Landing: b4a5597ccd6a

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Project / Subsystem

gcc / tree-optimization

Date

2026-09-25

Author

Richard Biener

Commit

b4a5597ccd6a38f5598c4c190f34162031ad6700

Source

github

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Breaking

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project: gcc
subsystem: tree-optimization
patch_id: —
commit_hash: b4a5597ccd6a38f5598c4c190f34162031ad6700
source_type: github
headline: tree-optimization: Disable SLP vectorization with gaps for negative steps
tldr: Disables SLP vectorization for negative step sizes when gaps are present, as the current implementation cannot handle them.
author: Richard Biener
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • optimization
• vectorization
• SLP
• loop analysis
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/b4a5597ccd6a38f5598c4c190f34162031ad6700
date: 2026-09-25T00:00:00.000Z

This commit disables Store-Load-Pair (SLP) vectorization for loops with negative step sizes and memory gaps. The existing vectorization path for strided SLP does not support handling smaller vectors to avoid gaps or using peeling to manage gaps encountered with the first vector load, thus preventing incorrect code generation.