Have wasm module export its memory in MINIMAL_RUNTIME mode.

See #12315

Author: sbc100

emcc.py

@@ -1739,6 +1739,9 @@ def include_and_export(name):
       # requires JS legalization
       shared.Settings.LEGALIZE_JS_FFI = 0
 
+    if shared.Settings.MINIMAL_RUNTIME or shared.Settings.STANDALONE_WASM:
+      shared.Settings.MEMORY_DEFINED_IN_WASM = 1
+
     if shared.Settings.WASM_BIGINT:
       shared.Settings.LEGALIZE_JS_FFI = 0
 

emscripten.py

@@ -536,10 +536,7 @@ def create_em_js(forwarded_json, metadata):
 
 
 def add_standard_wasm_imports(send_items_map):
-  # Normally we import these into the wasm (so that JS could use them even
-  # before the wasm loads), while in standalone mode we do not depend
-  # on JS to create them, but create them in the wasm and export them.
-  if not shared.Settings.STANDALONE_WASM:
+  if not shared.Settings.MEMORY_DEFINED_IN_WASM:
     memory_import = 'wasmMemory'
     if shared.Settings.MODULARIZE and shared.Settings.USE_PTHREADS:
       # Pthreads assign wasmMemory in their worker startup. In MODULARIZE mode, they cannot assign inside the

src/postamble_minimal.js

@@ -204,6 +204,26 @@ WebAssembly.instantiate(Module['wasm'], imports).then(function(output) {
   /*** ASM_MODULE_EXPORTS ***/
 #endif
   wasmTable = asm['__indirect_function_table'];
+  wasmMemory = asm['memory'];
+  buffer = wasmMemory.buffer;
+
+#if ASSERTIONS
+  assert(wasmTable);
+  assert(wasmMemory);
+  assert(buffer.byteLength === {{{ INITIAL_MEMORY }}});
+#if USE_PTHREADS
+  assert(buffer instanceof SharedArrayBuffer, 'requested a shared WebAssembly.Memory but the returned buffer is not a SharedArrayBuffer, indicating that while the browser has SharedArrayBuffer it does not have WebAssembly threads support - you may need to set a flag');
+#endif
+#endif
+
+  updateGlobalBufferAndViews(buffer);
+
+#if MEM_INIT_METHOD == 1 && !MEM_INIT_IN_WASM && !SINGLE_FILE
+#if ASSERTIONS
+  if (!Module['mem']) throw 'Must load memory initializer as an ArrayBuffer in to variable Module.mem before adding compiled output .js script to the DOM';
+#endif
+  HEAPU8.set(new Uint8Array(Module['mem']), {{{ GLOBAL_BASE }}});
+#endif
 
   initRuntime(asm);
 #if USE_PTHREADS && PTHREAD_POOL_SIZE

src/preamble_minimal.js

@@ -65,40 +65,15 @@ var wasmMaximumMemory = {{{ MAXIMUM_MEMORY >>> 16 }}};
 var wasmMaximumMemory = {{{ INITIAL_MEMORY >>> 16}}};
 #endif
 
-var wasmMemory = new WebAssembly.Memory({
-  'initial': {{{ INITIAL_MEMORY >>> 16 }}}
-#if USE_PTHREADS || !ALLOW_MEMORY_GROWTH || MAXIMUM_MEMORY != -1
-  , 'maximum': wasmMaximumMemory
-#endif
-#if USE_PTHREADS
-  , 'shared': true
-#endif
-  });
-
+// These get assigned from the WebAssembly module exports
 var wasmTable;
-var buffer = wasmMemory.buffer;
-
-#if USE_PTHREADS
-}
-#if ASSERTIONS
-assert(buffer instanceof SharedArrayBuffer, 'requested a shared WebAssembly.Memory but the returned buffer is not a SharedArrayBuffer, indicating that while the browser has SharedArrayBuffer it does not have WebAssembly threads support - you may need to set a flag');
-#endif
-#endif
+var wasmMemory;
+var buffer;
 
-#if ASSERTIONS
-#if USE_PTHREADS
-if (!ENVIRONMENT_IS_PTHREAD) {
-#endif
-assert(buffer.byteLength === {{{ INITIAL_MEMORY }}});
 #if USE_PTHREADS
 }
 #endif
-#endif // ASSERTIONS
 
