RFR: 8262355: Support for AVX-512 opmask register allocation. [v17]

[Jatin Bhateja]

On Mon, 29 Mar 2021 23:02:29 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   8262355: Updating copywriter for edited files.
>
> Few notes.
> 1. In `sharedRuntime_*.cpp` you have name `opmask_state_*` and `.ad` files also `opmask` and  `opmask_reg_k*'. But in C2 code you call them `vectmask` which is confusing. I prefer to use the same name everywhere - `vectmask`:
> const RegMask* Matcher::predicate_reg_mask(void) {
>    return &_OPMASK_REG_mask;
>  }
> 
>  const TypeVect* Matcher::predicate_reg_type(const Type* elemTy, int length) {
>    return new TypeVectMask(TypeInt::BOOL, length);
>  }
> 2. I assume that they are used only for vectors in compiled code and in other cases the don't need to be saved/restored at safepoints.
> 3. In C2 shared code names are mess too: `VectorM, VMASK, RegVMask, TypeVectMask, VectorMaskCmp`.  I suggest to use `VectorMask, VECTMASK, RegVectMask`.

Hi @vnkozlov , @iwanowww , your comments have been resolved, kindly share the results of tier4/tier5 testing.

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PR: https://git.openjdk.java.net/jdk/pull/2768