Clean up aligned allocation code in preparation for SIMD alignments.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 5a10a5cd210ac4da9700d1a746410fc787f93c6c..94e345e7f26fe4cfe3cc5686eb54160f34eacfe8 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -1975,31 +1975,45 @@ STATIC_ASSERT((HeapNumber::kValueOffset & kDoubleAlignmentMask) !=
 #endif
 
 
-HeapObject* Heap::EnsureAligned(HeapObject* object, int size,
-                                AllocationAlignment alignment) {
-  if (alignment == kDoubleAligned &&
-      (OffsetFrom(object->address()) & kDoubleAlignmentMask) != 0) {
-    CreateFillerObjectAt(object->address(), kPointerSize);
-    return HeapObject::FromAddress(object->address() + kPointerSize);
-  } else if (alignment == kDoubleUnaligned &&
-             (OffsetFrom(object->address()) & kDoubleAlignmentMask) == 0) {
-    CreateFillerObjectAt(object->address(), kPointerSize);
-    return HeapObject::FromAddress(object->address() + kPointerSize);
-  } else {
-    CreateFillerObjectAt(object->address() + size - kPointerSize, kPointerSize);
-    return object;
+int GetMaximumMisalignment(AllocationAlignment alignment) {
+  switch (alignment) {
+    case kWordAligned:
+      return 0;
+    case kDoubleAligned:
+    case kDoubleValueAligned:
+      return kDoubleSize / 2;
+    default:
+      UNREACHABLE();
   }
 }
 
 
-HeapObject* Heap::PrecedeWithFiller(HeapObject* object) {
-  CreateFillerObjectAt(object->address(), kPointerSize);
-  return HeapObject::FromAddress(object->address() + kPointerSize);
+int Heap::GetMisalignment(Address address, AllocationAlignment alignment) {
+  intptr_t offset = OffsetFrom(address);
+  if (alignment == kDoubleAligned && (offset & kDoubleAlignmentMask) != 0)
+    return kPointerSize;
+  if (alignment == kDoubleValueAligned && (offset & kDoubleAlignmentMask) == 0)
+    return kPointerSize;
+  return 0;
+}
+
+
+HeapObject* Heap::PrecedeWithFiller(HeapObject* object, int filler_size) {
+  CreateFillerObjectAt(object->address(), filler_size);
+  return HeapObject::FromAddress(object->address() + filler_size);
 }
 
 
 HeapObject* Heap::DoubleAlignForDeserialization(HeapObject* object, int size) {
-  return EnsureAligned(object, size, kDoubleAligned);
+  Address address = object->address();
+  int fill_size = GetMisalignment(address, kDoubleAligned);
+  // If object is not aligned, add fill to align it.
+  if (fill_size) return PrecedeWithFiller(object, kPointerSize);
+
+  // object is aligned. Add fill in the extra space at the end.
+  // TODO(bbudge) Calculate alignment fill earlier to avoid this.
+  CreateFillerObjectAt(address + size - kPointerSize, kPointerSize);
+  return object;
 }
 
 
@@ -2144,16 +2158,14 @@ class ScavengingVisitor : public StaticVisitorBase {
     }
   }
 
-  template <int alignment>
+  template <AllocationAlignment alignment>
   static inline bool SemiSpaceCopyObject(Map* map, HeapObject** slot,
                                          HeapObject* object, int object_size) {
     Heap* heap = map->GetHeap();
 
     DCHECK(heap->AllowedToBeMigrated(object, NEW_SPACE));
-    AllocationAlignment align =
-        alignment == kDoubleAlignment ? kDoubleAligned : kWordAligned;
     AllocationResult allocation =
-        heap->new_space()->AllocateRaw(object_size, align);
+        heap->new_space()->AllocateRaw(object_size, alignment);
 
     HeapObject* target = NULL;  // Initialization to please compiler.
     if (allocation.To(&target)) {
@@ -2175,15 +2187,13 @@ class ScavengingVisitor : public StaticVisitorBase {
   }
 
 
-  template <ObjectContents object_contents, int alignment>
+  template <ObjectContents object_contents, AllocationAlignment alignment>
   static inline bool PromoteObject(Map* map, HeapObject** slot,
                                    HeapObject* object, int object_size) {
     Heap* heap = map->GetHeap();
 
-    AllocationAlignment align =
-        alignment == kDoubleAlignment ? kDoubleAligned : kWordAligned;
     AllocationResult allocation =
-        heap->old_space()->AllocateRaw(object_size, align);
+        heap->old_space()->AllocateRaw(object_size, alignment);
 
     HeapObject* target = NULL;  // Initialization to please compiler.
     if (allocation.To(&target)) {
@@ -2207,7 +2217,7 @@ class ScavengingVisitor : public StaticVisitorBase {
   }
 
 
-  template <ObjectContents object_contents, int alignment>
+  template <ObjectContents object_contents, AllocationAlignment alignment>
   static inline void EvacuateObject(Map* map, HeapObject** slot,
                                     HeapObject* object, int object_size) {
     SLOW_DCHECK(object_size <= Page::kMaxRegularHeapObjectSize);
@@ -2257,12 +2267,17 @@ class ScavengingVisitor : public StaticVisitorBase {
     }
   }
 
