Landing: c743ce6b7554

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Project / Subsystem

gcc / bpf

Date

2026-07-20

Author

Vineet Gupta

Commit

c743ce6b75543fadea31ab8d518bba363bf5e44e

Source

github

Perf win

Yes

Breaking

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All attributes

project: gcc
subsystem: bpf
patch_id: —
commit_hash: c743ce6b75543fadea31ab8d518bba363bf5e44e
source_type: github
headline: bpf: Reduce cost of multiply/divide to avoid synthesis
tldr: Lowers the cost of BPF multiply and divide operations to match native ISA, preventing unnecessary synthesis.
author: Vineet Gupta
outcome: committed
performance_win: true
breaking_change: false
series_id: —
series_parts: []
tags: • bpf
• optimization
• cost model
• isa
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/c743ce6b75543fadea31ab8d518bba363bf5e44e
date: 2026-07-20T00:00:00.000Z

This commit reduces the estimated cost of multiplication, division, and modulo operations in GCC’s BPF backend. The default costs for these operations were high, leading the compiler to synthesize complex sequences instead of using native BPF instructions. By setting the cost for MPY, DIV, and MOD to 1, GCC now reliably generates direct BPF hardware instructions for these operations. A test case was also adjusted to ensure the signed argument handling is correct for the new cost model.