RFR: 8293198: [vectorapi] Improve the implementation of VectorMask.indexInRange()

[Quan Anh Mai]

On Thu, 19 Jan 2023 03:45:43 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

>> src/jdk.incubator.vector/share/classes/jdk/incubator/vector/AbstractMask.java line 219:
>> 
>>> 217:     @ForceInline
>>> 218:     public VectorMask<E> indexInRange(int offset, int limit) {
>>> 219:         if (offset < 0) {
>> 
>> These fast-paths penalise every usage of `VectorMask::indexInRange`, especially the common use case of tail processing an array. So I don't think it is needed, the user can implement it themselves if their use cases find it beneficial. Thanks.
>
> This "offset < 0" path can be optimized out by compiler if the "offset >= 0" in the common cases (i.e. normal loop with no tail loop).

Yes but I don't think it is common enough to deserve special treatment. A fast path should be common for this branch otherwise we are regressing the common path for the corner cases.

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PR: https://git.openjdk.org/jdk/pull/12064