Don't force the use of imported memory under WASM2JS

Setting `IMPORTED_MEMORY` can have other implications and don't want t
by default just because we chose WASM2JS.

See #21071

test/code_size/embind_val_wasm.json

@@ -1,10 +1,10 @@
 {
   "a.html": 673,
   "a.html.gz": 431,
-  "a.js": 7411,
-  "a.js.gz": 3140,
+  "a.js": 7387,
+  "a.js.gz": 3112,
   "a.wasm": 11433,
   "a.wasm.gz": 5725,
-  "total": 19517,
-  "total_gz": 9296
+  "total": 19493,
+  "total_gz": 9268
 }

test/code_size/hello_wasm_worker_wasm.json

@@ -1,10 +1,10 @@
 {
   "a.html": 737,
   "a.html.gz": 433,
-  "a.js": 667,
-  "a.js.gz": 458,
+  "a.js": 665,
+  "a.js.gz": 455,
   "a.wasm": 1852,
   "a.wasm.gz": 1049,
-  "total": 3256,
-  "total_gz": 1940
+  "total": 3254,
+  "total_gz": 1937
 }

test/code_size/hello_webgl2_wasm.json

@@ -1,10 +1,10 @@
 {
   "a.html": 569,
   "a.html.gz": 379,
-  "a.js": 4681,
-  "a.js.gz": 2412,
+  "a.js": 4671,
+  "a.js.gz": 2396,
   "a.wasm": 10388,
   "a.wasm.gz": 6692,
-  "total": 15638,
-  "total_gz": 9483
+  "total": 15628,
+  "total_gz": 9467
 }

test/code_size/hello_webgl2_wasm2js.json

@@ -1,10 +1,10 @@
 {
   "a.html": 567,
   "a.html.gz": 379,
-  "a.js": 17917,
-  "a.js.gz": 8089,
+  "a.js": 17766,
+  "a.js.gz": 7996,
   "a.mem": 3123,
   "a.mem.gz": 2693,
-  "total": 21607,
-  "total_gz": 11161
+  "total": 21456,
+  "total_gz": 11068
 }

test/code_size/hello_webgl_wasm.json

@@ -1,10 +1,10 @@
 {
   "a.html": 569,
   "a.html.gz": 379,
-  "a.js": 4167,
-  "a.js.gz": 2236,
+  "a.js": 4158,
+  "a.js.gz": 2220,
   "a.wasm": 10388,
   "a.wasm.gz": 6692,
-  "total": 15124,
-  "total_gz": 9307
+  "total": 15115,
+  "total_gz": 9291
 }

test/code_size/hello_webgl_wasm2js.json

@@ -1,10 +1,10 @@
 {
   "a.html": 567,
   "a.html.gz": 379,
-  "a.js": 17395,
-  "a.js.gz": 7900,
+  "a.js": 17239,
+  "a.js.gz": 7827,
   "a.mem": 3123,
   "a.mem.gz": 2693,
-  "total": 21085,
-  "total_gz": 10972
+  "total": 20929,
+  "total_gz": 10899
 }

test/code_size/hello_world_wasm.json

@@ -1,10 +1,10 @@
 {
   "a.html": 673,
   "a.html.gz": 431,
-  "a.js": 292,
-  "a.js.gz": 252,
+  "a.js": 291,
+  "a.js.gz": 249,
   "a.wasm": 103,
   "a.wasm.gz": 112,
-  "total": 1068,
-  "total_gz": 795
+  "total": 1067,
+  "total_gz": 792
 }

test/code_size/hello_world_wasm2js.js

@@ -1,59 +1,64 @@
-var b = Module, g = new function(a) {
-    this.buffer = new ArrayBuffer(65536 * a.initial);
-}({
-    initial: 256,
-    maximum: 256
-}), k = g.buffer, d = new Uint8Array(k), l = new TextDecoder("utf8"), m;
+var c = Module, g, h, k = new TextDecoder("utf8"), l;
 
