Landing: e07e140680c7

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Project / Subsystem

gcc / riscv

Date

2026-07-03

Author

Jeff Law

Commit

e07e140680c717cfc59a11bf2287ff6433ebddd2

Source

github

Perf win

Yes

Breaking

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project: gcc
subsystem: riscv
patch_id: —
commit_hash: e07e140680c717cfc59a11bf2287ff6433ebddd2
source_type: github
headline: RISC-V: Improve IOR/XOR synthesis for expensive constant cases
tldr: RISC-V backend improves constant synthesis for IOR/XOR operations to better utilize C extension instructions.
author: Jeff Law
outcome: committed
performance_win: true
breaking_change: false
series_id: —
series_parts: []
tags: • riscv
• optimization
• compiler
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/e07e140680c717cfc59a11bf2287ff6433ebddd2
date: 2026-07-03T00:00:00.000Z

The RISC-V backend now uses riscv_integer_cost instead of riscv_const_insns for synthesizing IOR and XOR operations with expensive constants. This change enables the use of C extension instructions like XNOR, ORN, and ANDN, which can improve code generation when constants require more than three instructions to synthesize, preventing previously observed suboptimal code by distinguishing costs.