cgen: ww str for-range loop-var narrows to MOVZBQ -- Phase 2 step-3 Fold 1 (align-up)

Ranging a str (for (let b .. = s)) and reading the loop var back emitted MOVZBQ on cstage (correct u8 zero-extend) but MOVQ on wwstage (the missed case, #14). Align wwstage UP. ww cgforrange derived the element-type node only for slice/array; for a str scrutinee it left elemt=nil, so the loop var registered with no type and localloadop short-circuited to MOVQ. Fix: for a str scrutinee, synthesize a u8 element node (type_ = str.sub = u8, from F1) as elemt, so localadd hands the loop var a u8 tnode and the GENERIC narrow-load fires (MOVZBQ) -- consuming str.sub as F1 intended, mirroring how []u8 supplies its element node. NOT an if-str special-case. cstage already correct, untouched (ww-only). str's own type stays nominal.

GATE is the ASM SHAPE byte-id (cstage==wwstage at the loop-var read), NOT a runtime probe: the divergence is runtime-benign (MOVQ and MOVZBQ read the same zero-extended byte) so a runtime test passes both ways and cannot distinguish -- it was a byte-id-INVISIBLE divergence (990-997 green despite cstage!=ww, since no bootstrap input exercises a narrow-read str loop var). Verified fail-pre (the cstage-MOVZBQ vs wwstage-MOVQ 1-line diff) / pass-post (.s byte-identical). []u8/slice/array for-range emission unchanged. test/wcc/940 carries the fixture (runtime corpus coverage, both drivers).

main.combined.ww regenerated via the canonical make path.
This commit is contained in:
2026-05-24 17:29:20 +09:00
parent 80527f3868
commit 3d7c707bd2
5 changed files with 239 additions and 0 deletions

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@@ -262,6 +262,7 @@ TESTS = $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
$(BIN)/test_str_arrfield_store_cap_run \
$(BIN)/test_str_chainfield_store_cap_run \
$(BIN)/test_str_massign_store_cap_run \
$(BIN)/test_str_forrange_loopvar_run \
$(BIN)/test_composite_call_arg \
$(BIN)/test_composite_call_arg_run \
$(BIN)/test_letdecl_zeroinit \
@@ -676,6 +677,12 @@ $(BIN)/test_str_massign_store_cap_run: test/wcc/939_str_massign_store_cap_run.c
$(LIB)/libwwrt.a | $(BIN)
$(CC) $(CFLAGS) -o $@ $<
$(BIN)/test_str_forrange_loopvar_run: test/wcc/940_str_forrange_loopvar_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 $@ $<

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@@ -21356,6 +21356,27 @@ fn cgforrange(c: *cgen, n: *node) void = {
let sk: nkind = slctn.kind;
if (sk == nkind.N_TSLICE) { elemt = slctn.lhs; };
if (sk == nkind.N_TARRAY) { elemt = slctn.lhs; };
// str IS []u8 (F1: tystr.sub = tyu8). []u8 hands cgen a real
// u8 element node (slctn.lhs); a str scrutinee has none, so the
// loop var would register tnode=nil and read back as a wide
// MOVQ. Synthesise the u8 element off str.sub so the loop-var
// registration carries a u8 tnode and localloadop narrows the
// read-back to MOVZBQ on its own — aligning wwstage up to
// cstage, whose checker stamps the binding u8. Kind-gated so
// str's own type stays nominal.
if (sk == nkind.N_TNAME) {
if (streq(slctn.str, "str")) {
let sti: *tinfo = slctn.type_: *tinfo;
if (sti != nil) {
if (sti.sub != nil) {
let u8n: *node = newnode(nkind.N_TNAME, slctn.file, slctn.line, slctn.col);
u8n.str = "u8";
u8n.type_ = sti.sub: *void;
elemt = u8n;
};
};
};
};
};
// esz: raw elem byte size. For tuple-element slices `[](T0, T1)`,
// C cgen reads the resolved tuple's size (sum of raw param sizes,

