5 files changed, 49 insertions, 2 deletions
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index 7e72b056f..9aa18f270 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -2793,6 +2793,8 @@ void WasmBinaryBuilder::processNames() {
         get->table = getTableName(index);
       } else if (auto* set = ref->dynCast<TableSet>()) {
         set->table = getTableName(index);
+      } else if (auto* size = ref->dynCast<TableSize>()) {
+        size->table = getTableName(index);
       } else {
         WASM_UNREACHABLE("Invalid type in table references");
       }
@@ -3613,8 +3615,10 @@ BinaryConsts::ASTNodes WasmBinaryBuilder::readExpression(Expression*& curr) {
       if (maybeVisitMemoryFill(curr, opcode)) {
         break;
       }
-      throwError("invalid code after nontrapping float-to-int prefix: " +
-                 std::to_string(opcode));
+      if (maybeVisitTableSize(curr, opcode)) {
+        break;
+      }
+      throwError("invalid code after misc prefix: " + std::to_string(opcode));
       break;
     }
     case BinaryConsts::SIMDPrefix: {
@@ -4918,6 +4922,22 @@ bool WasmBinaryBuilder::maybeVisitMemoryFill(Expression*& out, uint32_t code) {
   return true;
 }
 
+bool WasmBinaryBuilder::maybeVisitTableSize(Expression*& out, uint32_t code) {
+  if (code != BinaryConsts::TableSize) {
+    return false;
+  }
+  Index tableIdx = getU32LEB();
+  if (tableIdx >= tables.size()) {
+    throwError("bad table index");
+  }
+  auto* curr = allocator.alloc<TableSize>();
+  curr->finalize();
+  // Defer setting the table name for later, when we know it.
+  tableRefs[tableIdx].push_back(curr);
+  out = curr;
+  return true;
+}
+
 bool WasmBinaryBuilder::maybeVisitBinary(Expression*& out, uint8_t code) {
   Binary* curr;
 #define INT_TYPED_CODE(code)                                                   \
diff --git a/src/wasm/wasm-s-parser.cpp b/src/wasm/wasm-s-parser.cpp
index 854228e9f..6c41264a6 100644
--- a/src/wasm/wasm-s-parser.cpp
+++ b/src/wasm/wasm-s-parser.cpp
@@ -2462,6 +2462,15 @@ Expression* SExpressionWasmBuilder::makeTableSet(Element& s) {
   return Builder(wasm).makeTableSet(tableName, index, value);
 }
 
+Expression* SExpressionWasmBuilder::makeTableSize(Element& s) {
+  auto tableName = s[1]->str();
+  auto* table = wasm.getTableOrNull(tableName);
+  if (!table) {
+    throw ParseException("invalid table name in table.size", s.line, s.col);
+  }
+  return Builder(wasm).makeTableSize(tableName);
+}
+
 // try can be either in the form of try-catch or try-delegate.
 // try-catch is written in the folded wast format as
 // (try
diff --git a/src/wasm/wasm-stack.cpp b/src/wasm/wasm-stack.cpp
index 8f6581956..f81a0b7a0 100644
--- a/src/wasm/wasm-stack.cpp
+++ b/src/wasm/wasm-stack.cpp
@@ -1857,6 +1857,11 @@ void BinaryInstWriter::visitTableSet(TableSet* curr) {
   o << U32LEB(parent.getTableIndex(curr->table));
 }
 
+void BinaryInstWriter::visitTableSize(TableSize* curr) {
+  o << int8_t(BinaryConsts::MiscPrefix) << U32LEB(BinaryConsts::TableSize);
+  o << U32LEB(parent.getTableIndex(curr->table));
+}
+
 void BinaryInstWriter::visitTry(Try* curr) {
   breakStack.push_back(curr->name);
   o << int8_t(BinaryConsts::Try);
diff --git a/src/wasm/wasm-validator.cpp b/src/wasm/wasm-validator.cpp
index 0e362df9c..0271884a4 100644
--- a/src/wasm/wasm-validator.cpp
+++ b/src/wasm/wasm-validator.cpp
@@ -366,6 +366,7 @@ public:
   void visitRefEq(RefEq* curr);
   void visitTableGet(TableGet* curr);
   void visitTableSet(TableSet* curr);
+  void visitTableSize(TableSize* curr);
   void noteDelegate(Name name, Expression* curr);
   void noteRethrow(Name name, Expression* curr);
   void visitTry(Try* curr);
@@ -2063,6 +2064,14 @@ void FunctionValidator::visitTableSet(TableSet* curr) {
   }
 }
 
+void FunctionValidator::visitTableSize(TableSize* curr) {
+  shouldBeTrue(getModule()->features.hasReferenceTypes(),
+               curr,
+               "table.size requires reference types to be enabled");
+  auto* table = getModule()->getTableOrNull(curr->table);
+  shouldBeTrue(!!table, curr, "table.size table must exist");
+}
+
 void FunctionValidator::noteDelegate(Name name, Expression* curr) {
   if (name != DELEGATE_CALLER_TARGET) {
     shouldBeTrue(delegateTargetNames.count(name) != 0,
diff --git a/src/wasm/wasm.cpp b/src/wasm/wasm.cpp
index 4975f4597..c42a1089d 100644
--- a/src/wasm/wasm.cpp
+++ b/src/wasm/wasm.cpp
@@ -857,6 +857,10 @@ void TableSet::finalize() {
   }
 }
 
+void TableSize::finalize() {
+  // Nothing to do - the type must have been set already during construction.
+}
+
 void Try::finalize() {
   // If none of the component bodies' type is a supertype of the others, assume
   // the current type is already correct. TODO: Calculate a proper LUB.