It sounds like it essentially is written in C. INTRODUCTION.md says: > As for insufficiency in compiling optimization of go language, we decided to use C/Clang

It sounds like it essentially is written in C. INTRODUCTION.md says: > As for insufficiency in compiling optimization of go language, we decided to use C/Clang to write and compile core computational functions, and developed a set of asm2asm tools to translate the fully optimized x86 assembly into plan9 and finally load it into Golang runtime. Github says it's 59.6% assembly and 6.5% C. Possibly the assembly is just the checked-in result of compiling+translating the C? Gross that they have to do this. I know the Go folks really prioritize speed of compilation, but I wish they'd support debug builds with their own backend and release builds with LLVM so you could get this kind of performance when actually writing Go. I see there have been a few attempts at Go + general-purpose backend (gccgo, llgo, gollvm) but none seem to use the official Go frontend written in Go, so I think they're doomed to be second-class at best. edit: and/or, if the Go folks and GCC and/or LLVM coulds could negotiate a shared ABI (not necessarily switching to the platform's default C ABI but having "cc --abi=special-golang-stack-copying-thing"), folks could just link against something compiled in C/Rust/whatever without requiring this separate compilation+translation step (the high-maintenance, high-performance path) or CGo overhead (the easy but slow-for-frequent-calls path).