Run binaryen wasm-opt on wasm backend output (#6029)

* closure fixes for wasm backend

* run binaryen wasm-opt on wasm backend output by default, when optimizing

Author: kripken

emcc.py

@@ -707,8 +707,10 @@ def detect_fixed_language_mode(args):
           'BINARYEN_MEM_MAX': 'WASM_MEM_MAX',
           # TODO: change most (all?) other BINARYEN* names to WASM*
       }
+      settings_key_changes = set()
       def setting_sub(s):
         key, rest = s.split('=', 1)
+        settings_key_changes.add(key)
         return '='.join([settings_aliases.get(key, key), rest])
       settings_changes = list(map(setting_sub, settings_changes))
 
@@ -1172,6 +1174,12 @@ def check(input_file):
         options.js_opts = None
         shared.Settings.BINARYEN = shared.Settings.WASM = 1
 
+        # wasm backend output can benefit from the binaryen optimizer (in asm2wasm,
+        # we run the optimizer during asm2wasm itself). use it, if not overridden
+        if 'BINARYEN_PASSES' not in settings_key_changes:
+          if options.opt_level > 0 or options.shrink_level > 0:
+            shared.Settings.BINARYEN_PASSES = shared.Building.opt_level_to_str(options.opt_level, options.shrink_level)
+
         # to bootstrap struct_info, we need binaryen
         os.environ['EMCC_WASM_BACKEND_BINARYEN'] = '1'
 

emscripten.py

@@ -1782,7 +1782,7 @@ def emscript_wasm_backend(infile, settings, outfile, libraries=None, compiler_en
   receiving = create_receiving_wasm(exported_implemented_functions, settings)
 
   # finalize
-  module = create_module_wasm(sending, receiving, invoke_funcs, settings)
+  module = create_module_wasm(sending, receiving, invoke_funcs, exported_implemented_functions, settings)
 
   write_output_file(outfile, post, module)
   module = None
@@ -1948,7 +1948,7 @@ def create_receiving_wasm(exported_implemented_functions, settings):
   return receiving
 
 
-def create_module_wasm(sending, receiving, invoke_funcs, settings):
+def create_module_wasm(sending, receiving, invoke_funcs, exported_implemented_functions, settings):
   access_quote = access_quoter(settings)
   invoke_wrappers = create_invoke_wrappers(invoke_funcs)
 
@@ -1983,10 +1983,11 @@ def create_module_wasm(sending, receiving, invoke_funcs, settings):
 var establishStackSpace = Module['establishStackSpace'];
 ''' % shared.Settings.GLOBAL_BASE)
 
-  module.append('''
-var setTempRet0 = Module['setTempRet0'];
-var getTempRet0 = Module['getTempRet0'];
-''')
+  # some runtime functionality may not have been generated in
+  # the wasm; provide a JS shim for it
+  for name in ['setTempRet0', 'getTempRet0', 'stackSave', 'stackRestore', 'stackAlloc']:
+    if name not in exported_implemented_functions:
+      module.append('var %s;\n' % name)
 
   module.append(invoke_wrappers)
   return module