[heap] User safer root set accessor when possible.

R=mlippautz@chromium.org

Review URL: https://codereview.chromium.org/1312763006

Cr-Commit-Position: refs/heads/master@{#30377}

src/arm/macro-assembler-arm.cc

@@ -425,7 +425,7 @@ void MacroAssembler::LoadRoot(Register destination,
       !predictable_code_size()) {
     // The CPU supports fast immediate values, and this root will never
     // change. We will load it as a relocatable immediate value.
-    Handle<Object> root(&isolate()->heap()->roots_array_start()[index]);
+    Handle<Object> root = isolate()->heap()->root_handle(index);
     mov(destination, Operand(root), LeaveCC, cond);
     return;
   }

src/heap/heap.cc

@@ -3372,7 +3372,7 @@ bool Heap::RootCanBeWrittenAfterInitialization(Heap::RootListIndex root_index) {
 
 bool Heap::RootCanBeTreatedAsConstant(RootListIndex root_index) {
   return !RootCanBeWrittenAfterInitialization(root_index) &&
-         !InNewSpace(roots_array_start()[root_index]);
+         !InNewSpace(root(root_index));
 }
 
 

src/heap/heap.h

@@ -1207,6 +1207,9 @@ class Heap {
 #undef SYMBOL_ACCESSOR
 
   Object* root(RootListIndex index) { return roots_[index]; }
+  Handle<Object> root_handle(RootListIndex index) {
+    return Handle<Object>(&roots_[index]);
+  }
 
   // Generated code can embed this address to get access to the roots.
   Object** roots_array_start() { return roots_; }

src/ia32/macro-assembler-ia32.cc

@@ -66,8 +66,7 @@ void MacroAssembler::Store(Register src, const Operand& dst, Representation r) {
 
 void MacroAssembler::LoadRoot(Register destination, Heap::RootListIndex index) {
   if (isolate()->heap()->RootCanBeTreatedAsConstant(index)) {
-    Handle<Object> value(&isolate()->heap()->roots_array_start()[index]);
-    mov(destination, value);
+    mov(destination, isolate()->heap()->root_handle(index));
     return;
   }
   ExternalReference roots_array_start =
@@ -105,16 +104,14 @@ void MacroAssembler::CompareRoot(Register with,
 
 void MacroAssembler::CompareRoot(Register with, Heap::RootListIndex index) {
   DCHECK(isolate()->heap()->RootCanBeTreatedAsConstant(index));
-  Handle<Object> value(&isolate()->heap()->roots_array_start()[index]);
-  cmp(with, value);
+  cmp(with, isolate()->heap()->root_handle(index));
 }
 
 
 void MacroAssembler::CompareRoot(const Operand& with,
                                  Heap::RootListIndex index) {
   DCHECK(isolate()->heap()->RootCanBeTreatedAsConstant(index));
-  Handle<Object> value(&isolate()->heap()->roots_array_start()[index]);
-  cmp(with, value);
+  cmp(with, isolate()->heap()->root_handle(index));
 }
 
 

src/objects-debug.cc

@@ -1236,7 +1236,8 @@ bool CanLeak(Object* obj, Heap* heap, bool skip_weak_cell) {
   if (obj->IsMap()) {
     Map* map = Map::cast(obj);
     for (int i = 0; i < Heap::kStrongRootListLength; i++) {
-      if (map == heap->roots_array_start()[i]) return false;
+      Heap::RootListIndex root_index = static_cast<Heap::RootListIndex>(i);
+      if (map == heap->root(root_index)) return false;
     }
     return true;
   }

src/snapshot/serialize.cc

@@ -354,10 +354,9 @@ RootIndexMap::RootIndexMap(Isolate* isolate) {
   map_ = isolate->root_index_map();
   if (map_ != NULL) return;
   map_ = new HashMap(HashMap::PointersMatch);
-  Object** root_array = isolate->heap()->roots_array_start();
   for (uint32_t i = 0; i < Heap::kStrongRootListLength; i++) {
     Heap::RootListIndex root_index = static_cast<Heap::RootListIndex>(i);
-    Object* root = root_array[root_index];
+    Object* root = isolate->heap()->root(root_index);
     // Omit root entries that can be written after initialization. They must
     // not be referenced through the root list in the snapshot.
     if (root->IsHeapObject() &&
@@ -954,8 +953,9 @@ bool Deserializer::ReadData(Object** current, Object** limit, int source_space,
         emit_write_barrier = (space_number == NEW_SPACE);                      \
         new_object = GetBackReferencedObject(data & kSpaceMask);               \
       } else if (where == kRootArray) {                                        \
-        int root_id = source_.GetInt();                                        \
-        new_object = isolate->heap()->roots_array_start()[root_id];            \
+        int id = source_.GetInt();                                             \
+        Heap::RootListIndex root_index = static_cast<Heap::RootListIndex>(id); \
+        new_object = isolate->heap()->root(root_index);                        \
         emit_write_barrier = isolate->heap()->InNewSpace(new_object);          \
       } else if (where == kPartialSnapshotCache) {                             \
         int cache_index = source_.GetInt();                                    \
@@ -1229,8 +1229,9 @@ bool Deserializer::ReadData(Object** current, Object** limit, int source_space,
 
       SIXTEEN_CASES(kRootArrayConstants)
       SIXTEEN_CASES(kRootArrayConstants + 16) {
-        int root_id = data & kRootArrayConstantsMask;
-        Object* object = isolate->heap()->roots_array_start()[root_id];
+        int id = data & kRootArrayConstantsMask;
+        Heap::RootListIndex root_index = static_cast<Heap::RootListIndex>(id);
+        Object* object = isolate->heap()->root(root_index);
         DCHECK(!isolate->heap()->InNewSpace(object));
         UnalignedCopy(current++, &object);
         break;

src/x87/macro-assembler-x87.cc

@@ -66,8 +66,7 @@ void MacroAssembler::Store(Register src, const Operand& dst, Representation r) {
 
 void MacroAssembler::LoadRoot(Register destination, Heap::RootListIndex index) {
   if (isolate()->heap()->RootCanBeTreatedAsConstant(index)) {
-    Handle<Object> value(&isolate()->heap()->roots_array_start()[index]);
-    mov(destination, value);
+    mov(destination, isolate()->heap()->root_handle(index));
     return;
   }
   ExternalReference roots_array_start =
@@ -105,16 +104,14 @@ void MacroAssembler::CompareRoot(Register with,
 
 void MacroAssembler::CompareRoot(Register with, Heap::RootListIndex index) {
   DCHECK(isolate()->heap()->RootCanBeTreatedAsConstant(index));
-  Handle<Object> value(&isolate()->heap()->roots_array_start()[index]);
-  cmp(with, value);
+  cmp(with, isolate()->heap()->root_handle(index));
 }
 
 
 void MacroAssembler::CompareRoot(const Operand& with,
                                  Heap::RootListIndex index) {
   DCHECK(isolate()->heap()->RootCanBeTreatedAsConstant(index));
-  Handle<Object> value(&isolate()->heap()->roots_array_start()[index]);
-  cmp(with, value);
+  cmp(with, isolate()->heap()->root_handle(index));
 }