Index: wasm/Writer.cpp
===================================================================
--- wasm/Writer.cpp
+++ wasm/Writer.cpp
@@ -261,7 +261,7 @@
   raw_ostream &OS = Section->getStream();
 
   writeUleb128(OS, 1, "table count");
-  writeSleb128(OS, WASM_TYPE_ANYFUNC, "table type");
+  writeU8(OS, WASM_TYPE_ANYFUNC, "table type");
   writeUleb128(OS, WASM_LIMITS_FLAG_HAS_MAX, "table flags");
   writeUleb128(OS, TableSize, "table initial size");
   writeUleb128(OS, TableSize, "table max size");
@@ -427,7 +427,7 @@
       WasmSymbolType Kind = Sym->getWasmType();
       uint32_t Flags = getWasmFlags(Sym);
 
-      writeUleb128(Sub.OS, Kind, "sym kind");
+      writeU8(Sub.OS, Kind, "sym kind");
       writeUleb128(Sub.OS, Flags, "sym flags");
 
       switch (Kind) {
@@ -503,7 +503,7 @@
       writeUleb128(Sub.OS, 0, "comdat flags"); // flags for future use
       writeUleb128(Sub.OS, C.second.size(), "num entries");
       for (const ComdatEntry &Entry : C.second) {
-        writeUleb128(Sub.OS, Entry.Kind, "entry kind");
+        writeU8(Sub.OS, Entry.Kind, "entry kind");
         writeUleb128(Sub.OS, Entry.Index, "entry index");
       }
     }
Index: wasm/WriterUtils.h
===================================================================
--- wasm/WriterUtils.h
+++ wasm/WriterUtils.h
@@ -44,19 +44,19 @@
 
 void debugWrite(uint64_t Offset, const Twine &Msg);
 
-void writeUleb128(raw_ostream &OS, uint32_t Number, StringRef Msg);
+void writeUleb128(raw_ostream &OS, uint32_t Number, const Twine &Msg);
 
-void writeSleb128(raw_ostream &OS, int32_t Number, StringRef Msg);
+void writeSleb128(raw_ostream &OS, int32_t Number, const Twine &Msg);
 
-void writeBytes(raw_ostream &OS, const char *Bytes, size_t count, StringRef Msg);
+void writeBytes(raw_ostream &OS, const char *Bytes, size_t count, const Twine &Msg);
 
-void writeStr(raw_ostream &OS, StringRef String, StringRef Msg);
+void writeStr(raw_ostream &OS, StringRef String, const Twine &Msg);
 
-void writeU8(raw_ostream &OS, uint8_t byte, StringRef Msg);
+void writeU8(raw_ostream &OS, uint8_t byte, const Twine &Msg);
 
-void writeU32(raw_ostream &OS, uint32_t Number, StringRef Msg);
+void writeU32(raw_ostream &OS, uint32_t Number, const Twine &Msg);
 
-void writeValueType(raw_ostream &OS, int32_t Type, StringRef Msg);
+void writeValueType(raw_ostream &OS, uint8_t Type, const Twine &Msg);
 
 void writeSig(raw_ostream &OS, const llvm::wasm::WasmSignature &Sig);
 
Index: wasm/WriterUtils.cpp
===================================================================
--- wasm/WriterUtils.cpp
+++ wasm/WriterUtils.cpp
@@ -40,51 +40,54 @@
   DEBUG(dbgs() << format("  | %08lld: ", Offset) << Msg << "\n");
 }
 
-void wasm::writeUleb128(raw_ostream &OS, uint32_t Number, StringRef Msg) {
+void wasm::writeUleb128(raw_ostream &OS, uint32_t Number, const Twine &Msg) {
   debugWrite(OS.tell(), Msg + "[" + utohexstr(Number) + "]");
   encodeULEB128(Number, OS);
 }
 
-void wasm::writeSleb128(raw_ostream &OS, int32_t Number, StringRef Msg) {
+void wasm::writeSleb128(raw_ostream &OS, int32_t Number, const Twine &Msg) {
   debugWrite(OS.tell(), Msg + "[" + utohexstr(Number) + "]");
   encodeSLEB128(Number, OS);
 }
 
 void wasm::writeBytes(raw_ostream &OS, const char *Bytes, size_t Count,
-                      StringRef Msg) {
+                      const Twine &Msg) {
   debugWrite(OS.tell(), Msg + " [data[" + Twine(Count) + "]]");
   OS.write(Bytes, Count);
 }
 
-void wasm::writeStr(raw_ostream &OS, StringRef String, StringRef Msg) {
+void wasm::writeStr(raw_ostream &OS, StringRef String, const Twine &Msg) {
   debugWrite(OS.tell(),
              Msg + " [str[" + Twine(String.size()) + "]: " + String + "]");
   encodeULEB128(String.size(), OS);
   OS.write(String.data(), String.size());
 }
 
-void wasm::writeU8(raw_ostream &OS, uint8_t Byte, StringRef Msg) { OS << Byte; }
+void wasm::writeU8(raw_ostream &OS, uint8_t Byte, const Twine &Msg) {
+  debugWrite(OS.tell(), Msg + " [0x" + utohexstr(Byte) + "]");
+  OS << Byte;
+}
 
-void wasm::writeU32(raw_ostream &OS, uint32_t Number, StringRef Msg) {
+void wasm::writeU32(raw_ostream &OS, uint32_t Number, const Twine &Msg) {
   debugWrite(OS.tell(), Msg + "[" + utohexstr(Number) + "]");
   support::endian::Writer<support::little>(OS).write(Number);
 }
 
-void wasm::writeValueType(raw_ostream &OS, int32_t Type, StringRef Msg) {
-  debugWrite(OS.tell(), Msg + "[type: " + valueTypeToString(Type) + "]");
-  encodeSLEB128(Type, OS);
+void wasm::writeValueType(raw_ostream &OS, uint8_t Type, const Twine &Msg) {
+  writeU8(OS, Type, Twine(Msg) + "[type: " + valueTypeToString(Type) + "]");
 }
 
 void wasm::writeSig(raw_ostream &OS, const WasmSignature &Sig) {
-  writeSleb128(OS, WASM_TYPE_FUNC, "signature type");
+  writeU8(OS, WASM_TYPE_FUNC, "signature type");
   writeUleb128(OS, Sig.ParamTypes.size(), "param Count");
-  for (int32_t ParamType : Sig.ParamTypes) {
+
+  for (uint8_t ParamType : Sig.ParamTypes)
     writeValueType(OS, ParamType, "param type");
-  }
+
   if (Sig.ReturnType == WASM_TYPE_NORESULT) {
-    writeUleb128(OS, 0, "result Count");
+    writeU8(OS, 0, "result Count");
   } else {
-    writeUleb128(OS, 1, "result Count");
+    writeU8(OS, 1, "result Count");
     writeValueType(OS, Sig.ReturnType, "result type");
   }
 }