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[NFC] Update ChildTyper callback for unknown constaints #7814

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tlively merged 2 commits into from
Aug 11, 2025
Merged

[NFC] Update ChildTyper callback for unknown constaints #7814

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[NFC] Update ChildTyper callback for unknown constaints
tlively Aug 9, 2025
44ac3a6
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tlively Aug 11, 2025
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125 changes: 70 additions & 55 deletions src/ir/child-typer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -66,13 +66,9 @@ namespace wasm {
// two non-reference children of `select` must have the same type because that
// would require inspecting the types of those children.
//
// The skipUnreachable() hook function determines the behavior on code that
// we cannot process due to unreachability. For example, an unreachable
// StructNew has no struct type defined, so we cannot apply its heap type. By
// default we do not skip such unreachable code, and error in such such cases if
// the type is not provided (by passing the heap type as mentioned above, as a
// parameter to the visit* method). Optimization passes can often skip
// unreachable code (leaving it for DCE), while other operations might not.
// The noteUnknown() hook is called whenever there is insufficient type
// information to generate constraints for all the children. Some users may wish
// to ignore this situation and others may want to assert that it never occurs.
template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
Module& wasm;
Function* func;
Expand Down Expand Up @@ -105,8 +101,6 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {

Type getLabelType(Name label) { return self().getLabelType(label); }

bool skipUnreachable() { return false; }

void visitNop(Nop* curr) {}

void visitBlock(Block* curr) {
Expand Down Expand Up @@ -195,7 +189,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
}

void visitAtomicRMW(AtomicRMW* curr) {
if (self().skipUnreachable() && curr->type == Type::unreachable) {
if (curr->type == Type::unreachable) {
self().noteUnknown();
return;
}
assert(curr->type == Type::i32 || curr->type == Type::i64);
Expand Down Expand Up @@ -828,7 +823,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
void visitTupleExtract(TupleExtract* curr,
std::optional<size_t> arity = std::nullopt) {
if (!arity) {
if (self().skipUnreachable() && !curr->tuple->type.isTuple()) {
if (!curr->tuple->type.isTuple()) {
self().noteUnknown();
return;
}
assert(curr->tuple->type.isTuple());
Expand All @@ -845,7 +841,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {

void visitCallRef(CallRef* curr, std::optional<HeapType> ht = std::nullopt) {
if (!ht) {
if (self().skipUnreachable() && !curr->target->type.isRef()) {
if (!curr->target->type.isRef()) {
self().noteUnknown();
return;
}
ht = curr->target->type.getHeapType().getSignature();
Expand All @@ -859,36 +856,32 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
}

void visitRefTest(RefTest* curr) {
if (self().skipUnreachable() && !curr->castType.isRef()) {
return;
}
auto top = curr->castType.getHeapType().getTop();
note(&curr->ref, Type(top, Nullable));
}

void visitRefCast(RefCast* curr, std::optional<Type> target = std::nullopt) {
if (self().skipUnreachable() && !curr->type.isRef()) {
return;
if (!target) {
if (!curr->type.isRef()) {
self().noteUnknown();
return;
}
target = curr->type;
}
auto top = curr->type.getHeapType().getTop();
auto top = target->getHeapType().getTop();
note(&curr->ref, Type(top, Nullable));
if (curr->desc) {
if (!target) {
target = curr->type;
}
if (self().skipUnreachable() && !target->isRef()) {
return;
}
auto desc = target->getHeapType().getDescriptorType();
assert(desc);
note(&curr->desc, Type(*desc, Nullable, curr->type.getExactness()));
note(&curr->desc, Type(*desc, Nullable, target->getExactness()));
}
}

void visitRefGetDesc(RefGetDesc* curr,
std::optional<HeapType> ht = std::nullopt) {
if (!ht) {
if (self().skipUnreachable() && !curr->ref->type.isRef()) {
if (!curr->ref->type.isRef()) {
self().noteUnknown();
return;
}
ht = curr->ref->type.getHeapType();
Expand All @@ -900,18 +893,19 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
switch (curr->op) {
case BrOnNull:
case BrOnNonNull:
// br_on(_non)_null is polymorphic over reference types and does not
// take a type immediate.
assert(!target);
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@kripken kripken Aug 11, 2025

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I'm not sure why this is so. Perhaps add a comment?

