RFR: 8330181: Move PcDesc cache from nmethod header [v2]

[Dean Long]

On Wed, 24 Apr 2024 15:33:42 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Currently PcDescCache (32 bytes in 64-bit VM: PcDesc* _pc_descs[4]) is allocated in `nmethod` header.
>> 
>> Moved PcDescContainer (which includes cache) to C heap similar to ExceptionCache to reduce size of `nmethod` header and to remove WXWrite transition when we update the cache in `PcDescCache::add_pc_desc()`.
>> 
>> Removed `PcDescSearch` class which was leftover from `CompiledMethod` days.
>> 
>> Tested tier1-4,stress,xcomp and performance.
>
> Vladimir Kozlov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove unneeded ThreadWXEnable

Looks good.

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Marked as reviewed by dlong (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/18895#pullrequestreview-2020839010