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w6c: keep unwrap destination off the call stack

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Hojun-Cho
2026-08-09 03:44:12 +09:00
parent a030268c52
commit edacb40bfe
3 changed files with 113 additions and 28 deletions
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45
cmd/w6c/cgen.c
View File

@@ -39,6 +39,11 @@ static int *cg_frame;
* semantics for synthetic scratches). 0 means "not yet allocated";
* negative offsets returned by local_alloc are the live value. */
static int cg_retscr;
/* The aggregate-unwrap receiver must survive its producer call without
* perturbing SP: an outstanding PUSHQ at CALL violates SysV alignment.
* One BP-relative address spill per function mirrors wwstage's @-prefix
* scratch reuse. */
static int cg_unwrapdst;
/* Per-fn @tupfscr offset (single-slot SSoT). A multi-float tuple return
* (#164/#107) spills each float out of X0 to this scratch as the L→R
* element walk clobbers X0, then reloads X0/X1 by SSE index after the
@@ -5362,9 +5367,17 @@ cgexpr(Cg *c, Node *n, Local *locals)
fatal("#16: global/chained aggregate "
"unwrap field dest unresolved "
"(cgplaceaddr)");
ins1(c, A_PUSHQ, areg(D_BX));
int dstscr;
if (cg_unwrapdst != 0) {
dstscr = cg_unwrapdst;
} else {
dstscr = local_alloc(c, &locals, "@unwrapdst",
8, cg_frame);
cg_unwrapdst = dstscr;
}
ins2(c, A_MOVQ, areg(D_BX), amem(D_BP, dstscr));
cgexpr(c, n->rhs, locals);
ins1(c, A_POPQ, areg(D_BX));
ins2(c, A_MOVQ, amem(D_BP, dstscr), areg(D_BX));
cg_agg_reg_store(c, &locals, D_BX, 0, ssz, 0);
break;
}
@@ -5377,9 +5390,8 @@ cgexpr(Cg *c, Node *n, Local *locals)
* explicit-deref form `(*p).f = ...` where the parser emits
* N_UN(STAR, IDENT(p)). For (*p).f, retarget base to the
* inner IDENT so the via_ptr branch fires identically to
* `p.f = v`. v1 scope: bare-IDENT inner only; (*expr).f
* (non-IDENT inner) falls through to the existing drop
* behaviour pending follow-up task. */
* `p.f = v`. Other addressable bases fall through to the
* shared place resolver. */
if (!global_ptr_field_decline(n->lhs, n->op, locals)
&& n->lhs && n->lhs->kind == N_DOT && n->lhs->lhs &&
(n->lhs->lhs->kind == N_IDENT ||
@@ -5452,20 +5464,8 @@ cgexpr(Cg *c, Node *n, Local *locals)
if (strcmp(fl->name, n->lhs->str) == 0)
{ f = fl; break; }
if (f == NULL) break;
/* Tagged-union field: synthesise tag and store
* value bytes. Compound ops on tagged fields are
* not meaningful, so only plain `=` is wired.
* Three base shapes:
* - via_ptr: base is *struct local; address
* pre-loaded into BX. Buggy with a str
* variant since cgexpr will overwrite BX,
* but matches the existing pre-global
* behaviour.
* - is_global: struct global. LEAQ after
* cgexpr drops the slot address into CX
* without touching AX/BX, so str variants
* work cleanly.
* - else: struct local, BP-relative. */
/* Compound ops on tagged fields are not meaningful,
* so only plain `=` is wired. */
Type *ft = f->type;
/* Transitive chase (#5-F1 fold): 2-level alias
* slice/str field skipped the 3-word arm — ptr
@@ -11876,10 +11876,10 @@ cgexpr(Cg *c, Node *n, Local *locals)
* IDENT(p)) with type T (post-deref struct). Pull the inner
* IDENT in as dot_lhs so bt resolves to *T and the pointer-
* auto-deref branch below fires (mirror of the N_ASSIGN
* N_DOT lhs retarget). v1 scope: N_IDENT inner only;
* (*expr).f follow-up task pending. Branches that gate on
* N_DOT lhs retarget). Branches that gate on
* `n->lhs->kind == N_DOT/N_INDEX/...` keep checking the raw
* n->lhs since (*p) isn't either of those shapes. */
* n->lhs since (*p) isn't either of those shapes; remaining
* addressable bases use the shared place resolver. */
Node *dot_lhs = n->lhs;
if (dot_lhs && dot_lhs->kind == N_UN && dot_lhs->op == TK_STAR
&& dot_lhs->lhs && dot_lhs->lhs->kind == N_IDENT)
@@ -15803,6 +15803,7 @@ cgfn(Cg *c, FILE *out, Node *fn)
nloops = 0;
cg_ret_type = fn->type ? fn->type->ret : NULL;
cg_retscr = 0;
cg_unwrapdst = 0;
cg_tupfscr = 0;
cg_tupargscr = 0;
cg_tupargscr_sz = 0;

