RFR: 8282182: Document algorithm used to encode aarch64 logical immediate operands.

[Andrew Dinn]

On Mon, 21 Feb 2022 11:00:48 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> This *documentation only* change explains how logical immediate mask values are derived from valid logical instruction operands. The encoding function is used to populate a sparse array that maps valid masks to a unique set of input operand values and a reverse lookup array that maps inputs to the associated mask.
>
> src/hotspot/cpu/aarch64/immediate_aarch64.cpp line 129:
> 
>> 127: // SPEC
>> 128: //
>> 129: // bits(M*N) Replicate(bits(M) x, integer N);
> 
> Suggestion:
> 
> // bits(M*N) Replicate(bits(M) B, integer N);
> 
> ...because the next text references "bit string B"?

Indeed.

> src/hotspot/cpu/aarch64/immediate_aarch64.cpp line 226:
> 
>> 224: // implementation note:
>> 225: //
>> 226: // For hysterical reasons the implementation of this function is much
> 
> Suggestion:
> 
> // For historical reasons the implementation of this function is much

I keep misspelling that ;-)

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PR: https://git.openjdk.java.net/jdk/pull/7536