[master] RFR: Load Klass from header, C1 [v12]

[Roman Kennke]

> This implements loading the Klass* from object header (instead of dedicated Klass* field) in C1 generated code.
> 
> Testing:
>  - [x] tier1 (x86_64,x86_32, aarch64)
>  - [x] tier2 (x86_64,x86_32, aarch64)
>  - [x] tier3 (x86_64,x86_32, aarch64)
>  - [ ] tier4 (x86_64,x86_32, aarch64)

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

 - Merge remote-tracking branch 'origin/klass-from-header-c1' into klass-from-header-c1
 - Update src/hotspot/cpu/s390/c1_CodeStubs_s390.cpp
   
   Co-authored-by: Aleksey Shipilëv <shade at redhat.com>
 - Update src/hotspot/cpu/arm/c1_CodeStubs_arm.cpp
   
   Co-authored-by: Aleksey Shipilëv <shade at redhat.com>
 - Update src/hotspot/cpu/ppc/c1_CodeStubs_ppc.cpp
   
   Co-authored-by: Aleksey Shipilëv <shade at redhat.com>
 - Update src/hotspot/share/oops/oop.cpp
   
   Co-authored-by: Aleksey Shipilëv <shade at redhat.com>
 - Reinstate null-check for x86_32

-------------

Changes:
  - all: https://git.openjdk.java.net/lilliput/pull/20/files
  - new: https://git.openjdk.java.net/lilliput/pull/20/files/bc5b45e9..bbcb6153

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=lilliput&pr=20&range=11
 - incr: https://webrevs.openjdk.java.net/?repo=lilliput&pr=20&range=10-11

  Stats: 12 lines in 5 files changed: 6 ins; 4 del; 2 mod
  Patch: https://git.openjdk.java.net/lilliput/pull/20.diff
  Fetch: git fetch https://git.openjdk.java.net/lilliput pull/20/head:pull/20

PR: https://git.openjdk.java.net/lilliput/pull/20