Hojun-Cho
dd274315a0
Class A compile-time fatal retirement — `return f()` from an sret callee bailed both stages with "sret return-forwarding for >24B struct not wired (task #23)" at every site, forcing every caller into a `let r = f(); return r;` workaround that materialised an intermediate >24B copy in outer's frame. Forwarding now elides the copy: outer reloads its own @sretarg into RDI for the inner CALL via `MOVQ @sretarg(BP), DI` (NOT `LEAQ <local>, DI`), inner writes directly into outer's caller-prealloc dest, RAX (inner's returned dest pointer per the sret discipline) is already outer's return value. Wires 2 sites × 2 stages (same triangle as #23): caller arg-shift in cgcall/pushargsrev gains an RDI-source switch via cg_sret_forward / c.sretforward; callee return-arm in cgreturn replaces the fail-loud abort with cgexpr-into-cgcall + epilogue. The @sretscr scratch slot is still pre-allocated on the forwarding branch (unused) — eliding would need AST-walk awareness in scanlocals; symmetric-allocate is the simpler path and keeps byte-id with non-forwarding callers. Latent surfaced and filed during probe (NOT in this commit's scope): multi-sret-receive in a single fn diverges between stages — cstage always allocates @sretscr on first sret CALL, wwstage only when sretdestoff == 0. Bootstrap stays green because the selfhost corpus has zero >1-sret-receive call sites. Tests: - 721_sret_struct_return gains 2 forwarding rows + a 4th asm- presence sentinel: at the inner CALL site inside outer fn, the RDI source must be `MOVQ -K(BP), DI` (reload of outer's saved @sretarg) NOT `LEAQ -K(BP), DI` (a temporary local would write inner's payload into outer's frame, not caller's dest). - 925_sret_struct_return_run gains 3 forwarding rows: simple quad forward, multi-arg inner (pair-by-value + scalar args alongside the hidden RDI), and slice-payload (decoder { i64, []u8 } — the utf8 iterator shape, asserts ptr/len/cap survive the @sretarg chain). 90/90 ok. 995_self_rebuild stays green (ww2==ww3==ww4 byte-id).
254 KiB
254 KiB