[wasm] GrowMemory should update imported memory objects.

When the instance has imported memory, calling GrowMemory should update the memory object to have a consistent view of the memory. This fixes the failing emscripten test case, added a reduced test that simulates the same behavior.

R=titzer@chromium.org, dschuff@chromium.org

Review-Url: https://chromiumcodereview.appspot.com/2438673006
Cr-Commit-Position: refs/heads/master@{#40490}

src/wasm/wasm-js.cc

@@ -956,6 +956,12 @@ Handle<JSArrayBuffer> WasmJs::GetWasmMemoryArrayBuffer(Isolate* isolate,
   return Handle<JSArrayBuffer>::cast(buf);
 }
 
+void WasmJs::SetWasmMemoryArrayBuffer(Isolate* isolate, Handle<Object> value,
+                                      Handle<JSArrayBuffer> buffer) {
+  DCHECK(IsWasmMemoryObject(isolate, value));
+  JSObject::cast(*value)->SetInternalField(kWasmMemoryBuffer, *buffer);
+}
+
 uint32_t WasmJs::GetWasmMemoryMaximumSize(Isolate* isolate,
                                           Handle<Object> value) {
   DCHECK(IsWasmMemoryObject(isolate, value));

src/wasm/wasm-js.h

@@ -33,6 +33,9 @@ class WasmJs {
   static Handle<JSArrayBuffer> GetWasmMemoryArrayBuffer(Isolate* isolate,
                                                         Handle<Object> value);
 
+  static void SetWasmMemoryArrayBuffer(Isolate* isolate, Handle<Object> value,
+                                       Handle<JSArrayBuffer> buffer);
+
   static uint32_t GetWasmMemoryMaximumSize(Isolate* isolate,
                                            Handle<Object> value);
 

src/wasm/wasm-module.cc

@@ -1906,6 +1906,12 @@ int32_t wasm::GrowInstanceMemory(Isolate* isolate, Handle<JSObject> instance,
   Handle<FixedArray> code_table = GetCompiledModule(*instance)->code_table();
   RelocateMemoryReferencesInCode(code_table, old_mem_start, new_mem_start,
                                  old_size, new_size);
+  Handle<Object> memory_object(instance->GetInternalField(kWasmMemObject),
+                               isolate);
+  if (!memory_object->IsUndefined(isolate)) {
+    WasmJs::SetWasmMemoryArrayBuffer(isolate, memory_object, buffer);
+  }
+
   DCHECK(old_size % WasmModule::kPageSize == 0);
   return (old_size / WasmModule::kPageSize);
 }

test/mjsunit/wasm/import-memory.js

@@ -181,3 +181,21 @@ load("test/mjsunit/wasm/wasm-module-builder.js");
   }
   assertThrows(() => memory.grow(16381));
 })();
+
+(function ImportedMemoryBufferLength() {
+  print("ImportedMemoryBufferLength");
+  let memory = new WebAssembly.Memory({initial: 2, maximum: 10});
+  assertEquals(2*kPageSize, memory.buffer.byteLength);
+  let builder = new WasmModuleBuilder();
+  builder.addFunction("grow", kSig_i_i)
+      .addBody([kExprGetLocal, 0, kExprGrowMemory])
+      .exportFunc();
+  builder.addImportedMemory("mine");
+  let instance = builder.instantiate({mine: memory});
+  function grow(pages) { return instance.exports.grow(pages); }
+  assertEquals(2, grow(3));
+  assertEquals(5*kPageSize, memory.buffer.byteLength);
+  assertEquals(5, grow(5));
+  assertEquals(10*kPageSize, memory.buffer.byteLength);
+  assertThrows(() => memory.grow(1));
+})();