[Memory64] preamble JS changes for 64-bit (#15225)

Author: aardappel

src/preamble.js

@@ -263,8 +263,10 @@ var HEAP_DATA_VIEW;
 #endif
 
 #if WASM_BIGINT
-var HEAP64;
-var HEAPU64;
+/** @type {BigInt64Array} */
+var HEAP64,
+/** @type {BigUint64Array} */
+    HEAPU64;
 #endif
 
 #if USE_PTHREADS
@@ -736,6 +738,7 @@ function instrumentWasmTableWithAbort() {
   var realGet = wasmTable.get;
   var wrapperCache = {};
   wasmTable.get = function(i) {
+    {{{ from64('i') }}}
     var func = realGet.call(wasmTable, i);
     var cached = wrapperCache[i];
     if (!cached || cached.func !== func) {
@@ -749,6 +752,51 @@ function instrumentWasmTableWithAbort() {
 }
 #endif
 
+#if MEMORY64
+// In memory64 mode wasm pointers are 64-bit. To support that in JS we must use
+// BigInts. For now we keep JS as much the same as it always was, that is,
+// stackAlloc() receives and returns a Number from the JS point of view -
+// we translate BigInts automatically for that.
+// TODO: support minified export names
+function instrumentWasmExportsForMemory64(exports) {
+  var instExports = {};
+  for (var name in exports) {
+    (function(name) {
+      var original = exports[name];
+      var replacement = original;
+      if (name === 'stackAlloc' || name === 'malloc') {
+        // get one i64, return an i64
+        replacement = function(x) {
+          var r = Number(original(BigInt(x)));
+          return r;
+        };
+      } else if (name === 'free') {
+        // get one i64
+        replacement = function(x) {
+          original(BigInt(x));
+        };
+      } else if (name === 'emscripten_stack_get_end' ||
+                 name === 'emscripten_stack_get_base' ||
+                 name === 'emscripten_stack_get_current') {
+        // return an i64
+        replacement = function() {
+          var r = Number(original());
+          return r;
+        };
+      } else if (name === 'main') {
+        // get a i64 as second arg
+        replacement = function(x, y) {
+          var r = original(x, BigInt(y));
+          return r;
+        };
+      }
+      instExports[name] = replacement;
+    })(name);
+  }
+  return instExports;
+}
+#endif MEMORY64
+
 var wasmBinaryFile;
 #if EXPORT_ES6 && USE_ES6_IMPORT_META && !SINGLE_FILE
 if (Module['locateFile']) {
@@ -968,6 +1016,10 @@ function createWasm() {
     exports = relocateExports(exports, {{{ GLOBAL_BASE }}});
 #endif
 
+#if MEMORY64
+    exports = instrumentWasmExportsForMemory64(exports);
+#endif
+
 #if ASYNCIFY
     exports = Asyncify.instrumentWasmExports(exports);
 #endif