Landing: 3e43b55eb8fb
Project / Subsystem
gcc / tree-optimization
Date
2026-08-13
Author
Aldy Hernandez
Commit
3e43b55eb8fb520b6ed161697249fcef6699d11b
Source
github
Perf win
No
Breaking
No
All attributes
- project
- gcc
- subsystem
- tree-optimization
- patch_id
- —
- commit_hash
- 3e43b55eb8fb520b6ed161697249fcef6699d11b
- source_type
- github
- headline
- Backward threader handles abnormal PHIs
- tldr
- Improves the backward threader to correctly handle SSA names within abnormal PHI nodes, enabling better optimization for computed gotos.
- author
- Aldy Hernandez
- outcome
- committed
- performance_win
- false
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • optimization
- • gcc
- • control flow
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-08-13T00:00:00.000Z
The backward threader in GCC now correctly handles SSA names that appear in abnormal PHI nodes. Previously, it refused to process these, hindering optimizations like threading computed gotos where the destination might be part of an abnormal PHI. This change aligns with gimple_range_ssa_p’s ability to process such names, improving the path solver’s accuracy and enabling optimizations in complex control flow scenarios. New test cases verify the fix.