[turboprop] Only optimize prototype const fields in turboprop

This patch has the following improvement on v8.browsing_mobile:
- total-main-thread:duration improved by 1.7%
- js:duration improved by 1.3%

Change-Id: I1cdf2c181bfd991b67f31c5c2f32e3c2f909c67e
Bug: v8:9684, v8:10431
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2149433
Commit-Queue: Sathya Gunasekaran  <gsathya@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67405}

src/compiler/access-info.cc

@@ -390,6 +390,10 @@ PropertyAccessInfo AccessInfoFactory::ComputeDataFieldAccessInfo(
   PropertyConstness constness;
   if (details.IsReadOnly() && !details.IsConfigurable()) {
     constness = PropertyConstness::kConst;
+  } else if (FLAG_turboprop && !map->is_prototype_map()) {
+    // The constness feedback is too unstable for the aggresive compilation
+    // of turboprop.
+    constness = PropertyConstness::kMutable;
   } else {
     map_ref.SerializeOwnDescriptor(descriptor);
     constness = dependencies()->DependOnFieldConstness(map_ref, descriptor);

test/mjsunit/const-field-tracking-2.js

@@ -0,0 +1,225 @@
+// Copyright 2020 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.
+
+// TODO(gsathya): This test will probably break when v8 tiers up to turbofan
+// from turboprop.
+//
+// Flags: --allow-natives-syntax --opt --no-always-opt --turboprop
+
+var global = this;
+var unique_id = 0;
+// Creates a function with unique SharedFunctionInfo to ensure the feedback
+// vector is unique for each test case.
+function MakeFunctionWithUniqueSFI(...args) {
+  assertTrue(args.length > 0);
+  var body = `/* Unique comment: ${unique_id++} */ ` + args.pop();
+  return new Function(...args, body);
+}
+
+
+//
+// Load constant field from constant object directly.
+//
+function TestLoadFromConstantFieldOfAConstantObject(the_value, other_value) {
+  function A(v) { this.v = v; }
+  function O() { this.a = new A(the_value); }
+  var the_object = new O();
+
+  // Ensure that {the_object.a}'s map is not stable to complicate compiler's
+  // life.
+  new A(the_value).blah = 0;
+
+  // Ensure that constant tracking is enabled for {contant_object}.
+  delete global.constant_object;
+  global.constant_object = the_object;
+  assertEquals(the_object, constant_object);
+
+  assertTrue(%HasFastProperties(the_object));
+
+  // {constant_object} is known to the compiler via global property cell
+  // tracking.
+  var load = MakeFunctionWithUniqueSFI("return constant_object.a.v;");
+  %PrepareFunctionForOptimization(load);
+  load();
+  load();
+  %OptimizeFunctionOnNextCall(load);
+  assertEquals(the_value, load());
+  assertOptimized(load);
+  var a = new A(other_value);
+  assertTrue(%HaveSameMap(a, the_object.a));
+  // Make constant field mutable by assigning another value
+  // to some other instance of A.
+  new A(the_value).v = other_value;
+  assertTrue(%HaveSameMap(a, new A(the_value)));
+  assertTrue(%HaveSameMap(a, the_object.a));
+  assertOptimized(load);
+  assertEquals(the_value, load());
+  assertOptimized(load);
+  assertEquals(the_value, load());
+}
+
+//Test constant tracking with Smi value.
+(function() {
+  var the_value = 42;
+  var other_value = 153;
+  TestLoadFromConstantFieldOfAConstantObject(the_value, other_value);
+})();
+
+// Test constant tracking with double value.
+(function() {
+  var the_value = 0.9;
+  var other_value = 0.42;
+  TestLoadFromConstantFieldOfAConstantObject(the_value, other_value);
+})();
+
+// Test constant tracking with function value.
+(function() {
+  var the_value = function V() {};
+  var other_value = function W() {};
+  TestLoadFromConstantFieldOfAConstantObject(the_value, other_value);
+})();
+
+// Test constant tracking with heap object value.
+(function() {
+  function V() {}
+  var the_value = new V();
+  var other_value = new V();
+  TestLoadFromConstantFieldOfAConstantObject(the_value, other_value);
+})();
+
+
+//
+// Load constant field from a prototype.
+//
+function TestLoadFromConstantFieldOfAPrototype(the_value, other_value) {
+  function Proto() { this.v = the_value; }
+  var the_prototype = new Proto();
+
+  function O() {}
+  O.prototype = the_prototype;
+  var the_object = new O();
