Wwstage call-arg-emit recognized slice args only when source was
IDENT/SLICE/CAST/DOT. For N_CALL returning []T the natural-push
fallthrough emitted one PUSHQ AX (lost .len/.cap) and cgcall's
pop-count under-drained by 2 words — corrupting R8/R9 and every
subsequent arg. Class A runtime miscompile with stack misalignment
and 3-POPs-of-garbage at the receiving call. Sister to #21
(tagged-CALL arg) but for plain []u8 slice, not tagged-variant —
wwstage's pushargsrev grew the tagged-CALL arm at #21 and never
grew the plain-composite arm.
Surfaced by lib/strings landing's `bytes.X(toutf8(in), p)` call
sites: 995_self_rebuild's wwstage rebuild tripped on byte-id
divergence at w6c_ww + wwdump_ww emit. 967_bytes_run was green
because `ww run` exercises the cstage path. Corpus-coverage-blind
on the wwstage side until lib/strings pulled the chain through
wwstage compilation.
Fix is minimal: `nodeisslice` (selfhost/cmd/wcc/cgenutil.ww) gains
an N_CALL arm structurally identical to the existing N_CALL arm in
`nodeisstr` (only swap: isslicetype for isstrtype). The downstream
natural-push slice path (PUSHQ CX/BX/AX, extra=2 pop-count) was
already correct — it just needed the N_CALL-of-slice-return shape
to be recognized as a slice. pushargsrev and cgcall untouched.
Polarity catalog: wwstage UNDER — missing N_CALL arm in slice
shape recognition. Convergence wwstage → cstage per rule 10
(cstage reads typed-AST `type_isslice` natively).
Tests:
- 723_composite_call_arg pins the 3-PUSH order (CX, BX, AX)
between `CALL view` and next CALL on canonical `f(g())` shape,
plus cstage vs wwstage cmp -s byte-id.
- 927_composite_call_arg_run runtime-pins 7 rows × 2 stages =
14 fixtures: canonical, slice-CALL + let-slice (hasprefix
shape), two composite-CALL args (arg-shift collision),
middle-argpos, nested composite-in-composite, slice + scalar
pop-count mix, tagged-CALL regression alongside (confirms
#21 still holds).
95/95 ok. 995_self_rebuild stays green (ww2==ww3==ww4 byte-id).
Hojun-Cho
0e2c6cd893