Landing: 874c7fcb444f

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Project / Subsystem

gcc / RISC-V

Date

2026-09-08

Author

Wang Yaduo

Commit

874c7fcb444f67459dcf5156c6343031466c89b8

Source

github

Perf win

Yes

Breaking

No

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All attributes

project: gcc
subsystem: RISC-V
patch_id: —
commit_hash: 874c7fcb444f67459dcf5156c6343031466c89b8
source_type: github
headline: RISC-V: Avoid vector adjustments for scalar costing
tldr: Fixes incorrect cost calculations for scalar operations on RISC-V by preventing vectorization cost adjustments.
author: Wang Yaduo
outcome: committed
performance_win: true
breaking_change: false
series_id: —
series_parts: []
tags: • RISC-V
• optimization
• vectorization
• costing
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/874c7fcb444f67459dcf5156c6343031466c89b8
date: 2026-09-08T00:00:00.000Z

A bug in the RISC-V backend caused scalar operations to incur incorrect cost adjustments intended for vector operations. This occurred when recovering scalar types from vector-typed expressions, leading to misapplied scaling factors and suboptimal instruction selection. The fix ensures that vector-specific cost adjustments are skipped when computing costs for scalar code, preventing issues like the expansion of a constructor through large stack temporaries and the loss of intended vector instructions.