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@tlively tlively Aug 11, 2025

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Done.

noteAnyReference(&curr->ref);
return;
case BrOnCast:
case BrOnCastFail:
case BrOnCastDesc:
case BrOnCastDescFail: {
if (!target) {
assert(curr->castType.isRef());
target = curr->castType;
}
if (self().skipUnreachable() && !target->isRef()) {
return;
}
auto top = target->getHeapType().getTop();
note(&curr->ref, Type(top, Nullable));
if (curr->op == BrOnCastDesc || curr->op == BrOnCastDescFail) {
Expand All @@ -926,7 +920,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
}

void visitStructNew(StructNew* curr) {
if (self().skipUnreachable() && !curr->type.isRef()) {
if (!curr->type.isRef()) {
self().noteUnknown();
return;
}
if (!curr->isWithDefault()) {
Expand All @@ -945,7 +940,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
void visitStructGet(StructGet* curr,
std::optional<HeapType> ht = std::nullopt) {
if (!ht) {
if (self().skipUnreachable() && !curr->ref->type.isRef()) {
if (!curr->ref->type.isRef()) {
self().noteUnknown();
return;
}
ht = curr->ref->type.getHeapType();
Expand All @@ -956,7 +952,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
void visitStructSet(StructSet* curr,
std::optional<HeapType> ht = std::nullopt) {
if (!ht) {
if (self().skipUnreachable() && !curr->ref->type.isRef()) {
if (!curr->ref->type.isRef()) {
self().noteUnknown();
return;
}
ht = curr->ref->type.getHeapType();
Expand All @@ -970,7 +967,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
void visitStructRMW(StructRMW* curr,
std::optional<HeapType> ht = std::nullopt) {
if (!ht) {
if (self().skipUnreachable() && !curr->ref->type.isRef()) {
if (!curr->ref->type.isRef()) {
self().noteUnknown();
return;
}
ht = curr->ref->type.getHeapType();
Expand All @@ -984,7 +982,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
void visitStructCmpxchg(StructCmpxchg* curr,
std::optional<HeapType> ht = std::nullopt) {
if (!ht) {
if (self().skipUnreachable() && !curr->ref->type.isRef()) {
if (!curr->ref->type.isRef()) {
self().noteUnknown();
return;
}
ht = curr->ref->type.getHeapType();
Expand All @@ -999,7 +998,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {

void visitArrayNew(ArrayNew* curr) {
if (!curr->isWithDefault()) {
if (self().skipUnreachable() && !curr->type.isRef()) {
if (!curr->type.isRef()) {
self().noteUnknown();
return;
}
note(&curr->init, curr->type.getHeapType().getArray().element.type);
Expand All @@ -1018,7 +1018,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
}

