Use identifiers rather than string keys in wasmImports object. (#19808)

We should get a lot more code savings from this change once we switch
from using the underscore name mangling on the JS side.   Once we do
that most of the imports will use the abbreviated the object syntax of
just `foo,` rather then `foo = _foo,`

Author: sbc100

emscripten.py

@@ -719,8 +719,12 @@ def create_sending(metadata, library_symbols):
             continue
           send_items_map[demangled] = f
 
-  sorted_keys = sorted(send_items_map.keys())
-  return '{\n  ' + ',\n  '.join('"' + k + '": ' + send_items_map[k] for k in sorted_keys) + '\n}'
+  sorted_items = sorted(send_items_map.items())
+  prefix = ''
+  if settings.USE_CLOSURE_COMPILER:
+    # This prevents closure compiler from minifying the field names in this object.
+    prefix = '/** @export */\n  '
+  return '{\n  ' + ',\n  '.join(f'{prefix}{k}: {v}' for k, v in sorted_items) + '\n}'
 
 
 def make_export_wrappers(exports, delay_assignment):

test/optimizer/applyDCEGraphRemovals-output.js

@@ -1,8 +1,8 @@
 var name;
 
 var wasmImports = {
- "save1": 1,
- "save2": 2
+ save1: 1,
+ save2: 2
 };
 
 var expD1 = Module["expD1"] = asm["expD1"];

test/optimizer/applyDCEGraphRemovals.js

@@ -1,5 +1,5 @@
 var name;
-var wasmImports = { 'save1': 1, 'number': 33, 'name': name, 'func': function() {}, 'save2': 2 };
+var wasmImports = { save1: 1, number: 33, name: name, func: function() {}, save2: 2 };
 
 // exports gotten directly
 var expD1 = Module['expD1'] = asm['expD1'];

test/optimizer/applyImportAndExportNameChanges-output.js

@@ -1,17 +1,17 @@
 var name;
 
 var wasmImports = {
- "a": 1,
- "A": 33,
- "b": ___syscall6,
- "__setErrNo": ___setErrNo,
- "memset": _memset,
- "sbrk": _sbrk,
- "memcpy": _memcpy,
- "emscripten_memcpy_big": _emscripten_memcpy_big,
- "c": ___syscall54,
- "d": ___syscall140,
- "q": ___syscall146
+ a: 1,
+ A: 33,
+ b: ___syscall6,
+ __setErrNo: ___setErrNo,
+ memset: _memset,
+ sbrk: _sbrk,
+ memcpy: _memcpy,
+ emscripten_memcpy_big: _emscripten_memcpy_big,
+ c: ___syscall54,
+ d: ___syscall140,
+ q: ___syscall146
 };
 
 var expD1 = Module["expD1"] = asm["c"];

test/optimizer/applyImportAndExportNameChanges.js

@@ -1,16 +1,16 @@
 var name;
 var wasmImports = {
-  'save1': 1,
-  'number': 33,
-  "__syscall6": ___syscall6,
-  "__setErrNo": ___setErrNo,
-  "memset": _memset,
-  "sbrk": _sbrk,
-  "memcpy": _memcpy,
-  "emscripten_memcpy_big": _emscripten_memcpy_big,
-  "__syscall54": ___syscall54,
-  "__syscall140": ___syscall140,
-  "__syscall146": ___syscall146
+  save1: 1,
+  number: 33,
+  __syscall6: ___syscall6,
+  __setErrNo: ___setErrNo,
+  memset: _memset,
+  sbrk: _sbrk,
+  memcpy: _memcpy,
+  emscripten_memcpy_big: _emscripten_memcpy_big,
+  __syscall54: ___syscall54,
+  __syscall140: ___syscall140,
+  __syscall146: ___syscall146
 };
 
 // exports

test/optimizer/applyImportAndExportNameChanges2-output.js

@@ -213,14 +213,14 @@ if (ENVIRONMENT_IS_NODE) {
 }
 
 var wasmImports = {
- "b": abort,
- "h": ___syscall140,
- "a": ___syscall146,
- "g": ___syscall54,
- "f": ___syscall6,
- "e": _emscripten_get_now,
- "d": _emscripten_memcpy_big,
- "c": _emscripten_random
+ b: abort,
+ h: ___syscall140,
+ a: ___syscall146,
+ g: ___syscall54,
+ f: ___syscall6,
+ e: _emscripten_get_now,
+ d: _emscripten_memcpy_big,
+ c: _emscripten_random
 };
 
 function run() {

test/optimizer/applyImportAndExportNameChanges2.js

@@ -204,14 +204,14 @@ if (ENVIRONMENT_IS_NODE) {
     _emscripten_get_now = Date.now
 }
 var wasmImports = {
-    "abort": abort,
-    "___syscall140": ___syscall140,
-    "___syscall146": ___syscall146,
-    "___syscall54": ___syscall54,
-    "___syscall6": ___syscall6,
-    "_emscripten_get_now": _emscripten_get_now,
-    "_emscripten_memcpy_big": _emscripten_memcpy_big,
-    "_emscripten_random": _emscripten_random
+    abort: abort,
+    ___syscall140: ___syscall140,
+    ___syscall146: ___syscall146,
+    ___syscall54: ___syscall54,
+    ___syscall6: ___syscall6,
+    _emscripten_get_now: _emscripten_get_now,
+    _emscripten_memcpy_big: _emscripten_memcpy_big,
+    _emscripten_random: _emscripten_random
 };
 
 function run() {

test/optimizer/minimal-runtime-applyDCEGraphRemovals-output.js

@@ -1,8 +1,8 @@
 var name;
 
 var wasmImports = {
- "save1": 1,
- "save2": 2
+ save1: 1,
+ save2: 2
 };
 
 WebAssembly.instantiate(Module["wasm"], imports).then(output => {

test/optimizer/minimal-runtime-applyDCEGraphRemovals.js

@@ -1,5 +1,5 @@
 var name;
-var wasmImports = { 'save1': 1, 'number': 33, 'name': name, 'func': function() {}, 'save2': 2 };
+var wasmImports = { save1: 1, number: 33, name: name, func: function() {}, save2: 2 };
 
 // exports gotten directly in the minimal runtime style
 WebAssembly.instantiate(Module["wasm"], imports).then((output) => {

test/other/test_unoptimized_code_size.js.size

@@ -1 +1 @@
-59025
+59021

test/other/test_unoptimized_code_size_no_asserts.js.size

@@ -1 +1 @@
-32448
+32444

test/other/test_unoptimized_code_size_strict.js.size

@@ -1 +1 @@
-57991
+57987

tools/acorn-optimizer.js

@@ -513,8 +513,8 @@ function applyImportAndExportNameChanges(ast) {
     if (isWasmImportsAssign(node)) {
       const assignedObject = getWasmImportsValue(node);
       assignedObject.properties.forEach((item) => {
-        if (mapping[item.key.value]) {
-          setLiteralValue(item.key, mapping[item.key.value]);
+        if (mapping[item.key.name]) {
+          item.key.name = mapping[item.key.name];
         }
       });
     } else if (node.type === 'AssignmentExpression') {
@@ -982,7 +982,7 @@ function applyDCEGraphRemovals(ast) {
     if (isWasmImportsAssign(node)) {
       const assignedObject = getWasmImportsValue(node);
       assignedObject.properties = assignedObject.properties.filter((item) => {
-        const name = item.key.value;
+        const name = item.key.name;
         const value = item.value;
         const full = 'emcc$import$' + name;
         return !(unused.has(full) && !hasSideEffects(value));