Eliminated manual allocation folding in BuildCloneShallowArray.

src/hydrogen.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1661 matching lines @@
                                               AllocationSiteMode mode,
                                               ElementsKind kind,
                                               int length) {
   NoObservableSideEffectsScope no_effects(this);
 
   // All sizes here are multiples of kPointerSize.
   int size = JSArray::kSize;
   if (mode == TRACK_ALLOCATION_SITE) {
     size += AllocationMemento::kSize;
   }
-  int elems_offset = size;
-  InstanceType instance_type = IsFastDoubleElementsKind(kind) ?
-      FIXED_DOUBLE_ARRAY_TYPE : FIXED_ARRAY_TYPE;
-  if (length > 0) {
-    size += IsFastDoubleElementsKind(kind)
-        ? FixedDoubleArray::SizeFor(length)
-        : FixedArray::SizeFor(length);
-  }
 
   // Allocate both the JS array and the elements array in one big

[Michael Starzinger, 2013/08/16 20:02:11]

nit: Comment is outdated.

[Hannes Payer (out of office), 2013/08/28 13:10:59]

Done.

   // allocation. This avoids multiple limit checks.
   HValue* size_in_bytes = Add<HConstant>(size);
   HInstruction* object = Add<HAllocate>(size_in_bytes,
                                         HType::JSObject(),
                                         NOT_TENURED,
-                                        instance_type);
+                                        JS_OBJECT_TYPE);

[Michael Starzinger, 2013/08/16 20:02:11]

Nice, that would have been a disaster once we would have pretenured these.

 
   // Copy the JS array part.
   for (int i = 0; i < JSArray::kSize; i += kPointerSize) {
     if ((i != JSArray::kElementsOffset) || (length == 0)) {
       HObjectAccess access = HObjectAccess::ForJSArrayOffset(i);
       Add<HStoreNamedField>(object, access,
                             Add<HLoadNamedField>(boilerplate, access));
     }
   }
 
   // Create an allocation site info if requested.
   if (mode == TRACK_ALLOCATION_SITE) {
     BuildCreateAllocationMemento(object, JSArray::kSize, allocation_site);
   }
 
   if (length > 0) {
     // Get hold of the elements array of the boilerplate and setup the

[Michael Starzinger, 2013/08/16 20:02:11]

nit: Comment is outdated.

[Hannes Payer (out of office), 2013/08/28 13:10:59]

Done.

     // elements pointer in the resulting object.
     HValue* boilerplate_elements = AddLoadElements(boilerplate, NULL);
-    HValue* object_elements = Add<HInnerAllocatedObject>(object, elems_offset);
+    HValue* object_elements;
+    if (IsFastDoubleElementsKind(kind)) {
+      HValue* elems_size = Add<HConstant>(FixedDoubleArray::SizeFor(length));
+      object_elements = Add<HAllocate>(elems_size, HType::JSArray(),
+          NOT_TENURED, FIXED_DOUBLE_ARRAY_TYPE);
+    } else {
+      HValue* elems_size = Add<HConstant>(FixedArray::SizeFor(length));
+      object_elements = Add<HAllocate>(elems_size, HType::JSArray(),
+          NOT_TENURED, FIXED_ARRAY_TYPE);
+    }
     Add<HStoreNamedField>(object, HObjectAccess::ForElementsPointer(),
                           object_elements);
 
     // Copy the elements array header.
     for (int i = 0; i < FixedArrayBase::kHeaderSize; i += kPointerSize) {
       HObjectAccess access = HObjectAccess::ForFixedArrayHeader(i);
       Add<HStoreNamedField>(object_elements, access,
                             Add<HLoadNamedField>(boilerplate_elements, access));
     }
 
@@ skipping 8115 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal