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wcc/check+w6c+w6c_ww: materialize array-literal slice-borrow base into per-fn scratch (fix #25 + #31)

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A one-step `let xs: []T = [e0,e1,..]` had two faults. #31 (silent, cs!=ww):
the #258 array→slice borrow wrapped the un-addressable N_ARRLIT directly as
the N_SLICE base and cgen never spilled it to a stack slot, so .ptr dangled
(`let xs:[]i32=[10,20,30]; xs[1]` returned the un-stored header 1; []u8/[]str
segfaulted). #25 (over-strict): a slice target fell through to the exact-
element type_eq borrow gate, rejecting bare-int-width ([]u8=[1,2,3]) and str
elements the array-init path coerces.

Fix (re-stamp + per-borrow scratch; both stages byte-identical asm):
 - Checker re-stamps the slice arrlit as [count]T, reusing the array-init
   per-element coercion + range-check (#25): in-range accepts, out-of-range
   loud-rejects. cstage arrlit_init_fits gains a TY_SLICE arm; wwstage
   checkletassign mirrors it and stashes the synthesized [count]T tnode on
   arrlit.lhs (free for N_ARRLIT) so cgen can size the backing NODE-wise
   (elemsizeofc) and count from the tnode's .rhs intlit — the arrlit's own
   value tinfo carries the literal's untyped element (unsized), so node-first
   sizing is required (a cstage/wwstage representation divergence; cstage's
   Type IS sized and reads base->type).
 - cgen materialises the N_ARRLIT borrow base into a FRESH per-borrow
   @slicescr stack slot (distinct slot per borrow: a borrow's backing must
   outlive the lowering, so it can't share a cached @aggargscr/@tagscr-style
   slot — two live borrows would alias one backing; localalloc/local_alloc
   is always-fresh), filled by REUSING the array-init element fill extracted
   from the N_LET path (cstage cg_arrlit_fill_bp, wwstage cgarrlitfillbp —
   same store sequence the byte-id-green `let a:[N]T=[..]` uses, the
   frame-order + store-op guarantee), then LEAQ'd as the base.

Supported ONLY at a `let` init. In call-arg / return / assign position
there is no addressable backing, so both stages LOUD-REJECT ("bind it to a
`let` first") — aligning cstage DOWN to wwstage (which already refused the
untyped arrlit element) per rule-10; this closes #31's silent call-arg
segfault as a compile error. Full non-let support is deferred (#33).

Escape (rule-8 WHY): a `let xs:[]T=[..]; return xs;` returns a slice into a
freed frame slot = dangling, IDENTICAL to the pre-existing named-array
borrow and Hare-consistent (no escape analysis / GC / heap promotion).

Test 953_arrlit_slice_run: 8 accept rows (cstage runtime readback +
cs==ww byte-id, frame-size canary incl.) covering the #31 i32 pin, bare-int→u8
coercion, str readback, the multi-live soundness pin (xs[0]+ys[0]=5, not 8 —
proves fresh-per-borrow), and a mutate-through-borrow proof; 4 reject rows
(out-of-range element + the three non-let contexts, loud in both stages).
Tuple-element slices stay blocked by the pre-existing #30 array-init FATAL.
