126539b875
isl.py's UNIT_ARG decides whether a built-in's slot-4 operand prints as a unit name or a raw number. It was inferred statistically from operand ranges and, by its own comment, listed a slot "only when the ratio stayed below 1.0" -- conservative. The vtable base makes it a lookup instead: every unit-taking built-in's implementation opens with lwz 324(phase) / lwz 4(argbase) / rlwinm 2,0,29 / lwzx / lwz 4(rec). Read directly for all 147: implementation indexes [phase+324] by an argument 55 of the statistical set's 31, confirmed 31 (zero false positives) UNIT_ARG claims a unit, implementation does not 0 implementation says unit, UNIT_ARG missed it 24 The 24 include builtin80, group_ratio_pct, is_engaged, set_unit_flags, squadron_trace, wait_units_ready and deploy_and_wait. Hand-verified by reading builtin7, 16, 80, 105, 117 and 136. Recorded because it nearly passed: my FIRST control -- whether the additions' operands resolve to a symbol-table-2 index -- is worthless. The additions score 100.0%, but so do the 31 baseline (100.0%) AND the 92 built-ins in neither set (99.3%). Symtab 2 is dense enough that almost any small integer lands in it. A control the negative class also passes is not evidence. The control that discriminates is the tag word: a symbol operand is a two-word pair whose first word is the constant 1, so slot0 == 1 exactly when slot 4 is a unit -- 100.0% (13677 calls) / 100.0% (140) / 2.5% (2903). A 40x separation. Artefacts: isl-stage02.txt and -phase-ends.txt regenerate byte-identical; -conditions changes on 28 sites, every diff line pairing, each a raw number becoming a unit name. Left unnamed on purpose: all 24. builtin80 returns a small enum (tested 0..4 in a switch) but its body past the liveness check is unread; builtin103 is a predicate over [phase+10152]/[phase+10156]; builtin105 tests a unit record's +16 against 4.