I did notice this:"I updated the ldc D compiler earlier today (incidentally, as part of upgrading my system with pacman -Syu), and now it doesn't compile at all. It was previously compiling, and ran at around 90% the speed of C++ on ARM."Sigh.
I have deployed experimental LDC package exactly to be able to detect such issues, otherwise it will never get there. It will be either fixed within a week or reverted to old mode.