RFR: 8262355: Support for AVX-512 opmask register allocation. [v8]

[Ningsheng Jian]

On Sun, 21 Mar 2021 13:13:02 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

> Since newly introduced TypeVectMask is a valid vector type, its safe to include it into Type::is_vect and Type::isa_vect routines.
> Other proposal to have strict base type check ( _base >= VectorA && _base <= VectorZ) for isa_vect and a relaxed check for is_vect which include VectorM also looks workable, but it may be in-consistent w.r.t rest of the type checking routines.
> Instead including VectorM in both is_vect and isa_vect and a mechanism to prevent any general vector processing for masked types under a isa_vectomask type checks looks appealing. After evaluating existing backend I could see that there are only few places ( e.g. logic cone opts , MachSpillCopyNode::implimentation) where we need to restrict generic vector type processing for mask vector type node. These have been handled as special scenarios in the patch.
> 

I am not sure. Will leave this to @iwanowww . At least AArch64 MachSpillCopyNode::implementation() will also call isa_vect().

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