Dominance said a phase cannot end unless X. A port also needs "once X holds, it
must end", and that is a must-reach set: nodes from which END_PHASE is unavoidable,
as a least fixpoint where n qualifies when it has successors and ALL of them qualify.
The conservatism is deliberate and is the honest answer: a loop never enters the set,
because a poll loop reaches its exit only if the polled predicate eventually becomes
true, which is a liveness property rather than a graph one.
A dominating condition is a TRIGGER when the successor it takes on being satisfied
lies in that set. Over all 28 stages: 732 dominating conditions, 234 triggers
(31.97%). isl_report.py phase-guards now tags every line precond / TRIGGER.
The split lands where it should. Stage 02's phase-1 objective exit is six
preconditions -- player alive, TCN004 destroyed, t <= 210, ADT102/ADT107/ADT113
destroyed -- and exactly ONE trigger: hp_pct_test(ADN101, 0) != 1. Destroying ADN101
is what fires the phase. That is a sentence a port can implement.
Per-exit distribution over 172 reachable exits: 89 have exactly one trigger, 42 have
none, 41 have several. The 42 with none are not a failure -- they are the exits no
branch fires; Stage 02's 0x006260 ends on read_freg(0) < 1200, a timeout, and time
passing is not a property of the graph, so declining to call it a trigger is correct.
Recorded as a heuristic rather than a rule: "the first trigger is the point of no
return" holds for 33 of the 41 multi-trigger exits, with 8 counterexamples where a
precondition appears after a trigger. The likely cause is that the listing is
ordered by file offset, which is not execution order -- coroutines and jumps let a
lower offset run later. Not asserted.
calls, phase-ends and conditions all regenerate byte-identical; the two phase-guards
artefacts change only by gaining the tags.
6cbfe0524f