The IC exposes a register definition.

src/isolate.h

 // 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.
 
 #ifndef V8_ISOLATE_H_
 #define V8_ISOLATE_H_
 
 #include "include/v8-debug.h"
 #include "src/allocation.h"
 #include "src/assert-scope.h"
@@ skipping 13 matching lines @@
 #include "src/runtime-profiler.h"
 #include "src/zone.h"
 
 namespace v8 {
 namespace internal {
 
 class Bootstrapper;
 struct CallInterfaceDescriptor;
 class CodeGenerator;
 class CodeRange;
-struct CodeStubInterfaceDescriptor;
+class CodeStubInterfaceDescriptor;
 class CodeTracer;
 class CompilationCache;
 class ConsStringIteratorOp;
 class ContextSlotCache;
 class Counters;
 class CpuFeatures;
 class CpuProfiler;
 class DeoptimizerData;
 class Deserializer;
 class EmptyStatement;
@@ skipping 1458 matching lines @@
   }
 
   EmbeddedVector<char, 128> filename_;
   FILE* file_;
   int scope_depth_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_ISOLATE_H_