[turbofan] cleanup InstructionOperand a little

src/compiler/x64/code-generator-x64.cc

 // Copyright 2013 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/scopes.h"
@@ skipping 26 matching lines @@
 
   Operand OutputOperand() { return ToOperand(instr_->Output()); }
 
   Immediate ToImmediate(InstructionOperand* operand) {
     return Immediate(ToConstant(operand).ToInt32());
   }
 
   Operand ToOperand(InstructionOperand* op, int extra = 0) {
     DCHECK(op->IsStackSlot() || op->IsDoubleStackSlot());
     // The linkage computes where all spill slots are located.
-    FrameOffset offset = linkage()->GetFrameOffset(op->index(), frame(), extra);
+    FrameOffset offset = linkage()->GetFrameOffset(
+        AllocatedOperand::cast(op)->index(), frame(), extra);
     return Operand(offset.from_stack_pointer() ? rsp : rbp, offset.offset());
   }
 
   static size_t NextOffset(size_t* offset) {
     size_t i = *offset;
     (*offset)++;
     return i;
   }
 
   static ScaleFactor ScaleFor(AddressingMode one, AddressingMode mode) {
@@ skipping 1534 matching lines @@
     }
   }
   MarkLazyDeoptSite();
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace compiler
 }  // namespace v8