RFR: 8270848: Redundant unsafe opmask register allocation in some instruction patterns.

[Jatin Bhateja]

On Wed, 21 Jul 2021 00:23:09 GMT, Sandhya Viswanathan <sviswanathan at openjdk.org> wrote:

>> - Some string compare/array equality patters in x86_[32/64].ad files accept the temporary opmark register operands, instructions using these registers are guarded by target feature checks.
>> - Even if control path leading to these instructions is not chosen, RA will still allocate physical registers to these temporary operands.
>> - Pulling out the feature checks upto the instruction level can save redundant allocations which may effect spilling decisions.
>> - Also existing platform dependent routine Matcher::has_predicated_vector() check the existence of AVX512VL feature which is not required.
>
> The patch looks good to me.

Thanks @sviswa7 , do we need one more reviewer consent here.

-------------

PR: https://git.openjdk.java.net/jdk/pull/4813