compiler-rt-builtins

The LLVM compiler-rt builtins source, conveniently packaged as a Rust crate.

[dependencies]
compiler-rt-builtins = "0.1"

In your build.rs:

println!("cargo:rustc-link-lib=compiler-rt-builtins");

Created because when compiling C code to wasm32-unknown-unknown, some builtins are missing from Rust's compiler_builtins. Might have other uses too, who knows?