Minify JS in wasm mode too (#4999)

* minify the JS in wasm mode when possible. even if the compiled code is in a side wasm file, in small projects the JS can be of significant size

Author: kripken

emcc.py

@@ -1273,7 +1273,6 @@ def check(input_file):
         shared.Settings.ASMJS_CODE_FILE = os.path.basename(asm_target)
 
         shared.Settings.ASM_JS = 2 # when targeting wasm, we use a wasm Memory, but that is not compatible with asm.js opts
-        debug_level = max(1, debug_level) # keep whitespace readable, for asm.js parser simplicity
         shared.Settings.GLOBAL_BASE = 1024 # leave some room for mapping global vars
         assert not shared.Settings.SPLIT_MEMORY, 'WebAssembly does not support split memory'
         assert not shared.Settings.USE_PTHREADS, 'WebAssembly does not support pthreads'
@@ -2195,6 +2194,21 @@ def do_minify(): # minifies the code. this is also when we do certain optimizati
               os.unlink(js_target) # we don't need the js, it can just confuse
               os.unlink(asm_target) # we don't need the asm.js, it can just confuse
             sys.exit(0) # and we are done.
+        if opt_level >= 2:
+          # minify the JS
+          do_minify() # calculate how to minify
+          if JSOptimizer.cleanup_shell or JSOptimizer.minify_whitespace or use_closure_compiler:
+            misc_temp_files.note(final)
+            shutil.move(js_target, final)
+            if DEBUG: save_intermediate('preclean', 'js')
+            if use_closure_compiler:
+              logging.debug('running closure on shell code')
+              final = shared.Building.closure_compiler(final, pretty=not JSOptimizer.minify_whitespace)
+            else:
+              assert JSOptimizer.cleanup_shell
+              logging.debug('running cleanup on shell code')
+              final = shared.Building.js_optimizer_no_asmjs(final, ['noPrintMetadata', 'JSDCE', 'last'] + (['minifyWhitespace'] if JSOptimizer.minify_whitespace else []))
+            shutil.move(final, js_target)
 
       # If we were asked to also generate HTML, do that
       if final_suffix == 'html':

tests/test_other.py

@@ -7394,24 +7394,32 @@ def test_binaryen_ctors(self):
       seen = run_js('b.out.js', engine=SPIDERMONKEY_ENGINE)
       assert correct == seen, correct + '\n vs \n' + seen
 
-  def test_binaryen_debuginfo(self):
-    with clean_write_access_to_canonical_temp_dir():
+  # test debug info and debuggability of JS output
+  def test_binaryen_debug(self):
       if os.environ.get('EMCC_DEBUG'): return self.skip('cannot run in debug mode')
       try:
         os.environ['EMCC_DEBUG'] = '1'
-        for args, expect_dash_g, expect_emit_text in [
-            (['-O0'], False, False),
-            (['-O0', '-g1'], False, False),
-            (['-O0', '-g2'], True, False), # in -g2+, we emit -g to asm2wasm so function names are saved
-            (['-O0', '-g'], True, True),
-            (['-O0', '--profiling-funcs'], True, False),
-            (['-O1'], False, False),
+        for args, expect_dash_g, expect_emit_text, expect_clean_js, expect_whitespace_js, expect_closured in [
+            (['-O0'], False, False, False, True, False),
+            (['-O0', '-g1'], False, False, False, True, False),
+            (['-O0', '-g2'], True, False, False, True, False), # in -g2+, we emit -g to asm2wasm so function names are saved
+            (['-O0', '-g'], True, True, False, True, False),
+            (['-O0', '--profiling-funcs'], True, False, False, True, False),
+            (['-O1'],        False, False, False, True, False),
+            (['-O2'],        False, False, True,  False, False),
+            (['-O2', '-g1'], False, False, True,  True, False),
+            (['-O2', '-g'],  True,  True,  False, True, False),
+            (['-O2', '--closure', '1'],         False, False, True, False, True),
+            (['-O2', '--closure', '1', '-g1'],  False, False, True, True,  True),
+            (['-O2', '--js-opts', '1'], False, False, True,  False, False),
           ]:
           print args, expect_dash_g, expect_emit_text
           try_delete('a.out.wast')
           cmd = [PYTHON, EMCC, path_from_root('tests', 'hello_world.cpp'), '-s', 'WASM=1'] + args
           print ' '.join(cmd)
-          output, err = Popen(cmd, stdout=PIPE, stderr=PIPE).communicate()
+          proc = Popen(cmd, stdout=PIPE, stderr=PIPE)
+          output, err = proc.communicate()
+          assert proc.returncode == 0
           asm2wasm_line = filter(lambda x: 'asm2wasm' in x, err.split('\n'))[0]
           asm2wasm_line = asm2wasm_line.strip() + ' ' # ensure it ends with a space, for simpler searches below
           print '|' + asm2wasm_line + '|'
@@ -7421,6 +7429,10 @@ def test_binaryen_debuginfo(self):
             text = open('a.out.wast').read()
             assert ';;' in text, 'must see debug info comment'
             assert 'hello_world.cpp:6' in text, 'must be file:line info'
+          js = open('a.out.js').read()
+          assert expect_clean_js == ('// ' not in js), 'cleaned-up js must not have comments'
+          assert expect_whitespace_js == ('{\n  ' in js), 'whitespace-minified js must not have excess spacing'
+          assert expect_closured == ('var a;' in js), 'closured js must have tiny variable names'
       finally:
         del os.environ['EMCC_DEBUG']
 

tools/shared.py

@@ -2018,6 +2018,13 @@ def js_optimizer(filename, passes, debug=False, extra_info=None, output_filename
       ret = output_filename
     return ret
 
+  # run JS optimizer on some JS, ignoring asm.js contents if any - just run on it all
+  @staticmethod
+  def js_optimizer_no_asmjs(filename, passes):
+    next = filename + '.jso.js'
+    subprocess.check_call(NODE_JS + [js_optimizer.JS_OPTIMIZER, filename] + passes, stdout=open(next, 'w'))
+    return next
+
   @staticmethod
   def eval_ctors(js_file, mem_init_file):
     subprocess.check_call([PYTHON, path_from_root('tools', 'ctor_evaller.py'), js_file, mem_init_file, str(Settings.TOTAL_MEMORY), str(Settings.TOTAL_STACK), str(Settings.GLOBAL_BASE)])