Landing: 2fcbe075ec3b

← All landings

Project / Subsystem

gcc / tree-optimization

Date

2026-07-15

Author

Richard Biener

Commit

2fcbe075ec3b32f4a523ebae68a8a32381bb46a9

Source

github

Perf win

No

Breaking

No

View on GitHub →

All attributes

project: gcc
subsystem: tree-optimization
patch_id: —
commit_hash: 2fcbe075ec3b32f4a523ebae68a8a32381bb46a9
source_type: github
headline: Fix SCEV handling of INT_MIN subtraction to avoid UB
tldr: Ensures correct scalar evolution calculation for subtractions involving the most negative integer, preventing undefined behavior.
author: Richard Biener
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • optimization
• integer
• UB
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/2fcbe075ec3b32f4a523ebae68a8a32381bb46a9
date: 2026-07-15T00:00:00.000Z

This commit resolves an issue in Scalar Evolution (SCEV) analysis where subtracting the most negative value of a signed integer type could lead to undefined behavior and incorrect analysis results. Previously, only the negation of INT_MIN was guarded, but this did not correct the resulting SCEV direction when the operation was flipped from subtraction to addition. The fix now promotes the entire operation to unsigned, ensuring correct analysis even in these edge cases. New test cases verify the fix.