RFR: 8264954: unified handling for VectorMask object re-materialization during de-optimization [v3]

[Daniel D.Daugherty]

On Mon, 12 Apr 2021 09:33:14 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Following flow describes object reconstruction for de-optimization:-
>> 1)	PhaseVector::scalarize_vbox_node() creates SafePointScalarObjectNode to captures the box type information, also it connects to node holding the boxed value.
>> 2)	During code emit phase (PhaseOutput) C2 process above information to dumps ObjectValue holding the box information and LocationValue to holding the value information into ScopeDescriptor corresponding to Safepoint PC.
>> 3)	De-optimization blobs dump the value held in registers to the stack locations using RegisterSave::save_live_registers() and a mapping b/w register and its stack location is added to RegisterMap.
>> 4)	During de-optimization, compiled frame objects are re-allocated using identity information held in ObjectValue and their fields are initialized using values held in the stack locations accessed through register-stack mappings. 
>> 
>> By inserting a VectorStoreMaskNode before stitching the mask holding node to Safepoint we make sure that value held in opmask/vector register is transferred to a byte vector. Thus rest of the flow works as it is, stack location will hold the value in the form of a byte array irrespective of the box shape.
>> 
>> tier1-tier3 regressions are clean with UseAVX=2/3.
>
> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8264954: Incorporating closing comments.

<Remove comment posted in error>

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PR: https://git.openjdk.java.net/jdk/pull/3408