Landing: ae033e5cef61
Project / Subsystem
gcc / match
Date
2026-09-08
Author
Dominic P
Commit
ae033e5cef61cf9dd2a7489fbd2037d57f9483a7
Source
github
Perf win
Yes
Breaking
No
All attributes
- project
- gcc
- subsystem
- match
- patch_id
- —
- commit_hash
- ae033e5cef61cf9dd2a7489fbd2037d57f9483a7
- source_type
- github
- headline
- match.pd: Fold rounded-up average idiom, dual to floor rule
- tldr
- New pattern in match.pd recognizes and simplifies a common rounded-up average calculation, improving code generation for media codecs.
- author
- Dominic P
- outcome
- committed
- performance_win
- true
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • optimization
- • pattern matching
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-09-08T00:00:00.000Z
A new pattern has been added to match.pd to recognize and fold a specific idiom for calculating a rounded-up average: ((x >> 1) + (y >> 1)) + ((x | y) & 1). This idiom is mathematically equivalent to (x | y) - ((x ^ y) >> 1), which is a more optimized form. This change is particularly relevant for targets with averaging instructions and for vector types, where it reduces the number of instructions generated for motion-compensation averages in media codecs.