RFR: 8276314: [JVMCI] check alignment of call displacement during code installation

[Vladimir Kozlov]

On Wed, 3 Nov 2021 16:05:34 GMT, Tom Rodriguez <never at openjdk.org> wrote:

>> I will remove the `is_MP()` calls.
>> 
>>>while C2 always aligns to 4
>> 
>> I'm having trouble finding where that is done - can you please point it out.
>
> It's deeply hidden.  in x86_64.ad, it specifies the call alignment as [4](https://github.com/tkrodriguez/jdk/blob/master/src/hotspot/cpu/x86/x86_64.ad#L13028) and in [compute_padding](https://github.com/tkrodriguez/jdk/blob/master/src/hotspot/cpu/x86/x86_64.ad#L493) it uses that alignment value to align the offset of the displacement.

Should we fix C1 and JVMCI to do the same as C2? As separate RFE.

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PR: https://git.openjdk.java.net/jdk/pull/6218