Fork issue #1: `--audit_61_branch_probe_pcs` existed only on
`phase-a-tracing` and the 2026-07-28 snapshot, so `/sylph-canary` -- which
drives probe runs and parses hit counts -- could not work. Measured, not
assumed: `strings` on both built binaries gives zero hits for the cvar.
MERGE, NOT REBUILD. `phase-a-tracing` is ONE commit past the common ancestor
while `sylpheed-re` is 232 commits ahead of it, so rebuilding from that branch
would have discarded 232 commits including the RE-INPUT/RE-DRAW instrumentation.
Bringing the one commit forward is the cheap direction.
Cherry-picked a15430902 (30d05ee97 does NOT introduce the probe -- it is the
cross-build snapshot). Three conflicts, each resolved on evidence:
* `kernel/event_log.cc` looked like two rival implementations -- 726 lines
vs 709 -- but they share 709 lines and differ by 19: ours is a strict
SUPERSET, phase-a's file plus a later `phase_a_fileio_only` mode that
suppresses per-export log spam. Took ours whole.
* `cpu/cpu_flags.{cc,h}`: taken as a verified UNION rather than hand-edited.
Theirs contributes 11 cvars (audit_61 plus audit_67/68/69/70 and the demo
marker); ours contributes `phase_a_fileio_only` and
`kernel_emit_contention`. Asserted afterwards that no flag present on
either side is missing from the result -- which caught
`kernel_emit_contention`, that a take-theirs would have dropped silently.
All ten probe cvars are referenced by the cleanly-merged `x64_emitter.cc` and
`ppc_hir_builder.cc`, so they are load-bearing, not decoration. The three
`audit_jit_prolog_*` cvars that look undeclared are DEFINE_uint32 in the
translation unit that uses them -- pre-existing on sylpheed-re, not this merge.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
