RFR: JDK-8241503: C2: Share MacroAssembler between mach nodes during code emission [v5]

[Cesar Soares Lucas]

> # Description
> 
> Please review this PR with a patch to re-use the same C2_MacroAssembler object to emit all instructions in the same compilation unit.
> 
> Overall, the change is pretty simple. However, due to the renaming of the variable to access C2_MacroAssembler, from `_masm.` to `masm->`, and also some method prototype changes, the patch became quite large.
> 
> # Help Needed for Testing
> 
> I don't have access to all platforms necessary to test this. I hope some other folks can help with testing on `S390`, `RISC-V` and `PPC`.
> 
> # Testing status
> 
> ## tier1
> 
> |          |   Win   |   Mac   |  Linux  |
> |----------|---------|---------|---------|
> | ARM64    |         |         |         |
> | ARM32    |         |         |         |
> | x86      |         |         |         |
> | x64      |         |         |         |
> | PPC64    |         |         |         |
> | S390x    |         |         |         |
> | RiscV    |         |         |         |

Cesar Soares Lucas has updated the pull request incrementally with one additional commit since the last revision:

  Fix build, copyright dates, m4 files.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16484/files
  - new: https://git.openjdk.org/jdk/pull/16484/files/afe48fe7..d950806f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16484&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16484&range=03-04

  Stats: 18 lines in 12 files changed: 0 ins; 3 del; 15 mod
  Patch: https://git.openjdk.org/jdk/pull/16484.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16484/head:pull/16484

PR: https://git.openjdk.org/jdk/pull/16484