fs: fix deoptimizing use of arguments

benchmark/fs/read-write-file-params.js

@@ -0,0 +1,57 @@
+'use strict';
+
+const common = require('../common.js');
+const fs = require('fs');
+const path = require('path');
+
+const filePath = path.join(__dirname, 'read-write-file-params.txt');
+const data = Buffer.from('1');
+const options = {};
+const cb = () => {};
+
+const configs = {
+  n: [1e3],
+  methodName: ['readFile', 'writeFile'],
+  withOptions: ['true', 'false'],
+};
+
+const bench = common.createBenchmark(main, configs);
+
+function main(conf) {
+  const n = +conf.n;
+  const methodName = conf.methodName;
+  const withOptions = conf.withOptions;
+
+  const method = fs[methodName];
+
+  switch (methodName) {
+    case 'readFile':
+      switch (withOptions) {
+        case 'true':
+          bench.start();
+          for (let i = 0; i < n; i++) method(filePath, options, cb);
+          bench.end(n);
+          break;
+        case 'false':
+          bench.start();
+          for (let i = 0; i < n; i++) method(filePath, cb);
+          bench.end(n);
+          break;
+      }
+      break;
+    case 'writeFile':
+      switch (withOptions) {
+        case 'true':
+          bench.start();
+          for (let i = 0; i < n; i++) method(filePath, data, options, cb);
+          bench.end(n);
+          break;
+        case 'false':
+          bench.start();
+          for (let i = 0; i < n; i++) method(filePath, data, cb);
+          bench.end(n);
+          break;
+      }
+      break;
+  }
+}

benchmark/fs/read-write-file-params.txt

@@ -0,0 +1 @@
+1

lib/fs.js

@@ -271,7 +271,7 @@ fs.existsSync = function(path) {
 };
 
 fs.readFile = function(path, options, callback) {
-  callback = maybeCallback(arguments[arguments.length - 1]);
+  callback = maybeCallback(callback || options);
   options = getOptions(options, { flag: 'r' });
 
   if (handleError((path = getPathFromURL(path)), callback))
@@ -1166,9 +1166,7 @@ fs.futimesSync = function(fd, atime, mtime) {
   binding.futimes(fd, atime, mtime);
 };
 
-function writeAll(fd, isUserFd, buffer, offset, length, position, callback_) {
-  var callback = maybeCallback(arguments[arguments.length - 1]);
-
+function writeAll(fd, isUserFd, buffer, offset, length, position, callback) {
   // write(fd, buffer, offset, length, position, callback)
   fs.write(fd, buffer, offset, length, position, function(writeErr, written) {
     if (writeErr) {
@@ -1199,7 +1197,7 @@ function writeAll(fd, isUserFd, buffer, offset, length, position, callback_) {
 }
 
 fs.writeFile = function(path, data, options, callback) {
-  callback = maybeCallback(arguments[arguments.length - 1]);
+  callback = maybeCallback(callback || options);
   options = getOptions(options, { encoding: 'utf8', mode: 0o666, flag: 'w' });
   const flag = options.flag || 'w';