Add field nested_sites to AllocationSite. This field is used to maintain

allocation site information for nested array and object literals.
It's not used productively in this CL, merely maintained in a minimal
way. (that comes next :)).

BUG=
R=hpayer@chromium.org

Review URL: https://codereview.chromium.org/23463047

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16912 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/code-stubs-hydrogen.cc

@@ -486,6 +486,11 @@ HValue* CodeStubGraphBuilder<CreateAllocationSiteStub>::BuildCodeStub() {
                         HObjectAccess::ForAllocationSiteTransitionInfo(),
                         initial_elements_kind);
 
+  // Unlike literals, constructed arrays don't have nested sites
+  Add<HStoreNamedField>(object,
+                        HObjectAccess::ForAllocationSiteNestedSite(),
+                        graph()->GetConstant0());
+
   // Store an empty fixed array for the code dependency.
   HConstant* empty_fixed_array =
     Add<HConstant>(isolate()->factory()->empty_fixed_array());

src/heap-snapshot-generator.cc

@@ -1301,6 +1301,8 @@ void V8HeapExplorer::ExtractAllocationSiteReferences(int entry,
                                                      AllocationSite* site) {
   SetInternalReference(site, entry, "transition_info", site->transition_info(),
                        AllocationSite::kTransitionInfoOffset);
+  SetInternalReference(site, entry, "nested_site", site->nested_site(),
+                       AllocationSite::kNestedSiteOffset);
   SetInternalReference(site, entry, "dependent_code", site->dependent_code(),
                        AllocationSite::kDependentCodeOffset);
 }

src/hydrogen-instructions.h

@@ -5637,6 +5637,10 @@ class HObjectAccess V8_FINAL {
     return HObjectAccess(kInobject, AllocationSite::kTransitionInfoOffset);
   }
 
+  static HObjectAccess ForAllocationSiteNestedSite() {
+    return HObjectAccess(kInobject, AllocationSite::kNestedSiteOffset);
+  }
+
   static HObjectAccess ForAllocationSiteDependentCode() {
     return HObjectAccess(kInobject, AllocationSite::kDependentCodeOffset);
   }

src/objects-inl.h

@@ -1324,6 +1324,7 @@ bool JSObject::ShouldTrackAllocationInfo() {
 
 void AllocationSite::Initialize() {
   SetElementsKind(GetInitialFastElementsKind());
+  set_nested_site(Smi::FromInt(0));
   set_dependent_code(DependentCode::cast(GetHeap()->empty_fixed_array()),
                      SKIP_WRITE_BARRIER);
 }
@@ -4442,6 +4443,7 @@ ACCESSORS(SignatureInfo, args, Object, kArgsOffset)
 ACCESSORS(TypeSwitchInfo, types, Object, kTypesOffset)
 
 ACCESSORS(AllocationSite, transition_info, Object, kTransitionInfoOffset)
+ACCESSORS(AllocationSite, nested_site, Object, kNestedSiteOffset)
 ACCESSORS(AllocationSite, dependent_code, DependentCode,
           kDependentCodeOffset)
 ACCESSORS(AllocationSite, weak_next, Object, kWeakNextOffset)

src/objects-printer.cc

@@ -1102,7 +1102,8 @@ void AllocationSite::AllocationSitePrint(FILE* out) {
   weak_next()->ShortPrint(out);
   PrintF(out, "\n - dependent code: ");
   dependent_code()->ShortPrint(out);
-
+  PrintF(out, "\n - nested site: ");
+  nested_site()->ShortPrint(out);
   PrintF(out, "\n - transition_info: ");
   if (transition_info()->IsCell()) {
     Cell* cell = Cell::cast(transition_info());

src/objects.h

@@ -7827,6 +7827,10 @@ class AllocationSite: public Struct {
   static const uint32_t kMaximumArrayBytesToPretransition = 8 * 1024;
 
   DECL_ACCESSORS(transition_info, Object)
+  // nested_site threads a list of sites that represent nested literals
+  // walked in a particular order. So [[1, 2], 1, 2] will have one
+  // nested_site, but [[1, 2], 3, [4]] will have a list of two.
+  DECL_ACCESSORS(nested_site, Object)
   DECL_ACCESSORS(dependent_code, DependentCode)
   DECL_ACCESSORS(weak_next, Object)
 
@@ -7858,7 +7862,8 @@ class AllocationSite: public Struct {
   static inline bool CanTrack(InstanceType type);
 
   static const int kTransitionInfoOffset = HeapObject::kHeaderSize;
-  static const int kDependentCodeOffset = kTransitionInfoOffset + kPointerSize;
+  static const int kNestedSiteOffset = kTransitionInfoOffset + kPointerSize;
+  static const int kDependentCodeOffset = kNestedSiteOffset + kPointerSize;
   static const int kWeakNextOffset = kDependentCodeOffset + kPointerSize;
   static const int kSize = kWeakNextOffset + kPointerSize;