methodHandles, MethodOops and Method*

Nils Eliasson nils.eliasson at
Tue Dec 11 06:01:30 PST 2012

Looking at the compiler code I see two patterns, which one is correct? 
Which one should we use?

When we access things in a Method* from CompilerOracle we transition to 
native and use methodHandles.

check_is_loaded();  // check that ciMethod is loaded
VM_ENTRY_MARK; // Transition to VM from Native
methodHandle mh(THREAD, get_Method()); // create a handle to a Method* 
(methodOop with permgen)

But in other places I see a shorter form:

bool force_inline() { return get_Method()->force_inline(); }

Pre-permgen-removal - I belive the first example was the correct way to 
do things. We need to transition to VM-running, and to do that we need a 
methodHandle to the MethodOop to keep it from being reclaimed while we 
are looking at it. But how are things supposed to work post-permgen? Do 
we still need the methodHandle or is it direct access allowed like in 
the 2nd example?

//Nils E

More information about the hotspot-compiler-dev mailing list