Landing: 1bf9bb5f1c5b
Project / Subsystem
gcc / simplify-rtx
Date
2026-07-01
Author
Roger Sayle
Commit
1bf9bb5f1c5bdaf8f96c64fbf2a081aaaa2b9b2f
Source
github
Perf win
Yes
Breaking
No
All attributes
- project
- gcc
- subsystem
- simplify-rtx
- patch_id
- —
- commit_hash
- 1bf9bb5f1c5bdaf8f96c64fbf2a081aaaa2b9b2f
- source_type
- github
- headline
- simplify-rtx: Optimize nested vec_merge operations on x86
- tldr
- Simplifies sequences of vec_merge operations involving repeated operands into a single instruction.
- author
- Roger Sayle
- outcome
- committed
- performance_win
- true
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • optimization
- • rtl
- • vectorization
- • x86
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-07-01T00:00:00.000Z
This commit introduces a new optimization in simplify-rtx.cc that simplifies specific sequences of vec_merge operations. The optimization targets cases where a vec_merge is applied to the result of another vec_merge that uses a duplicated operand. For example, (vec_merge (vec_merge a b m) a n) can now be simplified to (vec_merge a b (m|~n)). This allows GCC to generate more efficient code, particularly for vector types on x86, by collapsing multiple vector manipulation instructions into a single, more powerful one.