Modifying graph to include InvokeNode

[Doug Simon]

On Jul 16, 2013, at 5:33 PM, Remi Forax <forax at univ-mlv.fr> wrote:

> On 07/16/2013 05:27 PM, Doug Simon wrote:
>> On Jul 16, 2013, at 4:41 PM, Christophe Dubach <christophe.dubach at ed.ac.uk> wrote:
>> 
>>> Dear Doug,
>>> 
>>> I'm currently supervising Chris with his work and have been following the discussion.
>>> 
>>> I am quite surprised that it is not possible to add an InvokeNode in a the graph of a method at runtime. When you say "We can only add static calls that are guaranteed to never be deoptimized" do you mean the callee or the caller? I am probably ignorant but I don't see what would be the difference between inserting an invokeNode to static method (not created dynamically) and an IntergerAdd node in the graph at runtime.
>> An invoke node (that doesn't get inlined) in method A that calls method B will result in a call in the generated code. During execution of B, something may happen to invalidate an assumption made when compiling A (e.g., class loading invalidating a class hierarchy speculation). This means A is now invalid and needs to be deoptimized upon return from B. In the current system, we rely on HotSpot's deoptimization infrastructure to continue execution at the return site of A in the interpreter. HotSpot only (currently) supports deoptimize-on-return for call sites that have the BCI of an invoke bytecode.
>> 
>> One could modify HotSpot to have more general deoptimization support or we could modify Graal to handle invokes inserted for instrumentation. However, both of these tasks are non-trivial. Since our current focus is not on making Graal an all purpose instrumentation framework, we probably won't invest much effort in them in the near future.
>> 
>>> Anyway, thanks for the suggestion of doing bytecode instrumentation. Is it possible to do this directly with Graal or where you talking about patching the method at class load time?
>> The latter. Although you could use Graal in conjunction with a bytecode instrumentation library such as ASM for building a graph from the bytecode and finding the loops.
>> 
>>> In our scenario, we want to limit our instrumentation to hot methods in order to further optimise them, therefore, we were aiming to do all this in the jit compiler.
>> What you really want is a Java interpreter based on Truffle[1][2]. We have gone someway down this path ourselves but don't yet have anything publicly available.
> 
> The other solution is to use invokedynamic, if Graal support it ?

It supports it but does not (yet) optimize it.

-Doug

> 
>>> Thanks,
>>> Christophe.
>>> 
>>> 
>>> On 16/07/13 14:43, Doug Simon wrote:
>>>> On Jul 16, 2013, at 3:27 PM, ATKIN-GRANVILLE Chris <s1255753 at sms.ed.ac.uk> wrote:
>>>> 
>>>>> Oh, that may have been a silly thing to say, I know you can't "get" the BCI of a method call that doesn't exist in the bytecode. Even still, it seems like quite a large omission from graal to not be able to add static method calls into a graph…
>>>> We can only add static calls that are guaranteed to never be deoptimized since there is no valid interpreter state to continue in for such invocations. I doubt that any bytecode compiler that relies on deoptimization could do any different…
>>>> 
>>>> For your use case, bytecode instrumentation is what you want. Especially since you (seem to) need complete dynamic coverage of the code patterns you are interested in instrumenting.
>>>> 
>>>> -Doug
>>>> 
>>>>> On 16 Jul 2013, at 14:19, ATKIN-GRANVILLE Chris <s1255753 at sms.ed.ac.uk>
>>>>> wrote:
>>>>> 
>>>>>> Is it not possible to somehow "get" that BCI? It doesn't seem like adding static method calls should be impossible when graph transformations are possible...
>>>>>> 
>>>>>> On 16 Jul 2013, at 14:14, Doug Simon <doug.simon at oracle.com>
>>>>>> wrote:
>>>>>> 
>>>>>>> This is almost certainly due to the fact that an invoke node must be associated with the BCI of a real invoke bytecode instruction. Otherwise, where would the interpreter resume if there is a deoptimization  during the invocation?
>>>>>>> 
>>>>>>> On Jul 16, 2013, at 2:22 PM, ATKIN-GRANVILLE Chris <s1255753 at sms.ed.ac.uk> wrote:
>>>>>>> 
>>>>>>>> Hi there,
>>>>>>>> 
>>>>>>>> I'm trying to modify the graph to include an invoke node to a static function after certain node types. I'm modifying the graph at a high level before LoweringPhase.class (not a requirement, can change if required). However, I'm running into issues with JVM fatal errors. The code I have at the moment looks like this:
>>>>>>>> 
>>>>>>>> public class MyPhase extends Phase {
>>>>>>>> 	public void run(StructuredGraph graph) {
>>>>>>>> 		for (Node node: graph.getNode()) {
>>>>>>>> 
>>>>>>>> 			if ( node instanceof RandomFixedNode) {
>>>>>>>> 				RandomFixedNode rfm = (RandomFixedNode) node;
>>>>>>>> 				
>>>>>>>> 				try {
>>>>>>>> 					ResolvedJavaMethod method = getMethod(…);
>>>>>>>> 					MethodCallTargetMode callTarget = graph.add(new MethodCallTargetNode(MethodCallTargetNode.InvokeKind.Static,
>>>>>>>> 						method, new ValueNode[] {}, new HotSpotResolvedPrimitiveType(Kind.Void)));
>>>>>>>> 
>>>>>>>> 					InvokeNode invoke = graph.add(new InvokeNode(callTarget, FrameState.UNKNOWN_BCI));
>>>>>>>> 					invoke.setStateAfter(graph.add(new FrameState(FrameState.UNKNOWN_BCI)));
>>>>>>>> 					graph.addAfterFixed(rfm, invoke);
>>>>>>>> 				
>>>>>>>> 				} catch (Exception e) {
>>>>>>>> 					e.printStackTrace();
>>>>>>>> 				}
>>>>>>>> 			}
>>>>>>>> 
>>>>>>>> 		}
>>>>>>>> 	}
>>>>>>>> }
>>>>>>>> 
>>>>>>>> I'm pretty sure the problem is do with the BCIs and/or the FrameStates, but I don't know how to fix it. The error that I get is:
>>>>>>>> 
>>>>>>>> Internal Error (/Volumes/Acme/Development/graal/src/share/vm/graal/graalCompilerToVM.cpp:44), pid=8466, tid=5379
>>>>>>>> assert(hotspot_method != NULL && hotspot_method->is_a(HotSpotResolvedJavaMethod::klass())) failed: sanity
>>>>>>>> 
>>>>>>>> Does anyone have any ideas?
>>>>>>>> 
>>>>>>>> Thanks, Chris
>>>>>>>> 
>>>>>>>> -- 
>>>>>>>> The University of Edinburgh is a charitable body, registered in
>>>>>>>> Scotland, with registration number SC005336.
>>>>>>>> 
>>>>>> 
>>>>>> -- 
>>>>>> The University of Edinburgh is a charitable body, registered in
>>>>>> Scotland, with registration number SC005336.
>>>>>> 
>>>>>> 
>>>>> 
>>>>> -- 
>>>>> The University of Edinburgh is a charitable body, registered in
>>>>> Scotland, with registration number SC005336.
>>>>> 
>>> 
>>> -- 
>>> The University of Edinburgh is a charitable body, registered in
>>> Scotland, with registration number SC005336.
>>> 
>