[turbofan] cleanup InstructionOperand a little

src/compiler/mips64/code-generator-mips64.cc

 // Copyright 2014 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.
 
 #include "src/compiler/code-generator.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
 #include "src/mips/macro-assembler-mips.h"
 #include "src/scopes.h"
@@ skipping 92 matching lines @@
   }
 
   MemOperand MemoryOperand(size_t index = 0) { return MemoryOperand(&index); }
 
   MemOperand ToMemOperand(InstructionOperand* op) const {
     DCHECK(op != NULL);
     DCHECK(!op->IsRegister());
     DCHECK(!op->IsDoubleRegister());
     DCHECK(op->IsStackSlot() || op->IsDoubleStackSlot());
     // The linkage computes where all spill slots are located.
-    FrameOffset offset = linkage()->GetFrameOffset(op->index(), frame(), 0);
+    FrameOffset offset = linkage()->GetFrameOffset(
+        AllocatedOperand::cast(op)->index(), frame(), 0);
     return MemOperand(offset.from_stack_pointer() ? sp : fp, offset.offset());
   }
 };
 
 
 static inline bool HasRegisterInput(Instruction* instr, size_t index) {
   return instr->InputAt(index)->IsRegister();
 }
 
 
@@ skipping 1230 matching lines @@
     }
   }
   MarkLazyDeoptSite();
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8