Provide a tagged allocation top pointer.

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

Index: src/crankshaft/mips/lithium-codegen-mips.cc
diff --git a/src/crankshaft/mips/lithium-codegen-mips.cc b/src/crankshaft/mips/lithium-codegen-mips.cc
index 490ed7a0ac58ced7fb6f95fd9f4deabd7a73236b..552d68da4cfef740a3bb2945ede0db2c9489e9de 100644
--- a/src/crankshaft/mips/lithium-codegen-mips.cc
+++ b/src/crankshaft/mips/lithium-codegen-mips.cc
@@ -5141,10 +5141,8 @@ void LCodeGen::DoDeferredAllocate(LAllocate* instr) {
     ExternalReference allocation_top =
         AllocationUtils::GetAllocationTopReference(isolate(), allocation_flags);
     Register top_address = scratch0();
-    __ Subu(v0, v0, Operand(kHeapObjectTag));
     __ li(top_address, Operand(allocation_top));
     __ sw(v0, MemOperand(top_address));
-    __ Addu(v0, v0, Operand(kHeapObjectTag));
   }
 }