, 'Must have source code or header inputs to use -c'
    target = target_basename + '.o'
    final_suffix = 'o'
  final_ending = ('.' + final_suffix) if len(final_suffix) > 0 else ''

  # Find library files
  for i, lib in libs:
    logging.debug('looking for library "%s"', lib)
    found = False
    for prefix in LIB_PREFIXES:
      for suff in STATICLIB_ENDINGS + DYNAMICLIB_ENDINGS:
        name = prefix + lib + suff
        for lib_dir in lib_dirs:
          path = os.path.join(lib_dir, name)
          if os.path.exists(path):
            logging.debug('found library "%s" at %s', lib, path)
            input_files.append((i, path))
            found = True
            break
        if found: break
      if found: break
    if not found and lib not in ['GL', 'GLU', 'glut']: # whitelist our default libraries
      logging.warning('emcc: cannot find library "%s"', lib)

  # If not compiling to JS, then we are compiling to an intermediate bitcode objects or library, so
  # ignore dynamic linking, since multiple dynamic linkings can interfere with each other
  if not filename_type_suffix(target) in JS_CONTAINING_SUFFIXES or ignore_dynamic_linking:
    def check(input_file):
      if filename_type_ending(input_file) in DYNAMICLIB_ENDINGS:
        if not ignore_dynamic_linking: logging.warning('ignoring dynamic library %s because not compiling to JS or HTML, remember to link it when compiling to JS or HTML at the end', os.path.basename(input_file))
        return False
      else:
        return True
    input_files = [(i, input_file) for (i, input_file) in input_files if check(input_file)]

  if len(input_files) == 0:
    logging.error('no input files\nnote that input files without a known suffix are ignored, make sure your input files end with one of: ' + str(SOURCE_ENDINGS + BITCODE_ENDINGS + DYNAMICLIB_ENDINGS + STATICLIB_ENDINGS + ASSEMBLY_ENDINGS + HEADER_ENDINGS))
    exit(0)

  newargs = CC_ADDITIONAL_ARGS + newargs

  assert not (Compression.on and final_suffix != 'html'), 'Compression only works when generating HTML'

  # If we are using embind and generating JS, now is the time to link in bind.cpp
  if bind and final_suffix in JS_CONTAINING_SUFFIXES:
    input_files.append((next_arg_index, shared.path_from_root('system', 'lib', 'embind', 'bind.cpp')))
    next_arg_index += 1

  # Apply optimization level settings
  shared.Settings.apply_opt_level(opt_level, noisy=True)

  fastcomp = os.environ.get('EMCC_FAST_COMPILER') != '0'
  if fastcomp:
    # Set ASM_JS default here so that we can override it from the command line.
    shared.Settings.ASM_JS = 1 if opt_level > 0 else 2

  # Apply -s settings in newargs here (after optimization levels, so they can override them)
  for change in settings_changes:
    key, value = change.split('=')
    if value[0] == '@':
      value = open(value[1:]).read()
    else:
      value = value.replace('\\', '\\\\')
    exec('shared.Settings.' + key + ' = ' + value)
    if key == 'EXPORTED_FUNCTIONS':
      shared.Settings.ORIGINAL_EXPORTED_FUNCTIONS = shared.Settings.EXPORTED_FUNCTIONS[:] # used for warnings in emscripten.py

  if fastcomp:
    try:
      assert shared.Settings.ASM_JS > 0, 'ASM_JS must be enabled in fastcomp'
      assert shared.Settings.UNALIGNED_MEMORY == 0, 'forced unaligned memory not supported in fastcomp'
      assert shared.Settings.CHECK_HEAP_ALIGN == 0, 'check heap align not supported in fastcomp - use SAFE_HEAP instead'
      assert shared.Settings.SAFE_DYNCALLS == 0, 'safe dyncalls not supported in fastcomp'
      assert shared.Settings.ASM_HEAP_LOG == 0, 'asm heap log not supported in fastcomp'
      assert shared.Settings.LABEL_DEBUG == 0, 'label debug not supported in fastcomp'
      assert shared.Settings.EXECUTION_TIMEOUT == -1, 'execution timeout not supported in fastcomp'
      assert shared.Settings.NAMED_GLOBALS == 0, 'named globals not supported in fastcomp'
      assert shared.Settings.PGO == 0, 'pgo not supported in fastcomp'
      assert shared.Settings.TARGET_ASMJS_UNKNOWN_EMSCRIPTEN == 1, 'fastcomp requires asmjs-unknown-emscripten'
      assert shared.Settings.USE_TYPED_ARRAYS == 2, 'fastcomp assumes ta2'
      assert not split_js_file, '--split-js is deprecated and not supported in fastcomp'
      assert shared.Settings.INIT_HEAP == 0, 'HEAP_INIT is not supported in fastcomp (and should never be needed except for debugging)'
      assert not shared.Settings.RUNTIME_TYPE_INFO, 'RUNTIME_TYPE_INFO is not supported in fastcomp'
      assert not shared.Settings.CORRUPTION_CHECK, 'CORRUPTION_CHECK is not supported in asm.js mode, which is what fastcomp can emit (you can use non-asm.js mode in non-fastcomp)'
      assert not shared.Settings.MAIN_MODULE and not shared.Settings.SIDE_MODULE, 'Linking modules is not supported in fastcomp'
    except Exception, e:
      logging.error('Compiler settings are incompatible with fastcomp. You can fall back to the older compiler core, although that is not recommended, see https://github.com/kripken/emscripten/wiki/LLVM-Backend')
      raise e

    if jcache:
      logging.warning('jcache is deprecated and not supported in fastcomp (you should not need it anyhow), disabling')
      jcache = False

