Landing: a7a008375aaa
Project / Subsystem
gcc / i386
Date
2026-08-10
Author
Uros Bizjak
Commit
a7a008375aaacb658bca0b57157366778a369ddf
Source
github
Perf win
Yes
Breaking
No
All attributes
- project
- gcc
- subsystem
- i386
- patch_id
- —
- commit_hash
- a7a008375aaacb658bca0b57157366778a369ddf
- source_type
- github
- headline
- i386: Split MOVBE alternatives out of *bswaphi2_movbe to drop flags clobber
- tldr
- Improves i386 code generation by splitting MOVBE instructions to avoid unnecessary flag clobbering.
- author
- Uros Bizjak
- outcome
- committed
- performance_win
- true
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • i386
- • optimization
- • codegen
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-08-10T00:00:00.000Z
This change refactors the i386 backend to separate MOVBE instruction alternatives from the *bswaphi2_movbe pattern. The MOVBE instruction does not affect the EFLAGS register, but the original pattern included a flags clobber that was only needed by other alternatives. By splitting the MOVBE cases into a new *movbehi2 pattern, this unnecessary clobber is removed, leading to cleaner and potentially more efficient machine code.