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

Mon Oct 31 15:36:24 UTC 2022

On Mon, 31 Oct 2022 15:02:56 GMT, Stuart Monteith <smonteith at openjdk.org> wrote:

>> 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.

I've opened https://bugs.openjdk.org/browse/JDK-8296132 , PR to follow.

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