diff --git a/llvm/include/llvm/Demangle/Demangle.h b/llvm/include/llvm/Demangle/Demangle.h
--- a/llvm/include/llvm/Demangle/Demangle.h
+++ b/llvm/include/llvm/Demangle/Demangle.h
@@ -28,8 +28,7 @@
   demangle_success = 0,
 };
 
-char *itaniumDemangle(const char *mangled_name, char *buf, size_t *n,
-                      int *status);
+char *itaniumDemangle(const char *mangled_name, int *status);
 
 enum MSDemangleFlags {
   MSDF_None = 0,
diff --git a/llvm/lib/Demangle/Demangle.cpp b/llvm/lib/Demangle/Demangle.cpp
--- a/llvm/lib/Demangle/Demangle.cpp
+++ b/llvm/lib/Demangle/Demangle.cpp
@@ -48,7 +48,7 @@
 bool llvm::nonMicrosoftDemangle(const char *MangledName, std::string &Result) {
   char *Demangled = nullptr;
   if (isItaniumEncoding(MangledName))
-    Demangled = itaniumDemangle(MangledName, nullptr, nullptr, nullptr);
+    Demangled = itaniumDemangle(MangledName, nullptr);
   else if (isRustEncoding(MangledName))
     Demangled = rustDemangle(MangledName);
   else if (isDLangEncoding(MangledName))
diff --git a/llvm/lib/Demangle/ItaniumDemangle.cpp b/llvm/lib/Demangle/ItaniumDemangle.cpp
--- a/llvm/lib/Demangle/ItaniumDemangle.cpp
+++ b/llvm/lib/Demangle/ItaniumDemangle.cpp
@@ -365,9 +365,8 @@
 
 using Demangler = itanium_demangle::ManglingParser<DefaultAllocator>;
 
-char *llvm::itaniumDemangle(const char *MangledName, char *Buf,
-                            size_t *N, int *Status) {
-  if (MangledName == nullptr || (Buf != nullptr && N == nullptr)) {
+char *llvm::itaniumDemangle(const char *MangledName, int *Status) {
+  if (MangledName == nullptr) {
     if (Status)
       *Status = demangle_invalid_args;
     return nullptr;
@@ -377,15 +376,14 @@
   Demangler Parser(MangledName, MangledName + std::strlen(MangledName));
   Node *AST = Parser.parse();
 
+  char *Buf;
   if (AST == nullptr)
     InternalStatus = demangle_invalid_mangled_name;
   else {
-    OutputBuffer OB(Buf, N);
+    OutputBuffer OB;
     assert(Parser.ForwardTemplateRefs.empty());
     AST->print(OB);
     OB += '\0';
-    if (N != nullptr)
-      *N = OB.getCurrentPosition();
     Buf = OB.getBuffer();
   }
 
diff --git a/llvm/lib/ProfileData/GCOV.cpp b/llvm/lib/ProfileData/GCOV.cpp
--- a/llvm/lib/ProfileData/GCOV.cpp
+++ b/llvm/lib/ProfileData/GCOV.cpp
@@ -339,7 +339,7 @@
       if (Name.startswith("_Z")) {
         int status = 0;
         // Name is guaranteed to be NUL-terminated.
-        char *res = itaniumDemangle(Name.data(), nullptr, nullptr, &status);
+        char *res = itaniumDemangle(Name.data(), &status);
         if (status == 0) {
           demangled = res;
           free(res);
diff --git a/llvm/lib/Support/Unix/Signals.inc b/llvm/lib/Support/Unix/Signals.inc
--- a/llvm/lib/Support/Unix/Signals.inc
+++ b/llvm/lib/Support/Unix/Signals.inc
@@ -653,7 +653,7 @@
     if (dlinfo.dli_sname != nullptr) {
       OS << ' ';
       int res;
-      char *d = itaniumDemangle(dlinfo.dli_sname, nullptr, nullptr, &res);
+      char *d = itaniumDemangle(dlinfo.dli_sname, &res);
       if (!d)
         OS << dlinfo.dli_sname;
       else
diff --git a/llvm/tools/llvm-cxxfilt/llvm-cxxfilt.cpp b/llvm/tools/llvm-cxxfilt/llvm-cxxfilt.cpp
--- a/llvm/tools/llvm-cxxfilt/llvm-cxxfilt.cpp
+++ b/llvm/tools/llvm-cxxfilt/llvm-cxxfilt.cpp
@@ -84,11 +84,11 @@
   char *Undecorated = nullptr;
 