    pre_fastcomp_opts = []
    fastcomp_opts = []
    if shared.Settings.NO_EXIT_RUNTIME:
      pre_fastcomp_opts += ['-emscripten-no-exit-runtime']
      if not llvm_lto: fastcomp_opts += ['-globalopt', '-globaldce']
    fastcomp_opts += ['-pnacl-abi-simplify-preopt', '-pnacl-abi-simplify-postopt']
    if shared.Settings.DISABLE_EXCEPTION_CATCHING != 1:
      fastcomp_opts += ['-enable-emscripten-cxx-exceptions']
      if shared.Settings.DISABLE_EXCEPTION_CATCHING == 2:
        fastcomp_opts += ['-emscripten-cxx-exceptions-whitelist=' + ','.join(shared.Settings.EXCEPTION_CATCHING_WHITELIST or ['fake'])]
    if shared.Settings.ASYNCIFY:
      fastcomp_opts += ['-emscripten-asyncify']
      fastcomp_opts += ['-emscripten-asyncify-functions=' + ','.join(shared.Settings.ASYNCIFY_FUNCTIONS)]
      fastcomp_opts += ['-emscripten-asyncify-whitelist=' + ','.join(shared.Settings.ASYNCIFY_WHITELIST)]

  else: # non-fastcomp
    logging.warning('Using old (non-fastcomp) compiler due to EMCC_FAST_COMPILER=0 in the env. This is dangerous, as there are known bugs, and this code path is no longer maintained. Please use emscripten in the default configuration (i.e., do not disable fastcomp)')

  if shared.Settings.ASM_JS:
    assert opt_level >= 1 or fastcomp, 'asm.js requires -O1 or above'

    if shared.Settings.CORRECT_SIGNS != 1:
      logging.warning('setting CORRECT_SIGNS to 1 for asm.js code generation')
      shared.Settings.CORRECT_SIGNS = 1
    if shared.Settings.CORRECT_OVERFLOWS != 1:
      logging.warning('setting CORRECT_OVERFLOWS to 1 for asm.js code generation')
      shared.Settings.CORRECT_OVERFLOWS = 1
    assert not shared.Settings.PGO, 'cannot run PGO in ASM_JS mode'

    if shared.Settings.SAFE_HEAP and not js_opts:
      js_opts = True
      logging.warning('enabling js opts to allow SAFE_HEAP to work properly')

    if shared.Settings.ALLOW_MEMORY_GROWTH and shared.Settings.ASM_JS != 2:
      logging.warning('Disabling asm.js validation for memory growth (memory can grow, but you lose some amount of speed)');
      shared.Settings.ASM_JS = 2

  if shared.Settings.CORRECT_SIGNS >= 2 or shared.Settings.CORRECT_OVERFLOWS >= 2 or shared.Settings.CORRECT_ROUNDINGS >= 2 or shared.Settings.SAFE_HEAP >= 2:
    debug_level = 4 # must keep debug info to do line-by-line operations

  if debug_level > 1 and closure:
    logging.warning('disabling closure because debug info was requested')
    closure = False

  assert not (shared.Settings.NO_DYNAMIC_EXECUTION and closure), 'cannot have both NO_DYNAMIC_EXECUTION and closure compiler enabled at the same time'

  if closure:
    shared.Settings.CLOSURE_COMPILER = closure
    assert os.path.exists(shared.CLOSURE_COMPILER), logging.error('fatal: Closure compiler (%s) does not exist', shared.CLOSURE_COMPILER)
    if closure == 2 and shared.Settings.ASM_JS == 1:
      logging.warning('not all asm.js optimizations are possible with --closure 2, disabling those - your code will be run more slowly')
      shared.Settings.ASM_JS = 2

  if shared.Settings.POINTER_MASKING:
    logging.warning('POINTER_MASKING is experimental')
    size = shared.Settings.POINTER_MASKING + 1 # size plus 1 should be a power of 2
    if size & (size-1) != 0:
      raise Exception('POINTER_MASKING value must be a power of 2 minus 1')

  assert shared.LLVM_TARGET in shared.COMPILER_OPTS
  if shared.LLVM_TARGET == 'i386-pc-linux-gnu':
    shared.Settings.TARGET_X86 = 1
    shared.Settings.TARGET_ASMJS_UNKNOWN_EMSCRIPTEN = 0
    assert 'asmjs-unknown-emscripten' not in shared.COMPILER_OPTS
  elif shared.LLVM_TARGET == 'asmjs-unknown-emscripten' or \
       shared.LLVM_TARGET == 'le32-unknown-nacl':
    # For temporary compatibility, treat 'le32-unknown-nacl' as 'asmjs-unknown-emscripten'.
    shared.Settings.TARGET_ASMJS_UNKNOWN_EMSCRIPTEN = 1
    shared.Settings.TARGET_X86 = 0
    assert 'i386-pc-linux-gnu' not in shared.COMPILER_OPTS
  else:
    raise Exception('unknown llvm target: ' + str(shared.LLVM_TARGET))

  if shared.Settings.USE_TYPED_ARRAYS != 2 and llvm_opts > 0:
    logging.warning('disabling LLVM optimizations, need typed arrays mode 2 for them')
    llvm_opts = 0

  if shared.Settings.MAIN_MODULE:
    assert not shared.Settings.SIDE_MODULE
    shared.Settings.INCLUDE_FULL_LIBRARY = 1
    shared.Settings.EXPORT_ALL = 1
  elif shared.Settings.SIDE_MODULE:
    assert not shared.Settings.MAIN_MODULE
    shared.Settings.FINALIZE_ASM_JS = 0 # side modules are not finalized until after relocation

  if shared.Settings.MAIN_MODULE or shared.Settings.SIDE_MODULE:
    memory_init_file = False # memory init file is not supported with module linking
    assert shared.Settings.ASM_JS, 'module linking requires asm.js output (-s ASM_JS=1)'
    shared.Settings.LINKABLE = 1 # TODO: add FORCE_DCE option for the brave people that do want to dce here and in side modules
    debug_level = max(debug_level, 2)

  if not fastcomp and shared.Settings.ASSERTIONS and shared.Settings.ALIASING_FUNCTION_POINTERS:
    logging.warning('ALIASING_FUNCTION_POINTERS is on, function pointer comparisons may be invalid across types')

