6 files changed, 32 insertions, 2 deletions
diff --git a/src/ir/cost.h b/src/ir/cost.h
index 823e58ded..ff9bade10 100644
--- a/src/ir/cost.h
+++ b/src/ir/cost.h
@@ -660,7 +660,8 @@ struct CostAnalyzer : public OverriddenVisitor<CostAnalyzer, CostType> {
   }
   CostType visitRefAs(RefAs* curr) { return 1 + visit(curr->value); }
   CostType visitStringNew(StringNew* curr) {
-    return 8 + visit(curr->ptr) + maybeVisit(curr->length);
+    return 8 + visit(curr->ptr) + maybeVisit(curr->length) +
+           maybeVisit(curr->start) + maybeVisit(curr->end);
   }
   CostType visitStringConst(StringConst* curr) { return 4; }
   CostType visitStringMeasure(StringMeasure* curr) {
diff --git a/src/wasm-builder.h b/src/wasm-builder.h
index 1faf95d73..3677b9796 100644
--- a/src/wasm-builder.h
+++ b/src/wasm-builder.h
@@ -934,6 +934,18 @@ public:
     ret->finalize();
     return ret;
   }
+  StringNew* makeStringNew(StringNewOp op,
+                           Expression* ptr,
+                           Expression* start,
+                           Expression* end) {
+    auto* ret = wasm.allocator.alloc<StringNew>();
+    ret->op = op;
+    ret->ptr = ptr;
+    ret->start = start;
+    ret->end = end;
+    ret->finalize();
+    return ret;
+  }
   StringConst* makeStringConst(Name string) {
     auto* ret = wasm.allocator.alloc<StringConst>();
     ret->string = string;
diff --git a/src/wasm-delegations-fields.def b/src/wasm-delegations-fields.def
index fa1fa229f..0e3f60826 100644
--- a/src/wasm-delegations-fields.def
+++ b/src/wasm-delegations-fields.def
@@ -698,6 +698,8 @@ switch (DELEGATE_ID) {
   case Expression::Id::StringNewId: {
     DELEGATE_START(StringNew);
     DELEGATE_FIELD_INT(StringNew, op);
+    DELEGATE_FIELD_OPTIONAL_CHILD(StringNew, end);
+    DELEGATE_FIELD_OPTIONAL_CHILD(StringNew, start);
     DELEGATE_FIELD_OPTIONAL_CHILD(StringNew, length);
     DELEGATE_FIELD_CHILD(StringNew, ptr);
     DELEGATE_END(StringNew);
diff --git a/src/wasm.h b/src/wasm.h
index d0f632829..04d4391a2 100644
--- a/src/wasm.h
+++ b/src/wasm.h
@@ -1657,6 +1657,10 @@ public:
   // Used only in linear memory variations.
   Expression* length = nullptr;
 
+  // Used only in GC variations.
+  Expression* start = nullptr;
+  Expression* end = nullptr;
+
   void finalize();
 };
 
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index b74ef017b..44b07f945 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -6981,6 +6981,8 @@ bool WasmBinaryBuilder::maybeVisitArrayCopy(Expression*& out, uint32_t code) {
 bool WasmBinaryBuilder::maybeVisitStringNew(Expression*& out, uint32_t code) {
   StringNewOp op;
   Expression* length = nullptr;
+  Expression* start = nullptr;
+  Expression* end = nullptr;
   if (code == BinaryConsts::StringNewWTF8) {
     auto policy = getU32LEB();
     switch (policy) {
@@ -7015,13 +7017,19 @@ bool WasmBinaryBuilder::maybeVisitStringNew(Expression*& out, uint32_t code) {
       default:
         throwError("bad policy for string.new");
     }
+    end = popNonVoidExpression();
+    start = popNonVoidExpression();
   } else if (code == BinaryConsts::StringNewWTF16Array) {
     op = StringNewWTF16Array;
   } else {
     return false;
   }
   auto* ptr = popNonVoidExpression();
-  out = Builder(wasm).makeStringNew(op, ptr, length);
+  if (length) {
+    out = Builder(wasm).makeStringNew(op, ptr, length);
+  } else {
+    out = Builder(wasm).makeStringNew(op, ptr, start, end);
+  }
   return true;
 }
 
diff --git a/src/wasm/wasm-s-parser.cpp b/src/wasm/wasm-s-parser.cpp
index f13091c91..c1285c647 100644
--- a/src/wasm/wasm-s-parser.cpp
+++ b/src/wasm/wasm-s-parser.cpp
@@ -2837,6 +2837,9 @@ Expression* SExpressionWasmBuilder::makeStringNew(Element& s, StringNewOp op) {
     } else {
       throw ParseException("bad string.new op", s.line, s.col);
     }
+    auto* start = parseExpression(s[i + 1]);
+    auto* end = parseExpression(s[i + 2]);
+    return Builder(wasm).makeStringNew(op, parseExpression(s[i]), start, end);
   }
   return Builder(wasm).makeStringNew(op, parseExpression(s[i]), length);
 }