1 files changed, 370 insertions, 0 deletions
diff --git a/js/src/vm/PIC.cpp b/js/src/vm/PIC.cpp
new file mode 100644
index 0000000000..a35677f79c
--- /dev/null
+++ b/js/src/vm/PIC.cpp
@@ -0,0 +1,370 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "vm/PIC.h"
+
+#include "gc/FreeOp.h"
+#include "gc/Marking.h"
+#include "vm/GlobalObject.h"
+#include "vm/JSContext.h"
+#include "vm/JSObject.h"
+#include "vm/Realm.h"
+#include "vm/SelfHosting.h"
+
+#include "vm/JSObject-inl.h"
+#include "vm/NativeObject-inl.h"
+
+using namespace js;
+
+template <typename Category>
+void PICChain<Category>::addStub(JSObject* obj, CatStub* stub) {
+  MOZ_ASSERT(stub);
+  MOZ_ASSERT(!stub->next());
+
+  AddCellMemory(obj, sizeof(CatStub), MemoryUse::ForOfPICStub);
+
+  if (!stubs_) {
+    stubs_ = stub;
+    return;
+  }
+
+  CatStub* cur = stubs_;
+  while (cur->next()) {
+    cur = cur->next();
+  }
+  cur->append(stub);
+}
+
+bool js::ForOfPIC::Chain::initialize(JSContext* cx) {
+  MOZ_ASSERT(!initialized_);
+
+  // Get the canonical Array.prototype
+  RootedNativeObject arrayProto(
+      cx, GlobalObject::getOrCreateArrayPrototype(cx, cx->global()));
+  if (!arrayProto) {
+    return false;
+  }
+
+  // Get the canonical ArrayIterator.prototype
+  RootedNativeObject arrayIteratorProto(
+      cx, GlobalObject::getOrCreateArrayIteratorPrototype(cx, cx->global()));
+  if (!arrayIteratorProto) {
+    return false;
+  }
+
+  // From this point on, we can't fail.  Set initialized and fill the fields
+  // for the canonical Array.prototype and ArrayIterator.prototype objects.
+  initialized_ = true;
+  arrayProto_ = arrayProto;
+  arrayIteratorProto_ = arrayIteratorProto;
+
+  // Shortcut returns below means Array for-of will never be optimizable,
+  // do set disabled_ now, and clear it later when we succeed.
+  disabled_ = true;
+
+  // Look up Array.prototype[@@iterator], ensure it's a slotful shape.
+  Shape* iterShape =
+      arrayProto->lookup(cx, SYMBOL_TO_JSID(cx->wellKnownSymbols().iterator));
+  if (!iterShape || !iterShape->isDataProperty()) {
+    return true;
+  }
+
+  // Get the referred value, and ensure it holds the canonical ArrayValues
+  // function.
+  Value iterator = arrayProto->getSlot(iterShape->slot());
+  JSFunction* iterFun;
+  if (!IsFunctionObject(iterator, &iterFun)) {
+    return true;
+  }
+  if (!IsSelfHostedFunctionWithName(iterFun, cx->names().ArrayValues)) {
+    return true;
+  }
+
+  // Look up the 'next' value on ArrayIterator.prototype
+  Shape* nextShape = arrayIteratorProto->lookup(cx, cx->names().next);
+  if (!nextShape || !nextShape->isDataProperty()) {
+    return true;
+  }
+
+  // Get the referred value, ensure it holds the canonical ArrayIteratorNext
+  // function.
+  Value next = arrayIteratorProto->getSlot(nextShape->slot());
+  JSFunction* nextFun;
+  if (!IsFunctionObject(next, &nextFun)) {
+    return true;
+  }
+  if (!IsSelfHostedFunctionWithName(nextFun, cx->names().ArrayIteratorNext)) {
+    return true;
+  }
+
+  disabled_ = false;
+  arrayProtoShape_ = arrayProto->lastProperty();
+  arrayProtoIteratorSlot_ = iterShape->slot();
+  canonicalIteratorFunc_ = iterator;
+  arrayIteratorProtoShape_ = arrayIteratorProto->lastProperty();
+  arrayIteratorProtoNextSlot_ = nextShape->slot();
+  canonicalNextFunc_ = next;
+  return true;
+}
+
+bool js::ForOfPIC::Chain::tryOptimizeArray(JSContext* cx,
+                                           HandleArrayObject array,
+                                           bool* optimized) {
+  MOZ_ASSERT(optimized);
+
+  *optimized = false;
+
+  if (!initialized_) {
+    // If PIC is not initialized, initialize it.
