Optimize AOT's switchable calls for the monomorphic case.

runtime/vm/simulator_arm64.cc

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include <setjmp.h>  // NOLINT
 #include <stdlib.h>
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_ARM64)
 
@@ skipping 247 matching lines @@
       return true;
     }
   }
   return false;
 }
 
 
 TokenPosition SimulatorDebugger::GetApproximateTokenIndex(const Code& code,
                                                             uword pc) {
   TokenPosition token_pos = TokenPosition::kNoSource;
-  uword pc_offset = pc - code.EntryPoint();
+  uword pc_offset = pc - code.PayloadStart();
   const PcDescriptors& descriptors =
       PcDescriptors::Handle(code.pc_descriptors());
   PcDescriptors::Iterator iter(descriptors, RawPcDescriptors::kAnyKind);
   while (iter.MoveNext()) {
     if (iter.PcOffset() == pc_offset) {
       return iter.TokenPos();
     } else if (!token_pos.IsReal() && (iter.PcOffset() > pc_offset)) {
       token_pos = iter.TokenPos();
     }
   }
@@ skipping 3326 matching lines @@
   set_register(NULL, kExceptionObjectReg, bit_cast<int64_t>(raw_exception));
   set_register(NULL, kStackTraceObjectReg, bit_cast<int64_t>(raw_stacktrace));
   buf->Longjmp();
 }
 
 }  // namespace dart
 
 #endif  // !defined(USING_SIMULATOR)
 
 #endif  // defined TARGET_ARCH_ARM64