Martin Vogel dcb72015ea perf(c-lsp): negative-lookup memo + module-prefix sprintf avoidance ...

Kernel-scale profiling put ~87% of the 361 s cross-file resolve phase inside
c_lookup_member_depth's miss cascade: in macro-heavy C nearly every member
lookup misses, identical (type_qn, member) pairs miss millions of times, and
each miss re-paid an arena_sprintf("%s.%s") (the strlen storm) plus the
O(type_count) short-name registry scan.

Fix, semantics preserved exactly:
- Per-file negative memo (open-addressing uint64 set) on (type_qn, member),
  active only at depth 0 under the shared READ-ONLY Tier-2 registry, where the
  registry-only cascades are pure functions of (type_qn, registry). The direct
  method lookup always runs first (collision/staleness guard) and the
  context-dependent scope-alias path is always evaluated; only the provably-
  NULL module-prefix/base-class/short-name cascades are skipped on a memo hit.
- Module-prefixed QN retries build into a stack buffer via cached
  module_qn_len (arena_sprintf only as truncation fallback).

Soundness: cbm_c_build_cross_registry finalizes then sets read_only=true;
cbm_registry_add_func/add_type hard-return when read_only, so no miss can
flip to a hit during resolve. Suites: c_lsp 748/0 (incl. the tier2 read-only
guards), pipeline+registry+scope+semantic 656/0. Graph equivalence verified
on fs/xfs: nodes 13341 / edges 58559 byte-identical with and without the fix.

Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>

2026-07-06 15:21:26 +02:00

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cbm

perf(c-lsp): negative-lookup memo + module-prefix sprintf avoidance

2026-07-06 15:21:26 +02:00