RFR: 8287373: remove unnecessary paddings in generated code [v3]

[Boris Ulasevich]

On Wed, 4 May 2022 15:52:19 GMT, Evgeny Astigeevich <duke at openjdk.java.net> wrote:

>> Boris Ulasevich has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   typo fix
>
> src/hotspot/cpu/aarch64/globals_aarch64.hpp line 40:
> 
>> 38: 
>> 39: define_pd_global(uintx, CodeCacheSegmentSize,    64 COMPILER1_AND_COMPILER2_PRESENT(+64)); // Tiered compilation has large code-entry alignment.
>> 40: define_pd_global(intx, CodeEntryAlignment,       64);
> 
> This change looks reasonable to me. I found the following in the N1 Opt Guide:
> 
> Consider aligning subroutine entry points and branch targets to 32B boundaries, within the bounds of the code-density requirements of the program. This will ensure that the subsequent fetch can maximize bandwidth following the taken branch by bringing in all useful instructions

I have rolled back CodeEntryAlignment 64->32 change as it shows different results on ARM platforms. I think it should be done in a separate PR. It can be tuned in vm_version after CPU architecture check.

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

PR: https://git.openjdk.org/jdk/pull/8453