  if shared.Settings.EMULATE_FUNCTION_POINTER_CASTS:
    shared.Settings.ALIASING_FUNCTION_POINTERS = 0

  if shared.Settings.STB_IMAGE and final_suffix in JS_CONTAINING_SUFFIXES:
    input_files.append((next_arg_index, shared.path_from_root('third_party', 'stb_image.c')))
    next_arg_index += 1
    shared.Settings.EXPORTED_FUNCTIONS += ['_stbi_load', '_stbi_load_from_memory', '_stbi_image_free']

  forced_stdlibs = []
  if shared.Settings.DEMANGLE_SUPPORT:
    shared.Settings.EXPORTED_FUNCTIONS += ['___cxa_demangle']
    forced_stdlibs += ['libcxxabi']

  if type(shared.Settings.EXPORTED_FUNCTIONS) in (list, tuple):
    # always need malloc and free to be kept alive and exported, for internal use and other modules
    for required_export in ['_malloc', '_free']:
      if required_export not in shared.Settings.EXPORTED_FUNCTIONS:
        shared.Settings.EXPORTED_FUNCTIONS.append(required_export)
  else:
    logging.debug('using response file for EXPORTED_FUNCTIONS, make sure it includes _malloc and _free')

  if shared.Settings.ASM_JS and shared.Settings.DLOPEN_SUPPORT:
    assert shared.Settings.DISABLE_EXCEPTION_CATCHING, 'no exceptions support with dlopen in asm yet'

  assert not (bind and shared.Settings.NO_DYNAMIC_EXECUTION), 'NO_DYNAMIC_EXECUTION disallows embind'

  if proxy_to_worker:
    shared.Settings.PROXY_TO_WORKER = 1

  if js_opts:
    shared.Settings.RUNNING_JS_OPTS = 1

  if shared.Settings.EMTERPRETIFY:
    shared.Settings.FINALIZE_ASM_JS = 0
    shared.Settings.GLOBAL_BASE = 8*256 # keep enough space at the bottom for a full stack frame
    shared.Settings.SIMPLIFY_IFS = 0 # this is just harmful for emterpreting

  shared.Settings.RUNNING_FASTCOMP = fastcomp

  shared.Settings.EMSCRIPTEN_VERSION = shared.EMSCRIPTEN_VERSION
  shared.Settings.OPT_LEVEL = opt_level
  shared.Settings.DEBUG_LEVEL = debug_level

  ## Compile source code to bitcode

  logging.debug('compiling to bitcode')

  temp_files = []

  log_time('parse arguments and setup')

  # Precompiled headers support
  if has_header_inputs:
    headers = [header for _, header in input_files]
    for header in headers:
      assert header.endswith(HEADER_ENDINGS), 'if you have one header input, we assume you want to precompile headers, and cannot have source files or other inputs as well: ' + str(headers) + ' : ' + header
    args = newargs + shared.EMSDK_CXX_OPTS + headers
    if specified_target:
      args += ['-o', specified_target]
    args = system_libs.process_args(args, shared.Settings)
    logging.debug("running (for precompiled headers): " + call + ' ' + ' '.join(args))
    execute([call] + args) # let compiler frontend print directly, so colors are saved (PIPE kills that)
    sys.exit(0)

  def get_bitcode_file(input_file):
    if final_suffix not in JS_CONTAINING_SUFFIXES:
      # no need for a temp file, just emit to the right place
      if len(input_files) == 1:
        # can just emit directly to the target
        if specified_target:
          if specified_target.endswith('/') or specified_target.endswith('\\') or os.path.isdir(specified_target):
            return os.path.join(specified_target, os.path.basename(unsuffixed(input_file))) + default_object_extension
          return specified_target
        return unsuffixed(input_file) + final_ending
      else:
        if has_dash_c: return unsuffixed(input_file) + default_object_extension
    return in_temp(unsuffixed(uniquename(input_file)) + default_object_extension)

  # Request LLVM debug info if explicitly specified, or building bitcode with -g, or if building a source all the way to JS with -g
  if debug_level >= 4 or ((final_suffix not in JS_CONTAINING_SUFFIXES or (has_source_inputs and final_suffix in JS_CONTAINING_SUFFIXES)) and requested_debug == '-g'):
    if debug_level == 4 or not (final_suffix in JS_CONTAINING_SUFFIXES and js_opts): # do not save llvm debug info if js optimizer will wipe it out anyhow (but if source maps are used, keep it)
      newargs.append('-g') # preserve LLVM debug info
      debug_level = 4

  # First, generate LLVM bitcode. For each input file, we get base.o with bitcode
  for i, input_file in input_files:
    file_ending = filename_type_ending(input_file)
    if file_ending.endswith(SOURCE_ENDINGS):
      logging.debug('compiling source file: ' + input_file)
      output_file = get_bitcode_file(input_file)
      temp_files.append((i, output_file))
      args = newargs + ['-emit-llvm', '-c', input_file, '-o', output_file]
      if file_ending.endswith(CXX_ENDINGS):
        args += shared.EMSDK_CXX_OPTS
      args = system_libs.process_args(args, shared.Settings)
      logging.debug("running: " + call + ' ' + ' '.join(args))
      execute([call] + args) # let compiler frontend print directly, so colors are saved (PIPE kills that)
      if not os.path.exists(output_file):
        logging.error('compiler frontend failed to generate LLVM bitcode, halting')
        sys.exit(1)
    else: # bitcode
      if file_ending.endswith(BITCODE_ENDINGS):
        logging.debug('using bitcode file: ' + input_file)
        temp_files.append((i, input_file))
      elif file_ending.endswith(DYNAMICLIB_ENDINGS) or shared.Building.is_ar(input_file):
        logging.debug('using library file: ' + input_file)
        temp_files.append((i, input_file))
      elif file_ending.endswith(ASSEMBLY_ENDINGS):
        if not LEAVE_INPUTS_RAW:
          logging.debug('assembling assembly file: ' + input_file)
          temp_file = in_temp(unsuffixed(uniquename(input_file)) + '.o')
          shared.Building.llvm_as(input_file, temp_file)
          temp_files.append((i, temp_file))
      else:
        logging.error(input_file + ': Unknown file suffix when compiling to LLVM bitcode!')
        sys.exit(1)

  log_time('bitcodeize inputs')

  if not LEAVE_INPUTS_RAW:
    assert len(temp_files) == len(input_files)