This commit is contained in:
Hojun-Cho
2026-06-04 01:32:27 +09:00
parent c490ed3ec1
commit bf1037d8c4
9 changed files with 1621 additions and 861 deletions
Download Patch File Download Diff File Expand all files Collapse all files

369
cmd/w6c/cgen.c
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@@ -2984,6 +2984,175 @@ cg_tagged_tuple_payload_shift(Cg *c, Type *tup)
ins2(c, A_MOVQ, areg(seq[i + 1]), areg(seq[i]));
}
/* cg_arrlit_fill_bp — #31: fill the [count]T destination at BP-relative
* `off` from an N_ARRLIT, extracted verbatim from the N_LET array-init
* path so the slice-borrow base materialisation (the N_SLICE-over-
* N_ARRLIT arm) reuses the identical element-store sequence. `lu` is the
* [count]T array type the checker re-stamped (#25); `arrlit` the literal. */
static void
cg_arrlit_fill_bp(Cg *c, Local **locals, Type *lu, Node *arrlit, int off)
{
Type *esub = lu->sub;
int esz = esub ? (int)esub->size : 1;
/* #270-1c: an AGGREGATE (struct/array/tuple) element
* of an array literal — the scalar per-element MOVQ
* below stores only the first 8 bytes (unpopulated
* tail). Fill each element slot from its literal
* (cg_structlit_fill_bp) or source ident (word-copy). */
Type *esubu = type_chase_named(esub);
int is_agg = esubu && (esubu->kind == TY_STRUCT
|| esubu->kind == TY_ARRAY
|| esubu->kind == TY_TUPLE);
/* #12: a tagged-union element. NOT folded into is_agg —
* is_agg's body does N_STRUCTLIT/N_IDENT word-copy and
* FATALs on the literal/scalar case, never boxing the
* tag+payload. Route each element through the same
* cg_widen_tagged_store choke-point every other tagged
* store uses (let-init, vararg gather, struct-field). */
int is_tagged_el = esubu && esubu->kind == TY_TAGGED;
int is_str_el = type_isstr(esub);
/* #20/#270 str-slice arm: a slice element is a 24B
* {ptr,len,cap} header just like str; cgexpr lowers it
* into AX/BX/CX. Both must store all three words — the
* scalar 1-word MOVQ below drops .len and .cap. */
int is_slice_el = type_isslice(esub);
/* float element → store FROM X0; the AX path stores
* raw double low-bits, garbage for f32 (#122, twin of
* the arr[i]= store fix and the cgen.c:6423 read). */
int is_float_el = type_isfloat(esub);
int fmov = type_isf32(esub) ? A_MOVSS : A_MOVSD;
int op = A_MOVQ;
if (!is_str_el) {
if (esz == 1) op = A_MOVB;
else if (esz == 2) op = A_MOVW;
else if (esz == 4) op = A_MOVL;
/* #128a: esz==2 routes to MOVW (A_MOVW landed in
* both stages' w6a). Pre-fix the 2-byte case fell
* through to MOVQ, over-writing 6B into the next
* element's slot; sequential adjacent writes
* accident-corrected fully-init arrays but
* partial inits clobbered neighbours. */
}
int idx = 0;
Node *last = NULL;
int repeat = 0;
for (Node *e = arrlit->list; e; e = e->next) {
if (e->kind == N_FIELD && e->str &&
strcmp(e->str, "...") == 0) {
repeat = 1;
break;
}
int base = off + idx * esz;
if (is_agg) {
if (e->kind == N_STRUCTLIT) {
cg_structlit_fill_bp(c, locals,
esubu, e, base);
} else if (e->kind == N_IDENT) {
int soff = localfind(*locals,
e->str);
int k = 0;
for (; k + 8 <= esz; k += 8) {
ins2(c, A_MOVQ,
amem(D_BP, soff + k),
areg(D_AX));
ins2(c, A_MOVQ,
areg(D_AX),