-function c(a) {
-    this.exports = function(h) {
-        function n(f) {
-            f.set = function(e, p) {
-                this[e] = p;
+function d(b) {
+    this.exports = function(f) {
+        function m(e) {
+            e.set = function(a, n) {
+                this[a] = n;
             };
-            f.get = function(e) {
-                return this[e];
+            e.get = function(a) {
+                return this[a];
             };
-            return f;
+            return e;
         }
-        return function(f) {
-            var e = f.a.a;
+        return function(e) {
+            var a = new ArrayBuffer(16777216), n = e.a.a;
+            e = m([]);
             return {
-                b: function() {},
-                c: function(p, q) {
-                    e(1024);
+                b: Object.create(Object.prototype, {
+                    grow: {},
+                    buffer: {
+                        get: function() {
+                            return a;
+                        }
+                    }
+                }),
+                c: function() {},
+                d: function(p, q) {
+                    n(1024);
                     return 0;
                 },
-                d: n([])
+                e: e
             };
-        }(h);
-    }(a);
+        }(f);
+    }(b);
 }
 
-(function(a, h) {
+(function(b, f) {
     return {
-        then: function(n) {
-            n({
-                instance: new c(h)
+        then: function(m) {
+            m({
+                instance: new d(f)
             });
         }
     };
-})(b.wasm, {
+})(c.wasm, {
     a: {
-        a: a => {
-            var h = console, n = h.log;
-            if (a) {
-                for (var f = a + void 0, e = a; !(e >= f) && d[e]; ) ++e;
-                a = l.decode(d.subarray(a, e));
-            } else a = "";
-            n.call(h, a);
-        },
-        memory: g
+        a: b => {
+            var f = console, m = f.log;
+            if (b) {
+                for (var e = b + void 0, a = b; !(a >= e) && g[a]; ) ++a;
+                b = k.decode(g.subarray(b, a));
+            } else b = "";
+            m.call(f, b);
+        }
     }
-}).then((a => {
-    a = a.instance.exports;
-    m = a.c;
-    d.set(new Uint8Array(b.mem), 1024);
-    a.b();
-    m();
+}).then((b => {
+    b = b.instance.exports;
+    l = b.d;
+    h = b.b;
+    g = new Uint8Array(h.buffer);
+    g.set(new Uint8Array(c.mem), 1024);
+    b.c();
+    l();
 }));

test/code_size/hello_world_wasm2js.json

@@ -1,10 +1,10 @@
 {
   "a.html": 671,
   "a.html.gz": 430,
-  "a.js": 694,
-  "a.js.gz": 433,
+  "a.js": 708,
+  "a.js.gz": 444,
   "a.mem": 6,
   "a.mem.gz": 32,
-  "total": 1371,
-  "total_gz": 895
+  "total": 1385,
+  "total_gz": 906
 }

test/code_size/math_wasm.json

@@ -1,10 +1,10 @@
 {
   "a.html": 673,
   "a.html.gz": 431,
-  "a.js": 111,
-  "a.js.gz": 127,
+  "a.js": 110,
+  "a.js.gz": 125,
   "a.wasm": 2728,
   "a.wasm.gz": 1672,
-  "total": 3512,
-  "total_gz": 2230
+  "total": 3511,
+  "total_gz": 2228
 }

test/code_size/random_printf_wasm2js.json

@@ -1,6 +1,6 @@
 {
-  "a.html": 17331,
-  "a.html.gz": 7543,
-  "total": 17331,
-  "total_gz": 7543
+  "a.html": 17279,
+  "a.html.gz": 7541,
+  "total": 17279,
+  "total_gz": 7541
 }

tools/link.py

@@ -1445,8 +1445,7 @@ def check_memory_setting(setting):
      (options.shell_path == DEFAULT_SHELL_HTML or options.shell_path == utils.path_from_root('src/shell_minimal.html')):
     exit_with_error(f'Due to collision in variable name "Module", the shell file "{options.shell_path}" is not compatible with build options "-sMODULARIZE -sEXPORT_NAME=Module". Either provide your own shell file, change the name of the export to something else to avoid the name collision. (see https://github.com/emscripten-core/emscripten/issues/7950 for details)')
 