    # Optimize source files
    if llvm_opts > 0:
      for pos, (_, input_file) in enumerate(input_files):
        file_ending = filename_type_ending(input_file)
        if file_ending.endswith(SOURCE_ENDINGS):
          temp_file = temp_files[pos][1]
          logging.debug('optimizing %s', input_file)
          #if DEBUG: shutil.copyfile(temp_file, os.path.join(TEMP_DIR, 'to_opt.bc') # useful when LLVM opt aborts
          new_temp_file = in_temp(unsuffixed(uniquename(temp_file)) + '.o')
          shared.Building.llvm_opt(temp_file, llvm_opts, new_temp_file)
          temp_files[pos] = (temp_files[pos][0], new_temp_file)

  # Decide what we will link
  linker_inputs = [val for _, val in sorted(temp_files + link_flags)]

  # If we were just asked to generate bitcode, stop there
  if final_suffix not in JS_CONTAINING_SUFFIXES:
    if not specified_target:
      assert len(temp_files) == len(input_files)
      for i in range(len(input_files)):
        safe_move(temp_files[i][1], unsuffixed_basename(input_files[i][1]) + final_ending)
    else:
      if len(input_files) == 1:
        _, input_file = input_files[0]
        _, temp_file = temp_files[0]
        bitcode_target = specified_target if specified_target else unsuffixed_basename(input_file) + final_ending
        if temp_file != input_file:
          safe_move(temp_file, bitcode_target)
        else:
          shutil.copyfile(temp_file, bitcode_target)
        temp_output_base = unsuffixed(temp_file)
        if os.path.exists(temp_output_base + '.d'):
          # There was a .d file generated, from -MD or -MMD and friends, save a copy of it to where the output resides,
          # adjusting the target name away from the temporary file name to the specified target.
          # It will be deleted with the rest of the temporary directory.
          deps = open(temp_output_base + '.d').read()
          deps = deps.replace(temp_output_base + default_object_extension, specified_target)
          with open(os.path.join(os.path.dirname(specified_target), os.path.basename(unsuffixed(input_file) + '.d')), "w") as out_dep:
            out_dep.write(deps)
      else:
        assert len(original_input_files) == 1 or not has_dash_c, 'fatal error: cannot specify -o with -c with multiple files' + str(sys.argv) + ':' + str(original_input_files)
        # We have a specified target (-o <target>), which is not JavaScript or HTML, and
        # we have multiple files: Link them
        logging.debug('link: ' + str(linker_inputs) + specified_target)
        # Sort arg tuples and pass the extracted values to link.
        shared.Building.link(linker_inputs, specified_target)
    logging.debug('stopping at bitcode')
    if final_suffix.lower() in ['so', 'dylib', 'dll']:
      logging.warning('Dynamic libraries (.so, .dylib, .dll) are currently not supported by Emscripten. For build system emulation purposes, Emscripten'
        + ' will now generate a static library file (.bc) with the suffix \'.' + final_suffix + '\'. For best practices,'
        + ' please adapt your build system to directly generate a static LLVM bitcode library by setting the output suffix to \'.bc.\')')
    exit(0)

  log_time('process inputs')

  ## Continue on to create JavaScript

  logging.debug('will generate JavaScript')

  extra_files_to_link = []

  if not LEAVE_INPUTS_RAW and \
     not shared.Settings.BUILD_AS_SHARED_LIB and \
     not shared.Settings.SIDE_MODULE: # shared libraries/side modules link no C libraries, need them in parent
    extra_files_to_link = system_libs.get_ports(shared.Settings)
    extra_files_to_link += system_libs.calculate([f for _, f in sorted(temp_files)] + extra_files_to_link, in_temp, stdout, stderr, forced=forced_stdlibs)

  log_time('calculate system libraries')

  # First, combine the bitcode files if there are several. We must also link if we have a singleton .a
  if len(input_files) + len(extra_files_to_link) > 1 or \
     (not LEAVE_INPUTS_RAW and not (suffix(temp_files[0][1]) in BITCODE_ENDINGS or suffix(temp_files[0][1]) in DYNAMICLIB_ENDINGS) and shared.Building.is_ar(temp_files[0][1])):
    linker_inputs += extra_files_to_link
    logging.debug('linking: ' + str(linker_inputs))
    shared.Building.link(linker_inputs, in_temp(target_basename + '.bc'), force_archive_contents=len([temp for i, temp in temp_files if not temp.endswith(STATICLIB_ENDINGS)]) == 0)
    final = in_temp(target_basename + '.bc')
  else:
    if not LEAVE_INPUTS_RAW:
      _, temp_file = temp_files[0]
      _, input_file = input_files[0]
      final = in_temp(target_basename + '.bc')
      if temp_file != input_file:
        shutil.move(temp_file, final)
      else:
        shutil.copyfile(temp_file, final)
    else:
      _, input_file = input_files[0]
      final = in_temp(input_file)
      shutil.copyfile(input_file, final)

  log_time('link')

  if DEBUG:
    logging.debug('saving intermediate processing steps to %s', shared.EMSCRIPTEN_TEMP_DIR)

    intermediate_counter = 0
    def save_intermediate(name=None, suffix='js'):
      global intermediate_counter
      shutil.copyfile(final, os.path.join(shared.EMSCRIPTEN_TEMP_DIR, 'emcc-%d%s.%s' % (intermediate_counter, '' if name is None else '-' + name, suffix)))
      intermediate_counter += 1

    if not LEAVE_INPUTS_RAW: save_intermediate('basebc', 'bc')

