[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();

[bradnelson, 2017/02/18 00:28:43]

Some reason this ended up indented by 4 (should be 2 by style guide)?

[Mircea Trofin, 2017/02/18 00:41:47]

huh... no idea. Emacs?

+    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 synchrnously, but we allow async compile

[bradnelson, 2017/02/18 00:28:42]

typo

[Mircea Trofin, 2017/02/18 00:41:47]

Acknowledged.

+%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);
+
+// not even async compile works.
+var ex;
+%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);
+
+
+// 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 TestReturnInBlock() {

[bradnelson, 2017/02/18 00:28:42]

Leftover?

[Mircea Trofin, 2017/02/18 00:41:47]

No! Intended. See comment above: we're making sure asm-wasm works, despite these
controls.

Or you mean the name "TestReturnInBlock"? ya... can be renamed.

+    "use asm";
+    function caller() {
+        return 43;
+    }
+
+    return {caller: caller};
+}
+
+assertWasm(43, TestReturnInBlock);