[vectorIntrinsics+mask] Integrated: 8273406: Optimize various masked vector operations for AVX512 target.

[Jatin Bhateja]

On Tue, 7 Sep 2021 14:53:25 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

> This patch is in continuation to X86 backend support for optimizing masked operations over AVX-512 targets (JDK-8262356).
> 
> Summary of changes:
> 
> 1) Support for masked rotate left and right operations over integer/long vectors.
> 
> 2) Support for masked square root operation over float/double vectors.
> 
> 3) Support for masked logical shiftleft and logical/arithmetic shiftright operation with constant shift count.
> 
> 4) Optimized VectorMask.not operation by emitting direct KNOT instruction.
> 
> 5) Extended masking optimization support for X86 KNL target which has limited set of AVX-512 features.
> 
>       - Currently vector type associated with VectorLoadMask operation is created during parsing stage.
>         For targets supporting opmask registers, lane type is explicitly set to BOOLEAN irrespective of the primitive
>         type of species i.e. for Int512 species ideal type TypeVectMask(16,BOOL) represent vector of 16 BOOLEAN elements
>         each of which represent a mask bit for corresponding vector lane.
>         This type information is also associated with respective mask boxes (Int512Mask).
>     
>       - During macro expansion vbox/vunbox nodes are broken down into granular target mappable ideal nodes.
> 
>           ``` 
>               VectorBoxNode   -> VectorStoreMask + StoreVector
> 
>               VectorUnboxNode -> LoadVector + VectorLoadMask 
>           ```
> 
>          At this stage vector type (TypeVectMask(16,BOOL)) earlier associated with vunbox node is used to create the
>         type for VectorLoadMask operation.
>     
>       - Masks can be propagated either though a vector (non-AVX512 targets) or using opmask registers (K1-K7).
>         Decision to create correct ideal type based on the target features is delegated to low level
>         type creation routine TypeVect::makemask.
>     
>       - This creates problem for targets like KNL which support limited set of AVX-512 features i.e. do
>         no support AVX512VL and AVX512BW feature.
>     
>       - For Int512 species initial ideal type constructed during parsing is based on primitive type and
>         lane count associated with species, but during macro expansion type creation
>         decision is based on vector type associated with v[u]box nodes i.e. TypeVectoMask(16,BOOL),
>         thus for KNL target incorrect vector mask type TypeVectX(16,BOOL) gets created since it does not
>         support vector length extension(128,256 bit operation over EVEX encoded instruction).
>     
>       - There are multiple ways to fix this discrepancy, cleanest approach is to create ideal type TypeVectoMask 
>         based on the primitive lane type of the species, instead of always setting the lane type as BOOLEAN.
>         This will also preserve the original lane type information which was needed in some cases e.g.
>         reinterpretation operation over mask. To circumvent such issue explicit src/dst primitive types
>         were added to ideal nodes.
>     
>       - Also this does not disturbs the register mask and spilling behavior associated with opmask registers
>         thus the change is transparent to backend passes.
> 	
> Validation:
> Patch regressed through tier1-3 tests at AVX Level=0,1,2,3 and UseKNLSetting

This pull request has now been integrated.

Changeset: ce330956
Author:    Jatin Bhateja <jbhateja at openjdk.org>
URL:       https://git.openjdk.java.net/panama-vector/commit/ce330956ee226efd263306ed6beba3c722e375f5
Stats:     837 lines in 14 files changed: 727 ins; 28 del; 82 mod

8273406: Optimize various masked vector operations for AVX512 target.

Reviewed-by: sviswanathan

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

PR: https://git.openjdk.java.net/panama-vector/pull/122