Landing: dfd857530e0b

← All landings

Project / Subsystem

gcc / tree-optimization

Date

2026-08-21

Author

Richard Biener

Commit

dfd857530e0bda541d4112c5c19bda0567b521ef

Source

github

Perf win

Breaking

View on GitHub →

All attributes

project: gcc
subsystem: tree-optimization
patch_id: —
commit_hash: dfd857530e0bda541d4112c5c19bda0567b521ef
source_type: github
headline: Limit recursive PRE expression generation to avoid cycles.
tldr: Prevents infinite loops in PRE optimization by limiting recursive expression generation.
author: Richard Biener
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • optimization
• PRE
• SSA
• compiler-bug
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/dfd857530e0bda541d4112c5c19bda0567b521ef
date: 2026-08-21T00:00:00.000Z

This commit limits the recursion depth during the generation of complex expressions within the PRE (Partial Redundancy Elimination) optimization pass. It was discovered that the value graph used by PRE can contain cycles, and recursive expression generation could enter infinite loops when encountering these cycles. A new test case exposed this issue, and the fix introduces a depth limit to prevent such recursions, ensuring stability and correctness of the PRE pass.