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Malte Ubl
3467efac73
Program builds that import runtime bitcode parsed and merged every unit's whole module, although the import can only ever take small bodies that need no second copy of unit-local state. The helper now reduces a unit's bitcode to exactly that set when the runtime pack is built: the importable bodies within the size limit at their call distance from any public function, and the constants they copy. Every other definition becomes a declaration, as the import would treat it. A program's selection starts from public functions, so it is always a subset of the pruned set, and programs import the same bodies as before. `runtime-unit` writes the pruned bitcode for speed units; the new `prune-import` command prunes a unit's bitcode as compiled, for units whose objects the runtime compiler emits itself. Linux x64 speed bitcode shrinks from 17.0 MB to 8.6 MB. Runtime objects are byte-identical, and import lists match the unpruned bitcode exactly. Interleaved cold builds of 53 programs in a Linux Vercel Sandbox: speed went from +21.4% to +12.1% over release.