More minor updates in preparation for llvm main-mangling change. NFC (#17124)

Followup to #17099

Author: sbc100

src/library_dylink.js

@@ -444,12 +444,12 @@ var LibraryDylink = {
 
       // Export native export on the Module object.
       // TODO(sbc): Do all users want this?  Should we skip this by default?
-#if HAS_MAIN
-      var module_sym = asmjsMangle(sym);
-#else
+#if !hasExportedFunction('_main')
       // If the main module doesn't define main it could be defined in one of
       // the side module, and we need to handle the mangled named.
       var module_sym = asmjsMangle(sym == '__main_argc_argv' ? 'main' : sym);
+#else
+      var module_sym = asmjsMangle(sym);
 #endif
       if (!Module.hasOwnProperty(module_sym)) {
         Module[module_sym] = exports[sym];

tests/test_other.py

@@ -527,7 +527,8 @@ def test_combining_object_files_from_archive(self):
     # Should be two symbols (and in the wasm backend, also __original_main)
     syms = building.llvm_nm('combined.o')
     self.assertIn('main', syms['defs'])
-    self.assertEqual(len(syms['defs']), 3)
+    # TODO(sbc): Should be 3 once https://reviews.llvm.org/D75277 lands
+    self.assertIn(len(syms['defs']), (3, 4))
 
     self.run_process([EMXX, 'combined.o', '-o', 'combined.o.js'])
     self.assertContained('side got: hello from main, over', self.run_js('combined.o.js'))

tools/building.py

@@ -999,6 +999,9 @@ def metadce(js_file, wasm_file, minify_whitespace, debug_info):
     exports = settings.WASM_EXPORTS
   else:
     exports = settings.WASM_FUNCTION_EXPORTS
+  if settings.MANGLED_MAIN and 'main' in exports:
+    exports.append('__main_argc_argv')
+
   extra_info = '{ "exports": [' + ','.join(f'["{asmjs_mangle(x)}", "{x}"]' for x in exports) + ']}'
 
   txt = acorn_optimizer(js_file, ['emitDCEGraph', 'noPrint'], return_output=True, extra_info=extra_info)