Landing: 492fbdbf99dc

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Project / Subsystem

gcc / gcc/tree-optimization

Date

2026-09-14

Author

Richard Biener

Commit

492fbdbf99dc9d8c4f13d8afe654f36d47811a2f

Source

github

Perf win

Breaking

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All attributes

project: gcc
subsystem: gcc/tree-optimization
patch_id: —
commit_hash: 492fbdbf99dc9d8c4f13d8afe654f36d47811a2f
source_type: github
headline: tree-optimization/127377 - Wrong pruning of non-constant partial defs
tldr: Fixes a bug in SSA SCCVN optimization where sub-byte padding was not correctly handled.
author: Richard Biener
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • gcc
• optimization
• SSA
• bugfix
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/492fbdbf99dc9d8c4f13d8afe654f36d47811a2f
date: 2026-09-14T00:00:00.000Z

This commit addresses a bug in GCC’s SSA SCCVN (Strongly Connected Components for Value Numbering) optimization pass, identified by PR tree-optimization/127377. The issue involved incorrect pruning of non-constant partial definitions. Specifically, the optimization failed to adjust for sub-byte padding before an object when pruning its size after the object. The fix ensures that the padding is properly considered, preventing incorrect value numberings and ensuring accurate optimization.