+
+  // Ensure O.prototype is in fast mode by loading from its field.
+  function warmup() { return new O().v; }
+  %EnsureFeedbackVectorForFunction(warmup);
+  warmup(); warmup(); warmup();
+  assertTrue(%HasFastProperties(O.prototype));
+
+  // The parameter object is not constant but all the values have the same
+  // map and therefore the compiler knows the prototype object and can
+  // optimize load of "v".
+  var load = MakeFunctionWithUniqueSFI("o", "return o.v;");
+  %PrepareFunctionForOptimization(load);
+  load(new O());
+  load(new O());
+  %OptimizeFunctionOnNextCall(load);
+  assertEquals(the_value, load(new O()));
+  assertOptimized(load);
+  // Invalidation of mutability should trigger deoptimization with a
+  // "field-owner" reason.
+  the_prototype.v = other_value;
+  assertUnoptimized(load);
+}
+
+// Test constant tracking with Smi value.
+(function() {
+  var the_value = 42;
+  var other_value = 153;
+  TestLoadFromConstantFieldOfAPrototype(the_value, other_value);
+})();
+
+// Test constant tracking with double value.
+(function() {
+  var the_value = 0.9;
+  var other_value = 0.42;
+  TestLoadFromConstantFieldOfAPrototype(the_value, other_value);
+})();
+
+// Test constant tracking with function value.
+(function() {
+  var the_value = function V() {};
+  var other_value = function W() {};
+  TestLoadFromConstantFieldOfAPrototype(the_value, other_value);
+})();
+
+// Test constant tracking with heap object value.
+(function() {
+  function V() {}
+  var the_value = new V();
+  var other_value = new V();
+  TestLoadFromConstantFieldOfAPrototype(the_value, other_value);
+})();
+
+
+//
+// Store to constant field of a constant object.
+//
+function TestStoreToConstantFieldOfConstantObject(the_value, other_value) {
+  function A(v) { this.v = v; }
+  function O() { this.a = new A(the_value); }
+  var the_object = new O();
+
+  // Ensure that {the_object.a}'s map is not stable to complicate compiler's
+  // life.
+  new A(the_value).blah = 0;
+
+  // Ensure that constant tracking is enabled for {contant_object}.
+  delete global.constant_object;
+  global.constant_object = the_object;
+  assertEquals(the_object, constant_object);
+
+  assertTrue(%HasFastProperties(the_object));
+
+  // {constant_object} is known to the compiler via global property cell
+  // tracking.
+  var store = MakeFunctionWithUniqueSFI("v", "constant_object.a.v = v;");
+  %PrepareFunctionForOptimization(store);
+  store(the_value);
+  store(the_value);
+  %OptimizeFunctionOnNextCall(store);
+  store(the_value);
+  assertEquals(the_value, constant_object.a.v);
+  assertOptimized(store);
+  // Storing of the same value does not deoptimize.
+  store(the_value);
+  assertEquals(the_value, constant_object.a.v);
+  assertOptimized(store);
+
+  var a = new A(other_value);
+
+  assertOptimized(store);
+  // Storing other value deoptimizes because of failed value check.
+  store(other_value);
+  assertOptimized(store);
+  assertEquals(other_value, constant_object.a.v);
+}
+
+// Test constant tracking with Smi values.
+(function() {
+  var the_value = 42;
+  var other_value = 153;
+  TestStoreToConstantFieldOfConstantObject(the_value, other_value);
+})();
+
+// Test constant tracking with double values.
+(function() {
+  var the_value = 0.9;
+  var other_value = 0.42
+  TestStoreToConstantFieldOfConstantObject(the_value, other_value);
+})();
+
+// Test constant tracking with function values.
+(function() {
+  var the_value = function V() {};
+  var other_value = function W() {};
+  TestStoreToConstantFieldOfConstantObject(the_value, other_value);
+})();
+
+// Test constant tracking with heap object values.
+(function() {
+  function V() {}
+  var the_value = new V();
+  var other_value = new V();
+  TestStoreToConstantFieldOfConstantObject(the_value, other_value);
+})();

test/mjsunit/mjsunit.status

@@ -1157,6 +1157,9 @@
   'deopt-recursive-soft-once': [SKIP],
   'regress/regress-3709': [SKIP],
   'regress/regress-5790': [SKIP],
+
+  # const field tracking is disabled in turboprop
+  'const-field-tracking': [SKIP],
 }],  # variant == turboprop
 
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