RFR(M): 8024069: replace_in_map() should operate on parent maps

[Vladimir Kozlov]

On 10/15/13 3:31 AM, Roland Westrelin wrote:
> Hi Vladimir,
>
> Thanks for reviewing this.
>
>> Why in LateInlineCallGenerator::do_late_inline() you pass NULL?:
>> _inline_cg->generate(jvms, NULL);
>
> What else could be passed? Parsing of callers is over and we don't have any Parse object to pass. It's too late to do the replace in the callers. Or am I missing something?

Yes, you are right. But you still have exit.jvms in which you can do 
replacement.

>
>> In general, why we should care about intrinsics? There should be no inlining in them. And we will get speculative argument for instrinsics without recording parent parser in them. If we ignore intrinsics, we will need only cases when is_Parse() returns Parse object and we don't need parent_parser(). What I am missing?
>
> You're right. We don't need to care about intrinsics.
>
> So in GraphKit::replace_in_map(). this:
>
>    if (parser == NULL) {
>      parser = parent_parser();
>    }
>
> is not needed but we still need the parent_parser() method to iterate over parsers. parent_parser() only needs to be defined in Parse.
>
>> Also why not use parser->caller()->map()? jvms() comes from GraphKit and if there was not inlined call before map() will point to it (deep clone) instead of the parent's map.
>
> I don't see a reason not to use parser->caller()->map(), indeed. I'll do the change. This change I don't understand why it matters either.
>
>>
>> And I don't understand where 1) requirement comes from.
>
> If we have something like this:
>
> void m(A a) {
>    if (some_condition) {
>      B b = (B)a;
>    } else {
>      // some other stuff
>    }
> }
>
> then we'll replace a with (B)a in the map of the if branch but we cannot replace a with (B)a in caller of m because it's only true under some particular control.

What about this case? We should be keeping the cast:

void m(A a) {
     if (some_condition) {
       // some other stuff
     }
     B b = (B)a;
}

I think you doing it in reverse order. You need to check that (B)a 
reaches exit point, it should not be matter what happened before. In 
your testcase there should be merge point after 'else' where the cast is 
invalidated (local will be dead or type will be widen).

Thanks,
Vladimir

>
> Roland.
>
>>
>> I am fine with moving is_uncommon_trap_*() mathods.
>>
>> Thanks,
>> Vladimir
>>
>> On 10/12/13 2:31 PM, Roland Westrelin wrote:
>>> The improved type coming from a type check when it is done inside an inlined method may be lost once compilation exits from the inlinee because GraphKit::replace_in_map() doesn't update the maps of caller methods.
>>>
>>> When updating the parent maps, the replacement must be safe. This is done 1) by following the control edges to check that the control of the inlinee's map post dominate the control of the parent's maps 2) not doing any update in parent maps if the replace_in_map is called inside a PreserveJVMState block because PreserveJVMState doesn't do a deep copy of the caller states. The update itself must be done in the exits maps of the Parsers of the caller. I've added code to chain them together so that replace_in_map can iterate over the Parsers of callers.
>>>
>>> http://cr.openjdk.java.net/~roland/8024069/webrev.00/
>>>
>>> Roland.
>>>
>