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cgen: sub-slice ptr = base + lo*esz (both stages, #76)

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A sub-slice base[lo:hi] advanced its data pointer by lo (element
COUNT) instead of lo*esz (BYTES), so the base pointer was wrong for
any esz>1 element. Pointer arithmetic is membsz-unit per the rt
invariant (ref/hare/rt/ensure.ha:30); esz==1 (u8/str) is unchanged.

Four emission sites, fixed byte-identically across stages (rule 10):
  - value path:  cmd/w6c/cgen.c N_SLICE  <-> cgenexpr.ww cgslice
  - call-arg:    cmd/w6c/cgen.c:4646     <-> cgenutil.ww pushargsrev

Scaling mirrors the cgindex idiom: esz from the type table (rule 13;
cstage bu->sub->size, wwstage elemsizeofc) gated to an N_IDENT base,
uniform IMULQ (no SHL special-case, no immediate form -- w6a is
reg-reg only). The live lo reg is the multiplicand so the one free
GP (DX value / BX arg) holds esz*lo; lo is preserved for len (hi-lo)
and cap (base_cap-lo, #20). The esz==1 path keeps the single ADDQ,
byte-identical to before (#75/#20/str unaffected). Non-ident bases
stay unscaled in both stages (wwstage has no tnode there), tracked
as a #76 residual alongside #74.

New 943_subslice_ptresz_run: table-driven, dual-driver (ww/ww_ww),
esz in {2,4,8} array+slice base, lo>0, let-form + call-arg form;
asserts s[0]==base[lo] & s[1]==base[lo+1]. Fails on every fixture
pre-fix on both stages, passes post-fix. Registered in Makefile
(TESTS + target) so test/run builds and runs it.
This commit is contained in:
Hojun-Cho
2026-05-25 02:26:15 +09:00
parent 8b23ff3517
commit ab9de65b8e
7 changed files with 397 additions and 19 deletions
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7
Makefile
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@@ -264,6 +264,7 @@ TESTS = $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
$(BIN)/test_str_massign_store_cap_run \
$(BIN)/test_slice_store_cap_run \
$(BIN)/test_subslice_cap_run \
$(BIN)/test_subslice_ptresz_run \
$(BIN)/test_str_forrange_loopvar_run \
$(BIN)/test_composite_call_arg \
$(BIN)/test_composite_call_arg_run \
@@ -697,6 +698,12 @@ $(BIN)/test_subslice_cap_run: test/wcc/942_subslice_cap_run.c \
$(LIB)/libwwrt.a | $(BIN)
$(CC) $(CFLAGS) -o $@ $<
$(BIN)/test_subslice_ptresz_run: test/wcc/943_subslice_ptresz_run.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_composite_call_arg: test/wcc/723_composite_call_arg.c \
$(BIN)/w6c $(BIN)/w6c_ww | $(BIN)
$(CC) $(CFLAGS) -o $@ $<