-  # TODO(sbc): Remove WASM2JS here once the size regression it would introduce has been fixed.
-  if settings.SHARED_MEMORY or settings.RELOCATABLE or settings.ASYNCIFY_LAZY_LOAD_CODE or settings.WASM2JS:
+  if settings.SHARED_MEMORY or settings.RELOCATABLE or settings.ASYNCIFY_LAZY_LOAD_CODE:
     settings.IMPORTED_MEMORY = 1
 
   if settings.WASM_BIGINT:
@@ -1974,6 +1973,7 @@ def fix_es6_import_statements(js_file):
   write_file(js_file, src
              .replace('EMSCRIPTEN$IMPORT$META', 'import.meta')
              .replace('EMSCRIPTEN$AWAIT$IMPORT', 'await import'))
+  save_intermediate('es6-module')
 
 
 def create_worker_file(input_file, target_dir, output_file):
@@ -2019,13 +2019,17 @@ def phase_final_emitting(options, state, target, wasm_target, memfile):
   # steps that occurred after Closure.
   if settings.MINIMAL_RUNTIME == 2 and settings.USE_CLOSURE_COMPILER and settings.DEBUG_LEVEL == 0:
     shared.run_js_tool(utils.path_from_root('tools/unsafe_optimizations.js'), [final_js, '-o', final_js], cwd=utils.path_from_root('.'))
+    save_intermediate('unsafe-optimizations')
     # Finally, rerun Closure compile with simple optimizations. It will be able
     # to further minify the code. (n.b. it would not be safe to run in advanced
     # mode)
     final_js = building.closure_compiler(final_js, advanced=False, extra_closure_args=options.closure_args)
+    # Run unsafe_optimizations.js once more.  This allows the cleanup of newly
+    # unused things that closure compiler leaves behing (e.g `new Float64Array(x)`).
+    shared.run_js_tool(utils.path_from_root('tools/unsafe_optimizations.js'), [final_js, '-o', final_js], cwd=utils.path_from_root('.'))
+    save_intermediate('unsafe-optimizations2')
 
   fix_es6_import_statements(final_js)
-  save_intermediate('es6-module')
 
   # Apply pre and postjs files
   if options.extern_pre_js or options.extern_post_js:

tools/unsafe_optimizations.js

@@ -68,27 +68,6 @@ function optPassSimplifyModularizeFunction(ast) {
   });
 }
 
-// Closure integration of the Module object generates an awkward "var b; b || (b = Module);" code.
-// 'b || (b = Module)' -> 'b = Module'.
-function optPassSimplifyModuleInitialization(ast) {
-  visitNodes(ast, ['BlockStatement', 'Program'], (node) => {
-    for (const n of node.body) {
-      if (
-        n.type == 'ExpressionStatement' &&
-        n.expression.type == 'LogicalExpression' &&
-        n.expression.operator == '||' &&
-        n.expression.left.name === n.expression.right.left?.name &&
-        n.expression.right.right.name == 'Module'
-      ) {
-        // Clear out the logical operator.
-        n.expression = n.expression.right;
-        // There is only one Module assignment, so can finish the pass here.
-        return false;
-      }
-    }
-  });
-}
-
 // Finds redundant operator new statements that are not assigned anywhere.
 // (we aren't interested in side effects of the calls if no assignment)
 function optPassRemoveRedundantOperatorNews(ast) {
@@ -225,7 +204,6 @@ function optPassMergeVarInitializationAssignments(ast) {
 function runOnJsText(js, pretty = false) {
   const ast = acorn.parse(js, {ecmaVersion: 2021});
 
-  optPassSimplifyModuleInitialization(ast);
   optPassRemoveRedundantOperatorNews(ast);
 
   let progress = true;
@@ -273,10 +251,6 @@ function runTests() {
     'var Module=function(f){};',
   );
 
-  // optPassSimplifyModuleInitialization:
-  test('b || (b = Module);', 'b=Module;');
-  test('function foo(){b || (b = Module);}', 'function foo(){b=Module}');
-
   // optPassRemoveRedundantOperatorNews:
   test('new Uint16Array(a);', '');
   test('new Uint16Array(a),new Uint16Array(a);', ';');