[vectorIntrinsics+mask] RFR: 8273406: Optimize various masked vector operations for AVX512 target. [v3]

[Sandhya Viswanathan]

On Mon, 13 Sep 2021 08:27:53 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
>
> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8273406: Removing duplicate case statement added in previous commit.

Marked as reviewed by sviswanathan (Committer).

The  patch looks good to me.

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

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