amem(D_BP, base + k));
}
if (k + 4 <= esz) {
ins2(c, A_MOVL,
amem(D_BP, soff + k),
areg(D_AX));
ins2(c, A_MOVL,
areg(D_AX),
amem(D_BP, base + k));
k += 4;
}
if (k + 2 <= esz) {
ins2(c, A_MOVW,
amem(D_BP, soff + k),
areg(D_AX));
ins2(c, A_MOVW,
areg(D_AX),
amem(D_BP, base + k));
k += 2;
}
if (k + 1 <= esz) {
ins2(c, A_MOVB,
amem(D_BP, soff + k),
areg(D_AX));
ins2(c, A_MOVB,
areg(D_AX),
amem(D_BP, base + k));
k += 1;
}
} else {
fatal("#270-1c: array-literal "
"aggregate element shape "
"unsupported (rule-7)");
}
last = e;
idx++;
continue;
}
if (is_tagged_el) {
cg_widen_tagged_store(c, locals, esub,
e, D_BP, base, esz);
last = e;
idx++;
continue;
}
cgexpr(c, e, *locals);
if (is_str_el || is_slice_el) {
ins2(c, A_MOVQ, areg(D_AX),
amem(D_BP, base));
ins2(c, A_MOVQ, areg(D_BX),
amem(D_BP, base + 8));
ins2(c, A_MOVQ, areg(D_CX),
amem(D_BP, base + 16));
} else if (is_float_el) {
ins2(c, fmov, areg(D_X0),
amem(D_BP, base));
} else {
ins2(c, op, areg(D_AX),
amem(D_BP, base));
}
last = e;
idx++;
}
if (repeat && is_agg)
fatal("#270-1c: `...` repeat of an aggregate "
"array-literal element not wired (rule-7)");
/* #12: `...` re-stores from AX, but cg_widen_tagged_store
* consumed the node and trashed AX — a repeat-fill would
* write garbage. No consumer needs `[N]tagged=[x,...]`. */
if (repeat && is_tagged_el)
fatal("#12: `...` repeat of a tagged-union "
"array-literal element not wired (rule-7)");
if (repeat && last) {
/* fill remaining slots with the value still in
* AX (and BX for str). */
while (idx < (int)lu->alen) {
int base = off + idx * esz;
if (is_str_el || is_slice_el) {
ins2(c, A_MOVQ, areg(D_AX),
amem(D_BP, base));
ins2(c, A_MOVQ, areg(D_BX),
amem(D_BP, base + 8));
ins2(c, A_MOVQ, areg(D_CX),
amem(D_BP, base + 16));
} else if (is_float_el) {
ins2(c, fmov, areg(D_X0),
amem(D_BP, base));
} else {
ins2(c, op, areg(D_AX),
amem(D_BP, base));
}
idx++;
}
}
}
static void
cgexpr(Cg *c, Node *n, Local *locals)
{
@@ -6428,7 +6597,8 @@ cgexpr(Cg *c, Node *n, Local *locals)
* silently wrong for non-u8). Other non-ident
* bases stay esz=1 (unscaled). */
int esz = (base && (base->kind == N_IDENT
|| base->kind == N_DOT)
|| base->kind == N_DOT
|| base->kind == N_ARRLIT)
&& bu && bu->sub)
? (int)bu->sub->size : 1;
/* base addr → push */
@@ -8685,7 +8855,8 @@ cgexpr(Cg *c, Node *n, Local *locals)
* non-ident bases stay esz=1 (unscaled) -- #76 residual,
* non-ident cluster #74. */
int esz = (base && (base->kind == N_IDENT
|| base->kind == N_DOT) && bu && bu->sub)
|| base->kind == N_DOT || base->kind == N_ARRLIT)
&& bu && bu->sub)
? (int)bu->sub->size : 1;
if (base && base->kind == N_IDENT) {
int boff = localfind(locals, base->str);
@@ -8701,6 +8872,40 @@ cgexpr(Cg *c, Node *n, Local *locals)
} else {
ins2(c, A_MOVQ, amem(D_BP, boff), areg(D_AX));
}
} else if (base && base->kind == N_ARRLIT && bu
&& bu->kind == TY_ARRAY) {
/* #31: an array LITERAL base — the desugared one-step
* `let xs: []T = [..]` borrow (the ONLY context that
* reaches here; call-arg/return/assign loud-reject at the
* checker, reject_arrlit_borrow, deferred to #33). The
* literal has no storage address — cgexpr would leave
* AX=garbage and the borrow's .ptr would dangle.
