[wasm/tools] Add import profiler

Add a profiler for functions imported to WASM instances. This profiler
is implemented entirely in JavaScript and monkey-patches
WebAssembly.instantiate() and new WebAssembly.Instance() to instrument
the imported functions to each instance in order to count their
invocations and cumulative time.

R=mstarzinger@chromium.org

Bug: v8:8423
Change-Id: If456355aba07dc69c5500bafbe35fc56b31486af
Reviewed-on: https://chromium-review.googlesource.com/c/1347488
Commit-Queue: Ben Titzer <titzer@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57746}

tools/wasm/wasm-import-profiler-end.js

@@ -0,0 +1,6 @@
+// Copyright 2018 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.
+
+// Code to run at shutdown: print out the profiles for all instances.
+if (typeof WebAssembly.dumpAllProfiles == "function") WebAssembly.dumpAllProfiles();

tools/wasm/wasm-import-profiler.js

@@ -0,0 +1,131 @@
+// Copyright 2018 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.
+
+(() => {
+  let all_profiles = [];
+  let instanceMap = new WeakMap();
+  let instanceCounter = 0;
+
+  function instrument(imports, profile) {
+    let orig_imports = imports;
+    return new Proxy(imports, {
+      get: (obj, module_name) => {
+        let orig_module = orig_imports[module_name];
+        return new Proxy(orig_module, {
+          get: (obj, item_name) => {
+            let orig_func = orig_module[item_name];
+            let item = orig_func;
+            if (typeof orig_func == "function") {
+              var full_name = module_name + "." + item_name;
+              print("instrumented " + full_name);
+              profile[full_name] = {name: full_name, count: 0, total: 0};
+              item = function profiled_func(...args) {
+                var before = performance.now();
+                var result = orig_func(...args);
+                var delta = performance.now() - before;
+                var data = profile[full_name];
+                data.count++;
+                data.total += delta;
+                return result;
+              }
+            }
+            return item;
+          }
+        })
+      }
+    });
+  }
+
+  function dumpProfile(profile) {
+    let array = [];
+    for (let key in profile) {
+      if (key == "instanceNum") continue;
+      let data = profile[key];
+      if (data.count == 0) continue;
+      array.push(data);
+    }
+    print(`--- Import profile for instance ${profile.instanceNum} ---`);
+    if (array.length == 0) return;
+    array.sort((a, b) => b.total - a.total);
+    for (let data of array) {
+      print(`${padl(data.name, 30)}: ${padr(data.count, 10)} ${padp(data.total, 10)}ms`);
+    }
+  }
+
+  function padl(s, len) {
+    s = s.toString();
+    while (s.length < len) s = s + " ";
+    return s;
+  }
+  function padr(s, len) {
+    s = s.toString();
+    while (s.length < len) s = " " + s;
+    return s;
+  }
+  function padp(s, len) {
+    s = s.toString();
+    var i = s.indexOf(".");
+    if (i == -1) i = s.length;
+    while (i++ < len) s = " " + s;
+    return s;
+  }
+
+  // patch: WebAssembly.instantiate (async)
+  let orig_instantiate = WebAssembly.instantiate;
+  WebAssembly.instantiate = (m, imports, ...args) => {
+    let profile = {};
+    let promise = orig_instantiate(m, instrument(imports, profile), ...args);
+    promise.then((instance) => {
+      instanceMap.set(instance, profile);
+      all_profiles.push(profile);
+      profile.instanceNum = instanceCounter++;
+    });
+    return promise;
+  }
+
+  // patch: new WebAssembly.Instance (sync)
+  let orig_new_instance = WebAssembly.Instance;
+  WebAssembly.Instance = new Proxy(orig_new_instance, {
+    construct: (target, args) => {
+      let profile = {};
+      args[1] = instrument(args[1], profile);
+      let instance = new orig_new_instance(...args);
+      instanceMap.set(instance, profile);
+      all_profiles.push(profile);
+      profile.instanceNum = instanceCounter++;
+      return instance;
+    }
+  });
+
+  // expose: WebAssembly.dumpProfile(instance)
+  WebAssembly.dumpProfile = (instance) => {
+    let profile = instanceMap.get(instance);
+    if (profile === undefined) return;
+    dumpProfile(profile);
+  }
+  // expose: WebAssembly.clearProfile(instance)
+  WebAssembly.clearProfile = (instance) => {
+    let profile = instanceMap.get(instance);
+    if (profile === undefined) return;
+    for (let key in profile) {
+      if (key == "instanceNum") continue;
+      let data = p[key];
+      data.count = 0;
+      data.total = 0;
+    }
+  }
+  // expose: WebAssembly.dumpAllProfiles()
+  WebAssembly.dumpAllProfiles = () => {
+    for (let profile of all_profiles) dumpProfile(profile);
+  }
+  // expose: WebAssembly.getProfile(instance)
+  // returns: {
+  //    func_name1: {name: func_name1, count: <num>, total: <num>}
+  //    func_name2: {name: func_name1, count: <num>, total: <num>}
+  //    ...
+  // }
+  WebAssembly.getProfile = (instance) => {
+    return instanceMap.get(instance);
+  }
+})();