Provide a tagged allocation top pointer.

src/mips/code-stubs-mips.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_MIPS
 
 #include "src/code-stubs.h"
 #include "src/api-arguments.h"
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
@@ skipping 4496 matching lines @@
 
   // Fall back to runtime if the target differs from the new target's
   // initial map constructor.
   __ lw(a0, FieldMemOperand(a2, Map::kConstructorOrBackPointerOffset));
   __ Branch(&new_object, ne, a0, Operand(a1));
 
   // Allocate the JSObject on the heap.
   Label allocate, done_allocate;
   __ lbu(t0, FieldMemOperand(a2, Map::kInstanceSizeOffset));
   __ Allocate(t0, v0, t1, a0, &allocate, SIZE_IN_WORDS);
+  __ Subu(t1, t1, Operand(kHeapObjectTag));  // Untag result end.
   __ bind(&done_allocate);
 
   // Initialize the JSObject fields.
   __ sw(a2, FieldMemOperand(v0, JSObject::kMapOffset));
   __ LoadRoot(a3, Heap::kEmptyFixedArrayRootIndex);
   __ sw(a3, FieldMemOperand(v0, JSObject::kPropertiesOffset));
   __ sw(a3, FieldMemOperand(v0, JSObject::kElementsOffset));
   STATIC_ASSERT(JSObject::kHeaderSize == 3 * kPointerSize);
   __ Addu(a1, v0, Operand(JSObject::kHeaderSize - kHeapObjectTag));
 
@@ skipping 123 matching lines @@
   __ bind(&no_rest_parameters);
   {
     // ----------- S t a t e -------------
     //  -- cp : context
     //  -- ra : return address
     // -----------------------------------
 
     // Allocate an empty rest parameter array.
     Label allocate, done_allocate;
     __ Allocate(JSArray::kSize, v0, a0, a1, &allocate, NO_ALLOCATION_FLAGS);
+    __ Subu(a0, a0, Operand(kHeapObjectTag));  // Untag result end.
     __ bind(&done_allocate);
 
     // Setup the rest parameter array in v0.
     __ LoadNativeContextSlot(Context::JS_ARRAY_FAST_ELEMENTS_MAP_INDEX, a1);
     __ sw(a1, FieldMemOperand(v0, JSArray::kMapOffset));
     __ LoadRoot(a1, Heap::kEmptyFixedArrayRootIndex);
     __ sw(a1, FieldMemOperand(v0, JSArray::kPropertiesOffset));
     __ sw(a1, FieldMemOperand(v0, JSArray::kElementsOffset));
     __ Move(a1, Smi::FromInt(0));
     __ Ret(USE_DELAY_SLOT);
@@ skipping 876 matching lines @@
                            kStackUnwindSpace, kInvalidStackOffset,
                            return_value_operand, NULL);
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS