[lilliput-jdk17u:lilliput] RFR: 8304410: [Lilliput/JDK17] Remove unneeded code in ContiguousSpace::object_iterate_from()

[Aleksey Shipilev]

On Fri, 17 Mar 2023 16:07:10 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

> There is some code in space.cpp that resolves a forwarding pointer to get to the Klass* of an object under Lilliput, but it is not necessary and actually causes harm (the null-check doesn't really make sense when the object is indeed forwarded, but we should not observe a forwarded object to begin with). It is not in upstream JDK(21) version of Lilliput and removing it causes no harm.
> 
> Testing:
>  - [x] tier1 -XX:+UseCompactHeaders
>  - [x] tier1 -XX:-UseCompactHeaders
>  - [x] tier2 -XX:+UseCompactHeaders
>  - [x] tier2 -XX:-UseCompactHeaders

Do you want to restore it to the actual upstream shape? The introduction of the local `oop obj` is superfluous. See the diff against upstream: https://builds.shipilev.net/patch-openjdk-lilliput-jdk17/src/hotspot/share/gc/shared/space.cpp.sdiff.html

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PR: https://git.openjdk.org/lilliput-jdk17u/pull/13