+    if (!initialize(cx)) {
+      return false;
+    }
+
+  } else if (!disabled_ && !isArrayStateStillSane()) {
+    // Otherwise, if array state is no longer sane, reinitialize.
+    reset(cx);
+
+    if (!initialize(cx)) {
+      return false;
+    }
+  }
+  MOZ_ASSERT(initialized_);
+
+  // If PIC is disabled, don't bother trying to optimize.
+  if (disabled_) {
+    return true;
+  }
+
+  // By the time we get here, we should have a sane array state to work with.
+  MOZ_ASSERT(isArrayStateStillSane());
+
+  // Ensure array's prototype is the actual Array.prototype
+  if (array->staticPrototype() != arrayProto_) {
+    return true;
+  }
+
+  // Check if stub already exists.
+  if (hasMatchingStub(array)) {
+    *optimized = true;
+    return true;
+  }
+
+  // Ensure array doesn't define @@iterator directly.
+  if (array->lookup(cx, SYMBOL_TO_JSID(cx->wellKnownSymbols().iterator))) {
+    return true;
+  }
+
+  // If the number of stubs is about to exceed the limit, throw away entire
+  // existing cache before adding new stubs.  We shouldn't really have heavy
+  // churn on these.
+  if (numStubs() >= MAX_STUBS) {
+    eraseChain(cx);
+  }
+
+  // Good to optimize now, create stub to add.
+  RootedShape shape(cx, array->lastProperty());
+  Stub* stub = cx->new_<Stub>(shape);
+  if (!stub) {
+    return false;
+  }
+
+  // Add the stub.
+  addStub(picObject_, stub);
+
+  *optimized = true;
+  return true;
+}
+
+bool js::ForOfPIC::Chain::tryOptimizeArrayIteratorNext(JSContext* cx,
+                                                       bool* optimized) {
+  MOZ_ASSERT(optimized);
+
+  *optimized = false;
+
+  if (!initialized_) {
+    // If PIC is not initialized, initialize it.
+    if (!initialize(cx)) {
+      return false;
+    }
+  } else if (!disabled_ && !isArrayNextStillSane()) {
+    // Otherwise, if array iterator state is no longer sane, reinitialize.
+    reset(cx);
+
+    if (!initialize(cx)) {
+      return false;
+    }
+  }
+  MOZ_ASSERT(initialized_);
+
+  // If PIC is disabled, don't bother trying to optimize.
+  if (disabled_) {
+    return true;
+  }
+
+  // By the time we get here, we should have a sane iterator state to work with.
+  MOZ_ASSERT(isArrayNextStillSane());
+
+  *optimized = true;
+  return true;
+}
+
+bool js::ForOfPIC::Chain::hasMatchingStub(ArrayObject* obj) {
+  // Ensure PIC is initialized and not disabled.
+  MOZ_ASSERT(initialized_ && !disabled_);
+
+  // Check if there is a matching stub.
+  for (Stub* stub = stubs(); stub != nullptr; stub = stub->next()) {
+    if (stub->shape() == obj->shape()) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+bool js::ForOfPIC::Chain::isArrayStateStillSane() {
+  // Ensure that canonical Array.prototype has matching shape.
+  if (arrayProto_->lastProperty() != arrayProtoShape_) {
+    return false;
+  }
+
+  // Ensure that Array.prototype[@@iterator] contains the
+  // canonical iterator function.
+  if (arrayProto_->getSlot(arrayProtoIteratorSlot_) != canonicalIteratorFunc_) {
+    return false;
+  }
+
+  // Chain to isArrayNextStillSane.
+  return isArrayNextStillSane();
+}
+
+void js::ForOfPIC::Chain::reset(JSContext* cx) {
+  // Should never reset a disabled_ stub.
+  MOZ_ASSERT(!disabled_);
+
+  // Erase the chain.
+  eraseChain(cx);
+
+  arrayProto_ = nullptr;
+  arrayIteratorProto_ = nullptr;
+
+  arrayProtoShape_ = nullptr;
+  arrayProtoIteratorSlot_ = -1;
+  canonicalIteratorFunc_ = UndefinedValue();
+
+  arrayIteratorProtoShape_ = nullptr;
+  arrayIteratorProtoNextSlot_ = -1;
+  canonicalNextFunc_ = UndefinedValue();
+
+  initialized_ = false;
+}
+
+void js::ForOfPIC::Chain::eraseChain(JSContext* cx) {
+  // Should never need to clear the chain of a disabled stub.
