Initial support for struct.wait

scripts/gen-s-parser.py

@@ -206,6 +206,7 @@
     ("i64.extend32_s",      "makeUnary(UnaryOp::ExtendS32Int64)"),
     # atomic instructions
     ("memory.atomic.notify",    "makeAtomicNotify()"),
+    ("struct.wait",             "makeStructWait()"),
     ("memory.atomic.wait32",    "makeAtomicWait(Type::i32)"),
     ("memory.atomic.wait64",    "makeAtomicWait(Type::i64)"),
     ("atomic.fence",            "makeAtomicFence()"),

src/gen-s-parser.inc

@@ -5400,6 +5400,12 @@ switch (buf[0]) {
                   return Ok{};
                 }
                 goto parse_error;
+              case 'w':
+                if (op == "struct.wait"sv) {
+                  CHECK_ERR(makeStructWait(ctx, pos, annotations));
+                  return Ok{};
+                }
+                goto parse_error;
               default: goto parse_error;
             }
           }

src/interpreter/interpreter.cpp

@@ -254,6 +254,7 @@ struct ExpressionInterpreter : OverriddenVisitor<ExpressionInterpreter, Flow> {
   Flow visitStructSet(StructSet* curr) { WASM_UNREACHABLE("TODO"); }
   Flow visitStructRMW(StructRMW* curr) { WASM_UNREACHABLE("TODO"); }
   Flow visitStructCmpxchg(StructCmpxchg* curr) { WASM_UNREACHABLE("TODO"); }
+  Flow visitStructWait(StructWait* curr) { WASM_UNREACHABLE("TODO"); }
   Flow visitArrayNew(ArrayNew* curr) { WASM_UNREACHABLE("TODO"); }
   Flow visitArrayNewData(ArrayNewData* curr) { WASM_UNREACHABLE("TODO"); }
   Flow visitArrayNewElem(ArrayNewElem* curr) { WASM_UNREACHABLE("TODO"); }

src/ir/ReFinalize.cpp

@@ -163,6 +163,7 @@ void ReFinalize::visitStructGet(StructGet* curr) { curr->finalize(); }
 void ReFinalize::visitStructSet(StructSet* curr) { curr->finalize(); }
 void ReFinalize::visitStructRMW(StructRMW* curr) { curr->finalize(); }
 void ReFinalize::visitStructCmpxchg(StructCmpxchg* curr) { curr->finalize(); }
+void ReFinalize::visitStructWait(StructWait* curr) { curr->finalize(); }
 void ReFinalize::visitArrayNew(ArrayNew* curr) { curr->finalize(); }
 void ReFinalize::visitArrayNewData(ArrayNewData* curr) { curr->finalize(); }
 void ReFinalize::visitArrayNewElem(ArrayNewElem* curr) { curr->finalize(); }

src/ir/child-typer.h

@@ -1007,6 +1007,21 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
     note(&curr->replacement, type);
   }
 
+  void visitStructWait(StructWait* curr,
+                       std::optional<HeapType> ht = std::nullopt) {
+    if (!ht) {
+      if (!curr->ref->type.isStruct()) {
+        self().noteUnknown();
+        return;
+      }
+      ht = curr->ref->type.getHeapType();
+    }
+
+    note(&curr->ref, Type(*ht, Nullable));
+    note(&curr->expected, Type(Type::BasicType::i32));
+    note(&curr->timeout, Type(Type::BasicType::i64));
+  }
+
   void visitArrayNew(ArrayNew* curr) {
     if (!curr->isWithDefault()) {
       if (!curr->type.isRef()) {

src/ir/cost.h

@@ -118,6 +118,10 @@ struct CostAnalyzer : public OverriddenVisitor<CostAnalyzer, CostType> {
     return AtomicCost + visit(curr->ptr) + visit(curr->expected) +
            visit(curr->timeout);
   }
+  CostType visitStructWait(StructWait* curr) {
+    return AtomicCost + nullCheckCost(curr->ref) + visit(curr->ref) +
+           visit(curr->expected) + visit(curr->timeout);
+  }
   CostType visitAtomicNotify(AtomicNotify* curr) {
     return AtomicCost + visit(curr->ptr) + visit(curr->notifyCount);
   }

