Both stages lowered the append element store as one sized mov from AX —
correct only for scalars <= 8B. A str/slice element kept only .ptr
(byte-id-blind), a tagged element got its raw payload written into the
tag slot (the #12 pathology, no boxing), a struct element kept only its
first qword. wwstage additionally fed rt_ensure membsz from bare
elemsizeof, whose 8-sentinel under-allocated and mis-strided named
tagged/struct elements (the #8 family; cs!=ww on the SI imm + stride).
Fix, keyed on the DECLARED slice local's element type (cstage
su->sub->size as before; wwstage elemsizeofc off the stamped tnode —
never the value node, the #25/#31 esz=0 trap), applied to both the
single-value and spread bodies (2 arms x 2 stages):
- scalar 1/2/4/8: untouched (u8 asm byte-identical to pre-fix).
- str/slice: AX/BX/CX pushed across rt_ensure, dst in DX (BX holds the
element .len after the pops — the #24 register discipline), 3-word
store.
- tagged: grow first, dst -> BX, box via the #12 widen choke-point
(cg_widen_tagged_store / cgwidentaggedstore via_outer).
- struct: grow first; literal -> dst spilled to per-fn @appendscr
(cached on cstage to mirror wwstage's @-prefix localadd dedup) +
structlit fill DST_PTR_LOCAL; local ident -> word-copy; any other
source shape is a rule-7 loud-stop, never a silent scalar
fall-through. struct-from-call deferred.
- spread: the source element is already a fully-formed T (tag
included), so the wide arm grows first and whole-width word-copies
&items[i] -> dst, recomputing both addresses from the slice headers
after the possibly-reallocating rt_ensure.
The elemsizeofc swap also corrects the named-scalar-alias membsz
(wwstage fed SI=$8 where cstage fed $4); no in-tree consumer appended
to such a slice, so nothing was riding the wrong 8 (lib/selfhost append
sites are all u8).
Test 800_append_wide_elem: 13 rows (runtime readback per kind, 2-append
realloc survival, spread str+tagged, @appendscr dedup, enum-alias esz,
loud-stop build-fail) + per-row cs==ww byte-id, which subsumes the
frame canary.
Hojun-Cho
faade48513