RFR: 8287373: remove unnecessary paddings in generated code

[Boris Ulasevich]

On Tue, 7 Jun 2022 17:29:27 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

> Why you changed tested alignment to 8 for JVMCI tests?

HotSpotCompiledCode.dataSectionAlignment value was changed to 8 to correspond the new CodeBuffer.constants code section alignment.

The jtreg tests issue was repoduced as "invalid data section alignment" JVMCI error in [CodeInstaller::initialize_fields](https://github.com/openjdk/jdk/blob/master/src/hotspot/share/jvmci/jvmciCodeInstaller.cpp#L598)

> src/hotspot/share/jvmci/jvmciCodeInstaller.cpp line 667:
> 
>> 665:   int total_size = align_up(_constants_size, CodeSection::alignment(CodeBuffer::SECT_INSTS)) +
>> 666:                    align_up(_code_size, CodeSection::alignment(CodeBuffer::SECT_STUBS)) +
>> 667:                    stubs_size;
> 
> At first look it is messed up. I understand that you are trying to take into account space between sections. It assumed the order of sections. 
> Add comment.

Ok. Thank you

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PR: https://git.openjdk.java.net/jdk/pull/8453