src/ir/effects.h

@@ -949,6 +949,39 @@ class EffectAnalyzer {
       assert(curr->order != MemoryOrder::Unordered);
       parent.isAtomic = true;
     }
+    void visitStructWait(StructWait* curr) {
+      parent.isAtomic = true;
+
+      // If the ref is null.
+      parent.implicitTrap = true;
+
+      // If the timeout is negative and no-one wakes us.
+      parent.mayNotReturn = true;
+
+      // struct.wait mutates an opaque waiter queue which isn't visible in user
+      // code. Model this as a struct write which prevents reorderings (since
+      // isAtomic == true).
+      parent.writesStruct = true;
+
+      if (curr->ref->type == Type::unreachable) {
+        return;
+      }
+
+      // If the ref isn't `unreachable`, then the field must exist and be a
+      // packed waitqueue due to validation.
+      assert(curr->ref->type.isStruct());
+      assert(curr->index <
+             curr->ref->type.getHeapType().getStruct().fields.size());
+      assert(curr->ref->type.getHeapType()
+               .getStruct()
+               .fields.at(curr->index)
+               .packedType == Field::PackedType::WaitQueue);
+
+      parent.readsMutableStruct |= curr->ref->type.getHeapType()
+                                     .getStruct()
+                                     .fields.at(curr->index)
+                                     .mutable_ == Mutable;
+    }
     void visitArrayNew(ArrayNew* curr) {}
     void visitArrayNewData(ArrayNewData* curr) {
       // Traps on out of bounds access to segments or access to dropped

src/ir/module-utils.cpp

@@ -427,6 +427,7 @@ struct CodeScanner : PostWalker<CodeScanner> {
   }
   void visitStructGet(StructGet* curr) { info.note(curr->ref->type); }
   void visitStructSet(StructSet* curr) { info.note(curr->ref->type); }
+  void visitStructWait(StructWait* curr) { info.note(curr->ref->type); }
   void visitArrayGet(ArrayGet* curr) { info.note(curr->ref->type); }
   void visitArraySet(ArraySet* curr) { info.note(curr->ref->type); }
   void visitContBind(ContBind* curr) {

src/ir/possible-constant.h

@@ -121,7 +121,7 @@ struct PossibleConstantValues {
         }
         break;
       case Field::WaitQueue:
-        WASM_UNREACHABLE("waitqueue not implemented");
+        value = val;
         break;
       case Field::NotPacked:
         WASM_UNREACHABLE("unexpected packed type");

src/ir/possible-contents.cpp

@@ -1080,6 +1080,7 @@ struct InfoCollector
     // the write.
     addRoot(curr);
   }
+  void visitStructWait(StructWait* curr) { addRoot(curr); }
   // Array operations access the array's location, parallel to how structs work.
   void visitArrayGet(ArrayGet* curr) {
     if (!isRelevant(curr->ref)) {

src/ir/subtype-exprs.h

@@ -372,6 +372,7 @@ struct SubtypingDiscoverer : public OverriddenVisitor<SubType> {
                         type.isRef() ? Type(HeapType::eq, Nullable) : type);
     self()->noteSubtype(curr->replacement, type);
   }
+  void visitStructWait(StructWait* curr) {}
   void visitArrayNew(ArrayNew* curr) {
     if (!curr->type.isArray() || curr->isWithDefault()) {
       return;

src/parser/contexts.h

@@ -804,6 +804,11 @@ struct NullInstrParserCtx {
     return Ok{};
   }
   template<typename HeapTypeT>
+  Result<>
+  makeStructWait(Index, const std::vector<Annotation>&, HeapTypeT, FieldIdxT) {
+    return Ok{};
+  }
+  template<typename HeapTypeT>
   Result<> makeArrayNew(Index, const std::vector<Annotation>&, HeapTypeT) {
     return Ok{};
   }
@@ -2712,6 +2717,13 @@ struct ParseDefsCtx : TypeParserCtx<ParseDefsCtx>, AnnotationParserCtx {
     return withLoc(pos, irBuilder.makeStructCmpxchg(type, field, order));
   }
 
+  Result<> makeStructWait(Index pos,
+                          const std::vector<Annotation>& annotations,
+                          HeapType type,
+                          Index field) {
+    return withLoc(pos, irBuilder.makeStructWait(type, field));
+  }
+
   Result<> makeArrayNew(Index pos,
                         const std::vector<Annotation>& annotations,
                         HeapType type) {

src/parser/parsers.h

@@ -2482,6 +2482,17 @@ Result<> makeStructCmpxchg(Ctx& ctx,
   return ctx.makeStructCmpxchg(pos, annotations, *type, *field, *order1);
 }
 
