Landing: 2ed77dddba2e
Project / Subsystem
gcc / gcc/match-sat-alu.pd
Date
2026-07-30
Author
Kyrylo Tkachov
Commit
2ed77dddba2e7f2d4e45ee8606e9b22acb6fb1f3
Source
github
Perf win
Yes
Breaking
No
All attributes
- project
- gcc
- subsystem
- gcc/match-sat-alu.pd
- patch_id
- —
- commit_hash
- 2ed77dddba2e7f2d4e45ee8606e9b22acb6fb1f3
- source_type
- github
- headline
- match-sat-alu.pd: Recognize more unsigned saturating subtraction forms
- tldr
- Improves recognition of unsigned saturating subtractions with swapped operands or reversed conditional arms.
- author
- Kyrylo Tkachov
- outcome
- committed
- performance_win
- true
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • gcc
- • optimization
- • aarch64
- • pattern matching
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-07-30T00:00:00.000Z
This commit enhances the recognition of unsigned saturating subtraction operations in GCC. It now correctly identifies forms where the comparison operands or conditional arms are reversed, such as ‘B < A ? A - B : 0’ or ‘A < B ? 0 : A - B’. This allows the compiler to apply more efficient instructions, like AArch64’s UQSUB, replacing sequences of comparisons, subtractions, and conditional selects, leading to better code generation.