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@@ -1504,6 +1504,27 @@ fn cgforrange(c: *cgen, n: *node) void = {
let sk: nkind = slctn.kind;
if (sk == nkind.N_TSLICE) { elemt = slctn.lhs; };
if (sk == nkind.N_TARRAY) { elemt = slctn.lhs; };
// str IS []u8 (F1: tystr.sub = tyu8). []u8 hands cgen a real
// u8 element node (slctn.lhs); a str scrutinee has none, so the
// loop var would register tnode=nil and read back as a wide
// MOVQ. Synthesise the u8 element off str.sub so the loop-var
// registration carries a u8 tnode and localloadop narrows the
// read-back to MOVZBQ on its own — aligning wwstage up to
// cstage, whose checker stamps the binding u8. Kind-gated so
// str's own type stays nominal.
if (sk == nkind.N_TNAME) {
if (streq(slctn.str, "str")) {
let sti: *tinfo = slctn.type_: *tinfo;
if (sti != nil) {
if (sti.sub != nil) {
let u8n: *node = newnode(nkind.N_TNAME, slctn.file, slctn.line, slctn.col);
u8n.str = "u8";
u8n.type_ = sti.sub: *void;
elemt = u8n;
};
};
};
};
};
// esz: raw elem byte size. For tuple-element slices `[](T0, T1)`,
// C cgen reads the resolved tuple's size (sum of raw param sizes,

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@@ -21356,6 +21356,27 @@ fn cgforrange(c: *cgen, n: *node) void = {
let sk: nkind = slctn.kind;
if (sk == nkind.N_TSLICE) { elemt = slctn.lhs; };
if (sk == nkind.N_TARRAY) { elemt = slctn.lhs; };
// str IS []u8 (F1: tystr.sub = tyu8). []u8 hands cgen a real
// u8 element node (slctn.lhs); a str scrutinee has none, so the
// loop var would register tnode=nil and read back as a wide
// MOVQ. Synthesise the u8 element off str.sub so the loop-var
// registration carries a u8 tnode and localloadop narrows the
// read-back to MOVZBQ on its own — aligning wwstage up to
// cstage, whose checker stamps the binding u8. Kind-gated so
// str's own type stays nominal.
if (sk == nkind.N_TNAME) {
if (streq(slctn.str, "str")) {
let sti: *tinfo = slctn.type_: *tinfo;
if (sti != nil) {
if (sti.sub != nil) {
let u8n: *node = newnode(nkind.N_TNAME, slctn.file, slctn.line, slctn.col);
u8n.str = "u8";
u8n.type_ = sti.sub: *void;
elemt = u8n;
};
};
};
};
};
// esz: raw elem byte size. For tuple-element slices `[](T0, T1)`,
// C cgen reads the resolved tuple's size (sum of raw param sizes,

