Linking is the slowest part of D's compilation process– can we use mold to speed it up?

[James Lu]

Linking is the slowest part of D's compilation process. It is 
what makes its compilation speed uncompetitive with interrpreted 
scripting languages like Python and JavaScript.

This project to make a faster linker is in alpha: 
https://github.com/rui314/mold

> Concretely speaking, I wanted to use the linker to link a 
> Chromium executable with full debug info (~2 GiB in size) just 
> in 1 second. LLVM's lld, the fastest open-source linker which I 
> originally created a few years ago, takes about 12 seconds to 
> link Chromium on my machine. So the goal is 12x performance 
> bump over lld. Compared to GNU gold, it's more than 50x.

> It looks like mold has achieved the goal. It can link Chromium 
> in 2 seconds with 8-cores/16-threads, and if I enable the 
> preloading feature (I'll explain it later), the latency of the 
> linker for an interactive use is less than 900 milliseconds. It 
> is actualy faster than cat.