emscripten.py

# Copyright 2010 The Emscripten Authors.  All rights reserved.
# Emscripten is available under two separate licenses, the MIT license and the
# University of Illinois/NCSA Open Source License.  Both these licenses can be
# found in the LICENSE file.

"""A small wrapper script around the core JS compiler. This calls that
compiler with the settings given to it. It can also read data from C/C++
header files (so that the JS compiler can see the constants in those
headers, for the libc implementation in JS).
"""

from __future__ import print_function

import difflib
import os
import json
import subprocess
import re
import time
import logging
import pprint
from collections import OrderedDict

from tools import shared
from tools import gen_struct_info
from tools import jsrun
from tools.response_file import substitute_response_files
from tools.shared import WINDOWS, asstr, path_from_root, exit_with_error, asmjs_mangle, treat_as_user_function
from tools.toolchain_profiler import ToolchainProfiler
from tools.minified_js_name_generator import MinifiedJsNameGenerator

logger = logging.getLogger('emscripten')

STDERR_FILE = os.environ.get('EMCC_STDERR_FILE')
if STDERR_FILE:
  STDERR_FILE = os.path.abspath(STDERR_FILE)
  logger.info('logging stderr in js compiler phase into %s' % STDERR_FILE)
  STDERR_FILE = open(STDERR_FILE, 'w')


def get_configuration():
  if hasattr(get_configuration, 'configuration'):
    return get_configuration.configuration

  configuration = shared.Configuration(environ=os.environ)
  get_configuration.configuration = configuration
  return configuration


def quote(prop):
  if shared.Settings.USE_CLOSURE_COMPILER == 2:
    return ''.join(["'" + p + "'" for p in prop.split('.')])
  else:
    return prop


def access_quote(prop):
  if shared.Settings.USE_CLOSURE_COMPILER == 2:
    return ''.join(["['" + p + "']" for p in prop.split('.')])
  else:
    return '.' + prop


def emscript_fastcomp(infile, outfile, memfile, compiler_engine,
                      temp_files, DEBUG):
  """Runs the emscripten LLVM-to-JS compiler.

  Args:
    infile: The path to the input LLVM assembly file.
    outfile: An open file object where the output is written.
  """

  assert shared.Settings.ASM_JS, 'fastcomp is asm.js-only (mode 1 or 2)'

  success = False

  try:

    # Overview:
    #   * Run LLVM backend to emit JS. JS includes function bodies, memory initializer,
    #     and various metadata
    #   * Run compiler.js on the metadata to emit the shell js code, pre/post-ambles,
    #     JS library dependencies, etc.

    # metadata is modified by reference in some of the below
    # these functions are split up to force variables to go out of scope and allow
    # memory to be reclaimed

    with ToolchainProfiler.profile_block('get_and_parse_backend'):
      backend_output = compile_js(infile, temp_files, DEBUG)
      funcs, metadata, mem_init = parse_fastcomp_output(backend_output, DEBUG)
      fixup_metadata_tables(metadata)
      funcs = fixup_functions(funcs, metadata)
    with ToolchainProfiler.profile_block('compiler_glue'):
      glue, forwarded_data = compiler_glue(metadata, compiler_engine, temp_files, DEBUG)

    with ToolchainProfiler.profile_block('function_tables_and_exports'):
      (post, function_table_data, bundled_args) = (
          function_tables_and_exports(funcs, metadata, mem_init, glue, forwarded_data, outfile, DEBUG))
    with ToolchainProfiler.profile_block('write_output_file'):
      finalize_output(outfile, post, function_table_data, bundled_args, metadata, DEBUG)
    success = True

  finally:
    outfile.close()
    if not success:
      shared.try_delete(outfile.name) # remove partial output


def compile_js(infile, temp_files, DEBUG):
  """Compile infile with asm.js backend, return the contents of the compiled js"""
  with temp_files.get_file('.4.js') as temp_js:
    backend_cmd = create_backend_cmd(infile, temp_js)

    if DEBUG:
      logger.debug('emscript: llvm backend: ' + ' '.join(backend_cmd))
      t = time.time()
    shared.print_compiler_stage(backend_cmd)
    with ToolchainProfiler.profile_block('emscript_llvm_backend'):
      shared.check_call(backend_cmd)
    if DEBUG:
      logger.debug('  emscript: llvm backend took %s seconds' % (time.time() - t))

    # Split up output
    backend_output = open(temp_js).read()
  return backend_output


def parse_fastcomp_output(backend_output, DEBUG):
  start_funcs_marker = '// EMSCRIPTEN_START_FUNCTIONS'
  end_funcs_marker = '// EMSCRIPTEN_END_FUNCTIONS'
  metadata_split_marker = '// EMSCRIPTEN_METADATA'

  start_funcs = backend_output.index(start_funcs_marker)
  end_funcs = backend_output.rindex(end_funcs_marker)
  metadata_split = backend_output.rindex(metadata_split_marker)

  funcs = backend_output[start_funcs + len(start_funcs_marker):end_funcs]
  metadata_raw = backend_output[metadata_split + len(metadata_split_marker):]
  mem_init = backend_output[end_funcs + len(end_funcs_marker):metadata_split]

  # we no longer use the "Runtime" object. TODO: stop emiting it in the backend
  mem_init = mem_init.replace('Runtime.', '')

  try:
    metadata = json.loads(metadata_raw, object_pairs_hook=OrderedDict)
  except ValueError:
    logger.error('emscript: failure to parse metadata output from compiler backend. raw output is: \n' + metadata_raw)
    raise

  # This key is being added to fastcomp but doesn't exist in the current
  # version.
  metadata.setdefault('externFunctions', [])

  if 'externUses' not in metadata:
    exit_with_error('Your fastcomp compiler is out of date, please update! (need >= 1.38.26)')

  # JS optimizer turns some heap accesses to others as an optimization, so make HEAP8 imply HEAPU8, HEAP16->HEAPU16, and HEAPF64->HEAPF32.
  if 'Int8Array' in metadata['externUses']:
    metadata['externUses'] += ['Uint8Array']
  if 'Int16Array' in metadata['externUses']:
    metadata['externUses'] += ['Uint16Array']
  if 'Float64Array' in metadata['externUses']:
    metadata['externUses'] += ['Float32Array']

  # If we are generating references to Math.fround() from here in emscripten.py, declare it used as well.
  if provide_fround() or metadata['simd']:
    metadata['externUses'] += ['Math.fround']

  # functions marked llvm.used in the code are exports requested by the user
  shared.Building.user_requested_exports += metadata['exports']

  # In MINIMAL_RUNTIME stackSave() and stackRestore are JS library functions. If LLVM backend generated
  # calls to invoke_*() functions that save and restore the stack, we must include the stack functions
  # explicitly into the build. (In traditional runtime the stack functions are always present, so this
  # tracking is not needed)
  if shared.Settings.MINIMAL_RUNTIME and (len(metadata['invokeFuncs']) > 0 or shared.Settings.LINKABLE):
    shared.Settings.EXPORTED_FUNCTIONS += ['stackSave', 'stackRestore']
    shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$stackSave', '$stackRestore']

  return funcs, metadata, mem_init


def fixup_metadata_tables(metadata):
  # if emulating pointer casts, force all tables to the size of the largest
  # (for wasm, we use binaryen's fpcast-emu pass, we don't need to do anything
  # here)
  if shared.Settings.EMULATE_FUNCTION_POINTER_CASTS and not shared.Settings.WASM:
    max_size = 0
    for k, v in metadata['tables'].items():
      max_size = max(max_size, v.count(',') + 1)
    for k, v in metadata['tables'].items():
      curr = v.count(',') + 1
      if curr < max_size:
        if v.count('[]') == 1:
          metadata['tables'][k] = v.replace(']', (','.join(['0'] * (max_size - curr)) + ']'))
        else:
          metadata['tables'][k] = v.replace(']', (',0' * (max_size - curr)) + ']')

  if shared.Settings.SIDE_MODULE:
    for k in metadata['tables'].keys():
      metadata['tables'][k] = metadata['tables'][k].replace('var FUNCTION_TABLE_', 'var SIDE_FUNCTION_TABLE_')


def fixup_functions(funcs, metadata):
  # function table masks
  table_sizes = {}
  for k, v in metadata['tables'].items():
    # undercounts by one, but that is what we want
    table_sizes[k] = str(v.count(','))
    # if shared.Settings.ASSERTIONS >= 2 and table_sizes[k] == 0:
    #   shared.warning('no function pointers with signature ' + k + ', but there is a call, which will abort if it occurs (this can result from undefined behavior, check for compiler warnings on your source files and consider -Werror)'
  funcs = re.sub(r"#FM_(\w+)#", lambda m: table_sizes[m.groups(0)[0]], funcs)

  # fix +float into float.0, if not running js opts
  if not shared.Settings.RUNNING_JS_OPTS:
    def fix_dot_zero(m):
      num = m.group(3)
      # TODO: handle 0x floats?
      if num.find('.') < 0:
        e = num.find('e')
        if e < 0:
          num += '.0'
        else:
          num = num[:e] + '.0' + num[e:]
      return m.group(1) + m.group(2) + num
    funcs = re.sub(r'([(=,+\-*/%<>:?] *)\+(-?)((0x)?[0-9a-f]*\.?[0-9]+([eE][-+]?[0-9]+)?)', fix_dot_zero, funcs)

  return funcs


def compiler_glue(metadata, compiler_engine, temp_files, DEBUG):
  if DEBUG:
    logger.debug('emscript: js compiler glue')
    t = time.time()

  # FIXME: do these one by one as normal js lib funcs
  metadata['declares'] = [i64_func for i64_func in metadata['declares'] if i64_func not in ['getHigh32', 'setHigh32']]

  update_settings_glue(metadata, DEBUG)

  assert not (metadata['simd'] and shared.Settings.WASM), 'SIMD is used, but not supported in WASM mode yet'
  assert not (shared.Settings.SIMD and shared.Settings.WASM), 'SIMD is requested, but not supported in WASM mode yet'

  glue, forwarded_data = compile_settings(compiler_engine, temp_files)

  if DEBUG:
    logger.debug('  emscript: glue took %s seconds' % (time.time() - t))

  return glue, forwarded_data


def analyze_table(function_table_data):
  def table_size(table):
    table_contents = table[table.index('[') + 1: table.index(']')]
    if len(table_contents) == 0: # empty table
      return 0
    return table_contents.count(',') + 1
  # note that this is a minimal estimate, as when asm2wasm lays out tables it adds padding
  table_total_size = sum(table_size(s) for s in function_table_data.values())
  shared.Settings.WASM_TABLE_SIZE = table_total_size


# Extracts from JS library code dependencies to runtime primitives.
def get_asm_extern_primitives(pre):
  primitives = re.search(r'\/\/ ASM_LIBRARY EXTERN PRIMITIVES: ([^\n]*)', pre)
  if primitives:
    return [x.strip().replace('Math_', 'Math.') for x in primitives.group(1).split(',')]
  else:
    return []


def compute_minimal_runtime_initializer_and_exports(post, initializers, exports, receiving):
  # Generate invocations for all global initializers directly off the asm export object, e.g. asm['__GLOBAL__INIT']();
  post = post.replace('/*** RUN_GLOBAL_INITIALIZERS(); ***/', '\n'.join(["asm['" + x + "']();" for x in global_initializer_funcs(initializers)]))

  if shared.Settings.WASM:
    # Declare all exports out to global JS scope so that JS library functions can access them in a way that minifies well with Closure
    # e.g. var a,b,c,d,e,f;
    exports_that_are_not_initializers = [x for x in exports if x not in initializers]
    if shared.Settings.WASM_BACKEND:
      # In Wasm backend the exports are still unmangled at this point, so mangle the names here
      exports_that_are_not_initializers = [asmjs_mangle(x) for x in exports_that_are_not_initializers]
    post = post.replace('/*** ASM_MODULE_EXPORTS_DECLARES ***/', 'var ' + ','.join(exports_that_are_not_initializers) + ';')

    # Generate assignments from all asm.js/wasm exports out to the JS variables above: e.g. a = asm['a']; b = asm['b'];
    post = post.replace('/*** ASM_MODULE_EXPORTS ***/', receiving)
    receiving = ''

  return post, receiving


def function_tables_and_exports(funcs, metadata, mem_init, glue, forwarded_data, outfile, DEBUG):
  if DEBUG:
    logger.debug('emscript: python processing: function tables and exports')
    t = time.time()

  forwarded_json = json.loads(forwarded_data)

  # merge in information from llvm backend

  function_table_data = metadata['tables']

  if shared.Settings.WASM:
    analyze_table(function_table_data)

  # merge forwarded data
  shared.Settings.EXPORTED_FUNCTIONS = forwarded_json['EXPORTED_FUNCTIONS']

  pre, post = glue.split('// EMSCRIPTEN_END_FUNCS')

  pre = apply_script_source(pre)
  asm_extern_primitives = get_asm_extern_primitives(pre)
  metadata['externUses'] += asm_extern_primitives

  pre = memory_and_global_initializers(pre, metadata, mem_init)
  pre, funcs_js = get_js_funcs(pre, funcs)
  all_exported_functions = get_all_exported_functions(function_table_data)
  all_implemented = get_all_implemented(forwarded_json, metadata)
  report_missing_symbols(all_implemented, pre)
  implemented_functions = get_implemented_functions(metadata)
  pre = include_asm_consts(pre, forwarded_json, metadata)
  pre = apply_table(pre)
  outfile.write(pre)
  pre = None

  # Move preAsms to their right place
  def move_preasm(m):
    contents = m.groups(0)[0]
    outfile.write(contents + '\n')
    return ''

  if not shared.Settings.BOOTSTRAPPING_STRUCT_INFO and len(funcs_js) > 1:
    funcs_js[1] = re.sub(r'/\* PRE_ASM \*/(.*)\n', move_preasm, funcs_js[1])

  if 'pre' in function_table_data:
    pre_tables = function_table_data['pre']
    del function_table_data['pre']
  else:
    pre_tables = ''

  function_table_sigs = list(function_table_data.keys())

  in_table, debug_tables, function_tables_defs = make_function_tables_defs(
    implemented_functions, all_implemented, function_table_data, metadata)

  exported_implemented_functions = get_exported_implemented_functions(
    all_exported_functions, all_implemented, metadata)

  # List of function signatures of used 'invoke_xxx()' functions in the application
  # For backwards compatibility if one might be using a mismatching Emscripten compiler version, if 'invokeFuncs' is not present in metadata,
  # use the full list of signatures in function table and generate invoke_() functions for all signatures in the program (producing excessive code size)
  # we must also emit the full list if we are emitting code that can be linked later
  if 'invokeFuncs' in metadata and not shared.Settings.LINKABLE:
    invoke_function_names = metadata['invokeFuncs']
  else:
    invoke_function_names = ['invoke_' + x for x in function_table_sigs]

  asm_setup = create_asm_setup(debug_tables, function_table_data, invoke_function_names, metadata)
  basic_funcs = create_basic_funcs(function_table_sigs, invoke_function_names)
  basic_vars = create_basic_vars(exported_implemented_functions, forwarded_json, metadata)

  funcs_js += create_mftCall_funcs(function_table_data)

  exports = create_exports(exported_implemented_functions, in_table, function_table_data, metadata)

