[threads][test][js-api] Add tests for wait/notify (#250)

Add JS API tests for Atomics.wait and Atomics.notify on WebAssembly.Memory.
- On shared memory: Atomics.notify should return the number of notified
  waiters, and Atomics.wait should return the appropriate wait status.
- On unshared memory: Atomics.notify should return 0, while Atomics.wait
  should trap (throwing a WebAssembly.RuntimeError).

Author: backes

test/js-api/memory/wait-notify-shared.any.js

@@ -0,0 +1,61 @@
+// META: global=window,dedicatedworker,jsshell
+// META: script=/wasm/jsapi/wasm-module-builder.js
+
+function createModule() {
+  const builder = new WasmModuleBuilder();
+  // Import memory instead of creating a local one.
+  builder.addImportedMemory('env', 'memory', 1, 1, true);  // shared
+  builder.exportMemoryAs('memory');
+
+  const kSig_i_iil = makeSig([kWasmI32, kWasmI32, kWasmI64], [kWasmI32]);
+  builder.addFunction('wait', kSig_i_iil)
+      .addBody([
+        kExprLocalGet, 0, kExprLocalGet, 1, kExprLocalGet, 2,
+        kAtomicPrefix, kExprI32AtomicWait, 2, 0
+      ])
+      .exportFunc();
+
+  builder.addFunction('notify', kSig_i_ii)
+      .addBody([
+        kExprLocalGet, 0, kExprLocalGet, 1,
+        kAtomicPrefix, kExprAtomicNotify, 2, 0
+      ])
+      .exportFunc();
+
+  return builder.toModule();
+}
+
+function createInstance(module, memory) {
+  if (!memory) {
+    memory = new WebAssembly.Memory({initial: 1, maximum: 1, shared: true});
+  }
+  return new WebAssembly.Instance(module, {env: {memory: memory}});
+}
+
+const module = createModule();
+
+test(() => {
+  const instance = createInstance(module);
+  const buffer = new Int32Array(instance.exports.memory.buffer);
+  buffer[0] = 0;
+
+  const result = instance.exports.wait(0, 1, -1n);
+  assert_equals(
+      result, 1, 'Wait32 should return 1 (not-equal) if value doesn\'t match');
+}, 'Wait32 (not-equal) on shared memory');
+
+test(() => {
+  const instance = createInstance(module);
+  const buffer = new Int32Array(instance.exports.memory.buffer);
+  buffer[0] = 0;
+
+  const result = instance.exports.wait(0, 0, 1000000n);  // 1ms timeout
+  assert_equals(result, 2, 'Wait32 should return 2 (timed-out) after timeout');
+}, 'Wait32 (timed-out) on shared memory');
+
+test(() => {
+  const instance = createInstance(module);
+  const result = instance.exports.notify(0, 1);
+  assert_equals(
+      result, 0, 'Notify should return 0 (number of waiters notified)');
+}, 'Notify on shared memory (0 waiters)');

test/js-api/memory/wait-notify-unshared.any.js

@@ -0,0 +1,34 @@
+// META: global=window,dedicatedworker,jsshell
+// META: script=/wasm/jsapi/wasm-module-builder.js
+
+test(() => {
+  const builder = new WasmModuleBuilder();
+  builder.addMemory(1, 1, false, false);
+  builder.addFunction('notify', kSig_i_ii)
+      .addBody([
+        kExprLocalGet, 0, kExprLocalGet, 1, kAtomicPrefix, kExprAtomicNotify, 2,
+        0
+      ])
+      .exportFunc();
+  const instance = builder.instantiate();
+  const result = instance.exports.notify(0, 1);
+  assert_equals(result, 0, 'Notify on unshared memory should return 0');
+}, 'Notify on unshared memory');
+
+test(() => {
+  const builder = new WasmModuleBuilder();
+  builder.addMemory(1, 1, false, false);
+  const kSig_i_iil = makeSig([kWasmI32, kWasmI32, kWasmI64], [kWasmI32]);
+  builder.addFunction('wait', kSig_i_iil)
+      .addBody([
+        kExprLocalGet, 0, kExprLocalGet, 1, kExprLocalGet, 2, kAtomicPrefix,
+        kExprI32AtomicWait, 2, 0
+      ])
+      .exportFunc();
+  const instance = builder.instantiate();
+  // This should trap. We use a non-infinite timeout to avoid hanging if the
+  // trap is not implemented.
+  assert_throws_js(
+      WebAssembly.RuntimeError, () => instance.exports.wait(0, 0, 1000n),
+      'Wait on unshared memory should trap');
+}, 'Wait on unshared memory traps');