Fix for bug 429168, PdfJs regression. We pay a very high cost for AllocationResult being a > kPointerSize struct. This can be avoided by using Smis to indicate failure with retry spaces.

BUG=429168
LOG=N
R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/699473002

Cr-Commit-Position: refs/heads/master@{#25057}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25057 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/globals.h

@@ -376,7 +376,6 @@ enum AllocationSpace {
   CELL_SPACE,           // Only and all cell objects.
   PROPERTY_CELL_SPACE,  // Only and all global property cell objects.
   LO_SPACE,             // Promoted large objects.
-  INVALID_SPACE,        // Only used in AllocationResult to signal success.
 
   FIRST_SPACE = NEW_SPACE,
   LAST_SPACE = LO_SPACE,

src/heap/heap-inl.h

@@ -458,8 +458,6 @@ bool Heap::AllowedToBeMigrated(HeapObject* obj, AllocationSpace dst) {
     case PROPERTY_CELL_SPACE:
     case LO_SPACE:
       return false;
-    case INVALID_SPACE:
-      break;
   }
   UNREACHABLE();
   return false;

src/heap/heap.cc

@@ -4545,8 +4545,6 @@ bool Heap::InSpace(Address addr, AllocationSpace space) {
       return property_cell_space_->Contains(addr);
     case LO_SPACE:
       return lo_space_->SlowContains(addr);
-    case INVALID_SPACE:
-      break;
   }
   UNREACHABLE();
   return false;

src/heap/spaces.h

@@ -1614,16 +1614,19 @@ class AllocationResult {
  public:
   // Implicit constructor from Object*.
   AllocationResult(Object* object)  // NOLINT
-      : object_(object),
-        retry_space_(INVALID_SPACE) {}
+      : object_(object) {
+    // AllocationResults can't return Smis, which are used to represent
+    // failure and the space to retry in.
+    CHECK(!object->IsSmi());
+  }
 
-  AllocationResult() : object_(NULL), retry_space_(INVALID_SPACE) {}
+  AllocationResult() : object_(Smi::FromInt(NEW_SPACE)) {}
 
   static inline AllocationResult Retry(AllocationSpace space = NEW_SPACE) {
     return AllocationResult(space);
   }
 
-  inline bool IsRetry() { return retry_space_ != INVALID_SPACE; }
+  inline bool IsRetry() { return object_->IsSmi(); }
 
   template <typename T>
   bool To(T** obj) {
@@ -1639,18 +1642,20 @@ class AllocationResult {
 
   AllocationSpace RetrySpace() {
     DCHECK(IsRetry());
-    return retry_space_;
+    return static_cast<AllocationSpace>(Smi::cast(object_)->value());
   }
 
  private:
   explicit AllocationResult(AllocationSpace space)
-      : object_(NULL), retry_space_(space) {}
+      : object_(Smi::FromInt(static_cast<int>(space))) {}
 
   Object* object_;
-  AllocationSpace retry_space_;
 };
 
 
+STATIC_ASSERT(sizeof(AllocationResult) == kPointerSize);
+
+
 class PagedSpace : public Space {
  public:
   // Creates a space with a maximum capacity, and an id.

src/serialize.cc

@@ -1903,7 +1903,7 @@ AllocationSpace Serializer::SpaceOfObject(HeapObject* object) {
     }
   }
   UNREACHABLE();
-  return INVALID_SPACE;
+  return FIRST_SPACE;
 }
 
 

src/serialize.h

@@ -296,7 +296,7 @@ class SerializerDeserializer: public ObjectVisitor {
 
   // No reservation for large object space necessary.
   static const int kNumberOfPreallocatedSpaces = LO_SPACE;
-  static const int kNumberOfSpaces = INVALID_SPACE;
+  static const int kNumberOfSpaces = LAST_SPACE + 1;
 
  protected:
   // Where the pointed-to object can be found:

test/cctest/test-alloc.cc

@@ -86,7 +86,7 @@ static AllocationResult AllocateAfterFailures() {
       Builtins::kIllegal)).ToObjectChecked();
 
   // Return success.
-  return Smi::FromInt(42);
+  return heap->true_value();
 }
 
 
@@ -100,7 +100,7 @@ TEST(StressHandles) {
   v8::Handle<v8::Context> env = v8::Context::New(CcTest::isolate());
   env->Enter();
   Handle<Object> o = Test();
-  CHECK(o->IsSmi() && Smi::cast(*o)->value() == 42);
+  CHECK(o->IsTrue());
   env->Exit();
 }
 
@@ -162,7 +162,7 @@ TEST(StressJS) {
   // Call the accessor through JavaScript.
   v8::Handle<v8::Value> result = v8::Script::Compile(
       v8::String::NewFromUtf8(CcTest::isolate(), "(new Foo).get"))->Run();
-  CHECK_EQ(42, result->Int32Value());
+  CHECK_EQ(true, result->BooleanValue());
   env->Exit();
 }