[wasm] Fix WasmInstanceWrapper allocation.

test/mjsunit/wasm/instance-memory-gc-stress.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --expose-wasm --expose-gc
+
+load("test/mjsunit/wasm/wasm-constants.js");
+load("test/mjsunit/wasm/wasm-module-builder.js");
+
+// This test verifies that when instances are exported, Gc'ed, the other
+// instances in the chain still maintain a consistent view of the memory.
+(function InstanceMemoryGcStress() {
+  print("InstanceMemoryGcStress");
+  let memory = new WebAssembly.Memory({initial: 100, maximum: 1500});
+  var builder = new WasmModuleBuilder();
+  builder.addImportedMemory("imported_mem");
+  builder.addFunction("mem_size", kSig_i_v)
+    .addBody([kExprMemorySize, kMemoryZero])
+    .exportFunc();
+  builder.addFunction("grow", kSig_i_i)
+    .addBody([kExprGetLocal, 0, kExprGrowMemory, kMemoryZero])
+    .exportFunc();
+  var instances = [];
+  for (var i = 0; i < 5; i++) {
+    gc();
+    instances.push(builder.instantiate({imported_mem: memory}));
+  }
+  function grow_instance_0(pages) { return instances[0].exports.grow(pages); }
+  function grow_instance_1(pages) { return instances[1].exports.grow(pages); }
+  function grow_instance_2(pages) { return instances[2].exports.grow(pages); }
+  function grow_instance_3(pages) { return instances[3].exports.grow(pages); }
+  function grow_instance_4(pages) { return instances[4].exports.grow(pages); }
+
+  var start_index = 0;
+  var end_index = 5;
+  function verify_mem_size(expected_pages) {
+    assertEquals(expected_pages*kPageSize, memory.buffer.byteLength);
+    for (var i = start_index; i < end_index; i++) {
+      assertEquals(expected_pages, instances[i].exports.mem_size());
+    }
+  }
+
+  // Verify initial memory size of all instances, grow and verify that all
+  // instances are updated correctly.
+  verify_mem_size(100);
+  assertEquals(100, memory.grow(500));
+  verify_mem_size(600);
+
+  instances[1] = null;
+  gc();
+  gc();
+
+  // i[0] - i[2] - i[3] - i[4]
+  start_index = 2;
+  verify_mem_size(600);
+  assertEquals(600, instances[0].exports.mem_size());
+  assertEquals(600, grow_instance_2(200));
+  assertEquals(800*kPageSize, memory.buffer.byteLength);
+  verify_mem_size(800);
+  assertEquals(800, instances[0].exports.mem_size());
+
+  // Instantiate a new instance and verify that it can be grown correctly.
+  instances.push(builder.instantiate({imported_mem: memory}));
+  function grow_instance_5(pages) { return instances[5].exports.grow(pages); }
+  gc();
+  gc();
+
+  // i[0] - i[2] - i[3] - i[4] - i[5]
+  start_index = 2;
+  end_index = 6;
+  verify_mem_size(800);
+  assertEquals(800, instances[0].exports.mem_size());
+  assertEquals(800, grow_instance_2(100));
+  assertEquals(900*kPageSize, memory.buffer.byteLength);
+  verify_mem_size(900);
+  assertEquals(900, instances[0].exports.mem_size());
+
+  instances[4] = null;
+
+  gc();
+  gc();
+
+  // i[0] - i[2] - i[3] - i[5]
+  assertEquals(900, instances[0].exports.mem_size());
+  assertEquals(900, instances[2].exports.mem_size());
+  assertEquals(900, instances[3].exports.mem_size());
+  assertEquals(900, instances[5].exports.mem_size());
+  assertEquals(900, memory.grow(100));
+  assertEquals(1000*kPageSize, memory.buffer.byteLength);
+  assertEquals(1000, instances[0].exports.mem_size());
+  assertEquals(1000, instances[2].exports.mem_size());
+  assertEquals(1000, instances[3].exports.mem_size());
+  assertEquals(1000, instances[5].exports.mem_size());
+
+  gc();
+  gc();
+
+  instances[3] = null;
+
+  // i[0] - i[2] - i[5]
+  assertEquals(1000, instances[0].exports.mem_size());
+  assertEquals(1000, instances[2].exports.mem_size());
+  assertEquals(1000, instances[5].exports.mem_size());
+  assertEquals(1000, memory.grow(100));
+  assertEquals(1100*kPageSize, memory.buffer.byteLength);
+  assertEquals(1100, instances[0].exports.mem_size());
+  assertEquals(1100, instances[2].exports.mem_size());
+  assertEquals(1100, instances[5].exports.mem_size());
+
+  instances[0] = null;
+  gc();
+  gc();
+
+  // i[2] - i[5]
+  assertEquals(1100, instances[2].exports.mem_size());
+  assertEquals(1100, instances[5].exports.mem_size());
+  assertEquals(1100, grow_instance_5(1));
+  gc();
+  gc();
+
+  assertEquals(1101*kPageSize, memory.buffer.byteLength);
+  assertEquals(1101, instances[2].exports.mem_size());
+  assertEquals(1101, instances[5].exports.mem_size());
+})();