The /tools directory contains user tools that accompany LDC and that should be part of LDC packages.
ldc-prune-cache helps keeping the size of LDC's object file cache (-cache) in check. See the original PR for more details.
ldc-profdata converts raw profiling data to a profile data format that can be used by LDC. The source is copied from LLVM (llvm-profdata), and is versioned for each LLVM version that we support because the version has to match exactly with LDC's LLVM version.
ldc-profgen converts perf sample profiling data to a profile data format that can be used by LDC. The source is copied from LLVM (llvm-profgen), and is versioned for each LLVM version that we support because the version has to match exactly with LDC's LLVM version.
timetrace2txt converts the .timetrace output of --ftime-trace (which is in Chromium's trace event JSON format) to a text file that is easier for humans to read.