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@@ -0,0 +1,169 @@
/*
* 940_str_forrange_loopvar_run — corpus coverage for the step-3 Fold 1
* fold: ranging a `str` value-form (`for (let b .. s)`) and reading the
* loop var `b` back must narrow to MOVZBQ (u8 zero-extend), matching
* cstage. Pre-fold the wwstage cgen registered the loop var with a nil
* tnode (str had no element node the way []u8 does), so the read-back
* fell through localloadop to a wide MOVQ; cstage's checker stamps the
* binding u8, so it narrowed. The fold synthesises the u8 element off
* str.sub (Phase 2 F1) so the loop var carries a u8 tnode and the
* existing narrow-load logic fires on its own.
*
* REAL GATE IS SHAPE BYTE-ID, NOT RUNTIME. The MOVQ-vs-MOVZBQ
* divergence is runtime-benign: the slot is always written by a
* MOVZBQ-into-AX then MOVQ-AX-into-slot, so the upper bytes are already
* zero — a MOVQ read-back yields the same value a MOVZBQ would. A
* runtime probe therefore passes on BOTH the buggy and the fixed code
* and CANNOT distinguish them. The load-bearing gate is diffing the
* cstage (w6c) and wwstage (w6c_ww) .s at the loop-var read:
* pre-fold: cstage MOVZBQ vs wwstage MOVQ (1-line diff)
* post-fold: byte-identical
* This fixture exists for corpus presence — it confirms the path lowers
* and runs correctly through both drivers; it does not by itself prove
* the narrow.
*
* Loop-var read-back is exercised two ways the fold touches:
* - Site A: pass `b` to a fn (`use1(b)` → cgident read into an arg).
* - Site B: use `b` in an arithmetic expression (`sum += b: i32`).
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/wait.h>
static int
runwait(const char *cmd)
{
int rc = system(cmd);
if (rc == -1) return -1;
if (WIFEXITED(rc)) return WEXITSTATUS(rc);
return -1;
}
struct row { const char *label; const char *src; int want; };
static const struct row rows[] = {
/* Site A — read-back into a fn arg. "AB" is 0x41,0x42; the callee
* checks each byte zero-extends to its exact value, so a botched
* wide read (had the slot held garbage) would mismatch. */
{ "sitea_arg_readback",
"fn check(x: u8) i32 = {\n"
" if (x: i32 < 65) { return 1; };\n"
" if (x: i32 > 66) { return 1; };\n"
" return 0;\n"
"};\n"
"export fn main() i32 = {\n"
" let s: str = \"AB\";\n"
" for (let b .. s) {\n"
" if (check(b) != 0) { return 1; };\n"
" };\n"
" return 0;\n"
"};\n",
0 },
/* Site B — read-back in an arithmetic expression. Sum the bytes of
* "AB" (0x41 + 0x42 = 131) and confirm. */
{ "siteb_expr_readback",
"export fn main() i32 = {\n"
" let s: str = \"AB\";\n"
" let sum: i32 = 0;\n"
" for (let b .. s) {\n"
" sum += b: i32;\n"
" };\n"
" if (sum != 131) { return 1; };\n"
" return 0;\n"
"};\n",
0 },
};
static int
run_driver(const char *driver, const struct row *r, int i)
{
char src[96], tmpdir[96], cmd[1024];
snprintf(src, sizeof src, "/tmp/strforrange_%d_%d.ww", getpid(), i);
snprintf(tmpdir, sizeof tmpdir, "/tmp/strforrange_%d_d_%d", getpid(), i);
FILE *f = fopen(src, "wb");
if (!f) return -1;
fputs(r->src, f);
fclose(f);
mkdir(tmpdir, 0755);
snprintf(cmd, sizeof cmd, "cd %s && %s build %s",
tmpdir, driver, src);
if (runwait(cmd) != 0) {
fprintf(stderr, "row[%s]: build via %s failed\n",
r->label, driver);
unlink(src); rmdir(tmpdir);
return -1;
}
const char *base = strrchr(src, '/');
base = base ? base + 1 : src;
char outbin[160];
snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
char *dot = strrchr(outbin, '.');
if (dot && strcmp(dot, ".ww") == 0) *dot = '\0';
int got = runwait(outbin);
unlink(src); unlink(outbin); rmdir(tmpdir);
return got;
}
int
main(void)
{
const char *bin = getenv("BIN");
if (!bin) bin = "out/bin";
char absbin[512];
if (bin[0] != '/') {
char cwd[256];
if (getcwd(cwd, sizeof cwd) == NULL) return 1;
snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
bin = absbin;
}
char cdrv[640];
snprintf(cdrv, sizeof cdrv, "%s/ww", bin);
char wdrv[640];
snprintf(wdrv, sizeof wdrv, "%s/ww_ww", bin);
struct { const char *name; const char *path; int gated_on_existence; }
drivers[] = {
{ "cstage", cdrv, 0 },
{ "wwstage", wdrv, 1 },
{ NULL, NULL, 0 },
};
int n = (int)(sizeof rows / sizeof rows[0]);
int total = 0, fail = 0;
for (int d = 0; drivers[d].name; d++) {
if (drivers[d].gated_on_existence
&& access(drivers[d].path, X_OK) != 0) {
fprintf(stderr,
"str_forrange_loopvar_run: skip %s (no %s)\n",
drivers[d].name, drivers[d].path);
continue;
}
for (int i = 0; i < n; i++) {
int got = run_driver(drivers[d].path, &rows[i], i);
total++;
if (got != rows[i].want) {
fprintf(stderr,
"str_forrange_loopvar_run[%s][%s]: exit=%d want=%d\n",
drivers[d].name, rows[i].label,
got, rows[i].want);
fail++;
}
}
}
if (fail) {
fprintf(stderr, "str_forrange_loopvar_run: %d/%d fixtures failed\n",
fail, total);
return 1;
}
printf("str_forrange_loopvar_run: %d/%d ok\n", total, total);
return 0;
}