* Materialise it into a FRESH per-borrow @slicescr stack
* slot (distinct slot per borrow: a borrow's backing must
* stay live for the slice's lifetime, so it can't share a
* cached SSoT slot the way @aggargscr/@tagscr — drained/
* consumed in place — do; two live borrows would otherwise
* alias one backing). Reuses local_alloc + the shared
* array-init fill; the checker re-stamped base->type to
* [count]T (#25) so the fill stores at the declared
* element width.
*
* Escape (WHY, rob): a `let xs: []T = [..]; return xs;`
* returns a slice pointing at this frame slot, freed on
* return = dangling. This is IDENTICAL to the pre-existing
* named-array borrow (`let a: [N]T = [..]; return a;`) and
* is Hare-consistent: ww has no escape analysis, no GC, no
* heap promotion — borrowing a local past its frame is a
* programmer footgun, not promoted. Don't "fix" this
* expecting heap promotion; ww deliberately doesn't, same
* as Hare. */
int cnt = (int)bu->alen;
int bsz = (bu->sub ? (int)bu->sub->size : 1) * cnt;
if (bsz < 1) bsz = 1;
int scr = local_alloc(c, &locals, "@slicescr", bsz,
cg_frame);
cg_arrlit_fill_bp(c, &locals, bu, base, scr);
ins2(c, A_LEAQ, amem(D_BP, scr), areg(D_AX));
} else if (base) {
/* #252: N_DOT `[N]T`-field base → field ADDRESS via
* cg_dotbase_addr (LEAQ), not the auto-deref VALUE load
@@ -9071,165 +9276,7 @@ cgstmt(Cg *c, Node *n, Local **locals, int *frame)
* (is_agg excludes TY_TAGGED) — tracked as task #12. */
if (n->rhs && n->rhs->kind == N_ARRLIT && lu
&& lu->kind == TY_ARRAY) {
Type *esub = lu->sub;
int esz = esub ? (int)esub->size : 1;
/* #270-1c: an AGGREGATE (struct/array/tuple) element
* of an array literal — the scalar per-element MOVQ
* below stores only the first 8 bytes (unpopulated
* tail). Fill each element slot from its literal
* (cg_structlit_fill_bp) or source ident (word-copy). */
Type *esubu = type_chase_named(esub);
int is_agg = esubu && (esubu->kind == TY_STRUCT
|| esubu->kind == TY_ARRAY
|| esubu->kind == TY_TUPLE);
/* #12: a tagged-union element. NOT folded into is_agg —
* is_agg's body does N_STRUCTLIT/N_IDENT word-copy and
* FATALs on the literal/scalar case, never boxing the
* tag+payload. Route each element through the same
* cg_widen_tagged_store choke-point every other tagged
* store uses (let-init, vararg gather, struct-field). */
int is_tagged_el = esubu && esubu->kind == TY_TAGGED;
int is_str_el = type_isstr(esub);
/* #20/#270 str-slice arm: a slice element is a 24B
* {ptr,len,cap} header just like str; cgexpr lowers it
* into AX/BX/CX. Both must store all three words — the
* scalar 1-word MOVQ below drops .len and .cap. */
int is_slice_el = type_isslice(esub);
/* float element → store FROM X0; the AX path stores
* raw double low-bits, garbage for f32 (#122, twin of
* the arr[i]= store fix and the cgen.c:6423 read). */
int is_float_el = type_isfloat(esub);
int fmov = type_isf32(esub) ? A_MOVSS : A_MOVSD;