-#if ALLOW_MEMORY_GROWTH
-// In ALLOW_MEMORY_GROWTH, we need to be able to re-initialize the
-// typed array buffer and heap views to the buffer whenever the heap
-// is resized.
 var HEAP8, HEAP16, HEAP32, HEAPU8, HEAPU16, HEAPU32, HEAPF32, HEAPF64;
 function updateGlobalBufferAndViews(b) {
   buffer = b;
@@ -111,31 +86,11 @@ function updateGlobalBufferAndViews(b) {
   HEAPF32 = new Float32Array(b);
   HEAPF64 = new Float64Array(b);
 }
-updateGlobalBufferAndViews(buffer);
-#else
-// In non-ALLOW_MEMORY_GROWTH scenario, we only need to initialize
-// the heap once, so optimize code size to do it statically here.
-var HEAP8 = new Int8Array(buffer);
-var HEAP16 = new Int16Array(buffer);
-var HEAP32 = new Int32Array(buffer);
-var HEAPU8 = new Uint8Array(buffer);
-var HEAPU16 = new Uint16Array(buffer);
-var HEAPU32 = new Uint32Array(buffer);
-var HEAPF32 = new Float32Array(buffer);
-var HEAPF64 = new Float64Array(buffer);
-#endif
 
 #if USE_PTHREADS && ((MEM_INIT_METHOD == 1 && !MEM_INIT_IN_WASM && !SINGLE_FILE) || USES_DYNAMIC_ALLOC)
 if (!ENVIRONMENT_IS_PTHREAD) {
 #endif
 
-#if MEM_INIT_METHOD == 1 && !MEM_INIT_IN_WASM && !SINGLE_FILE
-#if ASSERTIONS
-if (!Module['mem']) throw 'Must load memory initializer as an ArrayBuffer in to variable Module.mem before adding compiled output .js script to the DOM';
-#endif
-HEAPU8.set(new Uint8Array(Module['mem']), {{{ GLOBAL_BASE }}});
-#endif
-
 #if USE_PTHREADS && ((MEM_INIT_METHOD == 1 && !MEM_INIT_IN_WASM && !SINGLE_FILE) || USES_DYNAMIC_ALLOC)
 }
 #endif

src/settings_internal.js

@@ -187,3 +187,9 @@ var STRUCT_INFO = '';
 var MEMORYPROFILER = 0;
 
 var GENERATE_SOURCE_MAP = 0;
+
+// By default we set this to 0 meaning the wasm file does not defined its own
+// memory and instead the memory is defined in JavaScript.
+// This is set 1 in STANDALONE_WASM or MINIMAL_RUNTIME mode in which case
+// the wasm module exports its memory to JavaScript.
+var MEMORY_DEFINED_IN_WASM = 0;

tests/code_size/hello_webgl2_wasm.json

@@ -1,10 +1,10 @@
 {
   "a.html": 563,
   "a.html.gz": 377,
-  "a.js": 4957,
-  "a.js.gz": 2373,
-  "a.wasm": 10893,
-  "a.wasm.gz": 6923,
-  "total": 16413,
-  "total_gz": 9673
+  "a.js": 4935,
+  "a.js.gz": 2357,
+  "a.wasm": 10895,
+  "a.wasm.gz": 6927,
+  "total": 16393,
+  "total_gz": 9661
 }

tests/code_size/hello_webgl2_wasm2js.json

@@ -1,10 +1,10 @@
 {
   "a.html": 588,
   "a.html.gz": 386,
-  "a.js": 21297,
-  "a.js.gz": 8263,
+  "a.js": 21318,
+  "a.js.gz": 8287,
   "a.mem": 3171,
   "a.mem.gz": 2715,
-  "total": 25056,
-  "total_gz": 11364
+  "total": 25077,
+  "total_gz": 11388
 }

tests/code_size/hello_webgl_wasm.json

@@ -1,10 +1,10 @@
 {
   "a.html": 563,
   "a.html.gz": 377,
-  "a.js": 4444,
-  "a.js.gz": 2199,
-  "a.wasm": 10893,
-  "a.wasm.gz": 6923,
-  "total": 15900,
-  "total_gz": 9499
+  "a.js": 4418,
+  "a.js.gz": 2180,
+  "a.wasm": 10895,
+  "a.wasm.gz": 6927,
+  "total": 15876,
+  "total_gz": 9484
 }

tests/code_size/hello_webgl_wasm2js.json

@@ -1,10 +1,10 @@
 {
   "a.html": 588,
   "a.html.gz": 386,
-  "a.js": 20785,
-  "a.js.gz": 8102,
+  "a.js": 20802,
+  "a.js.gz": 8112,
   "a.mem": 3171,
   "a.mem.gz": 2715,
-  "total": 24544,
-  "total_gz": 11203
+  "total": 24561,
+  "total_gz": 11213
 }

tests/code_size/hello_world_wasm.json

@@ -1,10 +1,10 @@
 {
   "a.html": 665,
   "a.html.gz": 427,
-  "a.js": 360,
-  "a.js.gz": 281,
-  "a.wasm": 102,
-  "a.wasm.gz": 114,
-  "total": 1127,
-  "total_gz": 822
+  "a.js": 330,
+  "a.js.gz": 264,
+  "a.wasm": 104,
+  "a.wasm.gz": 112,
+  "total": 1099,
+  "total_gz": 803
 }