RFR: JDK-8241503: C2: Share MacroAssembler between mach nodes during code emission [v10]

[Amit Kumar]

On Fri, 22 Mar 2024 18:19:39 GMT, Cesar Soares Lucas <cslucas at openjdk.org> wrote:

>> # 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`.
>
> Cesar Soares Lucas has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix AArch64 build & improve comment about InstructionMark

I have done testing on s390 (z15) with: `{fastdebug, slowdebug, release} X {tier1}` and haven't seen new failure appearing due to this change. 

Rest of review leave to @RealLucy :-)

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Marked as reviewed by amitkumar (Committer).

PR Review: https://git.openjdk.org/jdk/pull/16484#pullrequestreview-1959188734