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.
Re-lands perf/h02-runtime-lto (6d373317, b62448f3) behind the speed
posture.
- Runtime packs gain an executable `speed` flavor whenever the host LLVM
helper can run. Its static units are emitted through the helper's
`runtime-unit` command (promoted unit-local symbols, object and import
bitcode from one module); its SCR_DYNAMIC variants reference the release
objects. Release, dev, and library flavors and the vendor archives are
built exactly as before (the rebuilt macOS pack's flavors and archives
are identical to the baseline's).
- Speed program builds load the speed flavor's bitcode and pass it to the
helper (`--import-bitcode`); release builds never do.
loadRuntimeBitcode only reads a real speed flavor, never release.
- The helper drops the emitter's inert sanitize_address attributes only
when it imports, so release modules reach the pipeline unchanged.
- Tests: runtime-pack.test.ts covers speed-variant bitcode selection,
verification, and that release-flavor bitcode is never imported;
native-codegen.test.ts covers helper arguments and cache keys.
Release executables stay byte-identical to the stack tip with the rebuilt
helper (14/14 workloads, macOS).
Malte Ubl