RFR: 8263361: Incorrect arraycopy stub selected by C2 for SATB collectors [v2]

[Vladimir Ivanov]

On Mon, 15 Mar 2021 15:51:21 GMT, Nils Eliasson <neliasso at openjdk.org> wrote:

>> This bug has only been reproduced with -XX:+StressReflectiveCode and -XX:-ReduceInitialCardMarks. If StressReflectiveCode is necessary isn't obvious.
>> 
>> I am fixing three things:
>> 
>> 1) When running with ReduceInitialCardMarks enabled the stubroutines for int- or long-arraycopy will be used for arraycopies to tightly allocated arrays (like when cloning). With ReduceInitialCardMarks disabled the oop-version will be used with barriers.
>> 
>> The generate_arraycopy method in PhaseMacroExpand have a bool dest_uninitialized field - but that field denotes that we have proven that no zeroing is necessary (since all fields will be written anyway). 
>> 
>> To fix this bug generate_unchecked_arraycopy with the param dest_uninitialized will need to be appended with a check for tighly coupled object-copies when ReduceInitialCardMarks is disabled.
>> 
>> 2) I also fix a bug in library_call kit where arraycopy for clones doesn't get marked as tightly coupled - The call to tightly_coupled_allocation can't be used when the IR isn't constructed yet.
>> 
>> 3) In stubroutines.cpp I fix so that the name of the arraycopy stubroutines gets appended with _uninit when appropriate. This shows up in ir-dumps and IGV.
>> 
>> Please review,
>> Nils Eliasson
>
> Nils Eliasson has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Rename and restructure

Looks good.

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Marked as reviewed by vlivanov (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/3008