> 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. ------------- Changes: - all: https://git.openjdk.org/jdk/pull/16354/files - new: https://git.openjdk.org/jdk/pull/16354/files/328b2217..a6f0f8cf Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=16354&range=07 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16354&range=06-07 Stats: 842039 lines in 5288 files changed: 204894 ins; 551932 del; 85213 mod Patch: https://git.openjdk.org/jdk/pull/16354.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/16354/head:pull/16354 PR: https://git.openjdk.org/jdk/pull/16354
