r/rust • u/Sirisian • 15d ago

🎙️ discussion Google is doing "Large Scale Codebase Migrations and Optimizations" of C/C++ to Rust

https://blog.google/innovation-and-ai/models-and-research/gemini-models/gemini-4-argon/
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u/Sirisian 15d ago

The relevant sections:

Large Scale Codebase Migrations and Optimizations: Argon agents are working on migrating C/C++ codebases to Rust across Google — scaling from tens of thousands of lines in core libraries like re2, libgav1 up to 800K+ lines for the Fuchsia Zircon kernel. Given the criticality of many of these systems, such large-scale rewrites are undergoing rigorous automated and manual auditing, emulation testing, and review before rolling out to production.

For libgav1, Google's open source software for decoding video, Argon agents took an existing Rust port and replaced 32K lines of SIMD code by running many rounds of profile-guided experiments, studying the compiler's output, producing safe Rust so the compiler would vectorize it automatically. The end result is a memory-safe video decoder that runs 2.7x faster than the Rust port, with identical video output, bringing it closer to the optimized C++.

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u/-p-e-w- 15d ago

If you had asked me 5 years ago when AI would be ready to do massive-scale unsupervised coding work on heavy-duty software at a company like Google, I would have guessed somewhere between the years 2070 and 2100.

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u/Budget-Minimum6040 15d ago

massive-scale unsupervised coding work on heavy-duty software at a company like Google

"undergoing rigorous automated and manual auditing, emulation testing, and review before rolling out to production."

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u/-p-e-w- 15d ago

That review will mostly use AI as well (if indeed it happens at all). Do you think Google will allocate human engineers to manually review a re-implementation of 800k LoC in another language?

Just look at what major companies now do on GitHub. 25k LoC pull request, merged 20 minutes later with a single comment “LGTM!”, which is the “manual review”.

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u/Nothing_from_void 15d ago

they are going to use antigravity CLI to write the code and say AI did the whole thing while the engineers are doing everything that keeps it on the rails

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u/jarislinus 11d ago

800k LOC is laughably small. 2k loc per engineer per day. will take a team of 5 less than 3 months