  # calculate globals
  try:
    del forwarded_json['Variables']['globals']['_llvm_global_ctors'] # not a true variable
  except KeyError:
    pass
  if not shared.Settings.RELOCATABLE:
    global_vars = metadata['externs']
  else:
    global_vars = [] # linkable code accesses globals through function calls
  global_funcs = set(key for key, value in forwarded_json['Functions']['libraryFunctions'].items() if value != 2)
  global_funcs = sorted(global_funcs.difference(set(global_vars)).difference(implemented_functions))
  if shared.Settings.RELOCATABLE:
    global_funcs += ['g$' + extern for extern in metadata['externs']]
    global_funcs += ['fp$' + extern for extern in metadata['externFunctions']]

  # Tracks the set of used (minified) function names in
  # JS symbols imported to asm.js module.
  minified_js_names = MinifiedJsNameGenerator()

  # Converts list of imports ['foo', 'bar', ...] to a dictionary of
  # name mappings in form { 'minified': 'unminified', ... }
  def define_asmjs_import_names(imports):
    if shared.Settings.MINIFY_ASMJS_IMPORT_NAMES:
      return [(minified_js_names.generate(), i) for i in imports]
    else:
      return [(i, i) for i in imports]

  basic_funcs = define_asmjs_import_names(basic_funcs)
  global_funcs = define_asmjs_import_names(global_funcs)
  basic_vars = define_asmjs_import_names(basic_vars)
  global_vars = define_asmjs_import_names(global_vars)

  bg_funcs = basic_funcs + global_funcs
  bg_vars = basic_vars + global_vars
  asm_global_funcs = create_asm_global_funcs(bg_funcs, metadata)
  asm_global_vars = create_asm_global_vars(bg_vars)

  the_global = create_the_global(metadata)
  sending_vars = bg_funcs + bg_vars

  sending = OrderedDict([(math_fix(minified), unminified) for (minified, unminified) in sending_vars])
  if shared.Settings.WASM:
    add_standard_wasm_imports(sending)
  sorted_sending_keys = sorted(sending.keys())
  sending = '{ ' + ', '.join('"' + k + '": ' + sending[k] for k in sorted_sending_keys) + ' }'

  receiving = create_receiving(function_table_data, function_tables_defs,
                               exported_implemented_functions, metadata['initializers'])

  post = apply_table(post)
  post = apply_static_code_hooks(post)

  if shared.Settings.MINIMAL_RUNTIME:
    post, receiving = compute_minimal_runtime_initializer_and_exports(post, metadata['initializers'], [mangled for mangled, unmangled in shared.Settings.MODULE_EXPORTS], receiving)

  function_tables_impls = make_function_tables_impls(function_table_data)
  final_function_tables = '\n'.join(function_tables_impls) + '\n' + function_tables_defs
  if shared.Settings.EMULATED_FUNCTION_POINTERS:
    final_function_tables = (
      final_function_tables
      .replace("asm['", '')
      .replace("']", '')
      .replace('var SIDE_FUNCTION_TABLE_', 'var FUNCTION_TABLE_')
      .replace('var dynCall_', '//')
    )

  if DEBUG:
    logger.debug('asm text sizes' + str([
      [len(s) for s in funcs_js], len(asm_setup), len(asm_global_vars), len(asm_global_funcs), len(pre_tables),
      len('\n'.join(function_tables_impls)), len(function_tables_defs) + (function_tables_defs.count('\n') * len('  ')),
      len(exports), len(the_global), len(sending), len(receiving)]))
    logger.debug('  emscript: python processing: function tables and exports took %s seconds' % (time.time() - t))

  bundled_args = (funcs_js, asm_setup, the_global, sending, receiving, asm_global_vars,
                  asm_global_funcs, pre_tables, final_function_tables, exports)
  return (post, function_table_data, bundled_args)


def finalize_output(outfile, post, function_table_data, bundled_args, metadata, DEBUG):
  function_table_sigs = function_table_data.keys()
  module = create_module_asmjs(function_table_sigs, metadata, *bundled_args)

  if DEBUG:
    logger.debug('emscript: python processing: finalize')
    t = time.time()

  write_output_file(outfile, post, module)
  module = None

  if DEBUG:
    logger.debug('  emscript: python processing: finalize took %s seconds' % (time.time() - t))

  write_cyberdwarf_data(outfile, metadata)


# Given JS code that consists only exactly of a series of "var a = ...;\n var b = ...;" statements,
# this function collapses the redundant 'var ' statements at the beginning of each line to a
# single var a =..., b=..., c=...; statement.
def collapse_redundant_vars(code):
  if shared.Settings.WASM:
    return code # Skip if targeting Wasm, this does not matter there

  old_code = ''
  while code != old_code: # Repeated vars overlap, so can't run in one regex pass. Runs in O(log(N)) time
    old_code = code
    code = re.sub(r'(var [^;]*);\s*var ', r'\1,\n  ', code)
  return code


def global_initializer_funcs(initializers):
  # If we have at most one global ctor, no need to group global initializers.
  # Also in EVAL_CTORS mode, we want to try to evaluate the individual ctor functions, so in that mode,
  # do not group ctors into one.
  return ['globalCtors'] if (len(initializers) > 1 and not shared.Settings.EVAL_CTORS) else initializers


# Each .cpp file with global constructors generates a __GLOBAL__init() function that needs to be
# called to construct the global objects in that compilation unit. This function groups all these
# global initializer functions together into a single globalCtors() function that lives inside the
# asm.js/wasm module, and gets exported out to JS scope to be called at the startup of the application.
def create_global_initializer(initializers):
  # If we have no global ctors, don't even generate a dummy empty function to save code space
  # Also in EVAL_CTORS mode, we want to try to evaluate the individual ctor functions, so in that mode,
  # we do not group ctors into one.
  if 'globalCtors' not in global_initializer_funcs(initializers):
    return ''

  global_initializer = '''  function globalCtors() {
    %s
  }''' % '\n    '.join(i + '();' for i in initializers)

  return global_initializer


def create_module_asmjs(function_table_sigs, metadata,
                        funcs_js, asm_setup, the_global, sending, receiving, asm_global_vars,
                        asm_global_funcs, pre_tables, final_function_tables, exports):
  receiving += create_named_globals(metadata)
  runtime_funcs = create_runtime_funcs_asmjs(exports, metadata)

  asm_start_pre = create_asm_start_pre(asm_setup, the_global, sending, metadata)
  memory_views = create_memory_views(metadata)
  asm_temp_vars = create_asm_temp_vars(metadata)
  asm_runtime_thread_local_vars = create_asm_runtime_thread_local_vars()

  stack = ''
  if not shared.Settings.RELOCATABLE and not (shared.Settings.WASM and shared.Settings.SIDE_MODULE):
    if 'STACKTOP' in shared.Settings.ASM_PRIMITIVE_VARS:
      stack += apply_memory('  var STACKTOP = {{{ STACK_BASE }}};\n')
    if 'STACK_MAX' in shared.Settings.ASM_PRIMITIVE_VARS:
      stack += apply_memory('  var STACK_MAX = {{{ STACK_MAX }}};\n')

  if 'tempFloat' in shared.Settings.ASM_PRIMITIVE_VARS:
    temp_float = '  var tempFloat = %s;\n' % ('Math_fround(0)' if provide_fround() else '0.0')
  else:
    temp_float = ''
  async_state = '  var asyncState = 0;\n' if shared.Settings.EMTERPRETIFY_ASYNC else ''
  f0_fround = '  const f0 = Math_fround(0);\n' if provide_fround() else ''

  replace_memory = create_replace_memory(metadata)

  start_funcs_marker = '\n// EMSCRIPTEN_START_FUNCS\n'

  asm_end = create_asm_end(exports)

  asm_variables = collapse_redundant_vars(memory_views + asm_global_vars + asm_temp_vars + asm_runtime_thread_local_vars + '\n' + asm_global_funcs + stack + temp_float + async_state + f0_fround)
  asm_global_initializer = create_global_initializer(metadata['initializers'])

  module = [
    asm_start_pre,
    asm_variables,
    replace_memory,
    start_funcs_marker,
    asm_global_initializer
  ] + runtime_funcs + funcs_js + [
    '\n  ',
    pre_tables, final_function_tables, asm_end,
    '\n', receiving, ';\n'
  ]

  if shared.Settings.SIDE_MODULE:
    module.append('''
parentModule['registerFunctions'](%s, Module);
''' % str([str(f) for f in function_table_sigs]))

  return module


def write_output_file(outfile, post, module):
  for i in range(len(module)): # do this loop carefully to save memory
    module[i] = normalize_line_endings(module[i])
    outfile.write(module[i])

  post = normalize_line_endings(post)
  outfile.write(post)


def write_cyberdwarf_data(outfile, metadata):
  if not shared.Settings.CYBERDWARF:
    return

  assert('cyberdwarf_data' in metadata)
  cd_file_name = outfile.name + ".cd"
  with open(cd_file_name, 'w') as f:
    json.dump({'cyberdwarf': metadata['cyberdwarf_data']}, f)


def create_backend_cmd(infile, temp_js):
  """Create asm.js backend command from settings dict"""
  args = [
    shared.LLVM_COMPILER, infile, '-march=js', '-filetype=asm', '-o', temp_js,
    '-emscripten-stack-size=%d' % shared.Settings.TOTAL_STACK,
    '-O%s' % shared.Settings.OPT_LEVEL,
  ]
  if shared.Settings.PRECISE_F32:
    args += ['-emscripten-precise-f32']
  if shared.Settings.USE_PTHREADS:
    args += ['-emscripten-enable-pthreads']
  if shared.Settings.WARN_UNALIGNED:
    args += ['-emscripten-warn-unaligned']
  if shared.Settings.RESERVED_FUNCTION_POINTERS > 0:
    args += ['-emscripten-reserved-function-pointers=%d' % shared.Settings.RESERVED_FUNCTION_POINTERS]
  if shared.Settings.ASSERTIONS > 0:
    args += ['-emscripten-assertions=%d' % shared.Settings.ASSERTIONS]
  if shared.Settings.ALIASING_FUNCTION_POINTERS == 0:
    args += ['-emscripten-no-aliasing-function-pointers']
  if shared.Settings.EMULATED_FUNCTION_POINTERS:
    args += ['-emscripten-emulated-function-pointers']
  if shared.Settings.EMULATE_FUNCTION_POINTER_CASTS:
    args += ['-emscripten-emulate-function-pointer-casts']
  if shared.Settings.RELOCATABLE:
    args += ['-emscripten-relocatable']
    args += ['-emscripten-global-base=0']
  elif shared.Settings.GLOBAL_BASE >= 0:
    args += ['-emscripten-global-base=%d' % shared.Settings.GLOBAL_BASE]
  if shared.Settings.SIDE_MODULE:
    args += ['-emscripten-side-module']
  if shared.Settings.LEGALIZE_JS_FFI != 1:
    args += ['-emscripten-legalize-javascript-ffi=0']
  if shared.Settings.DISABLE_EXCEPTION_CATCHING != 1:
    args += ['-enable-emscripten-cpp-exceptions']
    if shared.Settings.DISABLE_EXCEPTION_CATCHING == 2:
      args += ['-emscripten-cpp-exceptions-whitelist=' + ','.join(shared.Settings.EXCEPTION_CATCHING_WHITELIST or ['fake'])]
  if not shared.Settings.EXIT_RUNTIME:
    args += ['-emscripten-no-exit-runtime']
  if shared.Settings.WORKAROUND_IOS_9_RIGHT_SHIFT_BUG:
    args += ['-emscripten-asmjs-work-around-ios-9-right-shift-bug']
  if shared.Settings.WASM:
    args += ['-emscripten-wasm']
    if shared.Building.is_wasm_only():
      args += ['-emscripten-only-wasm']
  if shared.Settings.CYBERDWARF:
    args += ['-enable-cyberdwarf']
  return args


def optimize_syscalls(declares, DEBUG):
  """Disables filesystem if only a limited subset of syscalls is used.

  Our syscalls are static, and so if we see a very limited set of them - in particular,
  no open() syscall and just simple writing - then we don't need full filesystem support.
  If FORCE_FILESYSTEM is set, we can't do this. We also don't do it if INCLUDE_FULL_LIBRARY, since
  not including the filesystem would mean not including the full JS libraries, and the same for
  MAIN_MODULE since a side module might need the filesystem.
  """
  relevant_settings = ['FORCE_FILESYSTEM', 'INCLUDE_FULL_LIBRARY', 'MAIN_MODULE']
  if any(shared.Settings[s] for s in relevant_settings):
    return

  if shared.Settings.FILESYSTEM == 0:
    # without filesystem support, it doesn't matter what syscalls need
    shared.Settings.SYSCALLS_REQUIRE_FILESYSTEM = 0
  else:
    syscall_prefixes = ('__syscall', 'fd_', '__wasi_fd_')
    syscalls = [d for d in declares if d.startswith(syscall_prefixes)]
    # check if the only filesystem syscalls are in: close, ioctl, llseek, write
    # (without open, etc.. nothing substantial can be done, so we can disable
    # extra filesystem support in that case)
    if set(syscalls).issubset(set([
      '__syscall6', '__syscall54', '__syscall140',
      'fd_seek', '__wasi_fd_seek',
      'fd_write', '__wasi_fd_write',
      'fd_close', '__wasi_fd_close',
    ])):
      if DEBUG:
        logger.debug('very limited syscalls (%s) so disabling full filesystem support', ', '.join(str(s) for s in syscalls))
      shared.Settings.SYSCALLS_REQUIRE_FILESYSTEM = 0


def is_int(x):
  try:
    int(x)
    return True
  except ValueError:
    return False


def align_memory(addr):
  return (addr + 15) & -16


def align_static_bump(metadata):
  metadata['staticBump'] = align_memory(metadata['staticBump'])
  return metadata['staticBump']


def update_settings_glue(metadata, DEBUG):
  optimize_syscalls(metadata['declares'], DEBUG)

  if shared.Settings.CYBERDWARF:
    shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE.append("cyberdwarf_Debugger")
    shared.Settings.EXPORTED_FUNCTIONS.append("cyberdwarf_Debugger")

  # Integrate info from backend
  if shared.Settings.SIDE_MODULE:
    # we don't need any JS library contents in side modules
    shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE = []

  if metadata.get('cantValidate') and shared.Settings.ASM_JS != 2:
    shared.WarningManager.warn('ALMOST_ASM', 'disabling asm.js validation due to use of non-supported features: ' + metadata['cantValidate'])
    shared.Settings.ASM_JS = 2

  all_funcs = shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE + [shared.JS.to_nice_ident(d) for d in metadata['declares']]
  implemented_funcs = [x[1:] for x in metadata['implementedFunctions']]
  shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE = sorted(set(all_funcs).difference(implemented_funcs))

  shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += [x[1:] for x in metadata['externs']]

  if metadata['simd']:
    shared.Settings.SIMD = 1
    if shared.Settings.ASM_JS != 2:
      shared.WarningManager.warn('ALMOST_ASM', 'disabling asm.js validation due to use of SIMD')
      shared.Settings.ASM_JS = 2

  shared.Settings.MAX_GLOBAL_ALIGN = metadata['maxGlobalAlign']
  shared.Settings.IMPLEMENTED_FUNCTIONS = metadata['implementedFunctions']