  # Optimize, if asked to
  if not LEAVE_INPUTS_RAW:
    link_opts = [] if debug_level >= 4 else ['-strip-debug'] # remove LLVM debug if we are not asked for it

    if llvm_lto >= 2:
      logging.debug('running LLVM opts as pre-LTO')
      shared.Building.llvm_opt(in_temp(target_basename + '.bc'), llvm_opts)
      if DEBUG: save_intermediate('opt', 'bc')

    # If we can LTO, do it before dce, since it opens up dce opportunities
    if shared.Building.can_build_standalone() and llvm_lto and llvm_lto != 2 and shared.Building.can_use_unsafe_opts():
      if not shared.Building.can_inline(): link_opts.append('-disable-inlining')
      # do not internalize in std-link-opts - it ignores internalize-public-api-list - and add a manual internalize
      link_opts += ['-disable-internalize'] + shared.Building.get_safe_internalize() + ['-std-link-opts']
    else:
      # At minimum remove dead functions etc., this potentially saves a lot in the size of the generated code (and the time to compile it)
      link_opts += shared.Building.get_safe_internalize() + ['-globaldce']

    if (not save_bc and not fastcomp) or AUTODEBUG:
      # let llvm opt directly emit ll, to skip writing and reading all the bitcode
      link_opts += ['-S']
      shared.Building.llvm_opt(final, link_opts, final + '.link.ll')
      final = final + '.link.ll'
      if DEBUG: save_intermediate('linktime', 'll')
    else:
      if fastcomp and not save_bc:
        # Simplify LLVM bitcode for fastcomp
        link_opts = pre_fastcomp_opts + link_opts + fastcomp_opts
      shared.Building.llvm_opt(final, link_opts)
      if DEBUG: save_intermediate('linktime', 'bc')
      if save_bc:
        shutil.copyfile(final, save_bc)
        if fastcomp:
          shared.Building.llvm_opt(final, fastcomp_opts, final + '.adsimp.bc')
          final += '.adsimp.bc'
          if DEBUG: save_intermediate('adsimp', 'bc')

  # Prepare .ll for Emscripten
  if not LEAVE_INPUTS_RAW:
    if save_bc and not fastcomp:
      final = shared.Building.llvm_dis(final, final + '.ll')
  else:
    assert len(input_files) == 1
  if DEBUG and save_bc: save_intermediate('ll', 'll')

  if AUTODEBUG:
    logging.debug('autodebug')
    execute([shared.PYTHON, shared.AUTODEBUGGER, final, final + '.ad.ll'])
    final += '.ad.ll'
    if DEBUG: save_intermediate('autodebug', 'll')

  # Simplify bitcode after autodebug
  if fastcomp and (AUTODEBUG or LEAVE_INPUTS_RAW):
    shared.Building.llvm_opt(final, fastcomp_opts, final + '.adsimp.bc')
    final += '.adsimp.bc'
    if DEBUG: save_intermediate('adsimp', 'bc')

  log_time('post-link')

  # Emscripten
  logging.debug('LLVM => JS')
  extra_args = [] if not js_libraries else ['--libraries', ','.join(map(os.path.abspath, js_libraries))]
  if jcache: extra_args.append('--jcache')
  final = shared.Building.emscripten(final, append_ext=False, extra_args=extra_args)
  if DEBUG: save_intermediate('original')

  log_time('emscript (llvm=>js)')

  # Embed and preload files
  if len(preload_files) + len(embed_files) > 0:
    logging.debug('setting up files')
    file_args = []
    if len(preload_files) > 0:
      file_args.append('--preload')
      file_args += preload_files
    if len(embed_files) > 0:
      file_args.append('--embed')
      file_args += embed_files
    if len(exclude_files) > 0:
      file_args.append('--exclude')
      file_args += exclude_files
    if Compression.on:
      file_args += ['--compress', Compression.encoder, Compression.decoder, Compression.js_name]
    if use_preload_cache:
      file_args.append('--use-preload-cache')
    if no_heap_copy:
      file_args.append('--no-heap-copy')
    file_code = execute([shared.PYTHON, shared.FILE_PACKAGER, unsuffixed(target) + '.data'] + file_args, stdout=PIPE)[0]
    pre_js = file_code + pre_js

  # Apply pre and postjs files
  if pre_js or post_js:
    logging.debug('applying pre/postjses')
    src = open(final).read()
    final += '.pp.js'
    if WINDOWS: # Avoid duplicating \r\n to \r\r\n when writing out.
      if pre_js: pre_js = pre_js.replace('\r\n', '\n')
      if post_js: post_js = post_js.replace('\r\n', '\n')
    open(final, 'w').write(pre_js + src + post_js)
    if DEBUG: save_intermediate('pre-post')

  # Apply a source code transformation, if requested
  if js_transform:
    shutil.copyfile(final, final + '.tr.js')
    final += '.tr.js'
    posix = True if not shared.WINDOWS else False
    logging.debug('applying transform: %s', js_transform)
    subprocess.check_call(shlex.split(js_transform, posix=posix) + [os.path.abspath(final)])
    if DEBUG: save_intermediate('transformed')

  js_transform_tempfiles = [final]

