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cstage+test: skip redundant MOVL on u32 → enum-u32 cast (#25)

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cstage's N_CAST narrow-clamp emitted `MOVL AX, AX` on u32 → enum-u32
casts. wwstage's cgcast walker steps through N_TBANG / N_TNAME alias
links only; an enum's aliaslookup returns the N_TENUM body, which
breaks the loop and skips the clamp. The asymmetry surfaced during
#10 (lib/os/stat) when kstat.mode typed as u32 tripped the cross-
stage diff; worker-stat sidestepped by typing kstat.mode as `mode`.

Single-site gate: skip the narrow-clamp when the destination type is
TY_ENUM. Mirrors wwstage's N_TENUM lacuna exactly. Predicate
recursion (type_isint, type_isunsigned) over TY_ENUM stays intact —
this is emit-side only.

Wwstage unchanged.

Test 710 (cast_enum_movl): 5 rows × {exit-code per driver, asm
byte-id when w6c_ww built} = 10+ assertions. u32→enum-u32 headline,
enum-u32→u32 reverse (pins direction-of-asymmetry), u32→enum-u8
different-width, i64→enum-i32 signed-narrow, struct-field rt mirror
of `out.mode = k.mode` (the #10 trip-wire).

A principled identity-width identity-sign skip across both stages is
filed as #33. The lib/os.ww kstat.mode workaround revert is a
sibling cleanup, not in #25 scope.
This commit is contained in:
Hojun-Cho
2026-05-16 09:53:58 +09:00
parent 1292f98c91
commit b5632b1fbe
3 changed files with 326 additions and 1 deletions
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7
Makefile
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@@ -236,6 +236,7 @@ TESTS = $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
$(BIN)/test_cgreturn_variant_zero \
$(BIN)/test_param_shadow_mod \
$(BIN)/test_localoff_scope \
$(BIN)/test_cast_enum_movl \
$(BIN)/test_use_promote_alias \
$(BIN)/test_field_signed $(BIN)/test_frame_argcount \
$(BIN)/test_selfhost $(BIN)/test_w6a_ww $(BIN)/test_w6l_ww \
@@ -443,6 +444,12 @@ $(BIN)/test_localoff_scope: test/wcc/709_localoff_scope.c \
$(LIB)/libwwrt.a | $(BIN)
$(CC) $(CFLAGS) -o $@ $<
$(BIN)/test_cast_enum_movl: test/wcc/710_cast_enum_movl.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)