  # Extract the list of function signatures that MAIN_THREAD_EM_ASM blocks in
  # the compiled code have, each signature will need a proxy function invoker
  # generated for it.
  def read_proxied_function_signatures(asmConsts):
    proxied_function_signatures = set()
    for _, sigs, proxying_types in asmConsts.values():
      for sig, proxying_type in zip(sigs, proxying_types):
        if proxying_type == 'sync_on_main_thread_':
          proxied_function_signatures.add(sig + '_sync')
        elif proxying_type == 'async_on_main_thread_':
          proxied_function_signatures.add(sig + '_async')
    return list(proxied_function_signatures)

  shared.Settings.PROXIED_FUNCTION_SIGNATURES = read_proxied_function_signatures(metadata['asmConsts'])

  shared.Settings.STATIC_BUMP = align_static_bump(metadata)

  if shared.Settings.WASM_BACKEND:
    shared.Settings.BINARYEN_FEATURES = metadata['features']
    shared.Settings.WASM_TABLE_SIZE = metadata['tableSize']
    if shared.Settings.RELOCATABLE:
      # When building relocatable output (e.g. MAIN_MODULE) the reported table
      # size does not include the reserved slot at zero for the null pointer.
      # Instead we use __table_base to offset the elements by 1.
      shared.Settings.WASM_TABLE_SIZE += 1
    shared.Settings.MAIN_READS_PARAMS = metadata['mainReadsParams']


# static code hooks
class StaticCodeHooks:
  atinits = []
  atmains = []
  atexits = []


def apply_static_code_hooks(code):
  code = code.replace('{{{ ATINITS }}}', StaticCodeHooks.atinits)
  code = code.replace('{{{ ATMAINS }}}', StaticCodeHooks.atmains)
  code = code.replace('{{{ ATEXITS }}}', StaticCodeHooks.atexits)
  return code


def apply_forwarded_data(forwarded_data):
  forwarded_json = json.loads(forwarded_data)
  # Be aware of JS static allocations
  shared.Settings.STATIC_BUMP = forwarded_json['STATIC_BUMP']
  shared.Settings.DYNAMICTOP_PTR = forwarded_json['DYNAMICTOP_PTR']
  # Be aware of JS static code hooks
  StaticCodeHooks.atinits = str(forwarded_json['ATINITS'])
  StaticCodeHooks.atmains = str(forwarded_json['ATMAINS'])
  StaticCodeHooks.atexits = str(forwarded_json['ATEXITS'])


def compile_settings(compiler_engine, temp_files):
  # Save settings to a file to work around v8 issue 1579
  with temp_files.get_file('.txt') as settings_file:
    with open(settings_file, 'w') as s:
      json.dump(shared.Settings.to_dict(), s, sort_keys=True)

    # Call js compiler
    env = os.environ.copy()
    env['EMCC_BUILD_DIR'] = os.getcwd()
    out = jsrun.run_js_tool(path_from_root('src', 'compiler.js'), compiler_engine,
                            [settings_file], stdout=subprocess.PIPE, stderr=STDERR_FILE,
                            cwd=path_from_root('src'), env=env)
  assert '//FORWARDED_DATA:' in out, 'Did not receive forwarded data in pre output - process failed?'
  glue, forwarded_data = out.split('//FORWARDED_DATA:')

  apply_forwarded_data(forwarded_data)

  return glue, forwarded_data


class Memory():
  def __init__(self):
    # Note: if RELOCATABLE, then only relative sizes can be computed, and we don't
    #       actually write out any absolute memory locations ({{{ STACK_BASE }}}
    #       does not exist, etc.)

    # Memory layout:
    #  * first the static globals
    self.global_base = shared.Settings.GLOBAL_BASE
    self.static_bump = shared.Settings.STATIC_BUMP
    #  * then the stack (up on fastcomp, down on upstream)
    self.stack_low = align_memory(self.global_base + self.static_bump)
    self.stack_high = align_memory(self.stack_low + shared.Settings.TOTAL_STACK)
    if shared.Settings.WASM_BACKEND:
      self.stack_base = self.stack_high
      self.stack_max = self.stack_low
    else:
      self.stack_base = self.stack_low
      self.stack_max = self.stack_high
    #  * then dynamic memory begins
    self.dynamic_base = align_memory(self.stack_high)

    if self.dynamic_base >= shared.Settings.TOTAL_MEMORY:
     exit_with_error('Memory is not large enough for static data (%d) plus the stack (%d), please increase TOTAL_MEMORY (%d) to at least %d' % (self.static_bump, shared.Settings.TOTAL_STACK, shared.Settings.TOTAL_MEMORY, self.dynamic_base))


def apply_memory(js):
  # Apply the statically-at-compile-time computed memory locations.
  memory = Memory()

  # Write it all out
  js = js.replace('{{{ STATIC_BUMP }}}', str(memory.static_bump))
  js = js.replace('{{{ STACK_BASE }}}', str(memory.stack_base))
  js = js.replace('{{{ STACK_MAX }}}', str(memory.stack_max))
  js = js.replace('{{{ DYNAMIC_BASE }}}', str(memory.dynamic_base))

  logger.debug('global_base: %d stack_base: %d, stack_max: %d, dynamic_base: %d, static bump: %d', memory.global_base, memory.stack_base, memory.stack_max, memory.dynamic_base, memory.static_bump)

  shared.Settings.DYNAMIC_BASE = memory.dynamic_base

  return js


def apply_table(js):
  js = js.replace('{{{ WASM_TABLE_SIZE }}}', str(shared.Settings.WASM_TABLE_SIZE))

  return js


def apply_script_source(js):
  js = js.replace('{{{ TARGET_BASENAME }}}', shared.Settings.TARGET_BASENAME)

  return js


def memory_and_global_initializers(pre, metadata, mem_init):
  if shared.Settings.SIMD == 1:
    pre = open(path_from_root(os.path.join('src', 'ecmascript_simd.js'))).read() + '\n\n' + pre

  staticbump = shared.Settings.STATIC_BUMP

  pthread = ''
  if shared.Settings.USE_PTHREADS:
    pthread = 'if (!ENVIRONMENT_IS_PTHREAD)'

  global_initializers = ''
  if not shared.Settings.MINIMAL_RUNTIME:
    # In traditional runtime, global initializers are pushed to the __ATINIT__ array to be processed when runtime is loaded
    # In MINIMAL_RUNTIME global initializers are invoked directly off of the asm[''] export object, so this does not apply.
    global_initializers = global_initializer_funcs(metadata['initializers'])
    if len(global_initializers) > 0:
      global_initializers = ', '.join('{ func: function() { %s() } }' % i for i in global_initializers)
      global_initializers = '/* global initializers */ {pthread} __ATINIT__.push({global_initializers});'.format(pthread=pthread, global_initializers=global_initializers)
    else:
      global_initializers = '/* global initializers */ /*__ATINIT__.push();*/'

  pre = pre.replace('STATICTOP = STATIC_BASE + 0;', '''\
STATICTOP = STATIC_BASE + {staticbump};
{global_initializers}
{mem_init}'''.format(staticbump=staticbump,
                     global_initializers=global_initializers,
                     mem_init=mem_init))

  if shared.Settings.SIDE_MODULE:
    pre = pre.replace('GLOBAL_BASE', 'gb')

  pre = apply_memory(pre)
  pre = apply_static_code_hooks(pre)

  return pre


def get_js_funcs(pre, funcs):
  funcs_js = [funcs]
  parts = pre.split('// ASM_LIBRARY FUNCTIONS\n')
  if len(parts) > 1:
    pre = parts[0]
    funcs_js.append(parts[1])
  return pre, funcs_js


def get_all_exported_functions(function_table_data):
  # both asm.js and otherwise
  all_exported_functions = set(shared.Settings.EXPORTED_FUNCTIONS)

  # additional functions to export from asm, if they are implemented
  for additional_export in shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE:
    all_exported_functions.add('_' + additional_export)
  if shared.Settings.EXPORT_FUNCTION_TABLES:
    for table in function_table_data.values():
      for func in table.split('[')[1].split(']')[0].split(','):
        if func[0] == '_':
          all_exported_functions.add(func)
  return all_exported_functions


def get_all_implemented(forwarded_json, metadata):
  return set(metadata['implementedFunctions']).union(forwarded_json['Functions']['implementedFunctions'])


def report_missing_symbols(all_implemented, pre):
  # we are not checking anyway, so just skip this
  if not shared.Settings.ERROR_ON_UNDEFINED_SYMBOLS and not shared.Settings.WARN_ON_UNDEFINED_SYMBOLS:
    return

  # the initial list of missing functions are that the user explicitly exported
  # but were not implemented in compiled code
  missing = list(set(shared.Settings.USER_EXPORTED_FUNCTIONS) - all_implemented)

  for requested in missing:
    if ('function ' + asstr(requested)) in pre:
      continue
    # special-case malloc, EXPORTED by default for internal use, but we bake in a
    # trivial allocator and warn at runtime if used in ASSERTIONS
    if missing == '_malloc':
      continue
    if shared.Settings.ERROR_ON_UNDEFINED_SYMBOLS:
      exit_with_error('undefined exported function: "%s"', requested)
    elif shared.Settings.WARN_ON_UNDEFINED_SYMBOLS:
      shared.warning('undefined exported function: "%s"', requested)


def get_exported_implemented_functions(all_exported_functions, all_implemented, metadata):
  funcs = set(metadata['exports'])
  export_bindings = shared.Settings.EXPORT_BINDINGS
  export_all = shared.Settings.EXPORT_ALL
  for key in all_implemented:
    if key in all_exported_functions or export_all or (export_bindings and key.startswith('_emscripten_bind')):
      funcs.add(key)

  if not export_all:
    for name, alias in metadata['aliases'].items():
      # here we export the aliases,
      # if not the side module (which imports the alias)
      # will not be able to get to the actual implementation
      if alias in all_implemented and name in all_exported_functions:
        funcs.add(alias)

  funcs = list(funcs) + global_initializer_funcs(metadata['initializers'])

  if shared.Settings.ALLOW_MEMORY_GROWTH:
    funcs.append('_emscripten_replace_memory')
  if not shared.Settings.SIDE_MODULE and not shared.Settings.MINIMAL_RUNTIME:
    funcs += ['stackAlloc', 'stackSave', 'stackRestore', 'establishStackSpace']
  if shared.Settings.EMTERPRETIFY:
    funcs += ['emterpret']
    if shared.Settings.EMTERPRETIFY_ASYNC:
      funcs += ['setAsyncState', 'emtStackSave', 'emtStackRestore', 'getEmtStackMax', 'setEmtStackMax']

  return sorted(set(funcs))


def get_implemented_functions(metadata):
  return set(metadata['implementedFunctions'])


def proxy_debug_print(sync):
  if shared.Settings.PTHREADS_DEBUG:
    if sync:
      return 'warnOnce("sync proxying function " + code);'
    else:
      return 'warnOnce("async proxying function " + code);'
  return ''


def include_asm_consts(pre, forwarded_json, metadata):
  if shared.Settings.WASM and shared.Settings.SIDE_MODULE:
    if metadata['asmConsts']:
      exit_with_error('EM_ASM is not yet supported in shared wasm module (it cannot be stored in the wasm itself, need some solution)')

  asm_consts, all_sigs = all_asm_consts(metadata)
  asm_const_funcs = []
  for sig, call_type in all_sigs:
    if 'j' in sig:
      exit_with_error('emscript: EM_ASM should not receive i64s as inputs, they are not valid in JS')
    if '_emscripten_asm_const_' + call_type + sig in forwarded_json['Functions']['libraryFunctions']:
      continue # Only one invoker needs to be emitted for each ASM_CONST (signature x call_type) item
    forwarded_json['Functions']['libraryFunctions']['_emscripten_asm_const_' + call_type + sig] = 1
    args = ['a%d' % i for i in range(len(sig) - 1)]
    all_args = ['code'] + args

    pre_asm_const = ''

    if shared.Settings.USE_PTHREADS:
      sync_proxy = call_type == 'sync_on_main_thread_'
      async_proxy = call_type == 'async_on_main_thread_'
      proxied = sync_proxy or async_proxy
      if proxied:
        # In proxied function calls, positive integers 1, 2, 3, ... denote pointers
        # to regular C compiled functions. Negative integers -1, -2, -3, ... denote
        # indices to EM_ASM() blocks, so remap the EM_ASM() indices from 0, 1, 2,
        # ... over to the negative integers starting at -1.
        proxy_args = ['-1 - code', str(int(sync_proxy))] + args
        pre_asm_const += '  if (ENVIRONMENT_IS_PTHREAD) { ' + proxy_debug_print(sync_proxy) + 'return _emscripten_proxy_to_main_thread_js(' + ', '.join(proxy_args) + '); }\n'

    if shared.Settings.EMTERPRETIFY_ASYNC and shared.Settings.ASSERTIONS:
      # we cannot have an EM_ASM on the stack when saving/loading
      pre_asm_const += "  assert(typeof EmterpreterAsync !== 'object' || EmterpreterAsync.state !== 2, 'cannot have an EM_ASM on the stack when emterpreter pauses/resumes - the JS is not emterpreted, so we would end up running it again from the start');\n"

    asm_const_funcs.append(r'''
function _emscripten_asm_const_%s(%s) {
%s  return ASM_CONSTS[code](%s);
}''' % (call_type + asstr(sig), ', '.join(all_args), pre_asm_const, ', '.join(args)))

  asm_consts_text = '\nvar ASM_CONSTS = [' + ',\n '.join(asm_consts) + '];\n'
  asm_funcs_text = '\n'.join(asm_const_funcs) + '\n'

  em_js_funcs = create_em_js(forwarded_json, metadata)
  em_js_text = '\n'.join(em_js_funcs) + '\n'

  body_marker = '// === Body ==='
  return pre.replace(body_marker, body_marker + '\n' + asm_consts_text + asstr(asm_funcs_text) + em_js_text)


# Test if the parentheses at body[openIdx] and body[closeIdx] are a match to
# each other.
def parentheses_match(body, openIdx, closeIdx):
  if closeIdx < 0:
    closeIdx += len(body)
  count = 1
  for i in range(openIdx + 1, closeIdx + 1):
    if body[i] == body[openIdx]:
      count += 1
    elif body[i] == body[closeIdx]:
      count -= 1
      if count <= 0:
        return i == closeIdx
  return False


def trim_asm_const_body(body):
  body = body.strip()
  orig = None
  while orig != body:
    orig = body
    if len(body) > 1 and body[0] == '"' and body[-1] == '"':
      body = body[1:-1].replace('\\"', '"').strip()
    if len(body) > 1 and body[0] == '{' and body[-1] == '}' and parentheses_match(body, 0, -1):
      body = body[1:-1].strip()
    if len(body) > 1 and body[0] == '(' and body[-1] == ')' and parentheses_match(body, 0, -1):
      body = body[1:-1].strip()
  return body


def all_asm_consts(metadata):
  asm_consts = [0] * len(metadata['asmConsts'])
  all_sigs = []
  for k, v in metadata['asmConsts'].items():
    const, sigs, call_types = v
    const = asstr(const)
    const = trim_asm_const_body(const)
    const = '{ ' + const + ' }'
    args = []
    arity = max(len(s) for s in sigs) - 1
    for i in range(arity):
      args.append('$' + str(i))
    const = 'function(' + ', '.join(args) + ') ' + const
    asm_consts[int(k)] = const
    assert(len(sigs) == len(call_types))
    for sig, call_type in zip(sigs, call_types):
      all_sigs.append((sig, call_type))
  return asm_consts, all_sigs


def unfloat(s):
  """lower float to double for ffis"""
  return 'd' if s == 'f' else s


def make_function_tables_defs(implemented_functions, all_implemented, function_table_data, metadata):
  class Counter(object):
    next_bad_item = 0
    next_item = 0
    pre = []

  in_table = set()
  debug_tables = {}

  def make_params(sig):
    return ','.join('p%d' % p for p in range(len(sig) - 1))

  def make_coerced_params(sig):
    return ','.join(shared.JS.make_coercion('p%d', unfloat(sig[p + 1])) % p for p in range(len(sig) - 1))

  def make_coercions(sig):
    return ';'.join('p%d = %s' % (p, shared.JS.make_coercion('p%d' % p, sig[p + 1])) for p in range(len(sig) - 1)) + ';'

