Little Brainfuck interpreter in D/Rust for a benchmark

[emoon]

@Marthog

Looks like we got a bug in llvm here.

I rewrote the same code in C and it was about as fast as the naive code. Then I added __builtin_unreachable() to tell llvm that the default case is unreachable (which rust does for exhaustive matches) and suddenly it was a lot slower

That is very interesting. Could you post the generated disassembly for both these cases? (Using https://gist.github.com or something similar)

[Marthog]

here
Strange. The assembly code looks like there is just a different order of the branches.

I have filed a bug on llvm.org.

[leonardo]

@Marthog

I have filed a bug on llvm.org.

I guess it's this one:
https://llvm.org/bugs/show_bug.cgi?id=25952