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.
94 lines
3.9 KiB
Markdown
94 lines
3.9 KiB
Markdown
# ✅ Which built-ins take a unit — read from the implementations, and the old set was short
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`isl.py`'s `UNIT_ARG` decides whether a built-in's slot-4 operand is printed as
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a **unit name** or as a raw number. It was built **statistically**, from operand
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ranges, and its own comment says slots were listed *"only when the ratio stayed
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below 1.0"* — i.e. only when every observed value resolved. That is
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conservative, and it was.
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## The direct method
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[`isl-builtin-dispatch`](isl-builtin-dispatch.md) makes this a lookup: a
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built-in's stub tail-calls a fixed slot of the `ScriptPhase` vtable at
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`0x820A84BC`, so the implementation can simply be read. Every unit-taking
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built-in opens the same way — this is `unit_state`, `builtin80`, `builtin117`
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and `builtin136`, character for character:
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```
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lwz r10, 324(r31) ; the unit array
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lwz r11, 4(r30) ; r30 = the local[] base, so this is local[4]
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rlwinm r11, r11, 2, 0, 29 ; x4
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lwzx r11, r11, r10 ; -> the record
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lwz r11, 4(r11) ; the handle
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cmpli cr6, 0, r11, 0x0 ; "is this squadron gone?"
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```
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## ✅ Result: 31 → 55
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| | |
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|---|---|
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| built-ins whose implementation indexes `[phase+324]` by an argument | **55** |
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| of the statistical set's 31, confirmed | **31 — all of them** |
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| **UNIT_ARG claims a unit, the implementation does not** | **0** |
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| **implementation says unit, UNIT_ARG missed it** | **24** |
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The 24: `21, 22, 23, 32, 42, 44, 46 (squadron_trace), 49, 50, 51, 55, 60, 61,
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72 (group_ratio_pct), 80, 83, 94 (is_engaged), 101, 109 (set_unit_flags), 117,
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136, 137 (wait_units_ready), 141, 142 (deploy_and_wait)`.
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Zero false positives is worth stating on its own: the statistical method was
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**right about everything it claimed** and only too cautious about what it
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omitted.
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## ⚠️ The first control I chose was worthless — recorded because it nearly passed
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I first checked whether the additions' slot-4 operands resolve to a symbol-table-2
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index. They did, **100.0 %** — and it means nothing:
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| set | operands resolving to a symtab-2 unit |
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|---|---|
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| the 31 baseline | 100.0 % |
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| the 24 additions | 100.0 % |
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| **the 92 built-ins in neither set** | **99.3 %** |
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Symbol table 2 is dense enough that almost any small integer lands in it, so the
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test does not discriminate. A control that the negative class also passes is not
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evidence, and this one was one careless glance from being written up as proof.
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## ✅ The control that does discriminate
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`isl-builtins.md` documents that a symbol operand is a **two-word pair** — a tag
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holding the constant 1, then the index. So slot 0 should be 1 exactly when
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slot 4 is a unit:
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| set | calls with `slot0 == 1` |
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|---|---|
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| the 31 baseline | **100.0 %** (13 677 calls) |
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| the 24 additions | **100.0 %** (140 calls) |
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| the 92 in neither set | **2.5 %** (2 903 calls) |
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A 40× separation, and the additions sit exactly on the positive class.
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## Effect on the artefacts
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`data/isl-stage02.txt` and `-phase-ends.txt` regenerate **byte-identical**;
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`-conditions.txt` changes on 28 sites, every diff line pairing, all of them a
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raw number becoming a unit name:
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```
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- 0x01B6C0 if builtin80(0x8B) == 0 -> + 0x01B6C0 if builtin80(TCT206) == 0
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```
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## 🟡 Not settled
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* **The 24 are still unnamed.** Knowing an argument is a unit is not knowing what
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the built-in does. `builtin80` (69 operands disc-wide) is tested against
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0, 1, 2, 3, 4 in a switch chain, so it returns a small enumeration — but I am
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not naming it from that, and its body past the liveness check is unread.
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* `builtin103` (`0x8226BFA8`) is a predicate over **`[phase+10152]` and
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`[phase+10156]`**, neighbours of a value read out at `+10160`; it takes no unit.
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The fields have 9, 7 and 1 writers respectively, none of them read.
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* `builtin105` (`0x8226BFF0`) tests a unit record's **`+16` against 4**. What
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`rec+16` holds is not established — `isl-builtins.md` only rules out its being
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what `unit_state` reads.
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