Landing: 1a06a37611e3
Project / Subsystem
gcc / gcc
Date
2026-05-07
Author
Roger Sayle
Commit
1a06a37611e3b27889c595a17df13f6d27202a95
Source
github
Perf win
Yes
Breaking
No
All attributes
- project
- gcc
- subsystem
- gcc
- patch_id
- —
- commit_hash
- 1a06a37611e3b27889c595a17df13f6d27202a95
- source_type
- github
- headline
- Improve RTL expansion of doubleword multiplications.
- tldr
- Improves RTL expansion of doubleword multiplications by handling shifts greater than BITS_PER_WORD and preventing generation of unnecessary multiplications.
- author
- Roger Sayle
- outcome
- committed
- performance_win
- true
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • RTL expansion
- • doubleword multiplication
- • optimization
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-05-07T00:00:00.000Z
This commit improves RTL expansion of doubleword multiplications, specifically addressing cases where the constant being multiplied has BITS_PER_WORD or more trailing zeros. It teaches synth_mult that doubleword shifts by more than BITS_PER_WORD typically require two instructions. It also prevents RTL expansion from emitting multiply instructions by immediate constants 0, 1 or 2, speeding up compilation and reducing memory usage.