build: create V8 code cache after script is run

This patch makes it possible to generate the code cache
for the builtins directly from the original script object
(instead of compiling a new one) and after the script has
been run (via `NativeModule.require`). Before this patch
only the top level functions (the wrapped ones)
are included in the cache, after this patch the inner
functions in those modules will be included as well.

Also blacklists modules from dependencies like V8 and
node-inspect since we cannot guarantee that they are suitable
to be executed directly.

lib/internal/bootstrap/cache.js

@@ -9,23 +9,50 @@ const {
   NativeModule, internalBinding
 } = require('internal/bootstrap/loaders');
 
+function getCodeCache(id) {
+  const cached = NativeModule.getCached(id);
+  if (cached && (cached.loaded || cached.loading)) {
+    return cached.script.createCachedData();
+  }
+
+  // The script has not been compiled and run
+  NativeModule.require(id);
+  return getCodeCache(id);
+}
+
+const depsModule = Object.keys(NativeModule._source).filter(
+  (key) => NativeModule.isDepsModule(key) || key.startsWith('internal/deps')
+);
+
+// Modules with source code compiled in js2c that
+// cannot be compiled with the code cache
+const cannotUseCache = [
+  'config',
+  'sys',  // deprecated
+  'internal/v8_prof_polyfill',
+  'internal/v8_prof_processor',
+
+  'internal/per_context',
+
+  'internal/test/binding',
+  // TODO(joyeecheung): update the C++ side so that
+  // the code cache is also used when compiling these
+  // two files.
+  'internal/bootstrap/loaders',
+  'internal/bootstrap/node'
+].concat(depsModule);
+
 module.exports = {
+  cachableBuiltins: Object.keys(NativeModule._source).filter(
+    (key) => !cannotUseCache.includes(key)
+  ),
   builtinSource: Object.assign({}, NativeModule._source),
+  getCodeCache,
   codeCache: internalBinding('code_cache'),
   compiledWithoutCache: NativeModule.compiledWithoutCache,
   compiledWithCache: NativeModule.compiledWithCache,
   nativeModuleWrap(script) {
     return NativeModule.wrap(script);
   },
-  // Modules with source code compiled in js2c that
-  // cannot be compiled with the code cache
-  cannotUseCache: [
-    'config',
-    // TODO(joyeecheung): update the C++ side so that
-    // the code cache is also used when compiling these
-    // two files.
-    'internal/bootstrap/loaders',
-    'internal/bootstrap/node',
-    'internal/per_context',
-  ]
+  cannotUseCache
 };

lib/internal/bootstrap/loaders.js

@@ -118,6 +118,7 @@
     this.exportKeys = undefined;
     this.loaded = false;
     this.loading = false;
+    this.script = null;  // The ContextifyScript of the module
   }
 
   NativeModule._source = getBinding('natives');
@@ -165,11 +166,14 @@
     return nativeModule.exports;
   };
 
+  NativeModule.isDepsModule = function(id) {
+    return id.startsWith('node-inspect/') || id.startsWith('v8/');
+  };
+
   NativeModule.requireForDeps = function(id) {
     if (!NativeModule.exists(id) ||
         // TODO(TimothyGu): remove when DEP0084 reaches end of life.
-        id.startsWith('node-inspect/') ||
-        id.startsWith('v8/')) {
+        NativeModule.isDepsModule(id)) {
       id = `internal/deps/${id}`;
     }
     return NativeModule.require(id);
@@ -241,6 +245,8 @@
         codeCache[this.id], false, undefined
       );
 
+      this.script = script;
+
       // One of these conditions may be false when any of the inputs
       // of the `node_js2c` target in node.gyp is modified.
       // FIXME(joyeecheung):

test/code-cache/test-code-cache.js

@@ -12,9 +12,8 @@ const {
   }
 } = require('util');
 const {
-  builtinSource,
+  cachableBuiltins,
   codeCache,
-  cannotUseCache,
   compiledWithCache,
   compiledWithoutCache
 } = require('internal/bootstrap/cache');
@@ -35,8 +34,7 @@ for (const key of loadedModules) {
          `"${key}" should've been compiled with code cache`);
 }
 
-for (const key of Object.keys(builtinSource)) {
-  if (cannotUseCache.includes(key)) continue;
+for (const key of cachableBuiltins) {
   assert(isUint8Array(codeCache[key]) && codeCache[key].length > 0,
          `Code cache for "${key}" should've been generated`);
 }

tools/generate_code_cache.js

@@ -8,12 +8,10 @@
 // of `configure`.
 
 const {
-  nativeModuleWrap,
-  builtinSource,
-  cannotUseCache
+  getCodeCache,
+  cachableBuiltins
 } = require('internal/bootstrap/cache');
 
-const vm = require('vm');
 const fs = require('fs');
 
 const resultPath = process.argv[2];
@@ -72,25 +70,16 @@ const cacheInitializers = [];
 let totalCacheSize = 0;
 
 
-for (const key of Object.keys(builtinSource)) {
-  if (cannotUseCache.includes(key)) continue;
-  const code = nativeModuleWrap(builtinSource[key]);
-
-  // Note that this must corresponds to the code in
-  // NativeModule.prototype.compile
-  const script = new vm.Script(code, {
-    filename: `${key}.js`,
-    produceCachedData: true
-  });
-
-  if (!script.cachedData) {
+for (const key of cachableBuiltins) {
+  const cachedData = getCodeCache(key);
+  if (!cachedData.length) {
     console.error(`Failed to generate code cache for '${key}'`);
     process.exit(1);
   }
 
-  const length = script.cachedData.length;
+  const length = cachedData.length;
   totalCacheSize += length;
-  const { definition, initializer } = getInitalizer(key, script.cachedData);
+  const { definition, initializer } = getInitalizer(key, cachedData);
   cacheDefinitions.push(definition);
   cacheInitializers.push(initializer);
   console.log(`Generated cache for '${key}', size = ${formatSize(length)}` +