Hojun-Cho 533333bd1a wcc/ww: match on a tagged struct-field scrutinee reads it in place (#25) ...

wwstage cgmatch unconditionally spilled any non-ident match scrutinee
-- including an addressable BP-relative N_DOT struct field -- into
@match_spill and dispatched off the copy (frame $48); cstage reads
such a field in place at its BP offset ($32). Both stages were already
runtime-correct (latent rule-10 leanness, not a miscompile); this
aligns wwstage down to cstage so the asm is byte-identical.

The new in-place arm mirrors cstage cgen.c:10241-10296 verbatim: an
N_DOT scrutinee with a bare N_IDENT base whose type chases to a value
TY_STRUCT and whose field is found by name reads tag/payload at
localfind(base)+field.offset. The *ptr-field and call-result cases
stay on the spill path by construction (their base does not chase to
TY_STRUCT) -- no extra guard. A global value-struct base mis-resolves
identically in both stages (localfind returns 0); left untouched as a
shared latent (#29), since a ww-only guard would break byte-id.

Regenerates the w6c and wwdump combined.ww. Table-driven 831 test:
6 rows (local-field, *ptr-field, plain-ident, call-result, payload
remap, str payload) x runtime-both-stages + cs-vs-ww byte-id.

2026-06-14 11:59:11 +09:00

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