(bits) of a Libc, Optimized for Wasm
I make a no-CGO Go SQLite driver, by compiling the amalgamation to Wasm, then loading the result with wazero (a CGO-free Wasm runtime). To compile SQLite, I use wasi-sdk, which uses wasi-libc, which is based on musl. It's been said that musl is slow(er than glibc), which is true, to a point. musl uses SWAR on a size_t to implement various functions in string.h. This is fine, except size_t is just 32-bit on Wasm. I found that implementing a few of those functions with Wasm SIMD128 can make them go around 4x faster. Other functions don't even use SWAR; redoing those can make them 16x faster.…
In plain words
This is an optimized C standard library for WebAssembly, built on musl and designed to improve performance of Wasm-based applications. It replaces standard string and sorting functions with SIMD128 implementations that are significantly faster on 32-bit Wasm environments. The library is intended for developers building Wasm applications that need better performance from low-level C functions, such as Go programs using SQLite compiled to Wasm without CGO dependencies.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
I make a no-CGO Go SQLite driver, by compiling the amalgamation to Wasm, then loading the result with wazero (a CGO-free Wasm runtime). To compile SQLite, I use wasi-sdk, which uses wasi-libc, which is based on musl. It's been said that musl is slow(er than glibc), which is true, to a point. musl uses SWAR on a size_t to implement various functions in string.h. This is fine, except size_t is just 32-bit on Wasm. I found that implementing a few of those functions with Wasm SIMD128 can make them go around 4x faster. Other functions don't even use SWAR; redoing those can make them 16x faster. Smooth sort also has trouble pulling its own weight; a Shell sort seems both simpler and faster, while similarly avoiding recursion, allocations and the addressable stack. I found that using SIMD intrinsics (rather than SWAR) makes it easier to avoid UB, but the code would definitely benefit from more eyeballs. See this for some benchmarks on both x86-64 and Aarch64: https://github.com/ncruces/go-sqlite3/actions/runs/145169318...
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