  if memory_init_file:
    if shared.Settings.USE_TYPED_ARRAYS != 2:
      if type(memory_init_file) == int: logging.warning('memory init file requires typed arrays mode 2')
    else:
      memfile = target + '.mem'
      shared.try_delete(memfile)
      def repl(m):
        # handle chunking of the memory initializer
        s = m.groups(0)[0]
        if len(s) == 0 and not shared.Settings.EMTERPRETIFY: return m.group(0) # emterpreter must have a mem init file; otherwise, don't emit 0-size ones
        open(memfile, 'wb').write(''.join(map(lambda x: chr(int(x or '0')), s.split(','))))
        if DEBUG:
          # Copy into temp dir as well, so can be run there too
          shared.safe_copy(memfile, os.path.join(shared.EMSCRIPTEN_TEMP_DIR, os.path.basename(memfile)))
        return 'var memoryInitializer = "%s";' % os.path.basename(memfile)
      src = re.sub(shared.JS.memory_initializer_pattern, repl, open(final).read(), count=1)
      open(final + '.mem.js', 'w').write(src)
      final += '.mem.js'
      src = None
      js_transform_tempfiles[-1] = final # simple text substitution preserves comment line number mappings
      if DEBUG:
        if os.path.exists(memfile):
          save_intermediate('meminit')
          logging.debug('wrote memory initialization to %s', memfile)
        else:
          logging.debug('did not see memory initialization')
  elif shared.Settings.USE_TYPED_ARRAYS == 2 and not shared.Settings.MAIN_MODULE and not shared.Settings.SIDE_MODULE and debug_level < 4:
    # not writing a binary init, but we can at least optimize them by splitting them up
    src = open(final).read()
    src = shared.JS.optimize_initializer(src)
    if src is not None:
      logging.debug('optimizing memory initialization')
      open(final + '.mem.js', 'w').write(src)
      final += '.mem.js'
      src = None

  log_time('source transforms')

  # It is useful to run several js optimizer passes together, to save on unneeded unparsing/reparsing
  js_optimizer_queue = []
  js_optimizer_extra_info = {}
  js_optimizer_queue_history = []
  js_optimizer_blacklist = (os.environ.get('EMCC_JSOPT_BLACKLIST') or '').split(',')
  minify_whitespace = False

  def flush_js_optimizer_queue(title='js_opts'):
    global final, js_optimizer_queue, js_optimizer_extra_info, js_optimizer_queue_history

    js_optimizer_queue = filter(lambda p: p not in js_optimizer_blacklist, js_optimizer_queue)

    if js_optimizer_extra_info is not None and len(js_optimizer_extra_info) == 0:
      js_optimizer_extra_info = None

    if len(js_optimizer_queue) > 0 and not(not shared.Settings.ASM_JS and len(js_optimizer_queue) == 1 and js_optimizer_queue[0] == 'last'):

      def run_passes(passes, title, just_split, just_concat):
        global final, minify_whitespace, emit_symbol_map, target
        if shared.Settings.ASM_JS:
          passes = ['asm'] + passes
          if shared.Settings.PRECISE_F32:
            passes = ['asmPreciseF32'] + passes
        if emit_symbol_map and 'minifyNames' in passes:
          passes += ['symbolMap='+target+'.symbols']
        if minify_whitespace and 'last' in passes:
          passes += ['minifyWhitespace']
        logging.debug('applying js optimization passes: %s', passes)
        final = shared.Building.js_optimizer(final, passes, jcache, debug_level >= 4, js_optimizer_extra_info, just_split=just_split, just_concat=just_concat)
        js_transform_tempfiles.append(final)
        if DEBUG: save_intermediate(title, suffix='js' if 'emitJSON' not in passes else 'json')

      passes = js_optimizer_queue[:]

      if DEBUG != '2' or len(passes) < 2:
        # by assumption, our input is JS, and our output is JS. If a pass is going to run in the native optimizer in C++, then we
        # must give it JSON and receive from it JSON
        chunks = []
        curr = []
        for p in passes:
          if len(curr) == 0:
            curr.append(p)
          else:
            native = shared.js_optimizer.use_native(p, source_map=debug_level >= 4)
            last_native = shared.js_optimizer.use_native(curr[-1], source_map=debug_level >= 4)
            if native == last_native:
              curr.append(p)
            else:
              curr.append('emitJSON')
              chunks.append(curr)
              curr = ['receiveJSON', p]
        if len(curr) > 0:
          chunks.append(curr)
        if len(chunks) == 1:
          run_passes(chunks[0], title, just_split=False, just_concat=False)
        else:
          for i in range(len(chunks)):
            run_passes(chunks[i], 'js_opts_' + str(i), just_split='receiveJSON' in chunks[i], just_concat='emitJSON' in chunks[i])
      else:
        # DEBUG 2, run each pass separately
        for p in passes:
          js_optimizer_queue = [p]
          flush_js_optimizer_queue(p)
      js_optimizer_queue_history += js_optimizer_queue
      js_optimizer_queue = []
    js_optimizer_extra_info = {}

  if opt_level >= 1 and js_opts:
    logging.debug('running js post-opts')

    if DEBUG == '2':
      # Clean up the syntax a bit
      js_optimizer_queue += ['noop']

    def get_eliminate():
      if shared.Settings.ALLOW_MEMORY_GROWTH:
        return 'eliminateMemSafe'
      else:
        return 'eliminate'

    if opt_level >= 2:
      js_optimizer_queue += [get_eliminate()]

      if shared.Settings.AGGRESSIVE_VARIABLE_ELIMINATION:
        js_optimizer_queue += ['aggressiveVariableElimination']

      js_optimizer_queue += ['simplifyExpressions']

      if shared.Settings.EMTERPRETIFY: # emterpreter code will not run through a JS optimizing JIT, do more work ourselves
        js_optimizer_queue += ['localCSE']

      if shared.Settings.RELOOP and not shared.Settings.ASM_JS:
        js_optimizer_queue += ['optimizeShiftsAggressive', get_eliminate()] # aggressive shifts optimization requires loops, it breaks on switches