+template<typename Ctx>
+Result<> makeStructWait(Ctx& ctx,
+                        Index pos,
+                        const std::vector<Annotation>& annotations) {
+  auto type = typeidx(ctx);
+  CHECK_ERR(type);
+  auto field = fieldidx(ctx, *type);
+  CHECK_ERR(field);
+  return ctx.makeStructWait(pos, annotations, *type, *field);
+}
+
 template<typename Ctx>
 Result<> makeArrayNew(Ctx& ctx,
                       Index pos,

src/passes/Print.cpp

@@ -2404,6 +2404,13 @@ struct PrintExpressionContents
     o << ' ';
     printFieldName(heapType, curr->index);
   }
+  void visitStructWait(StructWait* curr) {
+    printMedium(o, "struct.wait");
+    o << ' ';
+    printHeapTypeName(curr->ref->type.getHeapType());
+    o << ' ';
+    o << curr->index;
+  }
   void visitArrayNew(ArrayNew* curr) {
     printMedium(o, "array.new");
     if (curr->isWithDefault()) {

src/passes/TypeGeneralizing.cpp

@@ -697,6 +697,8 @@ struct TransferFn : OverriddenVisitor<TransferFn> {
 
   void visitStructCmpxchg(StructCmpxchg* curr) { WASM_UNREACHABLE("TODO"); }
 
+  void visitStructWait(StructWait* curr) { WASM_UNREACHABLE("TODO"); }
+
   void visitArrayNew(ArrayNew* curr) {
     // We cannot yet generalize allocations. Push a requirement for the
     // reference type needed to initialize the array, if any.

src/wasm-binary.h

@@ -702,6 +702,7 @@ enum ASTNodes {
   I64AtomicWait = 0x02,
   AtomicFence = 0x03,
   Pause = 0x04,
+  StructWait = 0x05,
 
   I32AtomicLoad = 0x10,
   I64AtomicLoad = 0x11,

src/wasm-builder.h

@@ -1363,6 +1363,19 @@ class Builder {
     return ret;
   }
 
+  StructWait* makeStructWait(Index index,
+                             Expression* ref,
+                             Expression* expected,
+                             Expression* timeout) {
+    auto* ret = wasm.allocator.alloc<StructWait>();
+    ret->index = index;
+    ret->ref = ref;
+    ret->expected = expected;
+    ret->timeout = timeout;
+    ret->finalize();
+    return ret;
+  }
+
   // Additional helpers
 
   Drop* makeDrop(Expression* value) {

src/wasm-delegations-fields.def

@@ -887,6 +887,13 @@ DELEGATE_FIELD_CHILD_VECTOR(StackSwitch, operands)
 DELEGATE_FIELD_NAME_KIND(StackSwitch, tag, ModuleItemKind::Tag)
 DELEGATE_FIELD_CASE_END(StackSwitch)
 
+DELEGATE_FIELD_CASE_START(StructWait)
+DELEGATE_FIELD_CHILD(StructWait, timeout)
+DELEGATE_FIELD_CHILD(StructWait, expected)
+DELEGATE_FIELD_IMMEDIATE_TYPED_CHILD(StructWait, ref)
+DELEGATE_FIELD_INT(StructWait, index)
+DELEGATE_FIELD_CASE_END(StructWait)
+
 
 DELEGATE_FIELD_MAIN_END
 

src/wasm-delegations.def

@@ -115,5 +115,6 @@ DELEGATE(Suspend);
 DELEGATE(Resume);
 DELEGATE(ResumeThrow);
 DELEGATE(StackSwitch);
+DELEGATE(StructWait);
 
 #undef DELEGATE

src/wasm-interpreter.h

@@ -2243,6 +2243,11 @@ class ExpressionRunner : public OverriddenVisitor<SubType, Flow> {
     return oldVal;
   }
 
+  Flow visitStructWait(StructWait* curr) {
+    WASM_UNREACHABLE("struct.wait not implemented");
+    return Flow();
+  }
+
   // Arbitrary deterministic limit on size. If we need to allocate a Literals
   // vector that takes around 1-2GB of memory then we are likely to hit memory
   // limits on 32-bit machines, and in particular on wasm32 VMs that do not
@@ -2899,6 +2904,7 @@ class ConstantExpressionRunner : public ExpressionRunner<SubType> {
   }
   Flow visitAtomicWait(AtomicWait* curr) { return Flow(NONCONSTANT_FLOW); }
   Flow visitAtomicNotify(AtomicNotify* curr) { return Flow(NONCONSTANT_FLOW); }
+  Flow visitStructWait(StructWait* curr) { return Flow(NONCONSTANT_FLOW); }
   Flow visitSIMDLoad(SIMDLoad* curr) { return Flow(NONCONSTANT_FLOW); }
   Flow visitSIMDLoadSplat(SIMDLoad* curr) { return Flow(NONCONSTANT_FLOW); }
   Flow visitSIMDLoadExtend(SIMDLoad* curr) { return Flow(NONCONSTANT_FLOW); }

