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docs(cookbook): §471 — a launder's cost is an allocno, and $t0 belongs to reload

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From the S76 func_80032A74 agent (422 ins, 408 -> 12).

Refines §153: the launder was necessary but created an allocno outranking the
value it was protecting; the cure was pinning the launder itself to $10 — and
NOT $8, which evicts reload's $t0 parameter reloads. So '§461: the launder is
the defect' has a third resolution beyond remove-it or move-it: pin it, and
choose the register with reload's own needs in mind.

New general fact: $t0 is unreachable from C because reload owns it — the
target's table bases are reload rematerialisations of a reg_equiv_constant
there. A residual of the form 'the target uses $t0 and I cannot' is a reload
artifact, not an unfound spelling.

Also pairs with §463/§469: a frame slot nothing reads is either an 8-byte
rounded spill or a §172 combine USE-orphan — both reproducible, neither
padding.
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Drew T
2026-09-03 16:12:14 -06:00
parent 9467db409b
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@@ -35461,3 +35461,27 @@ allocno class choice) but it drags the `*24` shift chain into `$s1`; plus operan
`addu $s0,$s1,$s0`; plus the else-arm materialising `&D_800A46D2` into `$s1`. Law 1c verified: all 25
symbols match the target's relocations, and the only difference is `D_800A46D2`'s **count** (4 vs 6),
which is that residual rather than a wrong symbol.
#### §471 — A LAUNDER'S REAL COST IS AN ALLOCNO, AND `$t0` IS RELOAD'S (`main:func_80032A74`, 408 → 12)
**Source: the S76 agent.** Three facts, two of which refine entries already here.
**1. §172's combine USE-orphan buys a never-referenced stack slot.** Promoting an `s16` memory local
to `int` **twice** after a `CODE_LABEL` is the only way to produce the target's unused 8-byte slot at
`0x48`. Pair this with §463/§469: when a frame has a slot nothing reads, it is either a spill (8-byte
rounded) or an orphan of this kind — both are reproducible, neither is padding.
**2. 🔴 REFINEMENT OF §153: THE LAUNDER'S REAL COST IS AN ALLOCNO THAT OUTRANKS THE VALUE YOU CARE
ABOUT.** The §153 launder was necessary here, but it created an allocno outranking `vol` on priority.
The cure was pinning the launder to **`$10`** — and specifically *not* `$8`, which evicts reload's
`$t0` parameter reloads. So "the launder is the defect" (§461) has a third resolution beyond
*remove it* or *move it*: **pin the launder itself, and pick the register with reload's own needs in
mind.**
**3. `$t0` IS UNREACHABLE FROM C BECAUSE RELOAD OWNS IT.** The target's `table` / `D_800A4C28` bases
are reload **rematerialisations** of a `reg_equiv_constant` living in `$t0`. No C spelling or pin can
put a value there, because reload claims it for its own reloads. When a residual is "the target uses
`$t0` and I cannot", stop — that is a reload artifact, not a spelling you have not found yet.
*(Also: merging `vol` and `m` into one variable puts the volume chain in `$a0`. Residual 12 is this
`$t0` rematerialisation plus one `lh`/`lhu` row that is the orphan's only available site.)*