18
selfhost/cmd/wcc/cgenexpr.ww
View File

@@ -3623,10 +3623,10 @@ fn cgdot(c: *cgen, n: *syntax.node) void = {
// IDENT(p)). Substitute the inner IDENT as dotlhs so the
// pointer-auto-deref branch (lhs.kind == N_IDENT && N_TPTR
// tnode) fires the same as `p.f`. Mirror of the N_ASSIGN N_DOT
// lhs retarget in cgassign. v1 scope: N_IDENT inner only;
// (*expr).f follow-up task pending. Enum-leaf lookup above and
// lhs retarget in cgassign. Enum-leaf lookup above and
// chained-N_DOT branches below keep checking raw lhs since
// (*p) is neither shape.
// (*p) is neither shape; remaining addressable bases use the
// shared place resolver.
let dotlhs: *syntax.node = lhs;
if (dotlhs != nil) {
if (dotlhs.kind == syntax.nkind.N_UN) {
@@ -8780,9 +8780,14 @@ fn cgassign(c: *cgen, n: *syntax.node) void = {
os.write(2, m16.ptr, m16.len: u64);
os.exit(1);
};
emitline("\tPUSHQ\tBX\n");
let dstscr: i32 = localadd(c, "@unwrapdst", 8, nil);
emitline("\tMOVQ\tBX, ");
emitoff(dstscr: i64);
emitline("(BP)\n");
cgexpr(c, n.rhs);
emitline("\tPOPQ\tBX\n");
emitline("\tMOVQ\t");
emitoff(dstscr: i64);
emitline("(BP), BX\n");
cgaggregstore(c, "BX", 0, ssz, false);
return;
};
@@ -10876,7 +10881,8 @@ fn cgassign(c: *cgen, n: *syntax.node) void = {
// is rare and not yet needed by our fixtures). Base accepts the
// explicit-deref form `(*p).f = ...` (parser N_UN(STAR, IDENT))
// by retargeting to the inner IDENT so the via_ptr branch fires
// the same as auto-deref `p.f = v`. v1 scope: bare-IDENT inner.
// the same as auto-deref `p.f = v`. Other addressable bases use
// the shared place resolver below.
if (lhs != nil) {
if (lhs.kind == syntax.nkind.N_DOT) {
let base: *syntax.node = lhs.lhs;

78
test/asm/chain_test.ww
View File

@@ -271,3 +271,81 @@ fn dotbaserow(label: str, src: str, needle: str) void = {
"export fn main() i32 = { return 0; };\n"),
"\tMOVQ\t$32, CX\n");
};
fn unwrapaligncheck(label: str, stage: str, s: str) void = {
let w: str = probewindow(label, stage, s);
let call: i32 = testenv.pos(w, "\tCALL\tmain.mkpair(SB)\n");
if (call < 0) {
fail(label, strings.concat(stage, ": no CALL main.mkpair"));
};
let pre: str = strings.sub(w, 0, call);
let post: str = strings.sub(w, call, w.len);
if (testenv.has(pre, "\tPUSHQ\tBX\n")) {
fail(label, strings.concat(stage,
": destination PUSHQ remains outstanding at CALL"));
};
if (!testenv.has(pre, "\tMOVQ\tBX, -")) {
fail(label, strings.concat(stage,
": destination address is not spilled BP-relative"));
};
if (!testenv.has(post, "\tMOVQ\t-")
|| !testenv.has(post, "(BP), BX\n")) {
fail(label, strings.concat(stage,
": destination address is not reloaded after CALL"));
};
if (!testenv.has(w, "TEXT main.probe,$16")) {
fail(label, strings.concat(stage,
": dedicated address spill is absent from the frame"));
};
};
fn commandexit(dir: str, name: str, av: []str) i32 = {
let co: testenv.commandout;
testenv.runcommand(dir, dir, name, av, tmo(), &co);
if (co.termination != exec.termination.EXIT) { return -1; };
return co.code;
};
@test fn unwrapcallalign() void = {
let label: str = "global_unwrap_call_alignment";
let td: str = testenv.fresh();
let src: str = strings.concat(
"package main;\n",
"type e = !i32;\n",
"type pair = struct { a: i64, b: i64 };\n",
"type box = struct { f: pair, guard: i64 };\n",
"fn mkpair(x: f64) (pair | e) = {\n",
" return pair { a = 111i64, b = 222i64 };\n",
"};\n",
"let gb: box = box {\n",
" f = pair { a = 9i64, b = 9i64 }, guard = 7i64\n",
"};\n",
"fn probe() i32 = {\n",
" gb.f = mkpair(1.25f64)!;\n",
" if (gb.f.a != 111i64 || gb.f.b != 222i64",
" || gb.guard != 7i64) { return 91; };\n",
" return 37;\n",
"};\n",
"export fn main() i32 = { return probe(); };\n");
testenv.writefile(strings.concat(td, "/src.ww"), src);
emitstage(td, label, "cstage", testenv.driver("w6c"), "cs.s");
emitstage(td, label, "wwstage", testenv.driver("w6c_ww"), "ws.s");
let cs: str = testenv.readfile(strings.concat(td, "/cs.s"));
let ws: str = testenv.readfile(strings.concat(td, "/ws.s"));
unwrapaligncheck(label, "cstage", cs);
unwrapaligncheck(label, "wwstage", ws);
if (!testenv.same(cs, ws)) {
fail(label, "cstage vs wwstage asm differs");
};
let out: str = strings.concat(td, "/unwrapalign");
let bav: []str = [testenv.driver("ww"), "build", "-o", out,
"src.ww"];
if (commandexit(td, "build", bav) != 0) {
fail(label, "runtime pin build failed");
};
let rav: []str = [out];
if (commandexit(td, "run", rav) != 37) {
fail(label, "payload/neighbor runtime exit != 37");
};
testenv.clean(td);
};