Landing: c392d64098cc

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Project / Subsystem

gcc / tree-optimization

Date

2026-04-29

Author

Richard Biener

Commit

c392d64098cc675c804ff4f516548d023a4fe29a

Source

github

Perf win

Breaking

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All attributes

project: gcc
subsystem: tree-optimization
patch_id: —
commit_hash: c392d64098cc675c804ff4f516548d023a4fe29a
source_type: github
headline: SLP: Keep scalar statements for instance roots in externs
tldr: Fixes SLP vectorization to prevent errors when instance roots are mentioned in externs of other instances.
author: Richard Biener
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • optimization
• vectorization
• slp
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/c392d64098cc675c804ff4f516548d023a4fe29a
date: 2026-04-29T00:00:00.000Z

This commit fixes a bug in the SLP (superword level parallelism) vectorization pass that caused incorrect code generation when instance roots were referenced in externs of other instances. The fix ensures that instance root statements are kept scalar if they appear in externs, preventing the vectorization that would lead to errors. A new test case is added to verify the fix.