Provide a tagged allocation top pointer.

src/crankshaft/mips64/lithium-codegen-mips64.cc

Index: src/crankshaft/mips64/lithium-codegen-mips64.cc
diff --git a/src/crankshaft/mips64/lithium-codegen-mips64.cc b/src/crankshaft/mips64/lithium-codegen-mips64.cc
index 280b00cd840ff83b93704b384c1f4d5b5ff19b96..d1ca99a5de7475abd5cec8aa6e544c394bb31edf 100644
--- a/src/crankshaft/mips64/lithium-codegen-mips64.cc
+++ b/src/crankshaft/mips64/lithium-codegen-mips64.cc
@@ -5345,10 +5345,8 @@ void LCodeGen::DoDeferredAllocate(LAllocate* instr) {
     ExternalReference allocation_top =
         AllocationUtils::GetAllocationTopReference(isolate(), allocation_flags);
     Register top_address = scratch0();
-    __ Dsubu(v0, v0, Operand(kHeapObjectTag));
     __ li(top_address, Operand(allocation_top));
     __ sd(v0, MemOperand(top_address));
-    __ Daddu(v0, v0, Operand(kHeapObjectTag));
   }
 }