On Sun, 17 Dec 2023 17:55:11 GMT, Jatin Bhateja <jbhat...@openjdk.org> wrote:
>> Hi All, >> >> This patch optimizes sub-word gather operation for x86 targets with AVX2 and >> AVX512 features. >> >> Following is the summary of changes:- >> >> 1) Intrinsify sub-word gather using hybrid algorithm which initially >> partially unrolls scalar loop to accumulates values from gather indices into >> a quadword(64bit) slice followed by vector permutation to place the slice >> into appropriate vector lanes, it prevents code bloating and generates >> compact >> JIT sequence. This coupled with savings from expansive array allocation in >> existing java implementation translates into significant performance of >> 1.3-5x gains with included micro. >> >> >>  >> >> >> 2) Patch was also compared against modified java fallback implementation by >> replacing temporary array allocation with zero initialized vector and a >> scalar loops which inserts gathered values into vector. But, vector insert >> operation in higher vector lanes is a three step process which first >> extracts the upper vector 128 bit lane, updates it with gather subword value >> and then inserts the lane back to its original position. This makes inserts >> into higher order lanes costly w.r.t to proposed solution. In addition >> generated JIT code for modified fallback implementation was very bulky. This >> may impact in-lining decisions into caller contexts. >> >> 3) Some minor adjustments in existing gather instruction pattens for >> double/quad words. >> >> >> Kindly review and share your feedback. >> >> >> Best Regards, >> Jatin > > Jatin Bhateja has updated the pull request with a new target base due to a > merge or a rebase. The incremental webrev excludes the unrelated changes > brought in by the merge/rebase. The pull request contains ten additional > commits since the last revision: > > - Refined AVX3 implementation with integral gather. > - Merge branch 'master' of http://github.com/openjdk/jdk into JDK-8318650 > - Fix incorrect comment > - Review comments resolutions. > - Review comments resolutions. > - Review comments resolutions. > - Restricting masked sub-word gather to AVX512 target to align with integral > gather support. > - Review comments resolution. > - 8318650: Optimized subword gather for x86 targets. Latest performance number for E-Core and P-Core targets.     ------------- PR Comment: https://git.openjdk.org/jdk/pull/16354#issuecomment-1859238889
