HotSpot C2 on Linux/x64

`Compile::call_generator` -(bail out)-> `CallGenerator::for_virtual_call` -> `VirtualCallGenerator` -> `CallDynamicJavaNode`

```
// Call Java Dynamic Instruction
// Note: If this code changes, the corresponding ret_addr_offset() and
//       compute_padding() functions will have to be adjusted.
instruct CallDynamicJavaDirect(method meth)
%{
  match(CallDynamicJava);
  effect(USE meth);

  ins_cost(300);
  format %{ "movq    rax, #Universe::non_oop_word()\n\t"
            "call,dynamic " %}
  opcode(0xE8); /* E8 cd */
  ins_encode(Java_Dynamic_Call(meth), call_epilog);
  ins_pipe(pipe_slow);
  ins_pc_relative(1);
  ins_alignment(4);
%}
```

```c++
//-----------------------------------------------------------------------------
// The CompiledIC represents a compiled inline cache.
//
// In order to make patching of the inline cache MT-safe, we only allow the following
// transitions (when not at a safepoint):
//
//
//         [1] --<--  Clean -->---  [1]
//            /       (null)      \
//           /                     \      /-<-\
//          /          [2]          \    /     \
//      Interpreted  ---------> Monomorphic     | [3]
//  (compiledICHolderOop)        (klassOop)     |
//          \                        /   \     /
//       [4] \                      / [4] \->-/
//            \->-  Megamorphic -<-/
//                  (methodOop)
//
// The text in paranteses () refere to the value of the inline cache receiver (mov instruction)
//
// The numbers in square brackets refere to the kind of transition:
// [1]: Initial fixup. Receiver it found from debug information
// [2]: Compilation of a method
// [3]: Recompilation of a method (note: only entry is changed. The klassOop must stay the same)
// [4]: Inline cache miss. We go directly to megamorphic call.
//
// The class automatically inserts transition stubs (using the InlineCacheBuffer) when an MT-unsafe
// transition is made to a stub.
```

The fallback of a monomorphic IC is `SharedRuntime::resolve_virtual_call_C`.

And there's `SharedRuntime::handle_ic_miss_helper`.

In a true polymorphic call site, this kind of strategy may perform worse than just a plain v-table virtual call. The example in this gist shows that it `+UseFastAccessorMethods` may still be faster than going through the compiled VEP