LLVM's DTLTO Now More Efficiently Adding Files To The Link For Much Better Performance

A performance improvement merged into LLVM this week significantly reduces the time taken to add files to the link when using Distributed ThinLTO (DTLTO). By allowing clients to optionally provide an AddBufferFn callback to the DTLTO backend — enabling more efficient file addition via MemoryBuffer ownership transfer rather than disk reads — the patch cuts link times dramatically. On Windows with a 16-core AMD Ryzen, the mean time dropped from ~2799 ms to ~158 ms; on Linux it fell from ~255 ms to ~42 ms. The fix, landing in LLVM/Clang 23, achieves these gains with only a few dozen lines of code changed.