      # simplify ifs if it is ok to make the code somewhat unreadable, and unless outlining (simplified ifs
      # with commaified code breaks late aggressive variable elimination)
      if shared.Settings.SIMPLIFY_IFS and (debug_level == 0 or profiling) and shared.Settings.OUTLINING_LIMIT == 0: js_optimizer_queue += ['simplifyIfs']

      if shared.Settings.PRECISE_F32: js_optimizer_queue += ['optimizeFrounds']

  if closure and not shared.Settings.ASM_JS:
    flush_js_optimizer_queue()

    logging.debug('running closure')
    # no need to add this to js_transform_tempfiles, because closure and
    # debug_level > 0 are never simultaneously true
    final = shared.Building.closure_compiler(final)
    if DEBUG: save_intermediate('closure')

  def do_minify():
    global js_optimizer_queue

    if opt_level >= 2:
      if debug_level < 2 and shared.Settings.ASM_JS and not closure == 2:
        js_optimizer_queue += ['minifyNames']
      if debug_level == 0:
        global minify_whitespace
        minify_whitespace = True

    if shared.Settings.ASM_JS:
      if closure == 1:
        js_optimizer_queue += ['closure']
      elif debug_level <= 2 and not shared.Settings.MAIN_MODULE and shared.Settings.FINALIZE_ASM_JS and not closure:
        js_optimizer_queue += ['cleanup']

  if js_opts:
    if shared.Settings.ASM_JS and shared.Settings.SAFE_HEAP: js_optimizer_queue += ['safeHeap']

    if shared.Settings.OUTLINING_LIMIT > 0 and shared.Settings.ASM_JS:
      js_optimizer_queue += ['outline']
      js_optimizer_extra_info['sizeToOutline'] = shared.Settings.OUTLINING_LIMIT

    if opt_level >= 2 and (not closure or shared.Settings.ASM_JS or closure == 2) and shared.Settings.RELOOP and debug_level < 3:
      if shared.Settings.ASM_JS and opt_level >= 3:
        js_optimizer_queue += ['registerizeHarder']
      else:
        js_optimizer_queue += ['registerize']

    if shared.Settings.POINTER_MASKING and shared.Settings.ASM_JS: js_optimizer_queue += ['pointerMasking']

    if not shared.Settings.EMTERPRETIFY:
      do_minify()

    if shared.Settings.ASM_JS:
      js_optimizer_queue += ['asmLastOpts']

    if shared.Settings.FINALIZE_ASM_JS: js_optimizer_queue += ['last']

    flush_js_optimizer_queue()

  if shared.Settings.ASM_JS and closure == 2:
    flush_js_optimizer_queue()

    logging.debug('running closure')
    # no need to add this to js_transform_tempfiles, because closure and
    # debug_level > 0 are never simultaneously true
    final = shared.Building.closure_compiler(final, pretty=debug_level >= 1)
    if DEBUG: save_intermediate('closure')

  log_time('js opts')

  js_target = unsuffixed(target) + '.js'

  if shared.Settings.EMTERPRETIFY:
    logging.debug('emterpretifying')
    assert memory_init_file, 'emterpreter requires a mem init file'
    import json
    try:
      # move temp js to final position, alongside its mem init file
      shutil.move(final, js_target)
      execute([shared.PYTHON, shared.path_from_root('tools', 'emterpretify.py'), js_target, final + '.em.js', memfile, json.dumps(shared.Settings.EMTERPRETIFY_BLACKLIST)])
      final = final + '.em.js'
    finally:
      shared.try_delete(js_target)

    # minify (if requested) after emterpreter processing, and finalize output
    logging.debug('finalizing emterpreted code')
    shared.Settings.FINALIZE_ASM_JS = 1
    do_minify()
    js_optimizer_queue += ['last']
    flush_js_optimizer_queue()

    # finalize the original as well, if we will be swapping it in (TODO: add specific option for this)
    if shared.Settings.SWAPPABLE_ASM_MODULE:
      real = final
      original = js_target + '.orig.js' # the emterpretify tool saves the original here
      final = original
      logging.debug('finalizing original (non-emterpreted) code at ' + final)
      do_minify()
      js_optimizer_queue += ['last']
      flush_js_optimizer_queue()
      safe_move(final, original)
      final = real

  # Remove some trivial whitespace # TODO: do not run when compress has already been done on all parts of the code
  #src = open(final).read()
  #src = re.sub(r'\n+[ \n]*\n+', '\n', src)
  #open(final, 'w').write(src)

  def generate_source_map(map_file_base_name, offset=0):
    jsrun.run_js(shared.path_from_root('tools', 'source-maps', 'sourcemapper.js'),
      shared.NODE_JS, js_transform_tempfiles +
        ['--sourceRoot', os.getcwd(),
         '--mapFileBaseName', map_file_base_name,
         '--offset', str(offset)])

  # If we were asked to also generate HTML, do that
  if final_suffix == 'html':
    logging.debug('generating HTML')
    shell = open(shell_path).read()
    assert '{{{ SCRIPT }}}' in shell, 'HTML shell must contain  {{{ SCRIPT }}}  , see src/shell.html for an example'
    html = open(target, 'w')
    base_js_target = os.path.basename(js_target)
    if proxy_to_worker:
      child_js = shared.Settings.PROXY_TO_WORKER_FILENAME or target_basename
      html.write(shell.replace('{{{ SCRIPT }}}', '''
<script>
  if ((',' + window.location.search.substr(1) + ',').indexOf(',noProxy,') < 0) {
    console.log('running code in a web worker');
''' + open(shared.path_from_root('src', 'webGLClient.js')).read() + '\n' + open(shared.path_from_root('src', 'proxyClient.js')).read().replace('{{{ filename }}}', child_js) + '''
  } else {
    // note: no support for code mods (PRECISE_F32==2)
    console.log('running code on the main thread');
    var script = document.createElement('script');
    script.src = "%s.js";
    document.body.appendChild(script);
  }
</script>''' % child_js))
      shutil.move(final, js_target)
    elif not Compression.on:
      # Normal code generation path
      if debug_level >= 4:
        generate_source_map(target)
      shutil.move(final, js_target)
      need_mods = shared.Settings.PRECISE_F32 == 2
      if not need_mods:
        # Non-modifiable code, just load the code directly
        script_tag = '''<script async type="text/javascript" src="%s"></script>''' % base_js_target
      else:
        # Potentially-modifiable code, load as text, modify, then execute. This lets you
        # patch the code on the client machine right before it is executed, perhaps based
        # on information about the client.
        checks = []
        mods = []
        if shared.Settings.PRECISE_F32 == 2:
          checks.append('!Math.fround')
          if 'minifyNames' not in js_optimizer_queue_history:
            # simple dumb replace
            mods.append('''
console.log('optimizing out Math.fround calls');
code = code.replace(/Math_fround\(/g, '(').replace("'use asm'", "'almost asm'")
''')
          else:
            # minified, not quite so simple - TODO
            mods.append('''
try {
  console.log('optimizing out Math.fround calls');
  var m = /var ([^=]+)=global\.Math\.fround;/.exec(code);
  var minified = m[1];
  if (!minified) throw 'fail';
  var startAsm = code.indexOf('// EMSCRIPTEN_START_FUNCS');
  var endAsm = code.indexOf('// EMSCRIPTEN_END_FUNCS');
  var asm = code.substring(startAsm, endAsm);
  do {
    var moar = false; // we need to re-do, as x(x( will not be fixed
    asm = asm.replace(new RegExp('[^a-zA-Z0-9\\\\$\\\\_]' + minified + '\\\\(', 'g'), function(s) { moar = true; return s[0] + '(' });
  } while (moar);
  code = code.substring(0, startAsm) + asm + code.substring(endAsm);
  code = code.replace("'use asm'", "'almost asm'");
} catch(e) { console.log('failed to optimize out Math.fround calls ' + e) }
''')

