Landing: a33f26607eb4

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Project / Subsystem

gcc / gcc

Date

2026-07-19

Author

Jeff Law

Commit

a33f26607eb4f3e3d68e575a0395401c940cf1c7

Source

github

Perf win

Yes

Breaking

No

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All attributes

project: gcc
subsystem: gcc
patch_id: —
commit_hash: a33f26607eb4f3e3d68e575a0395401c940cf1c7
source_type: github
headline: Improve select across A/A OP C where C is 2^n
tldr: GCC opts for a more specialized instruction sequence for conditional adds on loongarch.
author: Jeff Law
outcome: committed
performance_win: true
breaking_change: false
series_id: —
series_parts: []
tags: • optimization
• loongarch
• compiler
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/a33f26607eb4f3e3d68e575a0395401c940cf1c7
date: 2026-07-19T00:00:00.000Z

This commit enhances GCC’s ability to generate conditional zero-based sequences for operations where one operand is a constant power of two. This often results in better code than generalized conditional moves. The change specifically addresses a regression on loongarch by favoring a specialized instruction sequence for conditional adds, ensuring better performance characteristics for that architecture. The optimization is applicable to various arithmetic and logical operations where zero is a neutral operand.