[jdk18] RFR: 8278508: Enable X86 maskAll instruction pattern for 32 bit JVM. [v2]

[Sandhya Viswanathan]

On Tue, 21 Dec 2021 16:24:01 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> src/hotspot/cpu/x86/x86.ad line 9457:
>> 
>>> 9455:   predicate(Matcher::vector_length(n) <= 32);
>>> 9456:   match(Set dst (MaskAll cnt));
>>> 9457:   effect(TEMP dst, TEMP tmp);
>> 
>> TEMP dst is not needed here.
>
> dst is both read and written to in macro assembly routine.

dst both written and read is not the criteria for TEMP dst effect. Only if the src is used after dest is written in the encoding for instruct, TEMP dst is needed.

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PR: https://git.openjdk.java.net/jdk18/pull/24