[13] RFR (S): 8192001: C2: inlining through dispatching MH linkers ignores speculative type of the receiver

[Vladimir Ivanov]

http://cr.openjdk.java.net/~vlivanov/8192001/webrev.00/
https://bugs.openjdk.java.net/browse/JDK-8192001

When inlining through MethodHandle calls, C2 can improve inlining 
decisions by taking speculative types into account (availability of type 
information is addressed by JDK-8191998 [1]).

There's no profiling performed at method handle linker call sites 
(MethodHandle::linkTo*), but type info can flow from other sources.

As an example, consider the following case:

   class A           { void m() { ... } }
   class B extends A { void m() { ... } }

   MH = LOOKUP.findVirtual(A.class, "m", ...);

   void test(A o) throws Throwable {
     MH.invokeExact(o);
   }

   test(new B());

Before (no inlining):
251   12   !b        TestMH::test (21 bytes)
   ...
   @ 16   TestMH1$A::m (1 bytes)   virtual call

After (guarded inlining):
251   12   !b        TestMH::test (21 bytes)
   ...
   @ 16   TestMH1$B1::m (1 bytes)   inline (hot)
      \-> TypeProfile (-1/6701 counts) = TestMH1$B1

Testing: hs-precheckin-comp, hs-tier1, hs-tier2.

Best regards,
Vladimir Ivanov

[1] https://bugs.openjdk.java.net/browse/JDK-8192001