Landing: d7f4fc514a7f
Project / Subsystem
gcc / match-sat-alu.pd
Date
2026-07-30
Author
Kyrylo Tkachov
Commit
d7f4fc514a7f5d951e9738fb3c23a14cf49bfd8d
Source
github
Perf win
Yes
Breaking
No
All attributes
- project
- gcc
- subsystem
- match-sat-alu.pd
- patch_id
- —
- commit_hash
- d7f4fc514a7f5d951e9738fb3c23a14cf49bfd8d
- source_type
- github
- headline
- AArch64 recognizes unsigned saturating subtraction.
- tldr
- Optimizes unsigned saturating subtraction on AArch64, reducing instruction count.
- author
- Kyrylo Tkachov
- outcome
- committed
- performance_win
- true
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • optimization
- • aarch64
- • saturating arithmetic
- • vector
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-07-30T00:00:00.000Z
GCC can now recognize patterns for unsigned saturating subtraction on AArch64, such as R = X - Y; R > X ? 0 : R. This optimization replaces sequences of three instructions with a single uqsub (unsigned saturating subtract) instruction. The change also removes several expected-failure test cases for these patterns.