Landing: 8add70670447
Project / Subsystem
gcc / x86
Date
2026-07-15
Author
H.J. Lu
Commit
8add706704470554130f04b63e6ea440a171b747
Source
github
Perf win
Yes
Breaking
No
All attributes
- project
- gcc
- subsystem
- x86
- patch_id
- —
- commit_hash
- 8add706704470554130f04b63e6ea440a171b747
- source_type
- github
- headline
- x86: Avoid misaligned prologue if count <= epilogue size
- tldr
- Prevents misaligned prologue generation for small memory blocks on x86.
- author
- H.J. Lu
- outcome
- committed
- performance_win
- true
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • x86
- • optimization
- • code generation
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-07-15T00:00:00.000Z
The x86 backend now prevents the use of a misaligned prologue when handling memory copy or set operations (ix86_expand_set_or_cpymem) if the block size is less than or equal to the epilogue size. This change addresses issues where vector instructions, designed for aligned data, could be used inappropriately on smaller blocks, potentially leading to performance degradation or incorrect behavior.