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wcc: tagged float-variant return packs float bits via X0-spill (#157)

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The N_RETURN tagged-pack scalar-variant arm did MOVQ AX,DX, but a float
variant's value is in X0 not AX -> packed stale int (broke stof64/stof32
return (f64|invalid|overflow)). Fix: float variant bridges X0->DX via a
stack slot (SUBQ $8,SP; MOVQ $0,(SP); MOVSS|MOVSD X0,(SP); MOVQ (SP),DX;
ADDQ $8,SP), gated type_isfloat/exprfloatkind. No MOVQ-xmm->gp form
exists, hence the spill (715-class, cgreturn-register-pack twin of 715's
store-to-slot). Zero-slot-first -> deterministic f32 high-4. AX-independent
-> also resolves the multi-variant cs!=ww. Bootstrap-NEUTRAL (compiler has
no float-tagged-return). Test 707 +3 rows (f64/f32/multi, slot+8 bit-exact;
f32 no-f32-arg to isolate #143). Make test 184/184 incl 990-997 byte-id.
This commit is contained in:
Hojun-Cho
2026-05-27 13:04:02 +09:00
parent cbeffea7d8
commit 4a91bdc8db
5 changed files with 158 additions and 4 deletions
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27
selfhost/cmd/w6c/main.combined.ww
View File

@@ -22060,6 +22060,31 @@ fn cgreturn(c: *cgen, n: *node) void = {
emitline("\tMOVQ\tCX, R8\n");
emitline("\tMOVQ\tBX, CX\n");
emitline("\tMOVQ\tAX, DX\n");
} else { if (exprfloatkind(c, rhs) != 0) {
// #157: float variant — cgexpr left the value
// in X0, not AX. No MOVQ-xmm->gp encoding, so
// bridge X0->DX through a stack slot (same arg-
// push idiom). Zero the slot first so the f32
// case (MOVSS writes only the low 4 bytes)
// leaves a deterministic high-4 — cs==ww byte-
// id, matching f64's MOVSD which fills all 8.
// The AX-independent spill also removes the
// stale-AX cs!=ww on multi-variant returns.
emitline("\tSUBQ\t$8, SP\n");
emitline("\tMOVQ\t$0, (SP)\n");
let mov: str = "MOVSD";
if (exprfloatkind(c, rhs) == 1) { mov = "MOVSS"; };
emitline("\t");
emitline(mov);
emitline("\tX0, (SP)\n");
emitline("\tMOVQ\t(SP), DX\n");
emitline("\tADDQ\t$8, SP\n");
if (rsz > 16) {
emitline("\tMOVQ\t$0, CX\n");
};
if (rsz > 24) {
emitline("\tMOVQ\t$0, R8\n");
};
} else {
emitline("\tMOVQ\tAX, DX\n");
// scalar fills DX only. Zero CX / R8 if dst
@@ -22070,7 +22095,7 @@ fn cgreturn(c: *cgen, n: *node) void = {
if (rsz > 24) {
emitline("\tMOVQ\t$0, R8\n");
};
};};
};};};
emitline("\tMOVQ\t$");
if (idx < 0) { idx = 0; };
emitint(idx: i64);

27
selfhost/cmd/wcc/cgenstmt.ww
View File

@@ -422,6 +422,31 @@ fn cgreturn(c: *cgen, n: *node) void = {
emitline("\tMOVQ\tCX, R8\n");
emitline("\tMOVQ\tBX, CX\n");
emitline("\tMOVQ\tAX, DX\n");
} else { if (exprfloatkind(c, rhs) != 0) {
// #157: float variant — cgexpr left the value
// in X0, not AX. No MOVQ-xmm->gp encoding, so
// bridge X0->DX through a stack slot (same arg-
// push idiom). Zero the slot first so the f32
// case (MOVSS writes only the low 4 bytes)
// leaves a deterministic high-4 — cs==ww byte-
// id, matching f64's MOVSD which fills all 8.
// The AX-independent spill also removes the
// stale-AX cs!=ww on multi-variant returns.
emitline("\tSUBQ\t$8, SP\n");
emitline("\tMOVQ\t$0, (SP)\n");
let mov: str = "MOVSD";
if (exprfloatkind(c, rhs) == 1) { mov = "MOVSS"; };
emitline("\t");
emitline(mov);
emitline("\tX0, (SP)\n");
emitline("\tMOVQ\t(SP), DX\n");
emitline("\tADDQ\t$8, SP\n");
if (rsz > 16) {
emitline("\tMOVQ\t$0, CX\n");
};
if (rsz > 24) {
emitline("\tMOVQ\t$0, R8\n");
};
} else {
emitline("\tMOVQ\tAX, DX\n");
// scalar fills DX only. Zero CX / R8 if dst
@@ -432,7 +457,7 @@ fn cgreturn(c: *cgen, n: *node) void = {
if (rsz > 24) {
emitline("\tMOVQ\t$0, R8\n");
};
};};
};};};
emitline("\tMOVQ\t$");
if (idx < 0) { idx = 0; };
emitint(idx: i64);

27
selfhost/cmd/wwdump/main.combined.ww
View File

@@ -22060,6 +22060,31 @@ fn cgreturn(c: *cgen, n: *node) void = {
emitline("\tMOVQ\tCX, R8\n");
emitline("\tMOVQ\tBX, CX\n");
emitline("\tMOVQ\tAX, DX\n");
} else { if (exprfloatkind(c, rhs) != 0) {
// #157: float variant — cgexpr left the value
// in X0, not AX. No MOVQ-xmm->gp encoding, so
// bridge X0->DX through a stack slot (same arg-
// push idiom). Zero the slot first so the f32
// case (MOVSS writes only the low 4 bytes)
// leaves a deterministic high-4 — cs==ww byte-
// id, matching f64's MOVSD which fills all 8.
// The AX-independent spill also removes the
// stale-AX cs!=ww on multi-variant returns.
emitline("\tSUBQ\t$8, SP\n");
emitline("\tMOVQ\t$0, (SP)\n");
let mov: str = "MOVSD";
if (exprfloatkind(c, rhs) == 1) { mov = "MOVSS"; };
emitline("\t");
emitline(mov);
emitline("\tX0, (SP)\n");
emitline("\tMOVQ\t(SP), DX\n");
emitline("\tADDQ\t$8, SP\n");
if (rsz > 16) {
emitline("\tMOVQ\t$0, CX\n");
};
if (rsz > 24) {
emitline("\tMOVQ\t$0, R8\n");
};
} else {
emitline("\tMOVQ\tAX, DX\n");
// scalar fills DX only. Zero CX / R8 if dst
@@ -22070,7 +22095,7 @@ fn cgreturn(c: *cgen, n: *node) void = {
if (rsz > 24) {
emitline("\tMOVQ\t$0, R8\n");
};
};};
};};};
emitline("\tMOVQ\t$");
if (idx < 0) { idx = 0; };
emitint(idx: i64);