blog/2023/02/23/SuperWord-Introduction

[utterances-bot]

SuperWord (Auto-Vectorization) - An Introduction | Emanuel’s Blog

Background: SIMD and Auto-Vectorization

https://eme64.github.io/blog/2023/02/23/SuperWord-Introduction.html

[jbhateja]

Nice blog comprehending SLP vectorization with code references and external links.
Thumbs up Emanuel Peter :-)

[jbhateja]

Minor correction is needed in the description of Escape Analysis[1] , its main job is to mark memory allocations whether they are escaping/non-escaping a region, the compiler can eliminate a non-escaping allocation and all read/write references to such an allocation are replaced by scalars (SROA),

The compiler does the necessary bookkeeping for the re-construction of such eliminated allocations at safe points over an auxiliary data structure named SafePointScalarObjecgtNode. Basically, it ties the initialization values to different fields of the eliminated instance.

SafepointScalarObjectNodes are then serialized into debug streams and runtime uses this information to re-materialize eliminated allocations.

Combining Escape analysis with partial redundancy is a compelling technique for removing allocations from frequently executed paths. This is at the heart of partial-escape analysis[2]. Instead of taking the global view in the context of an allocation's escapability, we remove the allocations from paths where they are non-escaping.

While the Graal JIT compiler has a matured PAE implementation in place, there have been some attempts for implementing PAE in the C2 JIT compiler[3][4].

With Project Valhalla[5] language gives the control for deterministic escape analysis to the user, by making a class a value type C2 compiler treats it as escapable right from the IR construction unless it finds a real need to buffer the instance

We can say that what VectorAPI (explicit vectorization) is to SuperWord (auto-vectorization), Valhalla is to Escape analysis :-)

[1] https://dl.acm.org/doi/10.1145/320385.320386
[2] https://ssw.jku.at/Teaching/PhDTheses/Stadler/Thesis_Stadler_14.pdf
[3] https://mail.openjdk.org/pipermail/hotspot-compiler-dev/2021-May/047486.html
[4] openjdk/jdk#14041
[5] https://openjdk.org/projects/valhalla/

[yiwu0b11]

Thanks! This is a really good guide