[lilliput-jdk17u:lilliput] RFR: 8317957: [Lilliput/JDK17] Make C2 LoadNKlassCompactHeader more robust [v3]

[Roman Kennke]

> Backport of https://github.com/openjdk/lilliput/pull/111. I needed to extract the body into helper methods in order to match mainline version. Other than that, the changes are identical.
> 
> Lilliput's C2 code for generating LoadNKlass currently assumes that the disp of the incoming address is klass_offset_in_bytes. It then extracts the base register and loads from the mark_offset_in_bytes instead.
> Sometimes (apparently very rarely) it happens that C2 emits code that pre-adds obj+klass_offset into a register, and uses that as base, but with offset 0. In this case we would trip the assert or crash in release builds.
> 
> - [x] specjvm derby (which triggered the bug)
> - [x] tier1 x86_64 +UCOH
> - [x] tier1 aarch64 +UCOH

Roman Kennke has updated the pull request incrementally with two additional commits since the last revision:

 - Merge remote-tracking branch 'origin/JDK-8317957' into JDK-8317957
 - Fix scale decoding

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Changes:
  - all: https://git.openjdk.org/lilliput-jdk17u/pull/57/files
  - new: https://git.openjdk.org/lilliput-jdk17u/pull/57/files/70902b69..ce805a8b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=lilliput-jdk17u&pr=57&range=02
 - incr: https://webrevs.openjdk.org/?repo=lilliput-jdk17u&pr=57&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/lilliput-jdk17u/pull/57.diff
  Fetch: git fetch https://git.openjdk.org/lilliput-jdk17u.git pull/57/head:pull/57

PR: https://git.openjdk.org/lilliput-jdk17u/pull/57