Landing: f3c628585322

← All landings

Project / Subsystem

gcc / ipa

Date

2026-09-02

Author

Richard Biener

Commit

f3c62858532248b2ee73e20f8d13019a4cb3a210

Source

github

Perf win

No

Breaking

No

View on GitHub →

All attributes

project: gcc
subsystem: ipa
patch_id: —
commit_hash: f3c62858532248b2ee73e20f8d13019a4cb3a210
source_type: github
headline: IPA predicates avoid matching bit-field conditions against byte offsets.
tldr: Fixes IPA predicate matching to correctly handle bit-fields, preventing incorrect optimization and code generation issues.
author: Richard Biener
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • ipa
• optimization
• bit-fields
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/f3c62858532248b2ee73e20f8d13019a4cb3a210
date: 2026-09-02T00:00:00.000Z

This commit addresses an issue where IPA predicates incorrectly matched bit-field conditions against byte offsets. The predicate conditions were stored as bit offsets, while jump function values used byte offsets. The existing logic divided bit offsets by 8, losing sub-byte position information and leading to incorrect matching. This caused a test case to misinterpret a bit-field, resulting in unreachable code elimination and a fall-through into _start. The fix ensures that lookups are skipped for non-byte-aligned conditions, resolving PR 126153.