[vectorIntrinsics] RFR: Improve mask reduction operations on AVX [v4]

[Sandhya Viswanathan]

On Wed, 17 Nov 2021 13:26:00 GMT, Mai Đặng Quân Anh <duke at openjdk.java.net> wrote:

>> src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp line 4058:
>> 
>>> 4056: void C2_MacroAssembler::vector_mask_operation(int opc, Register dst, KRegister mask,
>>> 4057:                                               int masklen, int masksize, int vec_enc) {
>>> 4058:   assert(VM_Version::supports_bmi1(), "Strange hardware");
>> 
>> Also need to check for supports_lzcnt().
>
> We have separate checks for all `popcnt`, `lzcnt` and `tzcnt`, do you think the function should verify or just let the assembler throw after?

Good to have assert here in this function as well.

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PR: https://git.openjdk.java.net/panama-vector/pull/158