void visitArrayNewFixed(ArrayNewFixed* curr) {
if (self().skipUnreachable() && !curr->type.isRef()) {
if (!curr->type.isRef()) {
self().noteUnknown();
return;
}
auto type = curr->type.getHeapType().getArray().element.type;
Expand All @@ -1030,7 +1031,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
void visitArrayGet(ArrayGet* curr,
std::optional<HeapType> ht = std::nullopt) {
if (!ht) {
if (self().skipUnreachable() && !curr->ref->type.isRef()) {
if (!curr->ref->type.isRef()) {
self().noteUnknown();
return;
}
ht = curr->ref->type.getHeapType();
Expand All @@ -1042,7 +1044,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
void visitArraySet(ArraySet* curr,
std::optional<HeapType> ht = std::nullopt) {
if (!ht) {
if (self().skipUnreachable() && !curr->ref->type.isRef()) {
if (!curr->ref->type.isRef()) {
self().noteUnknown();
return;
}
ht = curr->ref->type.getHeapType();
Expand All @@ -1061,13 +1064,15 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
std::optional<HeapType> dest = std::nullopt,
std::optional<HeapType> src = std::nullopt) {
if (!dest) {
if (self().skipUnreachable() && !curr->destRef->type.isRef()) {
if (!curr->destRef->type.isRef()) {
self().noteUnknown();
return;
}
dest = curr->destRef->type.getHeapType();
}
if (!src) {
if (self().skipUnreachable() && !curr->srcRef->type.isRef()) {
if (!curr->srcRef->type.isRef()) {
self().noteUnknown();
return;
}
src = curr->srcRef->type.getHeapType();
Expand All @@ -1082,7 +1087,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
void visitArrayFill(ArrayFill* curr,
std::optional<HeapType> ht = std::nullopt) {
if (!ht) {
if (self().skipUnreachable() && !curr->ref->type.isRef()) {
if (!curr->ref->type.isRef()) {
self().noteUnknown();
return;
}
ht = curr->ref->type.getHeapType();
Expand All @@ -1097,7 +1103,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
void visitArrayInitData(ArrayInitData* curr,
std::optional<HeapType> ht = std::nullopt) {
if (!ht) {
if (self().skipUnreachable() && !curr->ref->type.isRef()) {
if (!curr->ref->type.isRef()) {
self().noteUnknown();
return;
}
ht = curr->ref->type.getHeapType();
Expand All @@ -1111,7 +1118,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
void visitArrayInitElem(ArrayInitElem* curr,
std::optional<HeapType> ht = std::nullopt) {
if (!ht) {
if (self().skipUnreachable() && !curr->ref->type.isRef()) {
if (!curr->ref->type.isRef()) {
self().noteUnknown();
return;
}
ht = curr->ref->type.getHeapType();
Expand All @@ -1125,7 +1133,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
void visitArrayRMW(ArrayRMW* curr,
std::optional<HeapType> ht = std::nullopt) {
if (!ht) {
if (self().skipUnreachable() && !curr->ref->type.isRef()) {
if (!curr->ref->type.isRef()) {
self().noteUnknown();
return;
}
ht = curr->ref->type.getHeapType();
Expand All @@ -1139,7 +1148,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
void visitArrayCmpxchg(ArrayCmpxchg* curr,
std::optional<HeapType> ht = std::nullopt) {
if (!ht) {
if (self().skipUnreachable() && !curr->ref->type.isRef()) {
if (!curr->ref->type.isRef()) {
self().noteUnknown();
return;
}
ht = curr->ref->type.getHeapType();
Expand Down Expand Up @@ -1241,14 +1251,16 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
void visitContBind(ContBind* curr,
std::optional<HeapType> src = std::nullopt,
std::optional<HeapType> dest = std::nullopt) {
if (!src.has_value()) {
if (self().skipUnreachable() && !curr->cont->type.isRef()) {
if (!src) {
if (!curr->cont->type.isRef()) {
self().noteUnknown();
return;
}
src = curr->cont->type.getHeapType();
}
if (!dest.has_value()) {
if (self().skipUnreachable() && !curr->type.isRef()) {
if (!dest) {
if (!curr->type.isRef()) {
self().noteUnknown();
return;
}
dest = curr->type.getHeapType();
Expand All @@ -1273,8 +1285,9 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
}

void visitResume(Resume* curr, std::optional<HeapType> ct = std::nullopt) {
if (!ct.has_value()) {
if (self().skipUnreachable() && !curr->cont->type.isRef()) {
if (!ct) {
if (!curr->cont->type.isRef()) {
self().noteUnknown();
return;
}
ct = curr->cont->type.getHeapType();
Expand All @@ -1290,8 +1303,9 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {

void visitResumeThrow(ResumeThrow* curr,
std::optional<HeapType> ct = std::nullopt) {
if (!ct.has_value()) {
if (self().skipUnreachable() && !curr->cont->type.isRef()) {
if (!ct) {
if (!curr->cont->type.isRef()) {
self().noteUnknown();
return;
}
ct = curr->cont->type.getHeapType();
Expand All @@ -1307,8 +1321,9 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {

void visitStackSwitch(StackSwitch* curr,
std::optional<HeapType> ct = std::nullopt) {
if (!ct.has_value()) {
if (self().skipUnreachable() && !curr->cont->type.isRef()) {
if (!ct) {
if (!curr->cont->type.isRef()) {
self().noteUnknown();
return;
}
ct = curr->cont->type.getHeapType();
Expand Down
5 changes: 2 additions & 3 deletions src/passes/TypeSSA.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -238,9 +238,8 @@ struct Analyzer

Type getLabelType(Name label) { WASM_UNREACHABLE("unexpected branch"); }

// Skip unreachable code. If we cannot compute a constraint due to
// unreachability, we can ignore it.
bool skipUnreachable() { return true; }
// We don't mind if we cannot compute a constraint due to unreachability.
void noteUnknown() {}
} typer(*this);
typer.visit(curr);
}
Expand Down
5 changes: 5 additions & 0 deletions src/wasm/wasm-ir-builder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -401,6 +401,11 @@ struct IRBuilder::ChildPopper
// condition.
children.push_back({&curr->condition, {Subtype{Type::i32}}});
}

// It is a bug if we ever have insufficient type information.
void noteUnknown() {
WASM_UNREACHABLE("unexpected insufficient type information");
}
};

IRBuilder& builder;
Expand Down
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