  # when emulating function pointer casts, we need to know what is the target of each pointer
  if shared.Settings.EMULATE_FUNCTION_POINTER_CASTS and not shared.Settings.WASM:
    function_pointer_targets = {}
    for sig, table in function_table_data.items():
      start = table.index('[')
      end = table.rindex(']')
      body = table[start + 1:end].split(',')
      for i, parsed in enumerate(x.strip() for x in body):
        if parsed != '0':
          assert i not in function_pointer_targets
          function_pointer_targets[i] = [sig, str(parsed)]

  def make_table(sig, raw):
    if '[]' in raw:
      return ('', '') # empty table
    params = make_params(sig)
    coerced_params = make_coerced_params(sig)
    coercions = make_coercions(sig)

    def make_bad(target=None):
      i = Counter.next_bad_item
      Counter.next_bad_item += 1
      if target is None:
        target = i
      name = 'b' + str(i)
      if not shared.Settings.ASSERTIONS:
        if 'abort' in shared.Settings.RUNTIME_FUNCS_TO_IMPORT:
          code = 'abort(%s);' % target
        else:
          # Advanced use: developers is generating code that does not include the function 'abort()'. Generate invalid
          # function pointers to be no-op passthroughs that silently continue execution.
          code = '\n/*execution is supposed to abort here, but you did not include "abort" in RUNTIME_FUNCS_TO_IMPORT (to save code size?). Silently trucking through, enjoy :)*/\n'
      else:
        code = 'nullFunc_' + sig + '(%d);' % target
      if sig[0] != 'v':
        code += 'return %s' % shared.JS.make_initializer(sig[0]) + ';'
      return name, make_func(name, code, params, coercions)

    bad, bad_func = make_bad() # the default bad func
    if shared.Settings.ASSERTIONS <= 1:
      Counter.pre = [bad_func]
    else:
      Counter.pre = []
    start = raw.index('[')
    end = raw.rindex(']')
    body = raw[start + 1:end].split(',')
    if shared.Settings.EMULATED_FUNCTION_POINTERS:
      def receive(item):
        if item == '0':
          return item
        if item not in all_implemented:
          # this is not implemented; it would normally be wrapped, but with emulation, we just use it directly outside
          return item
        in_table.add(item)
        return "asm['" + item + "']"

      body = [receive(b) for b in body]
    for j in range(shared.Settings.RESERVED_FUNCTION_POINTERS):
      curr = 'jsCall_%s_%s' % (sig, j)
      body[1 + j] = curr
      implemented_functions.add(curr)
    Counter.next_item = 0

    def fix_item(item):
      j = Counter.next_item
      Counter.next_item += 1
      newline = Counter.next_item % 30 == 29
      if item == '0':
        # emulate all non-null pointer calls, if asked to
        if j > 0 and shared.Settings.EMULATE_FUNCTION_POINTER_CASTS and not shared.Settings.WASM and j in function_pointer_targets:
          proper_sig, proper_target = function_pointer_targets[j]
          if shared.Settings.EMULATED_FUNCTION_POINTERS:
            if proper_target in all_implemented:
              proper_target = "asm['" + proper_target + "']"

          def make_emulated_param(i):
            if i >= len(sig):
              return shared.JS.make_initializer(proper_sig[i]) # extra param, just send a zero
            return shared.JS.make_coercion('p%d' % (i - 1), proper_sig[i], convert_from=sig[i])

          proper_code = proper_target + '(' + ','.join([make_emulated_param(i + 1) for i in range(len(proper_sig) - 1)]) + ')'
          if proper_sig[0] != 'v':
            # proper sig has a return, which the wrapper may or may not use
            proper_code = shared.JS.make_coercion(proper_code, proper_sig[0])
            if proper_sig[0] != sig[0]:
              # first coercion ensured we call the target ok; this one ensures we return the right type in the wrapper
              proper_code = shared.JS.make_coercion(proper_code, sig[0], convert_from=proper_sig[0])
            if sig[0] != 'v':
              proper_code = 'return ' + proper_code
          else:
            # proper sig has no return, we may need a fake return
            if sig[0] != 'v':
              proper_code = 'return ' + shared.JS.make_initializer(sig[0])
          name = 'fpemu_%s_%d' % (sig, j)
          wrapper = make_func(name, proper_code, params, coercions)
          Counter.pre.append(wrapper)
          return name if not newline else (name + '\n')

        if shared.Settings.ASSERTIONS <= 1:
          return bad if not newline else (bad + '\n')

        specific_bad, specific_bad_func = make_bad(j)
        Counter.pre.append(specific_bad_func)
        return specific_bad if not newline else (specific_bad + '\n')

      clean_item = item.replace("asm['", '').replace("']", '')
      # when emulating function pointers, we don't need wrappers
      # but if relocating, then we also have the copies in-module, and do
      # in wasm we never need wrappers though
      if clean_item not in implemented_functions and not (shared.Settings.EMULATED_FUNCTION_POINTERS and not shared.Settings.RELOCATABLE) and not shared.Settings.WASM:
        # this is imported into asm, we must wrap it
        call_ident = clean_item
        if call_ident in metadata['redirects']:
          call_ident = metadata['redirects'][call_ident]
        if not call_ident.startswith('_') and not call_ident.startswith('Math_'):
          call_ident = '_' + call_ident
        code = call_ident + '(' + coerced_params + ')'
        if sig[0] != 'v':
          # ffis cannot return float
          if sig[0] == 'f':
            code = '+' + code
          code = 'return ' + shared.JS.make_coercion(code, sig[0])
        code += ';'
        Counter.pre.append(make_func(clean_item + '__wrapper', code, params, coercions))
        assert not sig == 'X', 'must know the signature in order to create a wrapper for "%s" (TODO for shared wasm modules)' % item
        return clean_item + '__wrapper'
      return item if not newline else (item + '\n')

    if shared.Settings.ASSERTIONS >= 2:
      debug_tables[sig] = body
    body = ','.join(fix_item(b) for b in body)
    return ('\n'.join(Counter.pre), ''.join([raw[:start + 1], body, raw[end:]]))

  infos = [make_table(sig, raw) for sig, raw in function_table_data.items()]
  Counter.pre = []

  function_tables_defs = '\n'.join([info[0] for info in infos]) + '\n'
  function_tables_defs += '\n// EMSCRIPTEN_END_FUNCS\n'
  function_tables_defs += '\n'.join([info[1] for info in infos])
  return in_table, debug_tables, function_tables_defs


def make_func(name, code, params, coercions):
  return 'function %s(%s) {\n %s %s\n}' % (name, params, coercions, code)


def math_fix(g):
  return g if not g.startswith('Math_') else g.split('_')[1]


# asm.js function tables have one table in each linked asm.js module, so we
# can't just dynCall into them - ftCall exists for that purpose. In wasm,
# even linked modules share the table, so it's all fine.
def asm_js_emulated_function_pointers():
  return shared.Settings.EMULATED_FUNCTION_POINTERS and not shared.Settings.WASM


def make_function_tables_impls(function_table_data):
  function_tables_impls = []
  for sig, table in function_table_data.items():
    args = ','.join(['a' + str(i) for i in range(1, len(sig))])
    arg_coercions = ' '.join(['a' + str(i) + '=' + shared.JS.make_coercion('a' + str(i), sig[i]) + ';' for i in range(1, len(sig))])
    coerced_args = ','.join([shared.JS.make_coercion('a' + str(i), sig[i]) for i in range(1, len(sig))])
    sig_mask = str(table.count(','))
    if not (shared.Settings.WASM and shared.Settings.EMULATED_FUNCTION_POINTERS):
      ret = 'FUNCTION_TABLE_%s[index&%s](%s)' % (sig, sig_mask, coerced_args)
    else:
      # for wasm with emulated function pointers, emit an mft_SIG(..) call, we avoid asm.js function tables there.
      ret = 'mftCall_%s(index%s%s)' % (sig, ',' if len(sig) > 1 else '', coerced_args)
    ret = ('return ' if sig[0] != 'v' else '') + shared.JS.make_coercion(ret, sig[0])
    if not asm_js_emulated_function_pointers():
      function_tables_impls.append('''
function dynCall_%s(index%s%s) {
  index = index|0;
  %s
  %s;
}
''' % (sig, ',' if len(sig) > 1 else '', args, arg_coercions, ret))
    else:
      function_tables_impls.append('''
var dynCall_%s = ftCall_%s;
''' % (sig, sig))

    ffi_args = ','.join([shared.JS.make_coercion('a' + str(i), sig[i], ffi_arg=True) for i in range(1, len(sig))])
    for i in range(shared.Settings.RESERVED_FUNCTION_POINTERS):
      jsret = ('return ' if sig[0] != 'v' else '') + shared.JS.make_coercion('jsCall_%s(%d%s%s)' % (sig, i, ',' if ffi_args else '', ffi_args), sig[0], ffi_result=True)
      function_tables_impls.append('''
function jsCall_%s_%s(%s) {
  %s
  %s;
}

''' % (sig, i, args, arg_coercions, jsret))
  return function_tables_impls


def create_mftCall_funcs(function_table_data):
  if not asm_js_emulated_function_pointers():
    return []
  if shared.Settings.WASM or not shared.Settings.RELOCATABLE:
    return []

  mftCall_funcs = []
  # in wasm, emulated function pointers are just simple table calls
  for sig, table in function_table_data.items():
    return_type, sig_args = sig[0], sig[1:]
    num_args = len(sig_args)
    params = ','.join(['ptr'] + ['p%d' % i for i in range(num_args)])
    coerced_params = ','.join([shared.JS.make_coercion('ptr', 'i')] + [shared.JS.make_coercion('p%d' % i, unfloat(sig_args[i])) for i in range(num_args)])
    coercions = ';'.join(['ptr = ptr | 0'] + ['p%d = %s' % (i, shared.JS.make_coercion('p%d' % i, unfloat(sig_args[i]))) for i in range(num_args)]) + ';'
    mini_coerced_params = ','.join([shared.JS.make_coercion('p%d' % i, sig_args[i]) for i in range(num_args)])
    maybe_return = '' if return_type == 'v' else 'return'
    final_return = maybe_return + ' ' + shared.JS.make_coercion('ftCall_' + sig + '(' + coerced_params + ')', unfloat(return_type)) + ';'
    if shared.Settings.EMULATED_FUNCTION_POINTERS == 1:
      body = final_return
    else:
      sig_mask = str(table.count(','))
      body = ('if (((ptr|0) >= (fb|0)) & ((ptr|0) < (fb + ' + sig_mask + ' | 0))) { ' + maybe_return + ' ' +
              shared.JS.make_coercion(
                'FUNCTION_TABLE_' + sig + '[(ptr-fb)&' + sig_mask + '](' +
                mini_coerced_params + ')', return_type, ffi_arg=True
              ) + '; ' + ('return;' if return_type == 'v' else '') + ' }' + final_return)
    mftCall_funcs.append(make_func('mftCall_' + sig, body, params, coercions) + '\n')
  return mftCall_funcs


def get_function_pointer_error(sig, function_table_sigs):
  if shared.Settings.ASSERTIONS == 0:
    # Release build: do the most minimal sized abort possible
    return "abort();"
  else:
    # ASSERTIONS-enabled build, identify the pointer and the failing signature.
    return "abortFnPtrError(x, '" + sig + "');"


def signature_sort_key(sig):
  def closure(other):
    ret = 0
    minlen = min(len(other), len(sig))
    maxlen = min(len(other), len(sig))
    if other.startswith(sig) or sig.startswith(other):
      ret -= 1000 # prioritize prefixes, could be dropped params
    ret -= 133 * difflib.SequenceMatcher(a=other, b=sig).ratio() # prioritize on diff similarity
    ret += 15 * abs(len(other) - len(sig)) / float(maxlen) # deprioritize the bigger the length difference is
    for i in range(minlen):
      if other[i] == sig[i]:
        ret -= 5 / float(maxlen) # prioritize on identically-placed params
    ret += 20 * len(other) # deprioritize on length
    return ret
  return closure


def asm_backend_uses(metadata, symbol):
  # If doing dynamic linking, we should generate full set of runtime primitives, since we cannot know up front ahead
  # of time what the dynamically linked in modules will need. Also with SAFE_HEAP and Emterpretify, generate full set of views.
  if shared.Settings.MAIN_MODULE or shared.Settings.SIDE_MODULE or shared.Settings.SAFE_HEAP or shared.Settings.EMTERPRETIFY:
    return True

  # Allow querying asm_backend_uses(metadata, 'Math.') to find if any of the Math objects are used
  if symbol.endswith('.'):
    return any(e.startswith(symbol) for e in metadata['externUses'])
  else:
    # Querying a single symbol
    return symbol in metadata['externUses']


def create_asm_global_funcs(bg_funcs, metadata):
  maths = ['Math.' + func for func in ['floor', 'abs', 'sqrt', 'pow', 'cos', 'sin', 'tan', 'acos', 'asin', 'atan', 'atan2', 'exp', 'log', 'ceil', 'imul', 'min', 'max', 'clz32']]
  if provide_fround():
    maths += ['Math.fround']

  asm_global_funcs = ''
  for math in maths:
    if asm_backend_uses(metadata, math):
      asm_global_funcs += '  var ' + math.replace('.', '_') + '=global' + access_quote(math) + ';\n'

  asm_global_funcs += ''.join(['  var ' + unminified + '=env' + access_quote(math_fix(minified)) + ';\n' for (minified, unminified) in bg_funcs])
  asm_global_funcs += global_simd_funcs(access_quote, metadata)
  if shared.Settings.USE_PTHREADS:
    asm_global_funcs += ''.join(['  var Atomics_' + ty + '=global' + access_quote('Atomics') + access_quote(ty) + ';\n' for ty in ['load', 'store', 'exchange', 'compareExchange', 'add', 'sub', 'and', 'or', 'xor']])
  return asm_global_funcs


def create_asm_global_vars(bg_vars):
  asm_global_vars = ''.join(['  var ' + unminified + '=env' + access_quote(minified) + '|0;\n' for (minified, unminified) in bg_vars])
  if shared.Settings.WASM and shared.Settings.SIDE_MODULE:
    # wasm side modules internally define their stack, these are set at module startup time
    asm_global_vars += '\n  var STACKTOP = 0, STACK_MAX = 0;\n'

  return asm_global_vars


def global_simd_funcs(access_quote, metadata):
  # Always import SIMD when building with -s SIMD=1, since in that mode memcpy is SIMD optimized.
  if not (metadata['simd'] or shared.Settings.SIMD):
    return ''

  def string_contains_any(s, str_list):
    return any(sub in s for sub in str_list)

  nonexisting_simd_symbols = ['Int8x16_fromInt8x16', 'Uint8x16_fromUint8x16', 'Int16x8_fromInt16x8', 'Uint16x8_fromUint16x8', 'Int32x4_fromInt32x4', 'Uint32x4_fromUint32x4', 'Float32x4_fromFloat32x4', 'Float64x2_fromFloat64x2']
  nonexisting_simd_symbols += ['Int32x4_addSaturate', 'Int32x4_subSaturate', 'Uint32x4_addSaturate', 'Uint32x4_subSaturate']
  nonexisting_simd_symbols += [(x + '_' + y) for x in ['Int8x16', 'Uint8x16', 'Int16x8', 'Uint16x8', 'Float64x2'] for y in ['load2', 'store2']]
  nonexisting_simd_symbols += [(x + '_' + y) for x in ['Int8x16', 'Uint8x16', 'Int16x8', 'Uint16x8'] for y in ['load1', 'store1']]

  simd = make_simd_types(metadata)

  simd_func_text = ''
  simd_func_text += ''.join(['  var SIMD_' + ty + '=global' + access_quote('SIMD') + access_quote(ty) + ';\n' for ty in simd['types']])

  def generate_symbols(types, funcs):
    symbols = ['  var SIMD_' + ty + '_' + g + '=SIMD_' + ty + access_quote(g) + ';\n' for ty in types for g in funcs]
    symbols = [x for x in symbols if not string_contains_any(x, nonexisting_simd_symbols)]
    return ''.join(symbols)

  simd_func_text += generate_symbols(simd['int_types'], simd['int_funcs'])
  simd_func_text += generate_symbols(simd['float_types'], simd['float_funcs'])
  simd_func_text += generate_symbols(simd['bool_types'], simd['bool_funcs'])

