Landing: 98298f05f6b1

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Project / Subsystem

gcc / aarch64

Date

2026-08-02

Author

Kyrylo Tkachov

Commit

98298f05f6b110e20714987829558bb77564a10a

Source

github

Perf win

Yes

Breaking

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All attributes

project: gcc
subsystem: aarch64
patch_id: —
commit_hash: 98298f05f6b110e20714987829558bb77564a10a
source_type: github
headline: aarch64: Use widening add instructions for sum reductions
tldr: Optimizes widening sum reductions on aarch64 by using [SU]ADDLP and [SU]ADALP, covering all SIMD shapes and improving performance.
author: Kyrylo Tkachov
outcome: committed
performance_win: true
breaking_change: false
series_id: —
series_parts: []
tags: • aarch64
• optimization
• SIMD
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/98298f05f6b110e20714987829558bb77564a10a
date: 2026-08-02T00:00:00.000Z

This commit enhances the optimization of widening sum reductions on aarch64 by fully utilizing the [SU]ADDLP and [SU]ADALP instructions. It adds support for previously uncovered SIMD shapes and ensures that all power-of-two widening sum reductions are expressed efficiently. This change improves performance by reducing the number of operations required for these reductions, particularly for summing bytes into 64-bit accumulators.