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cstage+selfhost+test: extend structlit-fill helper to N_ASSIGN N_DOT lhs (4 flavors)

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Sister fix to #17. The BP-rel helper from #17 covered N_LET /
N_ASSIGN N_IDENT-lhs / N_RETURN; the four N_ASSIGN N_DOT-lhs
structlit walks still went through the inline `cgexpr(field.lhs);
store-AX-sized` shape and silently dropped trailing bytes when a
struct-typed field's value was itself an N_STRUCTLIT. Affected dot
flavors: single-dot via_ptr / global / BP-rel and the chained-dot
walker (depth >= 2, all three root flavors).

Extend `cg_structlit_fill_bp` / `cgstructlitfillbp` into
`cg_structlit_fill` / `cgstructlitfill` taking a destination mode
(DST_BP / DST_PTR_LOCAL / DST_GLOBAL = 0/1/2), srcoff (PTR_LOCAL),
srcname (GLOBAL), and disp accumulator. `disp` grows by foff on
descent; srcoff/srcname stay constant across the call tree. The
pre-#17 wrappers are preserved byte-identically by delegating with
mode=DST_BP — 995_self_rebuild byte-identity holds for the no-
nested-STRUCTLIT case that selfhost source actually uses.

The non-BP modes reload BX before the ELLIPSIS zero-fill loop AND
before every field store (tagged, scalar, and the cgexpr leaf).
This is correctness-by-construction — cgexpr clobbers BX between
fields, and the redundant reload only fires on shapes that didn't
compile before. The four dot-flavor sites in each stage now compute
their dst mode + disp and call the shared helper (reducing each
from ~80-130 inline lines to ~5-12 lines of dispatch).

Stage signature asymmetry: cstage threads Local** for cgexpr; ww-
stage takes explicit totsize because #15 (split totsize into
naturalsize + slotsize) is still pending and the dot sites need
structnaturalsize while the BP-rel sites need si.totsize. Both
asymmetries are documented in the helper docstrings.

704 covers 8 rows (24 checks: 8 cstage exits, 8 wwstage exits, 8
cstage-vs-wwstage .s byte-identity diffs): 6 dst-flavors (single-
dot local/ptr/global, chained-dot local/ptr/global) plus single-
local 3-deep and single-ptr 3-deep to pin disp threading through
the helper's recursion and through DST_PTR_LOCAL BX reloads.

The nested struct-typed CALL rhs in field-walks has the same shape
as the STRUCTLIT bug fixed here but the helper only handles
STRUCTLIT — tracked as task #20.
This commit is contained in:
Hojun-Cho
2026-05-15 18:45:21 +09:00
parent 9d03e02881
commit 99a68a6a57
7 changed files with 1070 additions and 1450 deletions
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7
Makefile
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@@ -230,6 +230,7 @@ TESTS = $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
$(BIN)/test_cgassign_struct \
$(BIN)/test_dot_explicit_deref \
$(BIN)/test_nested_structlit \
$(BIN)/test_dot_structlit \
$(BIN)/test_use_promote_alias \
$(BIN)/test_field_signed $(BIN)/test_frame_argcount \
$(BIN)/test_selfhost $(BIN)/test_w6a_ww $(BIN)/test_w6l_ww \
@@ -395,6 +396,12 @@ $(BIN)/test_nested_structlit: test/wcc/703_nested_structlit.c \
$(LIB)/libwwrt.a | $(BIN)
$(CC) $(CFLAGS) -o $@ $<
$(BIN)/test_dot_structlit: test/wcc/704_dot_structlit.c \
$(BIN)/ww $(BIN)/w6c $(BIN)/w6a $(BIN)/w6l \
$(BIN)/ww_ww $(BIN)/w6c_ww $(BIN)/w6a_ww $(BIN)/w6l_ww \
$(LIB)/libwwrt.a | $(BIN)
$(CC) $(CFLAGS) -o $@ $<
$(BIN)/test_use_promote_alias: test/wcc/699_use_promote_alias.c \
$(BIN)/ww $(BIN)/w6c $(BIN)/w6a $(BIN)/w6l \
$(LIB)/libwwrt.a | $(BIN)