  # SIMD conversions (not bitcasts) between same lane sizes:
  def add_simd_cast(dst, src):
    return '  var SIMD_' + dst + '_from' + src + '=SIMD_' + dst + '.from' + src + ';\n'

  def add_simd_casts(t1, t2):
    return add_simd_cast(t1, t2) + add_simd_cast(t2, t1)

  # Bug: Skip importing conversions for int<->uint for now, they don't validate
  # as asm.js. https://bugzilla.mozilla.org/show_bug.cgi?id=1313512
  # This is not an issue when building SSEx code, because it doesn't use these.
  # (but it will be an issue if using SIMD.js intrinsics from vector.h to
  # explicitly call these)
  # if metadata['simdInt8x16'] and metadata['simdUint8x16']:
  #   simd_func_text += add_simd_casts('Int8x16', 'Uint8x16')
  # if metadata['simdInt16x8'] and metadata['simdUint16x8']:
  #   simd_func_text += add_simd_casts('Int16x8', 'Uint16x8')
  # if metadata['simdInt32x4'] and metadata['simdUint32x4']:
  #   simd_func_text += add_simd_casts('Int32x4', 'Uint32x4')

  if metadata['simdInt32x4'] and metadata['simdFloat32x4']:
    simd_func_text += add_simd_casts('Int32x4', 'Float32x4')
  if metadata['simdUint32x4'] and metadata['simdFloat32x4']:
    simd_func_text += add_simd_casts('Uint32x4', 'Float32x4')
  if metadata['simdInt32x4'] and metadata['simdFloat64x2']:
    simd_func_text += add_simd_cast('Int32x4', 'Float64x2') # Unofficial, needed for emscripten_int32x4_fromFloat64x2
  if metadata['simdUint32x4'] and metadata['simdFloat64x2']:
    simd_func_text += add_simd_cast('Uint32x4', 'Float64x2') # Unofficial, needed for emscripten_uint32x4_fromFloat64x2

  # Unofficial, Bool64x2 does not yet exist, but needed for Float64x2 comparisons.
  if metadata['simdFloat64x2']:
    simd_func_text += '  var SIMD_Int32x4_fromBool64x2Bits = global.SIMD.Int32x4.fromBool64x2Bits;\n'
  return simd_func_text


def make_simd_types(metadata):
  simd_float_types = []
  simd_int_types = []
  simd_bool_types = []
  simd_funcs = ['splat', 'check', 'extractLane', 'replaceLane']
  simd_intfloat_funcs = ['add', 'sub', 'neg', 'mul',
                         'equal', 'lessThan', 'greaterThan',
                         'notEqual', 'lessThanOrEqual', 'greaterThanOrEqual',
                         'select', 'swizzle', 'shuffle',
                         'load', 'store', 'load1', 'store1', 'load2', 'store2']
  simd_intbool_funcs = ['and', 'xor', 'or', 'not']
  if metadata['simdUint8x16']:
    simd_int_types += ['Uint8x16']
    simd_intfloat_funcs += ['fromUint8x16Bits']
  if metadata['simdInt8x16']:
    simd_int_types += ['Int8x16']
    simd_intfloat_funcs += ['fromInt8x16Bits']
  if metadata['simdUint16x8']:
    simd_int_types += ['Uint16x8']
    simd_intfloat_funcs += ['fromUint16x8Bits']
  if metadata['simdInt16x8']:
    simd_int_types += ['Int16x8']
    simd_intfloat_funcs += ['fromInt16x8Bits']
  if metadata['simdUint32x4']:
    simd_int_types += ['Uint32x4']
    simd_intfloat_funcs += ['fromUint32x4Bits']
  if metadata['simdInt32x4'] or shared.Settings.SIMD:
    # Always import Int32x4 when building with -s SIMD=1, since memcpy is SIMD optimized.
    simd_int_types += ['Int32x4']
    simd_intfloat_funcs += ['fromInt32x4Bits']
  if metadata['simdFloat32x4']:
    simd_float_types += ['Float32x4']
    simd_intfloat_funcs += ['fromFloat32x4Bits']
  if metadata['simdFloat64x2']:
    simd_float_types += ['Float64x2']
    simd_intfloat_funcs += ['fromFloat64x2Bits']
  if metadata['simdBool8x16']:
    simd_bool_types += ['Bool8x16']
  if metadata['simdBool16x8']:
    simd_bool_types += ['Bool16x8']
  if metadata['simdBool32x4']:
    simd_bool_types += ['Bool32x4']
  if metadata['simdBool64x2']:
    simd_bool_types += ['Bool64x2']

  simd_float_funcs = simd_funcs + simd_intfloat_funcs + ['div', 'min', 'max', 'minNum', 'maxNum', 'sqrt',
                                                         'abs', 'reciprocalApproximation', 'reciprocalSqrtApproximation']
  simd_int_funcs = simd_funcs + simd_intfloat_funcs + simd_intbool_funcs + ['shiftLeftByScalar', 'shiftRightByScalar', 'addSaturate', 'subSaturate']
  simd_bool_funcs = simd_funcs + simd_intbool_funcs + ['anyTrue', 'allTrue']
  simd_types = simd_float_types + simd_int_types + simd_bool_types
  return {
    'types': simd_types,
    'float_types': simd_float_types,
    'int_types': simd_int_types,
    'bool_types': simd_bool_types,
    'funcs': simd_funcs,
    'float_funcs': simd_float_funcs,
    'int_funcs': simd_int_funcs,
    'bool_funcs': simd_bool_funcs,
    'intfloat_funcs': simd_intfloat_funcs,
    'intbool_funcs': simd_intbool_funcs,
  }


def asm_safe_heap():
  """optimized safe heap in asm, when we can"""
  return shared.Settings.SAFE_HEAP and not shared.Settings.SAFE_HEAP_LOG and not shared.Settings.RELOCATABLE


def provide_fround():
  return shared.Settings.PRECISE_F32 or shared.Settings.SIMD


def create_asm_setup(debug_tables, function_table_data, invoke_function_names, metadata):
  function_table_sigs = function_table_data.keys()

  asm_setup = ''
  if shared.Settings.ASSERTIONS >= 2:
    debug_tables_map = 'var debug_tables = {\n'
    for sig in function_table_data:
      # if the table is empty, debug_tables will not contain it
      body = debug_tables.get(sig, [])
      asm_setup += 'var debug_table_' + sig + ' = [' + ','.join(['0' if x == '0' else "'" + x.replace("'", '"') + "'" for x in body]) + '];\n'
      debug_tables_map += "  '" + sig + "': debug_table_" + sig + ',\n'
    asm_setup += debug_tables_map + '};\n'

  if shared.Settings.ASSERTIONS:
    for sig in function_table_sigs:
      asm_setup += 'function nullFunc_' + sig + '(x) { ' + get_function_pointer_error(sig, function_table_sigs) + ' }\n'

  if shared.Settings.RELOCATABLE:
    if not shared.Settings.SIDE_MODULE:
      asm_setup += 'var gb = GLOBAL_BASE, fb = 0;\n'
    side = 'parent' if shared.Settings.SIDE_MODULE else ''

    def check(extern):
      if shared.Settings.ASSERTIONS:
        return ('\n  assert(%sModule["%s"] || %s, "external symbol `%s` is missing.' % (side, extern, extern, extern) +
                'perhaps a side module was not linked in? if this symbol was expected to arrive '
                'from a system library, try to build the MAIN_MODULE with '
                'EMCC_FORCE_STDLIBS=1 in the environment");')
      return ''

    for extern in metadata['externs']:
      asm_setup += 'var g$' + extern + ' = function() {' + check(extern) + '\n  return ' + side + 'Module["' + extern + '"];\n}\n'
    for extern in metadata['externFunctions']:
      barename, sig = extern.split('$')
      fullname = "fp$" + extern
      key = '%sModule["%s"]' % (side, fullname)
      asm_setup += '''\
    var %s = function() {
      if (!%s) { %s
        var fid = addFunction(%sModule["%s"] || %s, "%s");
        %s = fid;
      }
      return %s;
    }
    ''' % (fullname, key, check(barename), side, barename, barename, sig, key, key)

  asm_setup += create_invoke_wrappers(invoke_function_names)
  asm_setup += setup_function_pointers(function_table_sigs)

  if shared.Settings.EMULATED_FUNCTION_POINTERS:
    function_tables_impls = make_function_tables_impls(function_table_data)
    asm_setup += '\n' + '\n'.join(function_tables_impls) + '\n'

  return asm_setup


def setup_function_pointers(function_table_sigs):
  asm_setup = ''
  for sig in function_table_sigs:
    if shared.Settings.RESERVED_FUNCTION_POINTERS:
      asm_setup += '\n' + shared.JS.make_jscall(sig) + '\n'
    # nothing special to do here for wasm, we just use dynCalls
    if not shared.Settings.WASM:
      if shared.Settings.EMULATED_FUNCTION_POINTERS:
        args = ['a%d' % i for i in range(len(sig) - 1)]
        full_args = ['x'] + args
        table_access = 'FUNCTION_TABLE_' + sig
        if shared.Settings.SIDE_MODULE:
          table_access = 'parentModule["' + table_access + '"]' # side module tables were merged into the parent, we need to access the global one
        table_read = table_access + '[x]'
        prelude = ''
        if shared.Settings.ASSERTIONS:
          prelude = '''
    if (x < 0 || x >= %s.length) { err("Function table mask error (out of range)"); %s ; abort(x) }''' % (table_access, get_function_pointer_error(sig, function_table_sigs))
        asm_setup += '''
  function ftCall_%s(%s) {%s
    return %s(%s);
  }
  ''' % (sig, ', '.join(full_args), prelude, table_read, ', '.join(args))
  return asm_setup


def create_basic_funcs(function_table_sigs, invoke_function_names):
  basic_funcs = shared.Settings.RUNTIME_FUNCS_TO_IMPORT
  if shared.Settings.STACK_OVERFLOW_CHECK and not shared.Settings.MINIMAL_RUNTIME:
    basic_funcs += ['abortStackOverflow']
  if shared.Settings.EMTERPRETIFY:
    basic_funcs += ['abortStackOverflowEmterpreter']
  if shared.Settings.SAFE_HEAP:
    if asm_safe_heap():
      basic_funcs += ['segfault', 'alignfault', 'ftfault']
    else:
      # Binaryen generates calls to these two so they are always needed with wasm
      if shared.Settings.WASM:
        basic_funcs += ['segfault', 'alignfault']
      basic_funcs += ['SAFE_HEAP_LOAD', 'SAFE_HEAP_LOAD_D', 'SAFE_HEAP_STORE', 'SAFE_HEAP_STORE_D', 'SAFE_FT_MASK']

  if shared.Settings.ASSERTIONS:
    for sig in function_table_sigs:
      basic_funcs += ['nullFunc_' + sig]

  basic_funcs += invoke_function_names

  for sig in function_table_sigs:
    if shared.Settings.RESERVED_FUNCTION_POINTERS:
      basic_funcs.append('jsCall_%s' % sig)
    if asm_js_emulated_function_pointers():
      basic_funcs.append('ftCall_%s' % sig)
  return basic_funcs


def create_basic_vars(exported_implemented_functions, forwarded_json, metadata):
  basic_vars = []
  if 'tempDoublePtr' in shared.Settings.ASM_PRIMITIVE_VARS:
    basic_vars += ['tempDoublePtr']

  if shared.Settings.RELOCATABLE:
    if not (shared.Settings.WASM and shared.Settings.SIDE_MODULE):
      basic_vars += ['gb', 'fb', 'STACKTOP', 'STACK_MAX']
    else:
      # wasm side modules have a specific convention for these
      basic_vars += ['__memory_base', '__table_base']

  if shared.Settings.EMTERPRETIFY:
    basic_vars += ['EMTSTACKTOP', 'EMT_STACK_MAX', 'eb']

  return basic_vars


def create_exports(exported_implemented_functions, in_table, function_table_data, metadata):
  asm_runtime_funcs = create_asm_runtime_funcs()
  all_exported = exported_implemented_functions + asm_runtime_funcs + function_tables(function_table_data)
  # In asm.js + emulated function pointers, export all the table because we use
  # JS to add the asm.js module's functions to the table (which is external
  # in this mode). In wasm, we don't need that since wasm modules can
  # directly add functions to the imported Table.
  if not shared.Settings.WASM and shared.Settings.EMULATED_FUNCTION_POINTERS:
    all_exported += in_table
  exports = []
  for export in sorted(set(all_exported)):
    exports.append(quote(export) + ": " + export)
  if shared.Settings.WASM and shared.Settings.SIDE_MODULE:
    # named globals in side wasm modules are exported globals from asm/wasm
    for k, v in metadata['namedGlobals'].items():
      exports.append(quote('_' + str(k)) + ': ' + str(v))
    # aliases become additional exports
    for k, v in metadata['aliases'].items():
      exports.append(quote(str(k)) + ': ' + str(v))
  # shared wasm emulated function pointer mode requires us to know the function pointer for
  # each function. export fp$func => function pointer for func
  if shared.Settings.WASM and shared.Settings.RELOCATABLE and shared.Settings.EMULATE_FUNCTION_POINTER_CASTS:
    for k, v in metadata['functionPointers'].items():
      exports.append(quote('fp$' + str(k)) + ': ' + str(v))
  return '{ ' + ', '.join(exports) + ' }'


def create_asm_runtime_funcs():
  funcs = []
  if not (shared.Settings.WASM and shared.Settings.SIDE_MODULE) and not shared.Settings.MINIMAL_RUNTIME:
    funcs += ['stackAlloc', 'stackSave', 'stackRestore', 'establishStackSpace']
  return funcs


def function_tables(function_table_data):
  if not asm_js_emulated_function_pointers():
    return ['dynCall_' + table for table in function_table_data]
  else:
    return []


def create_the_global(metadata):
  # the global is only needed for asm.js
  if shared.Settings.WASM:
    return '{}'
  fundamentals = []
  if asm_backend_uses(metadata, 'Math.'):
    fundamentals += ['Math']
  for f in ['Int8Array', 'Int16Array', 'Int32Array', 'Uint8Array', 'Uint16Array', 'Uint32Array', 'Float32Array', 'Float64Array', 'NaN', 'Infinity']:
    if asm_backend_uses(metadata, f):
      fundamentals += [f]

  if metadata['simd'] or shared.Settings.SIMD:
    # Always import SIMD when building with -s SIMD=1, since in that mode memcpy is SIMD optimized.
    fundamentals += ['SIMD']
  return '{ ' + ', '.join(['"' + math_fix(s) + '": ' + s for s in fundamentals]) + ' }'


