AARCH64: VM crashes with -NearCpool +UseShenandoahGC options

[bulasevich]

Here is the fix for the problem:

• MacroAssembler::adrp should use oop_Relocation from movoop (call stack: MacroAssembler::movoop -> MacroAssembler::ldr_constant -> MacroAssembler::adrp -> code_section::relocate).
• Relocation::pd_set_data_value should account for the adrp+ldr sequence.

I have the following questions:

• Is the NearCpool JVM option truly necessary? How is it used?
• Although NearCpool is described as being related to the constant pool, it appears to be applied in loading nmethod.oops() rather than directly in constant pool loading.

Note. The same issue is reproduced on riscv platform.

A related change: #21276

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[theRealAph]

Here is the fix for the problem:

I have the following questions:

Is the NearCpool JVM option truly necessary? How is it used?

It was never clear whether the constant pool would always be in reach of a ldr. As far as I know it still isn't clear.
So -NearCpoolexists in case cpool isn't reachable. But as far as I know, the constant pool is always next to the code section and the offset is 19 bits, so I don't think that -NearCpool will ever be needed.

Although NearCpool is described as being related to the constant pool, it appears to be applied in loading nmethod.oops() rather than directly in constant pool loading. Could you clarify its purpose and implementation?

It's essentially the same problem that I described above. Will the nmethod oops table always be in range of an ldr?