A tour of the thirty-eight ideas that make rustc and the standard library fast: packed spans, min-rank dataflow, proof trees, lazy init masks, niche-packed capacities and more.
rustc’s pattern exhaustiveness analysis prunes constructor columns that match strictly fewer rows than a more general candidate, which fixed an exponential blowup in the usefulness …
rustc’s rmeta tables pick their element width at runtime by stripping trailing zero bytes, and interleave the bytes of integer pairs so both numbers benefit from the compression.
rustc’s Span is 64 bits with four internal layouts selected by a sentinel prefix, decoded by a macro-generated if-chain because the enum version did not optimise.
rustc’s DroplessArena bumps a pointer downwards from the end of a chunk, uses hint::assert_unchecked to let LLVM delete the alignment arithmetic, and doubles chunk sizes from 4 KiB …