Landing: 9b1c9b6436aa

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Project / Subsystem

gcc / gcc

Date

2026-08-04

Author

Richard Biener

Commit

9b1c9b6436aad6180192c175554d99f1e38bc7c8

Source

github

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Breaking

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project: gcc
subsystem: gcc
patch_id: —
commit_hash: 9b1c9b6436aad6180192c175554d99f1e38bc7c8
source_type: github
headline: Verify BB SLP scheduling to prevent SSA failures
tldr: SLP vectorization now verifies schedules, eliding unschedulable entries to prevent SSA verification failures.
author: Richard Biener
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • vectorization
• optimization
• SLP
• verification
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/9b1c9b6436aad6180192c175554d99f1e38bc7c8
date: 2026-08-04T00:00:00.000Z

This commit introduces verification for SLP (Superword Level Parallelism) node scheduling within basic blocks. It detects and rejects invalid schedules that would lead to SSA (Static Single Assignment) use-before-def errors, causing BB vectorization to fail gracefully. If an SLP graph entry cannot be scheduled, it is elided. This improvement ensures the integrity of the generated code and prevents incorrect vectorization due to scheduling issues.