Optimize lookups from wasm SIDE_MODULEs into MAIN_MODULE (emscripten-core#6437)

mdboom · kripken · commit 2e3ac3071654 · 2018-04-10T17:12:57.000-07:00
In current dynamic linking, the MAIN_MODULE's js sets up functions to provide all its exports. We had overly-dynamic code there that assumes those functions can change over time, but they can't.

This speeds up some benchmarks by a very large factor (5x or even more).
diff --git a/emscripten.py b/emscripten.py
@@ -1388,7 +1388,8 @@ def create_named_globals(metadata, settings):
       named_globals += '''
 for (var named in NAMED_GLOBALS) {
   (function(named) {
-    Module['g$_' + named] = function() { return Module['_' + named] };
+    var func = Module['_' + named];
+    Module['g$_' + named] = function() { return func };
   })(named);
 }
 '''
