Landing: 517d45af94f9

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Project / Subsystem

gcc / avoid-store-forwarding

Date

2026-03-31

Author

Konstantinos Eleftheriou

Commit

517d45af94f98f2c8c8bdf5231aa662c82b46c13

Source

github

Perf win

Breaking

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All attributes

project: gcc
subsystem: avoid-store-forwarding
patch_id: —
commit_hash: 517d45af94f98f2c8c8bdf5231aa662c82b46c13
source_type: github
headline: Reapply extension after bit insert in store-forwarding
tldr: GCC's avoid-store-forwarding pass now correctly reapplies sign/zero extensions to values after bit-field insertions for non-eliminated loads.
author: Konstantinos Eleftheriou
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • optimization
• rtl
• aarch64
• bugfix
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/517d45af94f98f2c8c8bdf5231aa662c82b46c13
date: 2026-03-31T00:00:00.000Z

This commit fixes a bug in the avoid-store-forwarding pass where SIGN_EXTEND or ZERO_EXTEND semantics were lost after a bit insert sequence. When an extending load was not fully eliminated, the bit-field insert operated on the full-width register but failed to reapply the extension, leading to stale upper bits. The fix ensures that the correct extension is re-applied, mirroring the behavior of fully eliminated loads, preventing incorrect values from propagating.