Landing: de3a13dd7f6c

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Project / Subsystem

gcc / tree-optimization

Date

2026-06-08

Author

Richard Biener

Commit

de3a13dd7f6c2856e96fc2b7924f9b34b638940f

Source

github

Perf win

Breaking

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All attributes

project: gcc
subsystem: tree-optimization
patch_id: —
commit_hash: de3a13dd7f6c2856e96fc2b7924f9b34b638940f
source_type: github
headline: SCEV constant folding avoids signed overflow undefined behavior.
tldr: A latent bug in SCEV's `chrec_fold_plus_poly_poly` that could lead to signed overflow undefined behavior has been addressed.
author: Richard Biener
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • optimization
• bugfix
• scev
• undefined-behavior
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/de3a13dd7f6c2856e96fc2b7924f9b34b638940f
date: 2026-06-08T00:00:00.000Z

This commit fixes a latent issue within GCC’s Scalar Evolution (SCEV) component, specifically in the chrec_fold_plus_poly_poly function. The function, responsible for folding additions of polynomial chain of recurrences (CHREC), was susceptible to signed integer overflow, resulting in undefined behavior. The current fix, similar to a previous one, addresses the most common cases involving constants to prevent this overflow, improving the reliability of loop-related optimizations.