Landing: ab0712667b04

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Project / Subsystem

gcc / gcc/auto-profile

Date

2026-08-21

Author

Kugan Vivekanandarajah

Commit

ab0712667b0461e34679cade62369a2c92fbc9be

Source

github

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Breaking

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All attributes

project: gcc
subsystem: gcc/auto-profile
patch_id: —
commit_hash: ab0712667b0461e34679cade62369a2c92fbc9be
source_type: github
headline: AutoFDO: Prevent entry block count from becoming zero after profile adjustment
tldr: Fixes AutoFDO profile adjustment to prevent the entry block count from being zeroed, avoiding LTO ICEs.
author: Kugan Vivekanandarajah
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • optimization
• AutoFDO
• LTO
• profile-guided
• compiler-error
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/ab0712667b0461e34679cade62369a2c92fbc9be
date: 2026-08-21T00:00:00.000Z

When adjusting profiles for AutoFDO, the entry block’s count could incorrectly be scaled to zero while other basic blocks retained non-zero counts. This discrepancy, particularly during LTO’s IPA passes, led to an internal compiler error (in apply_scale). This commit modifies afdo_adjust_guessed_profile to set the entry block count to half of the scaled sample count instead of zero, resolving the issue.