Remove legacy support for polyfilling Math.clz32, imul, trunc

src/preamble.js

@@ -1678,6 +1678,7 @@ function writeAsciiToMemory(str, buffer, dontAddNull) {
 {{{ unSign }}}
 {{{ reSign }}}
 
+#if LEGACY_VM_SUPPORT
 // check for imul support, and also for correctness ( https://bugs.webkit.org/show_bug.cgi?id=126345 )
 if (!Math['imul'] || Math['imul'](0xffffffff, 5) !== -5) Math['imul'] = function imul(a, b) {
   var ah  = a >>> 16;
@@ -1717,6 +1718,9 @@ if (!Math['trunc']) Math['trunc'] = function(x) {
   return x < 0 ? Math.ceil(x) : Math.floor(x);
 };
 Math.trunc = Math['trunc'];
+#else // LEGACY_VM_SUPPORT
+assert(Math['imul'] && Math['fround'] && Math['clz32'] && Math['trunc'], 'this is a legacy browser, build with LEGACY_VM_SUPPORT');
+#endif // LEGACY_VM_SUPPORT
 
 var Math_abs = Math.abs;
 var Math_cos = Math.cos;

src/settings.js

@@ -286,6 +286,9 @@ var STB_IMAGE = 0; // Enables building of stb-image, a tiny public-domain librar
                    // When enabled, stb-image will be used automatically from IMG_Load and IMG_Load_RW. You
                    // can also call the stbi_* functions directly yourself.
 
+var LEGACY_VM_SUPPORT = 0; // Enable this to get support for non-modern browsers, node.js, etc. This adds:
+                           //  * Polyfilling for Math.clz32, Math.trunc, Math.imul, Math.fround
+
 var LZ4 = 0; // Enable this to support lz4-compressed file packages. They are stored compressed in memory, and
              // decompressed on the fly, avoiding storing the entire decompressed data in memory at once.
              // If you run the file packager separately, you still need to build the main program with this flag,

tests/test_browser.py

@@ -2353,29 +2353,6 @@ def test_codemods(self):
       self.btest(path_from_root('tests', 'codemods.cpp'), expected='1', args=[opts, '-s', 'PRECISE_F32=1'])
       self.btest(path_from_root('tests', 'codemods.cpp'), expected='1', args=[opts, '-s', 'PRECISE_F32=2', '--separate-asm']) # empty polyfill, but browser has support, so semantics are like float
 
-      # now use a shell to remove the browser's fround support
-      open(self.in_dir('shell.html'), 'w').write(open(path_from_root('src', 'shell.html')).read().replace('var Module = {', '''
-  Math.fround = null;
-  var Module = {
-  '''))
-      self.btest(path_from_root('tests', 'codemods.cpp'), expected='2', args=[opts, '--shell-file', 'shell.html'])
-      self.btest(path_from_root('tests', 'codemods.cpp'), expected='1', args=[opts, '--shell-file', 'shell.html', '-s', 'PRECISE_F32=1'])
-      self.btest(path_from_root('tests', 'codemods.cpp'), expected='2', args=[opts, '--shell-file', 'shell.html', '-s', 'PRECISE_F32=2', '--separate-asm']) # empty polyfill, no browser support, so semantics are like double
-
-      # finally, remove fround, patch up fround as the code executes (after polyfilling etc.), to verify that we got rid of it entirely on the client side
-      fixer = 'python fix.py'
-      open('fix.py', 'w').write(r'''
-import sys
-filename = sys.argv[1]
-js = open(filename).read()
-replaced = js.replace("var Math_fround = Math.fround;", "var Math_fround = Math.fround = function(x) { return 0; }")
-assert js != replaced
-open(filename, 'w').write(replaced)
-  ''')
-      self.btest(path_from_root('tests', 'codemods.cpp'), expected='2', args=[opts, '--shell-file', 'shell.html', '--js-transform', fixer]) # no fround anyhow
-      self.btest(path_from_root('tests', 'codemods.cpp'), expected='121378', args=[opts, '--shell-file', 'shell.html', '--js-transform', fixer, '-s', 'PRECISE_F32=1']) # proper polyfill was enstated, then it was replaced by the fix so 0 is returned all the time, hence a different result here
-      self.btest(path_from_root('tests', 'codemods.cpp'), expected='2', args=[opts, '--shell-file', 'shell.html', '--js-transform', fixer, '-s', 'PRECISE_F32=2', '--separate-asm']) # we should remove the calls to the polyfill ENTIRELY here, on the clientside, so we should NOT see any calls to fround here, and result should be like double
-
   def test_wget(self):
     with open(os.path.join(self.get_dir(), 'test.txt'), 'w') as f:
       f.write('emscripten')

tests/test_other.py

@@ -3117,6 +3117,15 @@ def test_warn_unaligned(self):
     assert 'emcc: warning: unaligned store' in output[1], output[1]
     assert '@line 11 "src.cpp"' in output[1], output[1]
 
+  def test_LEGACY_VM_SUPPORT(self):
+    # when modern features are lacking, we can polyfill them or at least warn
+    with open('pre.js', 'w') as f: f.write('Math.imul = undefined;')
+    def test(expected, opts=[]):
+      subprocess.check_call([PYTHON, EMCC, path_from_root('tests', 'hello_world.c'), '--pre-js', 'pre.js'] + opts)
+      self.assertContained(expected, run_js('a.out.js', stderr=PIPE, full_output=True, engine=NODE_JS, assert_returncode=None))
+    test('this is a legacy browser, build with LEGACY_VM_SUPPORT')
+    test('hello, world!', ['-s', 'LEGACY_VM_SUPPORT=1'])
+
   def test_on_abort(self):
     expected_output = 'Module.onAbort was called'