On Wed, 25 Oct 2023 04:34:59 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 1.5-10x 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. > > Kindly review and share your feedback. > > Best Regards, > Jatin This pull request has now been integrated. Changeset: 185e711b Author: Jatin Bhateja <jbhat...@openjdk.org> URL: https://git.openjdk.org/jdk/commit/185e711bfe4c4d013b56e867f85cfb4177b3a2cf Stats: 1178 lines in 32 files changed: 1129 ins; 21 del; 28 mod 8318650: Optimized subword gather for x86 targets. Reviewed-by: sviswanathan, epeter, psandoz ------------- PR: https://git.openjdk.org/jdk/pull/16354
