8367984: Eliminate offset_of in vmStructs

[fandreuz]

There are several usages of offset_of in vmStructs, they can be replaced with standard offsetof due to JDK-8367016.

Passes tier1.

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Issue

• JDK-8367984: Eliminate offset_of in vmStructs (Enhancement - P4)

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[fandreuz]

I got a partial understanding about this change, I thought having JNIEXPORT and constexpr together wouldn't work. But the symbols are exported:

objdump --syms build/gcc/jdk/lib/server/libjvm.so | grep gHotSpotVMTypeEntryIsIntegerTypeOffset
000000000137ca78 g     O .rodata	0000000000000008              gHotSpotVMTypeEntryIsIntegerTypeOffset

and I tested that the values are still readable. I was wondering if this wouldn't be portable?

[mlbridge]

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