Bug 1733836 - Fix build issue with wasm::TagType. r=rhunt

Differential Revision: https://phabricator.services.mozilla.com/D127368

js/src/wasm/WasmModuleTypes.cpp

@@ -180,7 +180,6 @@ size_t GlobalDesc::sizeOfExcludingThis(MallocSizeOf mallocSizeOf) const {
   return initial_.sizeOfExcludingThis(mallocSizeOf);
 }
 
-#ifdef ENABLE_WASM_EXCEPTIONS
 bool TagType::computeLayout() {
   StructLayout layout;
   int32_t refCount = 0;
@@ -216,7 +215,6 @@ bool TagType::computeLayout() {
 
   return true;
 }
-#endif
 
 size_t ElemSegment::serializedSize() const {
   return sizeof(kind) + sizeof(tableIndex) + sizeof(elemType) +

js/src/wasm/WasmModuleTypes.h

@@ -279,13 +279,14 @@ using GlobalDescVector = Vector<GlobalDesc, 0, SystemAllocPolicy>;
 // A TagDesc represents fresh per-instance tags that are used for the
 // exception handling proposal and potentially other future proposals.
 
-#ifdef ENABLE_WASM_EXCEPTIONS
 // The TagOffsetVector represents the offsets in the layout of the
 // data stored in a Wasm exception. For non-reference values, it is
 // an offset in the ArrayBuffer and for reference values it is the
 // offset in the elements of the exception's ArrayObject.
 using TagOffsetVector = Vector<int32_t, 0, SystemAllocPolicy>;
 
+// Not guarded by #ifdef like TagDesc as this is required for Wasm JS
+// API classes in WasmJS.h.
 struct TagType {
   ValTypeVector argTypes;
   TagOffsetVector argOffsets;
@@ -314,6 +315,7 @@ struct TagType {
   }
 };
 
+#ifdef ENABLE_WASM_EXCEPTIONS
 struct TagDesc {
   TagKind kind;
   TagType type;