RFR: 8306706: Support out-of-line code generation for MachNodes [v5]

[Quan Anh Mai]

> Hi,
> 
> This patch adds supports for MachNodes to emit an out-of-line piece of code in the stub section of the compiled method. This allows the separation of the uncommon path from the common one, which speeds up the common path a little bit and increases compiled code density. Please take a look and leave reviews.
> 
> Thanks a lot.

Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:

  comments describe C2GeneralStub

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13602/files
  - new: https://git.openjdk.org/jdk/pull/13602/files/a17bcb76..76d181b4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13602&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13602&range=03-04

  Stats: 21 lines in 1 file changed: 21 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13602.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13602/head:pull/13602

PR: https://git.openjdk.org/jdk/pull/13602