int op = A_MOVQ;
if (!is_str_el) {
if (esz == 1) op = A_MOVB;
else if (esz == 2) op = A_MOVW;
else if (esz == 4) op = A_MOVL;
/* #128a: esz==2 routes to MOVW (A_MOVW landed in
* both stages' w6a). Pre-fix the 2-byte case fell
* through to MOVQ, over-writing 6B into the next
* element's slot; sequential adjacent writes
* accident-corrected fully-init arrays but
* partial inits clobbered neighbours. */
}
int idx = 0;
Node *last = NULL;
int repeat = 0;
for (Node *e = n->rhs->list; e; e = e->next) {
if (e->kind == N_FIELD && e->str &&
strcmp(e->str, "...") == 0) {
repeat = 1;
break;
}
int base = off + idx * esz;
if (is_agg) {
if (e->kind == N_STRUCTLIT) {
cg_structlit_fill_bp(c, locals,
esubu, e, base);
} else if (e->kind == N_IDENT) {
int soff = localfind(*locals,
e->str);
int k = 0;
for (; k + 8 <= esz; k += 8) {
ins2(c, A_MOVQ,
amem(D_BP, soff + k),
areg(D_AX));
ins2(c, A_MOVQ,
areg(D_AX),
amem(D_BP, base + k));
}
if (k + 4 <= esz) {
ins2(c, A_MOVL,
amem(D_BP, soff + k),
areg(D_AX));
ins2(c, A_MOVL,
areg(D_AX),
amem(D_BP, base + k));
k += 4;
}
if (k + 2 <= esz) {
ins2(c, A_MOVW,
amem(D_BP, soff + k),
areg(D_AX));
ins2(c, A_MOVW,
areg(D_AX),
amem(D_BP, base + k));
k += 2;
}
if (k + 1 <= esz) {
ins2(c, A_MOVB,
amem(D_BP, soff + k),
areg(D_AX));
ins2(c, A_MOVB,
areg(D_AX),
amem(D_BP, base + k));
k += 1;
}
} else {
fatal("#270-1c: array-literal "
"aggregate element shape "
"unsupported (rule-7)");
}
last = e;
idx++;
continue;
}
if (is_tagged_el) {
cg_widen_tagged_store(c, locals, esub,
e, D_BP, base, esz);
last = e;
idx++;
continue;
}
cgexpr(c, e, *locals);
if (is_str_el || is_slice_el) {
ins2(c, A_MOVQ, areg(D_AX),
amem(D_BP, base));
ins2(c, A_MOVQ, areg(D_BX),
amem(D_BP, base + 8));
ins2(c, A_MOVQ, areg(D_CX),
amem(D_BP, base + 16));
} else if (is_float_el) {
ins2(c, fmov, areg(D_X0),
amem(D_BP, base));
} else {
ins2(c, op, areg(D_AX),
amem(D_BP, base));
}
last = e;
idx++;
}
if (repeat && is_agg)
fatal("#270-1c: `...` repeat of an aggregate "
"array-literal element not wired (rule-7)");
/* #12: `...` re-stores from AX, but cg_widen_tagged_store
* consumed the node and trashed AX — a repeat-fill would
* write garbage. No consumer needs `[N]tagged=[x,...]`. */
if (repeat && is_tagged_el)
fatal("#12: `...` repeat of a tagged-union "
"array-literal element not wired (rule-7)");
if (repeat && last) {
/* fill remaining slots with the value still in
* AX (and BX for str). */
while (idx < (int)lu->alen) {
int base = off + idx * esz;
if (is_str_el || is_slice_el) {
ins2(c, A_MOVQ, areg(D_AX),
amem(D_BP, base));
ins2(c, A_MOVQ, areg(D_BX),
amem(D_BP, base + 8));
ins2(c, A_MOVQ, areg(D_CX),
amem(D_BP, base + 16));
} else if (is_float_el) {
ins2(c, fmov, areg(D_X0),
amem(D_BP, base));
} else {
ins2(c, op, areg(D_AX),
amem(D_BP, base));
}
idx++;
}
}
cg_arrlit_fill_bp(c, locals, lu, n->rhs, off);
break;
}
/* Struct ident copy: `let p2: T = p1;` where T is a struct