Ensure double arrays are filled with holes when extended from variations of empty arrays.

src/arm/stub-cache-arm.cc

 // Copyright 2012 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 4765 matching lines @@
            FieldMemOperand(receiver_reg, JSArray::kLengthOffset));
     __ ldr(elements_reg,
            FieldMemOperand(receiver_reg, JSObject::kElementsOffset));
     __ CompareRoot(elements_reg, Heap::kEmptyFixedArrayRootIndex);
     __ b(ne, &check_capacity);
 
     int size = FixedDoubleArray::SizeFor(JSArray::kPreallocatedArrayElements);
     __ AllocateInNewSpace(size, elements_reg, scratch1, scratch2, &slow,
                           TAG_OBJECT);
 
-    // Initialize the new FixedDoubleArray. Leave elements unitialized for
-    // efficiency, they are guaranteed to be initialized before use.
+    // Initialize the new FixedDoubleArray.
     __ LoadRoot(scratch1, Heap::kFixedDoubleArrayMapRootIndex);
     __ str(scratch1, FieldMemOperand(elements_reg, JSObject::kMapOffset));
     __ mov(scratch1,
            Operand(Smi::FromInt(JSArray::kPreallocatedArrayElements)));
     __ str(scratch1,
            FieldMemOperand(elements_reg, FixedDoubleArray::kLengthOffset));
 
+    __ mov(scratch1, Operand(kHoleNanLower32));
+    __ mov(scratch2, Operand(kHoleNanUpper32));
+    for (int i = 1; i < JSArray::kPreallocatedArrayElements; i++) {
+      int offset = FixedDoubleArray::OffsetOfElementAt(i);
+      __ str(scratch1, FieldMemOperand(elements_reg, offset));
+      __ str(scratch2, FieldMemOperand(elements_reg, offset + kPointerSize));
+    }
+
+    __ StoreNumberToDoubleElements(value_reg,
+                                   key_reg,
+                                   // All registers after this are overwritten.
+                                   elements_reg,
+                                   scratch1,
+                                   scratch2,
+                                   scratch3,
+                                   scratch4,
+                                   &transition_elements_kind);
+
     // Install the new backing store in the JSArray.
     __ str(elements_reg,
            FieldMemOperand(receiver_reg, JSObject::kElementsOffset));
     __ RecordWriteField(receiver_reg, JSObject::kElementsOffset, elements_reg,
                         scratch1, kLRHasNotBeenSaved, kDontSaveFPRegs,
                         EMIT_REMEMBERED_SET, OMIT_SMI_CHECK);
 
     // Increment the length of the array.
     __ mov(length_reg, Operand(Smi::FromInt(1)));
     __ str(length_reg, FieldMemOperand(receiver_reg, JSArray::kLengthOffset));
     __ ldr(elements_reg,
            FieldMemOperand(receiver_reg, JSObject::kElementsOffset));
-    __ jmp(&finish_store);
+    __ Ret();
 
     __ bind(&check_capacity);
     // Make sure that the backing store can hold additional elements.
     __ ldr(scratch1,
            FieldMemOperand(elements_reg, FixedDoubleArray::kLengthOffset));
     __ cmp(length_reg, scratch1);
     __ b(hs, &slow);
 
     // Grow the array and finish the store.
     __ add(length_reg, length_reg, Operand(Smi::FromInt(1)));
     __ str(length_reg, FieldMemOperand(receiver_reg, JSArray::kLengthOffset));
     __ jmp(&finish_store);
 
     __ bind(&slow);
     Handle<Code> ic_slow = masm->isolate()->builtins()->KeyedStoreIC_Slow();
     __ Jump(ic_slow, RelocInfo::CODE_TARGET);
   }
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM