LLVM is also slow in general. If you use it, it's likely the thing that's bottlenecking your language's compile-time unless you've done something insane like templates and `#include`, etc..
Inevitably it's the case that even if your source language doesn't do nearly as badly at the design stage when it comes to generics as C++ does, if you use LLVM your build stage is probably going to be unacceptably slow.
Agreed. But so is GCC. And I guess many of the 'zero cost' abstractions require some advanced optimizing compiler like LLVM to be zero cost (or move that complexity to compiler end).
They specifically mentioned the technical debt and poor LLVM IR Generation issue though. I wonder if it has yet gotten attention or fixed. Maybe @pcwalton knows.
Edit: well fast compile times at the expense of optimization. But that kind of proves the point.
The overlooked thing is rustc produces poor quality LLVM IR which is also mentioned in FAQ.
And generics reduce amount of manual for loop juggling code one has to write. I don't think adding generics makes much of a difference.