src/wasm-ir-builder.h

@@ -242,6 +242,7 @@ class IRBuilder : public UnifiedExpressionVisitor<IRBuilder, Result<>> {
   Result<>
   makeStructRMW(AtomicRMWOp op, HeapType type, Index field, MemoryOrder order);
   Result<> makeStructCmpxchg(HeapType type, Index field, MemoryOrder order);
+  Result<> makeStructWait(HeapType type, Index index);
   Result<> makeArrayNew(HeapType type);
   Result<> makeArrayNewDefault(HeapType type);
   Result<> makeArrayNewData(HeapType type, Name data);

src/wasm.h

@@ -758,8 +758,8 @@ class Expression {
     SuspendId,
     ResumeId,
     ResumeThrowId,
-    // Id for the stack switching `switch`
     StackSwitchId,
+    StructWaitId,
     NumExpressionIds
   };
   Id _id;
@@ -1758,6 +1758,19 @@ class StructCmpxchg : public SpecificExpression<Expression::StructCmpxchgId> {
   void finalize();
 };
 
+class StructWait : public SpecificExpression<Expression::StructWaitId> {
+public:
+  StructWait() = default;
+  StructWait(MixedArena& allocator) : StructWait() {}
+
+  Expression* ref;
+  Expression* expected;
+  Expression* timeout;
+  Index index;
+
+  void finalize();
+};
+
 class ArrayNew : public SpecificExpression<Expression::ArrayNewId> {
 public:
   ArrayNew() = default;

src/wasm/wasm-binary.cpp

@@ -3913,6 +3913,11 @@ Result<> WasmBinaryReader::readInst() {
           auto type = getIndexedHeapType();
           return builder.makeArrayCmpxchg(type, order);
         }
+        case BinaryConsts::StructWait: {
+          auto structType = getIndexedHeapType();
+          auto index = getU32LEB();
+          return builder.makeStructWait(structType, index);
+        }
       }
       return Err{"unknown atomic operation " + std::to_string(op)};
     }

src/wasm/wasm-ir-builder.cpp

@@ -536,6 +536,13 @@ struct IRBuilder::ChildPopper
     return popConstrainedChildren(children);
   }
 
+  Result<> visitStructWait(StructWait* curr,
+                           std::optional<HeapType> structType = std::nullopt) {
+    std::vector<Child> children;
+    ConstraintCollector{builder, children}.visitStructWait(curr, structType);
+    return popConstrainedChildren(children);
+  }
+
   Result<> visitArrayGet(ArrayGet* curr,
                          std::optional<HeapType> ht = std::nullopt) {
     std::vector<Child> children;
@@ -2237,6 +2244,19 @@ IRBuilder::makeStructCmpxchg(HeapType type, Index field, MemoryOrder order) {
   return Ok{};
 }
 
+Result<> IRBuilder::makeStructWait(HeapType type, Index index) {
+  if (!type.isStruct()) {
+    return Err{"expected struct type annotation on struct.wait"};
+  }
+  StructWait curr(wasm.allocator);
+  curr.index = index;
+  CHECK_ERR(ChildPopper{*this}.visitStructWait(&curr, type));
+  CHECK_ERR(validateTypeAnnotation(type, curr.ref));
+  push(
+    builder.makeStructWait(curr.index, curr.ref, curr.expected, curr.timeout));
+  return Ok{};
+}
+
 Result<> IRBuilder::makeArrayNew(HeapType type) {
   if (!type.isArray()) {
     return Err{"expected array type annotation on array.new"};

src/wasm/wasm-stack.cpp

@@ -2516,6 +2516,17 @@ void BinaryInstWriter::visitStructCmpxchg(StructCmpxchg* curr) {
   o << U32LEB(curr->index);
 }
 
+void BinaryInstWriter::visitStructWait(StructWait* curr) {
+  if (curr->ref->type.isNull()) {
+    emitUnreachable();
+    return;
+  }
+  o << static_cast<int8_t>(BinaryConsts::AtomicPrefix)
+    << U32LEB(BinaryConsts::StructWait);
+  parent.writeIndexedHeapType(curr->ref->type.getHeapType());
+  o << U32LEB(curr->index);
+}
+
 void BinaryInstWriter::visitArrayNew(ArrayNew* curr) {
   o << int8_t(BinaryConsts::GCPrefix);
   if (curr->isWithDefault()) {

src/wasm/wasm-type.cpp

@@ -1488,8 +1488,7 @@ unsigned Field::getByteSize() const {
     case Field::PackedType::NotPacked:
       return 4;
     case Field::PackedType::WaitQueue:
-      WASM_UNREACHABLE("waitqueue not implemented");
-      break;
+      return 4;
   }
   WASM_UNREACHABLE("impossible packed type");
 }