Landing: f1ea3d58f0ca
Project / Subsystem
gcc / gcc/forwprop
Date
2026-07-08
Author
Konstantinos Eleftheriou
Commit
f1ea3d58f0caf819042b0ca3981af1219a8fb461
Source
github
Perf win
Yes
Breaking
No
All attributes
- project
- gcc
- subsystem
- gcc/forwprop
- patch_id
- —
- commit_hash
- f1ea3d58f0caf819042b0ca3981af1219a8fb461
- source_type
- github
- headline
- Fold longhand wide-multiply idioms for improved performance
- tldr
- Optimize manual carry propagation in wide-multiply operations to use built-in widening multiply instructions.
- author
- Konstantinos Eleftheriou
- outcome
- committed
- performance_win
- true
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • optimization
- • performance
- • aarch64
- • x86-64
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-07-08T00:00:00.000Z
This commit optimizes code that manually computes a 2N-bit product on an N-bit target by folding the longhand arithmetic into a single widening multiply and a shift. This transformation leverages built-in widening multiply instructions, improving performance significantly on specific architectures. The change affects the forwprop and widening_mul passes, with performance gains up to 59% observed on certain processors. Compile times are negligibly impacted.