RUNTIME_ASSERTIONS = '''
  assert(runtimeInitialized, 'you need to wait for the runtime to be ready (e.g. wait for main() to be called)');
  assert(!runtimeExited, 'the runtime was exited (use NO_EXIT_RUNTIME to keep it alive after main() exits)');'''


def create_receiving(function_table_data, function_tables_defs, exported_implemented_functions, initializers):
  receiving = ''
  if not shared.Settings.ASSERTIONS or shared.Settings.MINIMAL_RUNTIME:
    runtime_assertions = ''
  else:
    runtime_assertions = RUNTIME_ASSERTIONS
    # assert on the runtime being in a valid state when calling into compiled code. The only exceptions are some support code.
    # WASM=1 already inserts runtime assertions, so no need to do it again here (see create_receiving_wasm)
    if not shared.Settings.WASM:
      receiving_functions = [f for f in exported_implemented_functions if f not in ('_memcpy', '_memset', '_emscripten_replace_memory', '__start_module')]

      wrappers = []
      for name in receiving_functions:
        wrappers.append('''\
var real_%(name)s = asm["%(name)s"];
asm["%(name)s"] = function() {%(runtime_assertions)s
  return real_%(name)s.apply(null, arguments);
};
''' % {'name': name, 'runtime_assertions': runtime_assertions})
      receiving = '\n'.join(wrappers)

  module_exports = exported_implemented_functions + function_tables(function_table_data)
  shared.Settings.MODULE_EXPORTS = [(f, f) for f in module_exports]

  if not shared.Settings.SWAPPABLE_ASM_MODULE:
    if shared.Settings.DECLARE_ASM_MODULE_EXPORTS:
      imported_exports = [s for s in module_exports if s not in initializers]

      if shared.Settings.WASM and shared.Settings.MINIMAL_RUNTIME:
        # In Wasm exports are assigned inside a function to variables existing in top level JS scope, i.e.
        # var _main;
        # WebAssembly.instantiate(Module["wasm"], imports).then((function(output) {
        # var asm = output.instance.exports;
        # _main = asm["_main"];
        receiving += '\n'.join([s + ' = asm["' + s + '"];' for s in imported_exports]) + '\n'
      else:
        if shared.Settings.MINIMAL_RUNTIME:
          # In asm.js exports can be directly processed at top level, i.e.
          # var asm = Module["asm"](asmGlobalArg, asmLibraryArg, buffer);
          # var _main = asm["_main"];
          receiving += '\n'.join(['var ' + s + ' = asm["' + s + '"];' for s in imported_exports]) + '\n'
        else:
          receiving += '\n'.join(['var ' + s + ' = Module["' + s + '"] = asm["' + s + '"];' for s in module_exports]) + '\n'
    else:
      if shared.Settings.target_environment_may_be('node') and shared.Settings.target_environment_may_be('web'):
        global_object = '(typeof process !== "undefined" ? global : this)'
      elif shared.Settings.target_environment_may_be('node'):
        global_object = 'global'
      else:
        global_object = 'this'

      if shared.Settings.MINIMAL_RUNTIME:
        module_assign = ''
      else:
        module_assign = 'Module[__exportedFunc] = '

      receiving += 'for(var __exportedFunc in asm) ' + global_object + '[__exportedFunc] = ' + module_assign + 'asm[__exportedFunc];\n'
  else:
    receiving += 'Module["asm"] = asm;\n'
    wrappers = []
    for name in module_exports:
      wrappers.append('''\
var %(name)s = Module["%(name)s"] = function() {%(runtime_assertions)s
  return Module["asm"]["%(name)s"].apply(null, arguments)
};
''' % {'name': name, 'runtime_assertions': runtime_assertions})
    receiving += '\n'.join(wrappers)

  if shared.Settings.EXPORT_FUNCTION_TABLES and not shared.Settings.WASM:
    for table in function_table_data.values():
      tableName = table.split()[1]
      table = table.replace('var ' + tableName, 'var ' + tableName + ' = Module["' + tableName + '"]')
      receiving += table + '\n'

  if shared.Settings.EMULATED_FUNCTION_POINTERS:
    # in asm.js emulated function tables, emit the table on the outside, where
    # JS can manage it (for wasm, a native wasm Table is used directly, and we
    # don't need this)
    if not shared.Settings.WASM:
      receiving += '\n' + function_tables_defs.replace('// EMSCRIPTEN_END_FUNCS\n', '')
    # wasm still needs definitions for dyncalls on the outside, for JS
    receiving += '\n' + ''.join(['Module["dynCall_%s"] = dynCall_%s\n' % (sig, sig) for sig in function_table_data])
    if not shared.Settings.WASM:
      for sig in function_table_data.keys():
        name = 'FUNCTION_TABLE_' + sig
        fullname = name if not shared.Settings.SIDE_MODULE else ('SIDE_' + name)
        receiving += 'Module["' + name + '"] = ' + fullname + ';\n'

  return receiving


def create_fp_accessors(metadata):
  if not shared.Settings.RELOCATABLE:
    return ''

  # Create `fp$XXX` handlers for determining function pionters (table addresses)
  # at runtime.
  # For SIDE_MODULEs these are generated by the proxyHandler at runtime.
  accessors = []
  for fullname in metadata['declares']:
    if not fullname.startswith('fp$'):
      continue
    _, name, sig = fullname.split('$')
    mangled = asmjs_mangle(name)
    side = 'parent' if shared.Settings.SIDE_MODULE else ''
    assertion = ('\n  assert(%sModule["%s"] || typeof %s !== "undefined", "external function `%s` is missing.' % (side, mangled, mangled, name) +
                 'perhaps a side module was not linked in? if this symbol was expected to arrive '
                 'from a system library, try to build the MAIN_MODULE with '
                 'EMCC_FORCE_STDLIBS=XX in the environment");')
    # the name of the original function is generally the normal function
    # name, unless it is legalized, in which case the export is the legalized
    # version, and the original provided by orig$X
    if shared.Settings.LEGALIZE_JS_FFI and not shared.JS.is_legal_sig(sig):
      name = 'orig$' + name

    accessors.append('''
Module['%(full)s'] = function() {
  %(assert)s
  // Use the wasm function itself, for the table.
  var func = Module['asm']['%(original)s'];
  // If there is no wasm function, this may be a JS library function or
  // something from another module.
  if (!func) func = Module['%(mangled)s'];
  if (!func) func = %(mangled)s;
  var fp = addFunction(func, '%(sig)s');
  Module['%(full)s'] = function() { return fp };
  return fp;
}
''' % {'full': asmjs_mangle(fullname), 'mangled': mangled, 'original': name, 'assert': assertion, 'sig': sig})

  return '\n'.join(accessors)


def create_named_globals(metadata):
  if not shared.Settings.RELOCATABLE:
    return ''

  named_globals = '''
var NAMED_GLOBALS = {
  %s
};
for (var named in NAMED_GLOBALS) {
  Module['_' + named] = gb + NAMED_GLOBALS[named];
}
Module['NAMED_GLOBALS'] = NAMED_GLOBALS;
''' % ',\n  '.join('"' + k + '": ' + str(v) for k, v in metadata['namedGlobals'].items())

  if shared.Settings.WASM:
    # wasm side modules are pure wasm, and cannot create their g$..() methods, so we help them out
    # TODO: this works if we are the main module, but if the supplying module is later, it won't, so
    #       we'll need another solution for that. one option is to scan the module imports, if/when
    #       wasm supports that, then the loader can do this.
    named_globals += '''
for (var named in NAMED_GLOBALS) {
  (function(named) {
    var addr = Module['_' + named];
    Module['g$_' + named] = function() { return addr };
  })(named);
}
'''
  named_globals += ''.join(["Module['%s'] = Module['%s']\n" % (k, v) for k, v in metadata['aliases'].items()])
  return named_globals


def create_runtime_funcs_asmjs(exports, metadata):
  if shared.Settings.ASSERTIONS or shared.Settings.STACK_OVERFLOW_CHECK >= 2:
    stack_check = '  if ((STACKTOP|0) >= (STACK_MAX|0)) abortStackOverflow(size|0);\n'
  else:
    stack_check = ''

  funcs = ['''
function stackAlloc(size) {
  size = size|0;
  var ret = 0;
  ret = STACKTOP;
  STACKTOP = (STACKTOP + size)|0;
  STACKTOP = (STACKTOP + 15)&-16;
  %s
  return ret|0;
}
function stackSave() {
  return STACKTOP|0;
}
function stackRestore(top) {
  top = top|0;
  STACKTOP = top;
}
function establishStackSpace(stackBase, stackMax) {
  stackBase = stackBase|0;
  stackMax = stackMax|0;
  STACKTOP = stackBase;
  STACK_MAX = stackMax;
}
''' % stack_check]

  if shared.Settings.MINIMAL_RUNTIME:
    # MINIMAL_RUNTIME moves stack functions to library.
    funcs = []

  if shared.Settings.EMTERPRETIFY:
    funcs.append('''
function emterpret(pc) { // this will be replaced when the emterpreter code is generated; adding it here allows validation until then
  pc = pc | 0;
  assert(0);
}''')

  if shared.Settings.EMTERPRETIFY_ASYNC:
    funcs.append('''
function setAsyncState(x) {
  x = x | 0;
  asyncState = x;
}
function emtStackSave() {
  return EMTSTACKTOP|0;
}
function emtStackRestore(x) {
  x = x | 0;
  EMTSTACKTOP = x;
}
function getEmtStackMax() {
  return EMT_STACK_MAX | 0;
}
function setEmtStackMax(x) {
  x = x | 0;
  EMT_STACK_MAX = x;
}
''')

  if asm_safe_heap():
    if '_sbrk' in metadata['implementedFunctions']:
      brk_check = 'if ((dest + bytes|0) > (HEAP32[(_emscripten_get_sbrk_ptr()|0)>>2]|0)) segfault();'
    else:
      # sbrk and malloc were not linked in, but SAFE_HEAP is used - so safe heap
      # can ignore the sbrk location.
      brk_check = ''
    funcs.append('''
function SAFE_HEAP_STORE(dest, value, bytes) {
  dest = dest | 0;
  value = value | 0;
  bytes = bytes | 0;
  if ((dest|0) <= 0) segfault();
  %(brk_check)s
  if ((bytes|0) == 4) {
    if ((dest&3)) alignfault();
    HEAP32[dest>>2] = value;
  } else if ((bytes|0) == 1) {
    HEAP8[dest>>0] = value;
  } else {
    if ((dest&1)) alignfault();
    HEAP16[dest>>1] = value;
  }
}
function SAFE_HEAP_STORE_D(dest, value, bytes) {
  dest = dest | 0;
  value = +value;
  bytes = bytes | 0;
  if ((dest|0) <= 0) segfault();
  %(brk_check)s
  if ((bytes|0) == 8) {
    if ((dest&7)) alignfault();
    HEAPF64[dest>>3] = value;
  } else {
    if ((dest&3)) alignfault();
    HEAPF32[dest>>2] = value;
  }
}
function SAFE_HEAP_LOAD(dest, bytes, unsigned) {
  dest = dest | 0;
  bytes = bytes | 0;
  unsigned = unsigned | 0;
  if ((dest|0) <= 0) segfault();
  %(brk_check)s
  if ((bytes|0) == 4) {
    if ((dest&3)) alignfault();
    return HEAP32[dest>>2] | 0;
  } else if ((bytes|0) == 1) {
    if (unsigned) {
      return HEAPU8[dest>>0] | 0;
    } else {
      return HEAP8[dest>>0] | 0;
    }
  }
  if ((dest&1)) alignfault();
  if (unsigned) return HEAPU16[dest>>1] | 0;
  return HEAP16[dest>>1] | 0;
}
function SAFE_HEAP_LOAD_D(dest, bytes) {
  dest = dest | 0;
  bytes = bytes | 0;
  if ((dest|0) <= 0) segfault();
  %(brk_check)s
  if ((bytes|0) == 8) {
    if ((dest&7)) alignfault();
    return +HEAPF64[dest>>3];
  }
  if ((dest&3)) alignfault();
  return +HEAPF32[dest>>2];
}
function SAFE_FT_MASK(value, mask) {
  value = value | 0;
  mask = mask | 0;
  var ret = 0;
  ret = value & mask;
  if ((ret|0) != (value|0)) ftfault();
  return ret | 0;
}
''' % {'brk_check': brk_check})

  return funcs


def create_asm_start_pre(asm_setup, the_global, sending, metadata):
  shared_array_buffer = ''
  if shared.Settings.USE_PTHREADS and not shared.Settings.WASM:
    shared_array_buffer = "asmGlobalArg['Atomics'] = Atomics;"

  module_global = 'var asmGlobalArg = ' + the_global + ';'
  module_library = 'var asmLibraryArg = ' + sending + ';'

  asm_function_top = ('// EMSCRIPTEN_START_ASM\n'
                      'var asm = (/** @suppress {uselessCode} */ function(global, env, buffer) {')

  use_asm = "'almost asm';"
  if shared.Settings.ASM_JS == 1:
    use_asm = "'use asm';"

  lines = [
    asm_setup,
    module_global,
    shared_array_buffer,
    module_library,
    asm_function_top,
    use_asm,
    create_first_in_asm(),
  ]
  return '\n'.join(lines)


def create_asm_temp_vars(metadata):
  temp_ints = ['__THREW__', 'threwValue', 'setjmpId', 'tempInt', 'tempBigInt', 'tempBigIntS', 'tempValue']
  temp_doubles = ['tempDouble']
  rtn = ''

  for i in temp_ints:
    if i in shared.Settings.ASM_PRIMITIVE_VARS:
      rtn += 'var ' + i + ' = 0;\n'

  for i in temp_doubles:
    if i in shared.Settings.ASM_PRIMITIVE_VARS:
      rtn += 'var ' + i + ' = 0.0;\n'

  if asm_backend_uses(metadata, 'NaN'):
    rtn += 'var nan = global%s;\n' % (access_quote('NaN'))

  if asm_backend_uses(metadata, 'Infinity'):
    rtn += 'var inf = global%s;\n' % (access_quote('Infinity'))

  return rtn


def create_asm_runtime_thread_local_vars():
  if not shared.Settings.USE_PTHREADS:
    return ''

  return '''
  var __pthread_ptr = 0;
  var __pthread_is_main_runtime_thread = 0;
  var __pthread_is_main_browser_thread = 0;
'''


def create_replace_memory(metadata):
  if not shared.Settings.ALLOW_MEMORY_GROWTH:
    return ''

  emscripten_replace_memory = '''
function _emscripten_replace_memory(newBuffer) {
'''
  for heap, view in [
    ('HEAP8', 'Int8Array'),
    ('HEAPU8', 'Uint8Array'),
    ('HEAP16', 'Int16Array'),
    ('HEAPU16', 'Uint16Array'),
    ('HEAP32', 'Int32Array'),
    ('HEAPU32', 'Uint32Array'),
    ('HEAPF32', 'Float32Array'),
    ('HEAPF64', 'Float64Array')]:
    if asm_backend_uses(metadata, view):
      emscripten_replace_memory += '  %s = new %s(newBuffer);\n' % (heap, view)

  emscripten_replace_memory += '''
  buffer = newBuffer;
  return true;
}
'''
  return emscripten_replace_memory


def create_asm_end(exports):
  if shared.Settings.MINIMAL_RUNTIME and shared.Settings.WASM:
    return '''
    return %s;
    })
    // EMSCRIPTEN_END_ASM
    ''' % (exports)

  return '''

  return %s;
})
// EMSCRIPTEN_END_ASM
(asmGlobalArg, asmLibraryArg, buffer);
''' % (exports)


def create_first_in_asm():
  return ''


def create_memory_views(metadata):
  """Generates memory views for the different heap types.