   if (Types)
-    Undecorated = itaniumDemangle(DecoratedStr, nullptr, nullptr, nullptr);
+    Undecorated = itaniumDemangle(DecoratedStr, nullptr);
 
   if (!Undecorated && strncmp(DecoratedStr, "__imp_", 6) == 0) {
     Prefix = "import thunk for ";
-    Undecorated = itaniumDemangle(DecoratedStr + 6, nullptr, nullptr, nullptr);
+    Undecorated = itaniumDemangle(DecoratedStr + 6, nullptr);
   }
 
   Result = Undecorated ? Prefix + Undecorated : Mangled;
diff --git a/llvm/tools/llvm-itanium-demangle-fuzzer/llvm-itanium-demangle-fuzzer.cpp b/llvm/tools/llvm-itanium-demangle-fuzzer/llvm-itanium-demangle-fuzzer.cpp
--- a/llvm/tools/llvm-itanium-demangle-fuzzer/llvm-itanium-demangle-fuzzer.cpp
+++ b/llvm/tools/llvm-itanium-demangle-fuzzer/llvm-itanium-demangle-fuzzer.cpp
@@ -15,8 +15,8 @@
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
   std::string NullTerminatedString((const char *)Data, Size);
   int status = 0;
-  if (char *demangle = llvm::itaniumDemangle(NullTerminatedString.c_str(), nullptr,
-                                         nullptr, &status))
+  if (char *demangle =
+          llvm::itaniumDemangle(NullTerminatedString.c_str(), &status))
     free(demangle);
 
   return 0;
diff --git a/llvm/tools/llvm-objdump/MachODump.cpp b/llvm/tools/llvm-objdump/MachODump.cpp
--- a/llvm/tools/llvm-objdump/MachODump.cpp
+++ b/llvm/tools/llvm-objdump/MachODump.cpp
@@ -7281,8 +7281,7 @@
       if (info->demangled_name != nullptr)
         free(info->demangled_name);
       int status;
-      info->demangled_name =
-          itaniumDemangle(SymbolName + 1, nullptr, nullptr, &status);
+      info->demangled_name = itaniumDemangle(SymbolName + 1, &status);
       if (info->demangled_name != nullptr) {
         *ReferenceName = info->demangled_name;
         *ReferenceType = LLVMDisassembler_ReferenceType_DeMangled_Name;
@@ -7381,8 +7380,7 @@
     if (info->demangled_name != nullptr)
       free(info->demangled_name);
     int status;
-    info->demangled_name =
-        itaniumDemangle(SymbolName + 1, nullptr, nullptr, &status);
+    info->demangled_name = itaniumDemangle(SymbolName + 1, &status);
     if (info->demangled_name != nullptr) {
       *ReferenceName = info->demangled_name;
       *ReferenceType = LLVMDisassembler_ReferenceType_DeMangled_Name;
diff --git a/llvm/tools/llvm-opt-report/OptReport.cpp b/llvm/tools/llvm-opt-report/OptReport.cpp
--- a/llvm/tools/llvm-opt-report/OptReport.cpp
+++ b/llvm/tools/llvm-opt-report/OptReport.cpp
@@ -339,8 +339,7 @@
             bool Printed = false;
             if (!NoDemangle) {
               int Status = 0;
-              char *Demangled =
-                itaniumDemangle(FuncName.c_str(), nullptr, nullptr, &Status);
+              char *Demangled = itaniumDemangle(FuncName.c_str(), &Status);
               if (Demangled && Status == 0) {
                 OS << Demangled;
                 Printed = true;