Landing: 1cca2bfbdaa4
Project / Subsystem
gcc / tree-optimization
Date
2026-01-14
Author
Zhongyao Chen
Commit
1cca2bfbdaa4433002d321b580b173294ee88460
Source
github
Perf win
Yes
Breaking
No
All attributes
- project
- gcc
- subsystem
- tree-optimization
- patch_id
- —
- commit_hash
- 1cca2bfbdaa4433002d321b580b173294ee88460
- source_type
- github
- headline
- SLP vectorizer now skips reduction subgroups of size one.
- tldr
- GCC’s SLP vectorizer now explicitly avoids creating size-one reduction subgroups, improving code generation quality.
- author
- Zhongyao Chen
- outcome
- committed
- performance_win
- true
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • optimization
- • vectorization
- • performance
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-01-14T00:00:00.000Z
GCC’s SLP vectorizer now requires reduction subgroups to have a size greater than one. Previously, size-one groups were analyzed, leading to inefficient code generation. The vect_analyze_slp_reduction_group function now returns false for groups of size one or less, ensuring these cases correctly fall back to single-lane reductions and avoiding suboptimal output.