Landing: 4ab2c727829c

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Project / Subsystem

gcc / backprop

Date

2026-06-08

Author

Richard Sandiford

Commit

4ab2c727829c53b87a8be43dc2d0d036d23a1700

Source

github

Perf win

No

Breaking

No

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All attributes

project: gcc
subsystem: backprop
patch_id: —
commit_hash: 4ab2c727829c53b87a8be43dc2d0d036d23a1700
source_type: github
headline: Backpropagation for abnormal PHI nodes is no longer prematurely terminated.
tldr: A bug in the backpropagation pass that caused an early return for abnormal PHI nodes has been corrected.
author: Richard Sandiford
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • optimization
• bugfix
• ssa
• data-flow
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/4ab2c727829c53b87a8be43dc2d0d036d23a1700
date: 2026-06-08T00:00:00.000Z

This commit fixes a bug in GCC’s backpropagation pass (gimple-ssa-backprop.cc) where an early return prevented the reprocessing of arguments for abnormal PHI nodes. This premature termination bypassed critical logic designed to refine initial optimistic assumptions made by the pass, potentially leading to incorrect analysis or missed optimization opportunities. The correction ensures that all necessary reprocessing occurs, improving the accuracy and effectiveness of the backpropagation pass.