Landing: f678eab4f721

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Project / Subsystem

gcc / tree-optimization

Date

2026-08-19

Author

Richard Biener

Commit

f678eab4f721ee3da1730e6c637b90a40aeb9d4d

Source

github

Perf win

No

Breaking

No

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All attributes

project: gcc
subsystem: tree-optimization
patch_id: —
commit_hash: f678eab4f721ee3da1730e6c637b90a40aeb9d4d
source_type: github
headline: Fix vectorization scheduling to exclude use statement from dominance check
tldr: Vectorization scheduling now correctly excludes the use statement from dominance checks to prevent incorrect scheduling.
author: Richard Biener
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • tree-optimization
• vectorization
• bugfix
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/f678eab4f721ee3da1730e6c637b90a40aeb9d4d
date: 2026-08-19T00:00:00.000Z

This patch corrects an issue in GCC’s vectorization scheduler where the use_stmt was incorrectly included in dominance checks for live lanes and reduction roots. The problem arises because vector definitions are inserted after the placement point, meaning the use_stmt should not be considered dominated by it. The fix modifies vect_bb_slp_mark_live_stmts and vect_schedule_slp to exclude the use_stmt from dominance checks, resolving a verification error. A new test case bb-slp-pr126936.c has been added to verify the fix.