benchmark: add FFI function preparation benchmark

Signed-off-by: umuoy1 <burningdian@gmail.com>

Author: umuoy1

benchmark/ffi/prepare-function.js

@@ -0,0 +1,76 @@
+'use strict';
+
+const assert = require('node:assert');
+const common = require('../common.js');
+const { libraryPath, ensureFixtureLibrary } = require('./common.js');
+
+// On x86-64 System V, cover both a register-only plan and one with stack-spilled
+// arguments. Both signatures bypass the V8 Fast API so trampoline allocation
+// does not dominate function preparation.
+const signatures = {
+  call_int_callback: {
+    return: 'i32',
+    arguments: ['function', 'i32'],
+  },
+  sum_8_i32: {
+    return: 'i32',
+    arguments: [
+      'i32', 'i32', 'i32', 'i32',
+      'i32', 'i32', 'i32', 'i32',
+    ],
+  },
+};
+
+const bench = common.createBenchmark(main, {
+  n: [1e4],
+  symbol: Object.keys(signatures),
+}, {
+  flags: ['--experimental-ffi', '--expose-gc', '--no-warnings'],
+});
+
+ensureFixtureLibrary();
+
+function main({ n, symbol }) {
+  const ffi = require('node:ffi');
+  const signature = signatures[symbol];
+
+  // Exclude one-time V8 template initialization from the measurement.
+  {
+    const library = new ffi.DynamicLibrary(libraryPath);
+    try {
+      library.getFunction(symbol, signature);
+    } finally {
+      library.close();
+    }
+  }
+
+  const libraries = new Array(n);
+  const functions = new Array(n);
+
+  try {
+    // Each library has its own function cache. Resolve symbols before timing so
+    // the measured work starts at signature parsing and function preparation.
+    for (let i = 0; i < n; i++) {
+      const library = new ffi.DynamicLibrary(libraryPath);
+      libraries[i] = library;
+      library.getSymbol(symbol);
+    }
+
+    // Avoid carrying garbage from setup into the measured window.
+    globalThis.gc();
+
+    bench.start();
+    for (let i = 0; i < n; i++) {
+      functions[i] = libraries[i].getFunction(symbol, signature);
+    }
+    bench.end(n);
+
+    assert.strictEqual(typeof functions[n - 1], 'function');
+  } finally {
+    for (let i = 0; i < n; i++) {
+      libraries[i]?.close();
+    }
+
+    functions.fill(null);
+  }
+}