  Generated symbols:
    Int8View    Int16View   Int32View
    Uint8View   Uint16View  Uint32View
    Float32View Float64View
  """
  ret = '\n'
  for info in HEAP_TYPE_INFOS:
    heap_name = '{}Array'.format(info.long_name)
    access = access_quote(heap_name)
    if asm_backend_uses(metadata, heap_name):
      format_args = {
        'heap': info.heap_name,
        'long': info.long_name,
        'access': access,
      }
      ret += '  var {heap} = new global{access}(buffer);\n'.format(**format_args)

  return ret


class HeapTypeInfo(object):
  """Struct that holds data for a type of HEAP* views."""
  def __init__(self, heap_name, long_name, shift_amount):
    assert heap_name.startswith('HEAP')
    self.heap_name = heap_name
    self.long_name = long_name
    self.shift_amount = shift_amount

  def short_name(self):
    """The unique part of the heap name for this type.

    Derive this from heap_name instead of the other way around so that searching,
    e.g. for HEAP8, from the generated JS code leads back here.
    """
    return self.heap_name[len('HEAP'):]

  def is_int(self):
    """Whether this heap type is an integer type or not."""
    return self.short_name()[0] != 'F'

  def coerce(self, expression):
    """Adds asm.js type coercion to a string expression."""
    if self.is_int():
      return expression + '| 0'
    else:
      return '+' + expression


HEAP_TYPE_INFOS = [
  HeapTypeInfo(heap_name='HEAP8',   long_name='Int8',    shift_amount=0),
  HeapTypeInfo(heap_name='HEAP16',  long_name='Int16',   shift_amount=1),
  HeapTypeInfo(heap_name='HEAP32',  long_name='Int32',   shift_amount=2),
  HeapTypeInfo(heap_name='HEAPU8',  long_name='Uint8',   shift_amount=0),
  HeapTypeInfo(heap_name='HEAPU16', long_name='Uint16',  shift_amount=1),
  HeapTypeInfo(heap_name='HEAPU32', long_name='Uint32',  shift_amount=2),
  HeapTypeInfo(heap_name='HEAPF32', long_name='Float32', shift_amount=2),
  HeapTypeInfo(heap_name='HEAPF64', long_name='Float64', shift_amount=3),
]


def emscript_wasm_backend(infile, outfile, memfile, compiler_engine,
                          temp_files, DEBUG):
  # Overview:
  #   * Run wasm-emscripten-finalize to extract metadata and modify the binary
  #     to use emscripten's wasm<->JS ABI
  #   * Use the metadata to generate the JS glue that goes with the wasm

  metadata = finalize_wasm(temp_files, infile, outfile, memfile, DEBUG)

  update_settings_glue(metadata, DEBUG)

  if shared.Settings.SIDE_MODULE:
    return

  if DEBUG:
    logger.debug('emscript: js compiler glue')

  if DEBUG:
    t = time.time()
  glue, forwarded_data = compile_settings(compiler_engine, temp_files)
  if DEBUG:
    logger.debug('  emscript: glue took %s seconds' % (time.time() - t))
    t = time.time()

  forwarded_json = json.loads(forwarded_data)
  # For the wasm backend the implementedFunctions from compiler.js should
  # alwasys be empty. This only gets populated for __asm function when using
  # the JS backend.
  assert not forwarded_json['Functions']['implementedFunctions']

  pre, post = glue.split('// EMSCRIPTEN_END_FUNCS')

  # memory and global initializers

  global_initializers = ', '.join('{ func: function() { %s() } }' % i for i in metadata['initializers'])

  staticbump = shared.Settings.STATIC_BUMP

  if shared.Settings.MINIMAL_RUNTIME:
    # In minimal runtime, global initializers are run after the Wasm Module instantiation has finished.
    global_initializers = ''
  else:
    # In regular runtime, global initializers are recorded in an __ATINIT__ array.
    global_initializers = '''/* global initializers */ %s __ATINIT__.push(%s);
''' % ('if (!ENVIRONMENT_IS_PTHREAD)' if shared.Settings.USE_PTHREADS else '',
       global_initializers)

  pre = pre.replace('STATICTOP = STATIC_BASE + 0;', '''STATICTOP = STATIC_BASE + %d;
%s
''' % (staticbump, global_initializers))

  pre = apply_memory(pre)
  pre = apply_static_code_hooks(pre) # In regular runtime, atinits etc. exist in the preamble part
  post = apply_static_code_hooks(post) # In MINIMAL_RUNTIME, atinit exists in the postamble part

  if shared.Settings.RELOCATABLE and not shared.Settings.SIDE_MODULE:
    pre += 'var gb = GLOBAL_BASE, fb = 0;\n'

  # merge forwarded data
  shared.Settings.EXPORTED_FUNCTIONS = forwarded_json['EXPORTED_FUNCTIONS']

  exports = metadata['exports']

  # Store exports for Closure compiler to be able to track these as globals in
  # -s DECLARE_ASM_MODULE_EXPORTS=0 builds.
  shared.Settings.MODULE_EXPORTS = [(asmjs_mangle(f), f) for f in exports]

  if shared.Settings.ASYNCIFY:
    exports += ['asyncify_start_unwind', 'asyncify_stop_unwind', 'asyncify_start_rewind', 'asyncify_stop_rewind']

  report_missing_symbols(set([asmjs_mangle(f) for f in exports]), pre)

  asm_consts, asm_const_funcs = create_asm_consts_wasm(forwarded_json, metadata)
  em_js_funcs = create_em_js(forwarded_json, metadata)
  asm_const_pairs = ['%s: %s' % (key, value) for key, value in asm_consts]
  asm_const_map = 'var ASM_CONSTS = {\n  ' + ',  \n '.join(asm_const_pairs) + '\n};\n'
  pre = pre.replace(
    '// === Body ===',
    ('// === Body ===\n\n' + asm_const_map +
     asstr('\n'.join(asm_const_funcs)) +
     '\n'.join(em_js_funcs) + '\n'))
  pre = apply_table(pre)
  outfile.write(pre)
  pre = None

  invoke_funcs = metadata['invokeFuncs']
  if shared.Settings.RELOCATABLE:
    invoke_funcs.append('invoke_X')

  try:
    del forwarded_json['Variables']['globals']['_llvm_global_ctors'] # not a true variable
  except KeyError:
    pass

  sending = create_sending_wasm(invoke_funcs, forwarded_json, metadata)
  receiving = create_receiving_wasm(exports, metadata['initializers'])

  if shared.Settings.MINIMAL_RUNTIME:
    post, receiving = compute_minimal_runtime_initializer_and_exports(post, metadata['initializers'], exports, receiving)

  module = create_module_wasm(sending, receiving, invoke_funcs, metadata)

  write_output_file(outfile, post, module)
  module = None

  outfile.close()


def remove_trailing_zeros(memfile):
  with open(memfile, 'rb') as f:
    mem_data = f.read()
  end = len(mem_data)
  while end > 0 and (mem_data[end - 1] == b'\0' or mem_data[end - 1] == 0):
    end -= 1
  with open(memfile, 'wb') as f:
    f.write(mem_data[:end])


def finalize_wasm(temp_files, infile, outfile, memfile, DEBUG):
  basename = shared.unsuffixed(outfile.name)
  wasm = basename + '.wasm'
  base_wasm = infile
  shared.Building.save_intermediate(infile, 'base.wasm')

  args = ['--detect-features']

  write_source_map = shared.Settings.DEBUG_LEVEL >= 4
  if write_source_map:
    shared.Building.emit_wasm_source_map(base_wasm, base_wasm + '.map')
    shared.Building.save_intermediate(base_wasm + '.map', 'base_wasm.map')
    args += ['--output-source-map-url=' + shared.Settings.SOURCE_MAP_BASE + os.path.basename(shared.Settings.WASM_BINARY_FILE) + '.map']

  # tell binaryen to look at the features section, and if there isn't one, to use MVP
  # (which matches what llvm+lld has given us)
  if shared.Settings.DEBUG_LEVEL >= 2 or shared.Settings.PROFILING_FUNCS or shared.Settings.EMIT_SYMBOL_MAP or shared.Settings.ASYNCIFY_WHITELIST or shared.Settings.ASYNCIFY_BLACKLIST:
    args.append('-g')
  if shared.Settings.LEGALIZE_JS_FFI != 1:
    args.append('--no-legalize-javascript-ffi')
  if not shared.Settings.MEM_INIT_IN_WASM:
    args.append('--separate-data-segments=' + memfile)
  if shared.Settings.SIDE_MODULE:
    args.append('--side-module')
  else:
    # --global-base is used by wasm-emscripten-finalize to calculate the size
    # of the static data used.  The argument we supply here needs to match the
    # global based used by lld (see Building.link_lld).  For relocatable this is
    # zero for the global base although at runtime __memory_base is used.
    # For non-relocatable output we used shared.Settings.GLOBAL_BASE.
    # TODO(sbc): Can we remove this argument infer this from the segment
    # initializer?
    if shared.Settings.RELOCATABLE:
      args.append('--global-base=0')
    else:
      args.append('--global-base=%s' % shared.Settings.GLOBAL_BASE)
  if shared.Settings.WASM_BACKEND and shared.Settings.STACK_OVERFLOW_CHECK >= 2:
    args.append('--check-stack-overflow')
  if shared.Settings.STANDALONE_WASM:
    args.append('--standalone-wasm')
  # When we dynamically link our JS loader adds functions from wasm modules to
  # the table. It must add the original versions of them, not legalized ones,
  # so that indirect calls have the right type, so export those.
  if shared.Settings.RELOCATABLE:
    args.append('--pass-arg=legalize-js-interface-export-originals')
  stdout = shared.Building.run_binaryen_command('wasm-emscripten-finalize',
                                                infile=base_wasm,
                                                outfile=wasm,
                                                args=args,
                                                stdout=subprocess.PIPE)
  if write_source_map:
    shared.Building.save_intermediate(wasm + '.map', 'post_finalize.map')
  shared.Building.save_intermediate(wasm, 'post_finalize.wasm')

  if not shared.Settings.MEM_INIT_IN_WASM:
    # we have a separate .mem file. binaryen did not strip any trailing zeros,
    # because it's an ABI question as to whether it is valid to do so or not.
    # we can do so here, since we make sure to zero out that memory (even in
    # the dynamic linking case, our loader zeros it out)
    remove_trailing_zeros(memfile)

  return load_metadata_wasm(stdout, DEBUG)


def create_asm_consts_wasm(forwarded_json, metadata):
  asm_consts = {}
  all_sigs = []
  for k, v in metadata['asmConsts'].items():
    const, sigs, call_types = v
    const = asstr(const)
    const = trim_asm_const_body(const)
    args = []
    max_arity = 16
    arity = 0
    for i in range(max_arity):
      if ('$' + str(i)) in const:
        arity = i + 1
    for i in range(arity):
      args.append('$' + str(i))
    const = 'function(' + ', '.join(args) + ') {' + const + '}'
    asm_consts[int(k)] = const
    for sig, call_type in zip(sigs, call_types):
      all_sigs.append((sig, call_type))

  asm_const_funcs = []

  if all_sigs:
    # emit the signature-reading helper function only if we have any EM_ASM
    # functions in the module
    check = ''
    if shared.Settings.ASSERTIONS:
      check = ' else abort("unexpected char in asm const signature " + ch);'
    asm_const_funcs.append(r'''
// Avoid creating a new array
var _readAsmConstArgsArray = [];

function readAsmConstArgs(sigPtr, buf) {
  var args = _readAsmConstArgsArray;
  args.length = 0;
  while (1) {
    var ch = HEAPU8[sigPtr++];
    if (!ch) return args;
    if (ch === 'd'.charCodeAt(0) || ch === 'f'.charCodeAt(0)) {
      buf = alignMemory(buf, 8);
      args.push(HEAPF64[(buf >> 3)]);
      buf += 8;
    } else if (ch === 'i'.charCodeAt(0)) {
      buf = alignMemory(buf, 4);
      args.push(HEAP32[(buf >> 2)]);
      buf += 4;
    }%s
  }
}
''' % check)

  for sig, call_type in set(all_sigs):
    const_name = '_emscripten_asm_const_' + call_type + sig
    forwarded_json['Functions']['libraryFunctions'][const_name] = 1

    preamble = ''
    if shared.Settings.USE_PTHREADS:
      sync_proxy = call_type == 'sync_on_main_thread_'
      async_proxy = call_type == 'async_on_main_thread_'
      proxied = sync_proxy or async_proxy
      if proxied:
        # In proxied function calls, positive integers 1, 2, 3, ... denote pointers
        # to regular C compiled functions. Negative integers -1, -2, -3, ... denote
        # indices to EM_ASM() blocks, so remap the EM_ASM() indices from 0, 1, 2,
        # ... over to the negative integers starting at -1.
        preamble += ('\n  if (ENVIRONMENT_IS_PTHREAD) { ' +
                     proxy_debug_print(sync_proxy) +
                     'return _emscripten_proxy_to_main_thread_js(-1 - code, ' +
                     str(int(sync_proxy)) +
                     ', code, sigPtr, argbuf); }')

    if shared.Settings.RELOCATABLE:
      preamble += '\n  code -= %s;\n' % shared.Settings.GLOBAL_BASE

    asm_const_funcs.append(r'''
function %s(code, sigPtr, argbuf) {%s
  var args = readAsmConstArgs(sigPtr, argbuf);
  return ASM_CONSTS[code].apply(null, args);
}''' % (const_name, preamble))
  asm_consts = [(key, value) for key, value in asm_consts.items()]
  asm_consts.sort()
  return asm_consts, asm_const_funcs


def create_em_js(forwarded_json, metadata):
  em_js_funcs = []
  separator = '<::>'
  for name, raw in metadata.get('emJsFuncs', {}).items():
    assert separator in raw
    args, body = raw.split(separator, 1)
    args = args[1:-1]
    if args == 'void':
      args = []
    else:
      args = args.split(',')
    arg_names = [arg.split()[-1].replace("*", "") for arg in args if arg]
    func = 'function {}({}){}'.format(name, ','.join(arg_names), asstr(body))
    em_js_funcs.append(func)
    forwarded_json['Functions']['libraryFunctions'][name] = 1

  return em_js_funcs


def add_standard_wasm_imports(send_items_map):
  # Normally we import these into the wasm (so that JS could use them even
  # before the wasm loads), while in standalone mode we do not depend
  # on JS to create them, but create them in the wasm and export them.
  if not shared.Settings.STANDALONE_WASM:
    memory_import = 'wasmMemory'
    if shared.Settings.MODULARIZE and shared.Settings.USE_PTHREADS:
      # Pthreads assign wasmMemory in their worker startup. In MODULARIZE mode, they cannot assign inside the
      # Module scope, so lookup via Module as well.
      memory_import += " || Module['wasmMemory']"
    send_items_map['memory'] = memory_import

    send_items_map['table'] = 'wasmTable'

