Closes the backlog's "which condition guards each END_PHASE". With the CFG from the
previous commit this is a graph query, not new machinery.
The obvious query is WRONG for this language, and I implemented it first: "one
successor reaches END_PHASE and the other does not" finds 1/62/1 guards across Stage
02's three phases, and the 1s are both the same read_freg(0) < 1200 timeout -- every
objective test missed. The cause is the dominant idiom: a POLL LOOP's loop-back
branch also reaches the exit, one iteration later, so neither successor discriminates.
The asymmetric 1/62/1 is what exposed it; a uniform number would have read as
plausible.
Dominance has no such blind spot: a condition dominates an exit when every path from
an entry passes through it, so it is NECESSARY for the phase to end that way, and a
poll loop's test dominates its own exit by construction. Iterative dominators
converge in 3 passes over 15670/18739 instructions (83.6%).
Result for Stage 02 -- every exit in all three phases is dominated by
unit_hp_pct(TCN001, Character_Player_Test) != 0, the player's ship being alive, which
falls out rather than being assumed. Beyond that, phase 1's objective exit requires
hp_pct_test on ADT102, ADT107 and ADT113; phase 3's requires ADT301 and ADT302;
read_freg(0) gates at 210 / 300 and times out at 1200; random(3) and random(5)
dominate only the exits that pick one of several closing lines.
Two of the 15 exits are reachable from NO static entry, both FORCE_END_PHASE. That
agrees with the independently measured 389 unreachable routines: they are started from
the trigger queue at phase+272, by data rather than code.
Practical note recorded: the first dominator run was OOM-killed -- 6743 nodes each
holding a Python set of up to 6743 elements. Integer bitmasks run in seconds.
Not settled, and said so: dominance gives necessary, not sufficient, conditions; only
Stage 02's artefact is committed; one listed condition is still an unresolved
<unknown>; read_freg's units are inferred from the gate values, not read.
calls, phase-ends and conditions all regenerate byte-identical.
983c5d112c