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re: the sufficient side -- each phase exit now names the condition that FIRES it

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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.
This commit is contained in:
Sylpheed RE agent
2026-08-27 06:34:39 +00:00
parent 7bd6342061
commit a2c9486b20
6 changed files with 1048 additions and 797 deletions
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15
docs/re/BACKLOG.md
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@@ -1498,7 +1498,20 @@ premise was wrong.**
`unit_hp_pct(TCN001, Character_Player_Test) != 0`** (the player alive); phase 1's
objective exit additionally requires `hp_pct_test(ADT102/ADT107/ADT113, 0) != 1`,
phase 3's requires `ADT301`/`ADT302`, and `read_freg(0)` gates at 210/300/1200.
🟡 Dominance gives NECESSARY not sufficient conditions. 🟡 2 of 15 exits are
~~🟡 Dominance gives NECESSARY not sufficient conditions.~~ ✅ **(2026-08-27)
THE SUFFICIENT SIDE IS DONE.** `isl_cfg.must_reach_exit()` = a least fixpoint of
nodes from which `END_PHASE` is unavoidable (n qualifies when it has successors
and ALL qualify — conservative, so a loop never enters, which is correct because
a poll loop's exit depends on a LIVENESS property). A dominating condition is a
**TRIGGER** when its satisfying successor is in that set. **732 dominating
conditions, 234 triggers (31.97 %)**, and the artefacts now tag every line
`precond` / `TRIGGER`. Stage 02 phase 1's objective exit = 6 preconditions plus
ONE trigger, `hp_pct_test(ADN101, 0) != 1` — destroying ADN101 is what fires it.
Per-exit: **89 of 172 have exactly one trigger**, 42 have none (those are the
timeout exits — time passing is not a graph property, so declining to call it a
trigger is correct), 41 have several. 🟡 "the FIRST trigger is the point of no
return" holds **33/41**, not universally — the listing is ordered by file offset,
which is not execution order — so it is recorded as a heuristic, not a rule. 🟡 2 of 15 exits are
reachable from NO static entry — consistent with the trigger queue at `phase+272`.
✅ **(2026-08-27) EXTENDED TO ALL 28 STAGES** — `data/isl-phase-guards-all.txt`
(`isl_report.py <dir> phase-guards`). **177 exits, only 5 (2.8 %) unreachable**;