+  MOZ_ASSERT(!disabled_);
+  freeAllStubs(cx->defaultFreeOp());
+}
+
+// Trace the pointers stored directly on the stub.
+void js::ForOfPIC::Chain::trace(JSTracer* trc) {
+  TraceEdge(trc, &picObject_, "ForOfPIC object");
+
+  if (!initialized_ || disabled_) {
+    return;
+  }
+
+  TraceEdge(trc, &arrayProto_, "ForOfPIC Array.prototype.");
+  TraceEdge(trc, &arrayIteratorProto_, "ForOfPIC ArrayIterator.prototype.");
+
+  TraceEdge(trc, &arrayProtoShape_, "ForOfPIC Array.prototype shape.");
+  TraceEdge(trc, &arrayIteratorProtoShape_,
+            "ForOfPIC ArrayIterator.prototype shape.");
+
+  TraceEdge(trc, &canonicalIteratorFunc_, "ForOfPIC ArrayValues builtin.");
+  TraceEdge(trc, &canonicalNextFunc_,
+            "ForOfPIC ArrayIterator.prototype.next builtin.");
+
+  if (trc->isMarkingTracer()) {
+    // Free all the stubs in the chain.
+    freeAllStubs(trc->runtime()->defaultFreeOp());
+  }
+}
+
+static void ForOfPIC_finalize(JSFreeOp* fop, JSObject* obj) {
+  MOZ_ASSERT(fop->maybeOnHelperThread());
+  if (ForOfPIC::Chain* chain =
+          ForOfPIC::fromJSObject(&obj->as<NativeObject>())) {
+    chain->finalize(fop, obj);
+  }
+}
+
+void js::ForOfPIC::Chain::finalize(JSFreeOp* fop, JSObject* obj) {
+  freeAllStubs(fop);
+  fop->delete_(obj, this, MemoryUse::ForOfPIC);
+}
+
+void js::ForOfPIC::Chain::freeAllStubs(JSFreeOp* fop) {
+  Stub* stub = stubs_;
+  while (stub) {
+    Stub* next = stub->next();
+    fop->delete_(picObject_, stub, MemoryUse::ForOfPICStub);
+    stub = next;
+  }
+  stubs_ = nullptr;
+}
+
+static void ForOfPIC_traceObject(JSTracer* trc, JSObject* obj) {
+  if (ForOfPIC::Chain* chain =
+          ForOfPIC::fromJSObject(&obj->as<NativeObject>())) {
+    chain->trace(trc);
+  }
+}
+
+static const JSClassOps ForOfPICClassOps = {
+    nullptr,               // addProperty
+    nullptr,               // delProperty
+    nullptr,               // enumerate
+    nullptr,               // newEnumerate
+    nullptr,               // resolve
+    nullptr,               // mayResolve
+    ForOfPIC_finalize,     // finalize
+    nullptr,               // call
+    nullptr,               // hasInstance
+    nullptr,               // construct
+    ForOfPIC_traceObject,  // trace
+};
+
+const JSClass ForOfPICObject::class_ = {
+    "ForOfPIC", JSCLASS_HAS_PRIVATE | JSCLASS_BACKGROUND_FINALIZE,
+    &ForOfPICClassOps};
+
+/* static */
+NativeObject* js::ForOfPIC::createForOfPICObject(JSContext* cx,
+                                                 Handle<GlobalObject*> global) {
+  cx->check(global);
+  ForOfPICObject* obj =
+      NewTenuredObjectWithGivenProto<ForOfPICObject>(cx, nullptr);
+  if (!obj) {
+    return nullptr;
+  }
+  ForOfPIC::Chain* chain = cx->new_<ForOfPIC::Chain>(obj);
+  if (!chain) {
+    return nullptr;
+  }
+  InitObjectPrivate(obj, chain, MemoryUse::ForOfPIC);
+  obj->setPrivate(chain);
+  return obj;
+}
+
+/* static */ js::ForOfPIC::Chain* js::ForOfPIC::create(JSContext* cx) {
+  MOZ_ASSERT(!cx->global()->getForOfPICObject());
+  Rooted<GlobalObject*> global(cx, cx->global());
+  NativeObject* obj = GlobalObject::getOrCreateForOfPICObject(cx, global);
+  if (!obj) {
+    return nullptr;
+  }
+  return fromJSObject(obj);
+}