  # With the wasm backend __memory_base and __table_base and only needed for
  # relocatable output.
  if shared.Settings.RELOCATABLE or not shared.Settings.WASM_BACKEND: # FIXME
    send_items_map['__memory_base'] = str(shared.Settings.GLOBAL_BASE) # tell the memory segments where to place themselves
    # the wasm backend reserves slot 0 for the NULL function pointer
    table_base = '1' if shared.Settings.WASM_BACKEND else '0'
    send_items_map['__table_base'] = table_base
  if shared.Settings.RELOCATABLE and shared.Settings.WASM_BACKEND: # FIXME
    send_items_map['__stack_pointer'] = 'STACK_BASE'

  if shared.Settings.MAYBE_WASM2JS or shared.Settings.AUTODEBUG or shared.Settings.LINKABLE:
    # legalization of i64 support code may require these in some modes
    send_items_map['setTempRet0'] = 'setTempRet0'
    send_items_map['getTempRet0'] = 'getTempRet0'

  if shared.Settings.AUTODEBUG:
    send_items_map['log_execution'] = '''function(loc) {
      console.log('log_execution ' + loc);
    }'''
    send_items_map['get_i32'] = '''function(loc, index, value) {
      console.log('get_i32 ' + [loc, index, value]);
      return value;
    }'''
    send_items_map['get_i64'] = '''function(loc, index, low, high) {
      console.log('get_i64 ' + [loc, index, low, high]);
      setTempRet0(high);
      return low;
    }'''
    send_items_map['get_f32'] = '''function(loc, index, value) {
      console.log('get_f32 ' + [loc, index, value]);
      return value;
    }'''
    send_items_map['get_f64'] = '''function(loc, index, value) {
      console.log('get_f64 ' + [loc, index, value]);
      return value;
    }'''
    send_items_map['get_anyref'] = '''function(loc, index, value) {
      console.log('get_anyref ' + [loc, index, value]);
      return value;
    }'''
    send_items_map['get_exnref'] = '''function(loc, index, value) {
      console.log('get_exnref ' + [loc, index, value]);
      return value;
    }'''
    send_items_map['set_i32'] = '''function(loc, index, value) {
      console.log('set_i32 ' + [loc, index, value]);
      return value;
    }'''
    send_items_map['set_i64'] = '''function(loc, index, low, high) {
      console.log('set_i64 ' + [loc, index, low, high]);
      setTempRet0(high);
      return low;
    }'''
    send_items_map['set_f32'] = '''function(loc, index, value) {
      console.log('set_f32 ' + [loc, index, value]);
      return value;
    }'''
    send_items_map['set_f64'] = '''function(loc, index, value) {
      console.log('set_f64 ' + [loc, index, value]);
      return value;
    }'''
    send_items_map['set_anyref'] = '''function(loc, index, value) {
      console.log('set_anyref ' + [loc, index, value]);
      return value;
    }'''
    send_items_map['set_exnref'] = '''function(loc, index, value) {
      console.log('set_exnref ' + [loc, index, value]);
      return value;
    }'''
    send_items_map['load_ptr'] = '''function(loc, bytes, offset, ptr) {
      console.log('load_ptr ' + [loc, bytes, offset, ptr]);
      return ptr;
    }'''
    send_items_map['load_val_i32'] = '''function(loc, value) {
      console.log('load_val_i32 ' + [loc, value]);
      return value;
    }'''
    send_items_map['load_val_i64'] = '''function(loc, low, high) {
      console.log('load_val_i64 ' + [loc, low, high]);
      setTempRet0(high);
      return low;
    }'''
    send_items_map['load_val_f32'] = '''function(loc, value) {
      console.log('loaload_val_i32d_ptr ' + [loc, value]);
      return value;
    }'''
    send_items_map['load_val_f64'] = '''function(loc, value) {
      console.log('load_val_f64 ' + [loc, value]);
      return value;
    }'''
    send_items_map['store_ptr'] = '''function(loc, bytes, offset, ptr) {
      console.log('store_ptr ' + [loc, bytes, offset, ptr]);
      return ptr;
    }'''
    send_items_map['store_val_i32'] = '''function(loc, value) {
      console.log('store_val_i32 ' + [loc, value]);
      return value;
    }'''
    send_items_map['store_val_i64'] = '''function(loc, low, high) {
      console.log('store_val_i64 ' + [loc, low, high]);
      setTempRet0(high);
      return low;
    }'''
    send_items_map['store_val_f32'] = '''function(loc, value) {
      console.log('loastore_val_i32d_ptr ' + [loc, value]);
      return value;
    }'''
    send_items_map['store_val_f64'] = '''function(loc, value) {
      console.log('store_val_f64 ' + [loc, value]);
      return value;
    }'''


def create_sending_wasm(invoke_funcs, forwarded_json, metadata):
  basic_funcs = []
  if shared.Settings.SAFE_HEAP:
    basic_funcs += ['segfault', 'alignfault']

  em_asm_sigs = [zip(sigs, call_types) for _, sigs, call_types in metadata['asmConsts'].values()]
  # flatten em_asm_sigs
  em_asm_sigs = [sig for sigs in em_asm_sigs for sig in sigs]
  em_asm_funcs = ['_emscripten_asm_const_' + call_type + sig for sig, call_type in em_asm_sigs]
  em_js_funcs = list(metadata['emJsFuncs'].keys())
  declared_items = ['_' + item for item in metadata['declares']]
  send_items = set(basic_funcs + invoke_funcs + em_asm_funcs + em_js_funcs + declared_items)

  def fix_import_name(g):
    if g.startswith('Math_'):
      return g.split('_')[1]
    # Unlike fastcomp the wasm backend doesn't use the '_' prefix for native
    # symbols.  Emscripten currently expects symbols to start with '_' so we
    # artificially add them to the output of emscripten-wasm-finalize and them
    # strip them again here.
    # note that we don't do this for EM_JS functions (which, rarely, may have
    # a '_' prefix)
    if g.startswith('_') and g not in metadata['emJsFuncs']:
      return g[1:]
    return g

  send_items_map = OrderedDict()
  for name in send_items:
    internal_name = fix_import_name(name)
    if internal_name in send_items_map:
      exit_with_error('duplicate symbol in exports to wasm: %s', name)
    send_items_map[internal_name] = name

  add_standard_wasm_imports(send_items_map)

  sorted_keys = sorted(send_items_map.keys())
  return '{ ' + ', '.join('"' + k + '": ' + send_items_map[k] for k in sorted_keys) + ' }'


def create_receiving_wasm(exports, initializers):
  exports_that_are_not_initializers = [x for x in exports if x not in initializers]

  receiving = []
  if shared.Settings.MINIMAL_RUNTIME or not shared.Settings.ASSERTIONS:
    runtime_assertions = ''
  else:
    runtime_assertions = RUNTIME_ASSERTIONS
    # assert on the runtime being in a valid state when calling into compiled code. The only exceptions are
    # some support code
    for e in exports:
      receiving.append('''\
var real_%(mangled)s = asm["%(e)s"];
asm["%(e)s"] = function() {%(assertions)s
  return real_%(mangled)s.apply(null, arguments);
};
''' % {'mangled': asmjs_mangle(e), 'e': e, 'assertions': runtime_assertions})

  if not shared.Settings.SWAPPABLE_ASM_MODULE:
    if shared.Settings.DECLARE_ASM_MODULE_EXPORTS:
      if shared.Settings.WASM and shared.Settings.MINIMAL_RUNTIME:
        # In Wasm exports are assigned inside a function to variables existing in top level JS scope, i.e.
        # var _main;
        # WebAssembly.instantiate(Module["wasm"], imports).then((function(output) {
        # var asm = output.instance.exports;
        # _main = asm["_main"];
        receiving += [asmjs_mangle(s) + ' = asm["' + s + '"];' for s in exports_that_are_not_initializers]
      else:
        if shared.Settings.MINIMAL_RUNTIME:
          # In wasm2js exports can be directly processed at top level, i.e.
          # var asm = Module["asm"](asmGlobalArg, asmLibraryArg, buffer);
          # var _main = asm["_main"];
          receiving += ['var ' + asmjs_mangle(s) + ' = asm["' + asmjs_mangle(s) + '"];' for s in exports_that_are_not_initializers]
        else:
          receiving += ['var ' + asmjs_mangle(s) + ' = Module["' + asmjs_mangle(s) + '"] = asm["' + s + '"];' for s in exports]
    else:
      if shared.Settings.target_environment_may_be('node') and shared.Settings.target_environment_may_be('web'):
        global_object = '(typeof process !== "undefined" ? global : this)'
      elif shared.Settings.target_environment_may_be('node'):
        global_object = 'global'
      else:
        global_object = 'this'

      if shared.Settings.MINIMAL_RUNTIME:
        module_assign = ''
      else:
        module_assign = 'Module[asmjs_mangle(__exportedFunc)] = '

      receiving.append('''
  function asmjs_mangle(x) {
    var unmangledSymbols = %s;
    return x.indexOf('dynCall_') == 0 || unmangledSymbols.indexOf(x) != -1 ? x : '_' + x;
  }
''' % shared.Settings.WASM_FUNCTIONS_THAT_ARE_NOT_NAME_MANGLED)
      receiving.append('for(var __exportedFunc in asm) ' + global_object + '[asmjs_mangle(__exportedFunc)] = ' + module_assign + 'asm[__exportedFunc];')
  else:
    receiving.append('Module["asm"] = asm;')
    for e in exports:
      receiving.append('''\
var %(mangled)s = Module["%(mangled)s"] = function() {%(assertions)s
  return Module["asm"]["%(e)s"].apply(null, arguments)
};
''' % {'mangled': asmjs_mangle(e), 'e': e, 'assertions': runtime_assertions})

  return '\n'.join(receiving) + '\n'


def create_module_wasm(sending, receiving, invoke_funcs, metadata):
  invoke_wrappers = create_invoke_wrappers(invoke_funcs)
  receiving += create_named_globals(metadata)
  receiving += create_fp_accessors(metadata)
  module = []
  module.append('var asmGlobalArg = {};\n')
  if shared.Settings.USE_PTHREADS and not shared.Settings.WASM:
    module.append("if (typeof SharedArrayBuffer !== 'undefined') asmGlobalArg['Atomics'] = Atomics;\n")

  module.append('var asmLibraryArg = %s;\n' % (sending))
  if shared.Settings.ASYNCIFY and shared.Settings.ASSERTIONS:
    module.append('Asyncify.instrumentWasmImports(asmLibraryArg);\n')

  if not shared.Settings.MINIMAL_RUNTIME:
    module.append("var asm = createWasm();\n")

  module.append(receiving)
  module.append(invoke_wrappers)
  return module


def load_metadata_wasm(metadata_raw, DEBUG):
  try:
    metadata_json = json.loads(metadata_raw)
  except Exception:
    logger.error('emscript: failure to parse metadata output from wasm-emscripten-finalize. raw output is: \n' + metadata_raw)
    raise

  metadata = {
    'aliases': {},
    'declares': [],
    'implementedFunctions': [],
    'externs': [],
    'simd': False,
    'maxGlobalAlign': 0,
    'staticBump': 0,
    'tableSize': 0,
    'initializers': [],
    'exports': [],
    'namedGlobals': {},
    'emJsFuncs': {},
    'asmConsts': {},
    'invokeFuncs': [],
    'features': [],
    'mainReadsParams': 1,
  }

  assert 'tableSize' in metadata_json.keys()
  for key, value in metadata_json.items():
    # json.loads returns `unicode` for strings but other code in this file
    # generally works with utf8 encoded `str` objects, and they don't alwasy
    # mix well.  e.g. s.replace(x, y) will blow up is `s` a uts8 str containing
    # non-ascii and either x or y are unicode objects.
    # TODO(sbc): Remove this encoding if we switch to unicode elsewhere
    # (specifically the glue returned from compile_settings)
    if type(value) == list:
      value = [asstr(v) for v in value]
    if key not in metadata:
      exit_with_error('unexpected metadata key received from wasm-emscripten-finalize: %s', key)
    metadata[key] = value

  if not shared.Settings.MINIMAL_RUNTIME:
    # In regular runtime initializers call the global var version of the export, so they get the mangled name.
    # In MINIMAL_RUNTIME, the initializers are called directly off the export object for minimal code size.
    metadata['initializers'] = [asmjs_mangle(i) for i in metadata['initializers']]

  if DEBUG:
    logger.debug("Metadata parsed: " + pprint.pformat(metadata))

  # Calculate the subset of exports that were explicitly marked with llvm.used.
  # These are any exports that were not requested on the command line and are
  # not known auto-generated system functions.
  unexpected_exports = [e for e in metadata['exports'] if treat_as_user_function(e)]
  unexpected_exports = [asmjs_mangle(e) for e in unexpected_exports]
  unexpected_exports = [e for e in unexpected_exports if e not in shared.Settings.EXPORTED_FUNCTIONS]
  shared.Building.user_requested_exports += unexpected_exports

  return metadata


def create_invoke_wrappers(invoke_funcs):
  """Asm.js-style exception handling: invoke wrapper generation."""
  invoke_wrappers = ''
  for invoke in invoke_funcs:
    sig = invoke[len('invoke_'):]
    invoke_wrappers += '\n' + shared.JS.make_invoke(sig) + '\n'
  return invoke_wrappers


def normalize_line_endings(text):
  """Normalize to UNIX line endings.

  On Windows, writing to text file will duplicate \r\n to \r\r\n otherwise.
  """
  if WINDOWS:
    return text.replace('\r\n', '\n')
  return text


def run(infile, outfile, memfile):
  temp_files = get_configuration().get_temp_files()
  infile, outfile = substitute_response_files([infile, outfile])

  if not shared.Settings.BOOTSTRAPPING_STRUCT_INFO:
    generated_struct_info_name = 'generated_struct_info.json'

    def generate_struct_info():
      with ToolchainProfiler.profile_block('gen_struct_info'):
        out = shared.Cache.get_path(generated_struct_info_name)
        gen_struct_info.main(['-q', '-c', '-o', out])
        return out

    shared.Settings.STRUCT_INFO = shared.Cache.get(generated_struct_info_name, generate_struct_info)
  # do we need an else, to define it for the bootstrap case?

  outfile_obj = open(outfile, 'w')

  emscripter = emscript_wasm_backend if shared.Settings.WASM_BACKEND else emscript_fastcomp
  return temp_files.run_and_clean(lambda: emscripter(
      infile, outfile_obj, memfile, shared.NODE_JS, temp_files, shared.DEBUG)
  )