+#if V8_HOST_ARCH_64_BIT
+#define kObjectAligned kDoubleAligned
+#else
+#define kObjectAligned kWordAligned
+#endif
 
   static inline void EvacuateFixedArray(Map* map, HeapObject** slot,
                                         HeapObject* object) {
     int object_size = FixedArray::BodyDescriptor::SizeOf(map, object);
-    EvacuateObject<POINTER_OBJECT, kObjectAlignment>(map, slot, object,
-                                                     object_size);
+    EvacuateObject<POINTER_OBJECT, kObjectAligned>(map, slot, object,
+                                                   object_size);
   }
 
 
@@ -2270,32 +2285,28 @@ class ScavengingVisitor : public StaticVisitorBase {
                                               HeapObject* object) {
     int length = reinterpret_cast<FixedDoubleArray*>(object)->length();
     int object_size = FixedDoubleArray::SizeFor(length);
-    EvacuateObject<DATA_OBJECT, kDoubleAlignment>(map, slot, object,
-                                                  object_size);
+    EvacuateObject<DATA_OBJECT, kDoubleAligned>(map, slot, object, object_size);
   }
 
 
   static inline void EvacuateFixedTypedArray(Map* map, HeapObject** slot,
                                              HeapObject* object) {
     int object_size = reinterpret_cast<FixedTypedArrayBase*>(object)->size();
-    EvacuateObject<DATA_OBJECT, kObjectAlignment>(map, slot, object,
-                                                  object_size);
+    EvacuateObject<DATA_OBJECT, kObjectAligned>(map, slot, object, object_size);
   }
 
 
   static inline void EvacuateFixedFloat64Array(Map* map, HeapObject** slot,
                                                HeapObject* object) {
     int object_size = reinterpret_cast<FixedFloat64Array*>(object)->size();
-    EvacuateObject<DATA_OBJECT, kDoubleAlignment>(map, slot, object,
-                                                  object_size);
+    EvacuateObject<DATA_OBJECT, kDoubleAligned>(map, slot, object, object_size);
   }
 
 
   static inline void EvacuateByteArray(Map* map, HeapObject** slot,
                                        HeapObject* object) {
     int object_size = reinterpret_cast<ByteArray*>(object)->ByteArraySize();
-    EvacuateObject<DATA_OBJECT, kObjectAlignment>(map, slot, object,
-                                                  object_size);
+    EvacuateObject<DATA_OBJECT, kObjectAligned>(map, slot, object, object_size);
   }
 
 
@@ -2303,8 +2314,7 @@ class ScavengingVisitor : public StaticVisitorBase {
                                               HeapObject* object) {
     int object_size = SeqOneByteString::cast(object)
                           ->SeqOneByteStringSize(map->instance_type());
-    EvacuateObject<DATA_OBJECT, kObjectAlignment>(map, slot, object,
-                                                  object_size);
+    EvacuateObject<DATA_OBJECT, kObjectAligned>(map, slot, object, object_size);
   }
 
 
@@ -2312,8 +2322,7 @@ class ScavengingVisitor : public StaticVisitorBase {
                                               HeapObject* object) {
     int object_size = SeqTwoByteString::cast(object)
                           ->SeqTwoByteStringSize(map->instance_type());
-    EvacuateObject<DATA_OBJECT, kObjectAlignment>(map, slot, object,
-                                                  object_size);
+    EvacuateObject<DATA_OBJECT, kObjectAligned>(map, slot, object, object_size);
   }
 
 
@@ -2350,8 +2359,8 @@ class ScavengingVisitor : public StaticVisitorBase {
     }
 
     int object_size = ConsString::kSize;
-    EvacuateObject<POINTER_OBJECT, kObjectAlignment>(map, slot, object,
-                                                     object_size);
+    EvacuateObject<POINTER_OBJECT, kObjectAligned>(map, slot, object,
+                                                   object_size);
   }
 
   template <ObjectContents object_contents>
@@ -2360,14 +2369,14 @@ class ScavengingVisitor : public StaticVisitorBase {
     template <int object_size>
     static inline void VisitSpecialized(Map* map, HeapObject** slot,
                                         HeapObject* object) {
-      EvacuateObject<object_contents, kObjectAlignment>(map, slot, object,
-                                                        object_size);
+      EvacuateObject<object_contents, kObjectAligned>(map, slot, object,
+                                                      object_size);
     }
 
     static inline void Visit(Map* map, HeapObject** slot, HeapObject* object) {
       int object_size = map->instance_size();
-      EvacuateObject<object_contents, kObjectAlignment>(map, slot, object,
-                                                        object_size);
+      EvacuateObject<object_contents, kObjectAligned>(map, slot, object,
+                                                      object_size);
     }
   };
 
@@ -2850,7 +2859,7 @@ AllocationResult Heap::AllocateHeapNumber(double value, MutableMode mode,
   HeapObject* result;
   {
     AllocationResult allocation =
-        AllocateRaw(size, space, OLD_SPACE, kDoubleUnaligned);
+        AllocateRaw(size, space, OLD_SPACE, kDoubleValueAligned);
     if (!allocation.To(&result)) return allocation;
   }