Landing: c62176c0ea0d

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Project / Subsystem

gcc / gcc/aarch64

Date

2026-07-30

Author

Kyrylo Tkachov

Commit

c62176c0ea0d8139161ebb82fabfa0a02e493e2e

Source

github

Perf win

No

Breaking

No

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All attributes

project: gcc
subsystem: gcc/aarch64
patch_id: —
commit_hash: c62176c0ea0d8139161ebb82fabfa0a02e493e2e
source_type: github
headline: Fixes incorrect code generation for aarch64 max/min-of-add/sub.
tldr: Ensures correct condition code handling for aarch64 conditional selects.
author: Kyrylo Tkachov
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • aarch64
• code generation
• compiler bug
• optimization
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/c62176c0ea0d8139161ebb82fabfa0a02e493e2e
date: 2026-07-30T00:00:00.000Z

A bug in aarch64 code generation for max/min-of-add/sub patterns caused incorrect results by not properly indicating that these instructions clobber condition codes. This led to the compiler removing necessary comparison instructions, resulting in a conditional select (csel) using stale flags. The fix adds a (clobber (reg:CC CC_REGNUM)) to the relevant instruction patterns, ensuring that condition codes are correctly marked as modified. This preserves the necessary comparison instructions and resolves the miscompilation.