RFR: JDK-8241503: C2: Share MacroAssembler between mach nodes during code emission [v6]

[Cesar Soares Lucas]

On Wed, 20 Dec 2023 20:01:43 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Cesar Soares Lucas has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains seven commits:
>> 
>>  - Merge with origin/master
>>  - Fix build, copyright dates, m4 files.
>>  - Fix merge
>>  - Catch up with master branch.
>>    
>>    Merge remote-tracking branch 'origin/master' into reuse-macroasm
>>  - Some inst_mark fixes; Catch up with master.
>>  - Catch up with changes on master
>>  - Reuse same C2_MacroAssembler object to emit instructions.
>
> src/hotspot/cpu/x86/assembler_x86.cpp line 4248:
> 
>> 4246: void Assembler::vpermb(XMMRegister dst, XMMRegister nds, XMMRegister src, int vector_len) {
>> 4247:   assert(VM_Version::supports_avx512_vbmi(), "");
>> 4248:   InstructionMark im(this);
> 
> May be add short comment why you need `InstructionMark` in these instructions but not in others.

I expanded the comment in declaration of InstructionMark class with more information. I'm pushing the changes in a few minutes.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16484#discussion_r1535969395