[wasm] Embedder can control what buffers wasm compilation works on.

test/mjsunit/wasm/test-wasm-compilation-control.js

+// Copyright 2017 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: --allow-natives-syntax --validate-asm
+
+load("test/mjsunit/wasm/wasm-constants.js");
+load("test/mjsunit/wasm/wasm-module-builder.js");
+
+let buffer = (() => {
+  var builder = new WasmModuleBuilder();
+  builder.addFunction("f", kSig_i_v)
+    .addBody([kExprI32Const, 42])
+    .exportAs("f");
+  return builder.toBuffer();
+})();
+
+// allow up to the buffer size
+%SetWasmCompileControls(buffer.byteLength, true);
+%SetWasmInstantiateControls();
+var m = new WebAssembly.Module(buffer);
+var i = new WebAssembly.Instance(m);
+assertEquals(i.exports.f(), 42);
+
+// the buffer can't compile synchronously, but we allow async compile
+%SetWasmCompileControls(buffer.byteLength - 1, true);
+// test first that we can't sync-instantiate this module anymore
+try {
+  i = new WebAssembly.Instance(m);
+} catch (e) {
+  assertTrue(e instanceof RangeError);
+}
+
+//...but we can async-instantiate it
+WebAssembly.instantiate(m)
+  .then(instance => i = instance,
+        assertUnreachable);
+%RunMicrotasks();
+assertTrue(i instanceof WebAssembly.Instance);
+
+try {
+  m = new WebAssembly.Module(buffer);
+  assertUnreachable();
+} catch (e) {
+  assertTrue(e instanceof RangeError);
+}
+
+WebAssembly.compile(buffer)
+  .then(res => m = res,
+        m = null);
+
+%RunMicrotasks();
+assertTrue(m instanceof WebAssembly.Module)
+
+WebAssembly.instantiate(buffer)
+  .then(res => m = res.module,
+        m = null);
+
+%RunMicrotasks();
+assertTrue(m instanceof WebAssembly.Module);
+
+// Async compile works, but using the sync instantiate doesn't
+i = undefined;
+m = undefined;
+var ex = undefined;
+WebAssembly.compile(buffer)
+  .then(mod => {
+    m = mod;
+    try {
+      i = new WebAssembly.Instance(m);
+    } catch (e) {
+      ex = e;
+    }
+  },
+        e => ex = e);
+%RunMicrotasks();
+assertTrue(ex instanceof RangeError);
+assertEquals(i, undefined);
+assertTrue(m instanceof WebAssembly.Module);
+
+// Now block async compile works.
+%SetWasmCompileControls(buffer.byteLength - 1, false);
+WebAssembly.compile(buffer)
+  .then(ex = null,
+        e => ex = e);
+
+%RunMicrotasks();
+assertTrue(ex instanceof RangeError);
+
+WebAssembly.instantiate(buffer)
+  .then(ex = null,
+        e => ex = e);
+%RunMicrotasks();
+assertTrue(ex instanceof RangeError);
+
+
+// Verify that, for asm-wasm, these controls are ignored.
+%SetWasmCompileControls(0, false);
+function assertValidAsm(func) {
+  assertTrue(%IsAsmWasmCode(func));
+}
+
+function assertWasm(expected, func) {
+  assertEquals(
+    expected, func(undefined, undefined, new ArrayBuffer(1024)).caller());
+  assertValidAsm(func);
+}
+
+function TestAsmWasmIsUnaffected() {
+  "use asm";
+  function caller() {
+    return 43;
+  }
+
+  return {caller: caller};
+}
+
+assertWasm(43, TestAsmWasmIsUnaffected);