Landing: 0caa152ba34d
Project / Subsystem
gcc / gcc
Date
2026-05-28
Author
Roger Sayle
Commit
0caa152ba34d2cf53a6555455fa10d6130fd7dc5
Source
github
Perf win
Yes
Breaking
No
All attributes
- project
- gcc
- subsystem
- gcc
- patch_id
- —
- commit_hash
- 0caa152ba34d2cf53a6555455fa10d6130fd7dc5
- source_type
- github
- headline
- x86_64: Improves Cost Estimation for SSE 128-bit Rotations
- tldr
- Corrects the cost estimation for 128-bit rotations using SSE instructions on x86_64, fixing a performance regression in code generation.
- author
- Roger Sayle
- outcome
- committed
- performance_win
- true
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • x86_64
- • sse
- • optimization
- • code generation
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-05-28T00:00:00.000Z
The cost estimation for 128-bit rotations using SSE instructions on x86_64 architectures was tweaked. The previous cost was underestimated, leading to suboptimal code generation, and causing a test case (gcc.target/i386/rotate-2.c) to fail when compiled with -march=cascadelake. The corrected cost reflects the actual number of instructions required for the rotation, resolving the performance regression.