RFR: 8294194: [AArch64] Create intrinsics compress and expand [v2]

[Stuart Monteith]

On Tue, 25 Oct 2022 09:40:25 GMT, Andrew Dinn <adinn at openjdk.org> wrote:

>> I suppose the predicate-stmt is not needed here, since the check has already been done in `match_rule_supported()` helper.
>
> That's a good point. x86 rules all appear to omit any checks that appear in `match_rule_supported` (in most cases they have no predicate, in others they have a predicate that includes a further sub-constraint).
> 
> For AArch64 the predicate test in `match_rule_supported` is omitted for `OP_OnSpinWait` but retained for `Op_CacheWB`, `CacheWBPreSync` and `CacheWBPostSync`. We should probably make this consistent by removing the repeat predicates for those last three cases as well.

The CompressBits and ExpandBits nodes won't even be emitted, so the predicates would be redundant here - this is a consequence of them being intrinsics - otherwise it would be the Java implementations of the methods.
I can deal with the CacheWBs in a separate PR.

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PR: https://git.openjdk.org/jdk/pull/10537