Landing: 019ccd080992
Project / Subsystem
gcc / aarch64
Date
2026-08-04
Author
Kyrylo Tkachov
Commit
019ccd080992657b08900692386b65ee4a6679fd
Source
github
Perf win
Yes
Breaking
No
All attributes
- project
- gcc
- subsystem
- aarch64
- patch_id
- —
- commit_hash
- 019ccd080992657b08900692386b65ee4a6679fd
- source_type
- github
- headline
- aarch64: Use dot product for byte-to-word widening sum
- tldr
- Replaces multiple add operations with a single dot product for widening sums on aarch64, 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
- —
- date
- 2026-08-04T00:00:00.000Z
This change optimizes widening sum operations on aarch64 by utilizing the dot product instruction ([SU]DOT). Previously, summing bytes into 64-bit elements required multiple add operations. The new approach uses a single dot product instruction, which, while not reducing instruction count, better distributes the vector work and yields a performance improvement of up to 24% for unsigned char sums into long on compatible processors.