We started with a compilation time of 108 seconds for the matmul
benchmarks, which was reduced to only 1 second after all the
optimizations. The most effective optimization was the element-type
generics swap, where we instantiated generic functions with predefined
"faked" element types to reduce the amount of LLVM code generated. The
second optimization also had a major impact, further reducing the
compilation time by nearly 3×. This was achieved by using our comptime
system instead of associated const generics to represent the matmul
instruction sizes. Finally, the last optimization—also the
simplest—was to reduce the LLVM optimization level to zero, which is
particularly useful for debug builds, such as tests.

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Nathaniel Simard shares his experience in reducing the compilation time for a Rust project from 108 seconds to just 1 second. Effective optimizations included using element-type generics, swapping const generics for a comptime system, and adjusting the LLVM optimization level. This approach was particularly useful for CubeCL, a GPU programming dialect, by leveraging JIT compilation to dynamically handle instruction sizes and reduce binary size.

Improve Rust Compile Time by 108X