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Bernard K
Bernard K

Posted on • Updated on

Exploring the Rust 1.70 Update and LLVM 16: A Comprehensive Look

Understanding the Impact of Rust 1.70 and LLVM 16 on Runtime Performance

As a Rust developer, keeping up with updates is key to optimizing your projects. The Rust 1.70 update, along with its integration of LLVM 16, brings a range of internal improvements. This article explores these updates, the concept of MSRV, and their impact on development.

What Is MSRV?

The Minimum Supported Rust Version (MSRV) is the earliest Rust compiler version that can compile specific code or a crate. Adhering to an MSRV ensures compatibility across versions, essential for broadening your project's usability, particularly for library authors.

The Rust 1.70 Update and LLVM 16

Rust 1.70 introduces several internal changes, including compatibility with LLVM 16. This update potentially optimizes the speed and efficiency of code compilation due to LLVM's modular compiler and toolchain technologies.

Key Changes in Rust 1.70

  • Enhanced Compilation Speed: The update may optimize compilation speed through LLVM 16's advancements.
  • Improved Code Generation: LLVM 16's integration could lead to more efficient machine code production.
  • Broader Platform Support: Expands Rust's compatibility with more platforms, thanks to LLVM's target support.

Assessing Performance Improvements

While some community discussions, such as a specific Reddit thread, suggest performance improvements like a 17% increase for particular applications on ARM64 architecture, these are not universally applicable across all Rust applications. The official Rust 1.70 release notes primarily discuss internal changes without specifying such performance figures.

Example for Benchmarking

fn calculate_primes(limit: usize) -> Vec<usize> {
    // Prime number calculation logic
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Benchmarking this function in both Rust 1.70 and earlier versions can provide insights into specific performance improvements.

Implications for Developers

Any improvements in runtime speed can reduce latency and enhance user experience, particularly in compute-intensive tasks. However, the extent of these gains may vary based on application and use case.

The Broader Impact on the Rust Ecosystem

Internal improvements and optimizations, like those in Rust 1.70, can positively influence future updates and the Rust ecosystem, potentially affecting performance-critical applications.


The Rust 1.70 update, with LLVM 16 integration, represents a step forward in Rust's evolution, potentially offering performance benefits in certain scenarios. Developers are encouraged to benchmark their applications and stay informed through Rust release notes and LLVM updates. Keeping up with Rust's advancements benefits your projects and contributes to the Rust community's growth and stability.

Top comments (7)

rdarrylr profile image
Darryl Ruggles

It’s great to see something that is already very fast still getting faster! Thanks for sharing!

bernardkibathi profile image
Bernard K

Thank you! It's always exciting to see technology evolve and improve.

pgradot profile image
Pierre Gradot

Can we see any sources for this information? Do we have any benchmark figures? What kind of code will benefit from Rust 1.70 (because I guess not everything is 17% faster)?

bernardkibathi profile image
Bernard K • Edited

Great questions! For detailed benchmark figures and specific sources, I recommend checking the official Rust 1.70 release notes and the LLVM 16 documentation. These resources typically include comprehensive benchmarks and use cases. You're right that the 17% improvement might not apply universally; it often depends on the nature of the code. Generally, compute-intensive tasks and applications that heavily rely on the compiler's optimization capabilities tend to benefit the most from such updates. I'll look to include more specific examples and data in future posts. For more bench marks .

pgradot profile image
Pierre Gradot

The official release notes for version 1.70 don't mention any performance improvements. I simply says:

Internal Changes #

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.

  • Upgrade to LLVM 16
  • Use SipHash-1-3 instead of SipHash-2-4 for StableHasher

The links point to this PR, which again don't mention important performance gains. At some point, it's even the opposite (here and there)/. In the end, the gains seemed small.

The benchmarks in your links are about build duration, not execution performances (and it very cool to see how the build are getting better version after version!)

The only place where I could find this "17%" figure is this reddit thread. And it's not "Rust is 17% faster", it's "our product is 17% after updating to Rust 1.7.0" (and it's only on ARM64).

Thread Thread
bernardkibathi profile image
Bernard K

Thank you, Pierre, for your insightful observations. I appreciate the time you took to delve into the details and bring these points to light.

You're absolutely right about the nuances in the Rust 1.70 release notes and the specific nature of the performance improvements discussed in community forums. In the spirit of providing accurate and valuable content to our readers, I agree that it's essential to revise the article to reflect this more nuanced understanding.

I will update the article to clarify that the performance improvements, particularly the 17% figure mentioned, are specific to certain use cases and not a blanket improvement for all Rust applications. This will ensure the article presents a balanced view and aligns accurately with the official release notes and actual benchmarks.

Adapting our content in response to new information and community feedback is a crucial part of responsible tech journalism. Your feedback is instrumental in this process, and I'm grateful for the opportunity to enhance the article's accuracy and usefulness.

Look forward to the updated piece, and thank you once again for contributing to a more informed and engaging discussion.

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Sloan the DEV Moderator

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