The profiling added with the cursor path was local to `bnode`, so it could only
answer questions about the cursor path. Moved to `compiler/icprof.nim` — no
compiler imports, so any stage can use it without a cycle — and extended to the
stage boundaries: the closure load and its three phases, `transformBody`,
`handOffBody`, `genProcBody`.
The budget that produces, on a cold `--ic:on` build of a 68-module target
(10.1s wall, summed over 177 backend processes):
loadDepClosure 3306ms of which moduleId 1285ms
processTopLevel 1516ms
interface tbls 1323ms
genProcBody 333ms
handOffBody 60ms
transformBody 28ms
This is worth having written down because it reprices the migration this branch
is doing. Reading a routine body off a cursor rather than a tree is finished and
costs nothing — `genProcBody` is the same either way. But FINISHING the job,
reading a `.t.bif` body directly and never materialising the `PNode`, can only
win back `handOffBody` + `transformBody`: under 1% of the build. The 41% is in
getting the closure's INTERFACE into memory, which no amount of body-reading
touches.
The remaining blockers in `bnode`'s header — `TLoc.lode` above all, 72 call
sites and hard, because a symbol's `loc.lode` outlives the body it was built in
and `lode == nil` is a sentinel — are worth exactly that under 1% until
something else changes. Said so in the header, replacing the older 0.20s/0.16s
figures, since that paragraph is the map read first.
The obvious lever on the real cost was tried and is not taken:
`{SkipInterfaceTables}` for dep-of-a-dep loads in `loadDepClosure` builds and
runs correctly but returns ~200ms, because most of that phase is the target and
system modules rather than the transitive ones. Not worth a name that silently
fails to resolve, so the flag stays restricted to `loadTransitiveHooks`.
Verified: both configurations build; `tests/ic` 40/40; the instrumentation
changes no codegen — 67/67 `.c` identical, cursor still identical to `PNode`.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FMyRHByv7hhaQJ4Pa1bHbE
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