Measuring Performance

submited by

Style Pass

2024-10-05 02:00:02

Nobody likes waiting for code to finish compiling. Today, Rust's Cranelift backend can be used to make debug builds faster, but there's still room for improvement. I spent the last few months working on a register allocator which, when used with Cranelift, speeds up the Rust compiler by up to 18%.

I've finally completed the allocator and my PR has been merged. It ended up being pretty similar to the one described in the previous post; a description of the final state of the algorithm can be found here.

Of course, performance engineering is a complex topic that can't be fully described with a single number. The rest of this post goes into some detail about the performance measurements and how to replicate them.

Here's a snapshot of running the Rust compiler benchmarks, comparing the speed of the compiler using Cranelift with the main Ion allocator vs Fastalloc:

The picture shows the performance improvements measured with the no. of instructions metric for the primary benchmarks. Some parts of the primary benchmarks failed because my computer doesn't support LTO.