Hojun-Cho
f2643a846a
Receive side of #4's cgreturn ABI (aee8149) for TY_STRUCT lvalues of size <=24B. Producer materialises rhs into AX=bytes[0..7], DX=[8..15], CX=[16..23], zero-padded to 24B; receive sites here read the regs and write only `declared sz` bytes — MOVQ for full 8B chunks plus a sized tail (MOVL/MOVW/MOVB) by the *declared* struct size. ASYMMETRY: do NOT mirror the sender's three uniform MOVQs, else trailing 1..7B chunks overrun the next local slot. Tail chunks in {3,5,6,7} are unreachable under WW struct align rules (size%align==0) and fall through. Five sites wired in each stage (cstage cgen.c, wwstage cgenexpr.ww + cgenstmt.ww), call-result + structlit rhs at each: - N_LET `let s: T = bar()` / `= T{...}` cgenstmt cglet - N_ASSIGN N_IDENT-lhs `s = bar()` / `= T{...}` cgenexpr cgassign - N_ASSIGN single-DOT local-base `o.f = ...` - N_ASSIGN single-DOT ptr-base auto-deref `p.f = ...` - N_ASSIGN single-DOT global-base `g.f = ...` - N_ASSIGN chained-DOT depth>=2 `o.m.in = ...` (The four dot-flavors share one shape pattern, hence "5 sites".) Where the dst addr needs scratch (ptr-base/global-base/via_cx), it is loaded into BX after the call so CX stays as the third value word; for structlit field-walks BX is reloaded before each store since cgexpr clobbers AX/BX between fields. wwstage needed a new `structnaturalsize(si)` helper (cgenutil.ww): si.totsize is mis-named — it's slot-padded to 8 by registerstruct for stack-slot use, while the receive ABI wants the type's natural size (max(foff+fsz)). Splitting si.totsize into naturalsize + slotsize is tracked as the wwstage struct sizing follow-up (task #15); until that lands, the helper recovers the natural size at receive sites. Test 701_cgassign_struct.c (18 rows, 3 checks each — cstage value, wwstage value, asm byte-identity), wired in Makefile after 698. The headline ASYMMETRY case is the 20B `{i32×5}` row: sender pads to 24B via three MOVQs, receiver writes MOVQ AX +0, MOVQ DX +8, MOVL CX +16. A regression to a MOVQ tail there overruns 4B past the slot and flips the exit-code check. smoke.combined.ww is the auto-regen ride-along of strings.freeall landing in714d089(worker-shlex). Pre-existing gaps surfaced and tracked separately (not fixed here, out of scope): - task #16: silent drop of `(*p).f = ...` explicit-deref dot lhs. - task #17: silent zero of nested STRUCTLIT field in N_LET / N_ASSIGN initializer — the field_chain and field_global test rows use explicit field writes (`o.m.t = 10i64;`) rather than nested literals as a fixture-level workaround. - task #9: module-name-mangle for fn labels avoided in the field_global_call fixture by `let g: outer;` (no init). make test: 59/59. 994_w6c_ww + 995_self_rebuild PASS — bootstrap byte-identity is the load-bearing proof for this commit's scope.