First implementation of allocation elimination in Hydrogen.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index 796439a8d394887ad15ed9432cb6ba6b02290407..d61d0d7a22848f008274ff0b95bbfe48511d2544 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -4475,7 +4475,8 @@ void Heap::InitializeJSObjectFromMap(JSObject* obj,
 }
 
 
-MaybeObject* Heap::AllocateJSObjectFromMap(Map* map, PretenureFlag pretenure) {
+MaybeObject* Heap::AllocateJSObjectFromMap(
+    Map* map, PretenureFlag pretenure, bool allocate_properties) {
   // JSFunctions should be allocated using AllocateFunction to be
   // properly initialized.
   ASSERT(map->instance_type() != JS_FUNCTION_TYPE);
@@ -4486,11 +4487,15 @@ MaybeObject* Heap::AllocateJSObjectFromMap(Map* map, PretenureFlag pretenure) {
   ASSERT(map->instance_type() != JS_BUILTINS_OBJECT_TYPE);
 
   // Allocate the backing storage for the properties.
-  int prop_size = map->InitialPropertiesLength();
-  ASSERT(prop_size >= 0);
-  Object* properties;
-  { MaybeObject* maybe_properties = AllocateFixedArray(prop_size, pretenure);
-    if (!maybe_properties->ToObject(&properties)) return maybe_properties;
+  FixedArray* properties;
+  if (allocate_properties) {
+    int prop_size = map->InitialPropertiesLength();
+    ASSERT(prop_size >= 0);
+    { MaybeObject* maybe_properties = AllocateFixedArray(prop_size, pretenure);
+      if (!maybe_properties->To(&properties)) return maybe_properties;
+    }
+  } else {
+    properties = empty_fixed_array();
   }
 
   // Allocate the JSObject.
@@ -4502,17 +4507,15 @@ MaybeObject* Heap::AllocateJSObjectFromMap(Map* map, PretenureFlag pretenure) {
   if (!maybe_obj->To(&obj)) return maybe_obj;
 
   // Initialize the JSObject.
-  InitializeJSObjectFromMap(JSObject::cast(obj),
-                            FixedArray::cast(properties),
-                            map);
+  InitializeJSObjectFromMap(JSObject::cast(obj), properties, map);
   ASSERT(JSObject::cast(obj)->HasFastElements() ||
          JSObject::cast(obj)->HasExternalArrayElements());
   return obj;
 }
 
 
-MaybeObject* Heap::AllocateJSObjectFromMapWithAllocationSite(Map* map,
-    Handle<AllocationSite> allocation_site) {
+MaybeObject* Heap::AllocateJSObjectFromMapWithAllocationSite(
+    Map* map, Handle<AllocationSite> allocation_site) {
   // JSFunctions should be allocated using AllocateFunction to be
   // properly initialized.
   ASSERT(map->instance_type() != JS_FUNCTION_TYPE);
@@ -4525,9 +4528,9 @@ MaybeObject* Heap::AllocateJSObjectFromMapWithAllocationSite(Map* map,
   // Allocate the backing storage for the properties.
   int prop_size = map->InitialPropertiesLength();
   ASSERT(prop_size >= 0);
-  Object* properties;
+  FixedArray* properties;
   { MaybeObject* maybe_properties = AllocateFixedArray(prop_size);
-    if (!maybe_properties->ToObject(&properties)) return maybe_properties;
+    if (!maybe_properties->To(&properties)) return maybe_properties;
   }
 
   // Allocate the JSObject.
@@ -4539,9 +4542,7 @@ MaybeObject* Heap::AllocateJSObjectFromMapWithAllocationSite(Map* map,
   if (!maybe_obj->To(&obj)) return maybe_obj;
 
   // Initialize the JSObject.
-  InitializeJSObjectFromMap(JSObject::cast(obj),
-                            FixedArray::cast(properties),
-                            map);
+  InitializeJSObjectFromMap(JSObject::cast(obj), properties, map);
   ASSERT(JSObject::cast(obj)->HasFastElements());
   return obj;
 }