        fixes = ''
        for i in range(len(checks)):
          fixes += 'if (' + checks[i] + ') { ' + mods[i] + ' }\n'

        # if all the checks are negative, just emit a script tag normally, that's better.
        # otherwise, do an xhr to get the code as text, modify, and load asynchronously
        code = 'if (!(' + ' || '.join(checks) + ''')) {
  var script = document.createElement('script');
  script.src = "''' + base_js_target + '''";
  document.body.appendChild(script);
} else {
  var codeXHR = new XMLHttpRequest();
  codeXHR.open('GET', '%s', true);
  codeXHR.onload = function() {
    var code = codeXHR.responseText;
    %s
    var blob = new Blob([code], { type: 'text/javascript' });
    codeXHR = null;
    var src = URL.createObjectURL(blob);
    var script = document.createElement('script');
    script.src = URL.createObjectURL(blob);
    script.onload = function() {
      URL.revokeObjectURL(script.src);
    };
    document.body.appendChild(script);
  };
  codeXHR.send(null);
}
''' % (base_js_target, fixes)
        script_tag = '''<script>%s</script>''' % code
      html.write(shell.replace('{{{ SCRIPT }}}', script_tag))
    else:
      # Compress the main code
      shutil.move(final, js_target)
      Compression.compress(js_target)

      # Run the decompressor in a worker, and add code to
      #   1. download the compressed file
      #   2. decompress to a typed array
      #   3. convert to a string of source code
      #   4. insert a script element with that source code (more effective than eval)
      decoding = '''
        var decompressWorker = new Worker('decompress.js');
        var decompressCallbacks = [];
        var decompressions = 0;
        Module["decompress"] = function(data, callback) {
          var id = decompressCallbacks.length;
          decompressCallbacks.push(callback);
          decompressWorker.postMessage({ data: data, id: id });
          if (Module['setStatus']) {
            decompressions++;
            Module['setStatus']('Decompressing...');
          }
        };
        decompressWorker.onmessage = function(event) {
          decompressCallbacks[event.data.id](event.data.data);
          decompressCallbacks[event.data.id] = null;
          if (Module['setStatus']) {
            decompressions--;
            if (decompressions == 0) {
              Module['setStatus']('');
            }
          }
        };
        var compiledCodeXHR = new XMLHttpRequest();
        compiledCodeXHR.open('GET', '%s', true);
        compiledCodeXHR.responseType = 'arraybuffer';
        compiledCodeXHR.onload = function() {
          var arrayBuffer = compiledCodeXHR.response;
          if (!arrayBuffer) throw('Loading compressed code failed.');
          var byteArray = new Uint8Array(arrayBuffer);
          Module.decompress(byteArray, function(decompressed) {
            var source = Array.prototype.slice.apply(decompressed).map(function(x) { return String.fromCharCode(x) }).join(''); // createObjectURL instead?
            var scriptTag = document.createElement('script');
            scriptTag.setAttribute('type', 'text/javascript');
            scriptTag.innerHTML = source;
            document.body.appendChild(scriptTag);
          });
        };
        compiledCodeXHR.send(null);
''' % Compression.compressed_name(base_js_target)
      html.write(shell.replace('{{{ SCRIPT }}}', '<script>' + decoding + '</script>'))

      # Add decompressor with web worker glue code
      decompressor = open('decompress.js', 'w')
      decompressor.write(open(Compression.decoder).read())
      decompressor.write('''
        onmessage = function(event) {
          postMessage({ data: %s(event.data.data), id: event.data.id });
        };
''' % Compression.js_name)
      decompressor.close()

    html.close()
  else:
    if split_js_file:
      from tools.split import split_javascript_file
      split_javascript_file(final, unsuffixed(target), split_js_file)
    else:
      if debug_level >= 4: generate_source_map(target)
      if proxy_to_worker:
        worker_target_basename = target_basename + '.worker'
        open(target, 'w').write(open(shared.path_from_root('src', 'webGLClient.js')).read() + '\n' + open(shared.path_from_root('src', 'proxyClient.js')).read().replace('{{{ filename }}}', shared.Settings.PROXY_TO_WORKER_FILENAME or worker_target_basename))
        shutil.move(final, target[:-3] + '.worker.js')
      else:
        # copy final JS to output normally
        shutil.move(final, target)

  log_time('final emitting')

  if DEBUG: logging.debug('total time: %.2f seconds', (time.time() - start_time))

finally:
  if not TEMP_DIR:
    try:
      shutil.rmtree(temp_dir)
    except:
      pass
  else:
    logging.info('emcc saved files are in:' + temp_dir)