Modifying graph to include InvokeNode

[Remi Forax]

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 ?

>
> -Doug
>
> [1] http://www.christianwimmer.at/Publications/Wimmer12b/
> [2] http://www.cs.purdue.edu/homes/jv/events/ESS13/

Rémi

>> 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.
>>