Index: tools/llvm-xray/func-id-helper.h
===================================================================
--- tools/llvm-xray/func-id-helper.h
+++ tools/llvm-xray/func-id-helper.h
@@ -13,6 +13,7 @@
 #ifndef LLVM_TOOLS_LLVM_XRAY_FUNC_ID_HELPER_H
 #define LLVM_TOOLS_LLVM_XRAY_FUNC_ID_HELPER_H
 
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/DebugInfo/Symbolize/Symbolize.h"
 #include <unordered_map>
 
@@ -28,6 +29,7 @@
   std::string BinaryInstrMap;
   symbolize::LLVMSymbolizer &Symbolizer;
   const FunctionAddressMap &FunctionAddresses;
+  mutable llvm::DenseMap<int32_t, std::string> CachedNames;
 
 public:
   FuncIdConversionHelper(std::string BinaryInstrMap,
Index: tools/llvm-xray/func-id-helper.cc
===================================================================
--- tools/llvm-xray/func-id-helper.cc
+++ tools/llvm-xray/func-id-helper.cc
@@ -19,6 +19,10 @@
 using namespace xray;
 
 std::string FuncIdConversionHelper::SymbolOrNumber(int32_t FuncId) const {
+  auto CacheIt = CachedNames.find(FuncId);
+  if (CacheIt != CachedNames.end())
+    return CacheIt->second;
+
   std::ostringstream F;
   auto It = FunctionAddresses.find(FuncId);
   if (It == FunctionAddresses.end()) {
@@ -37,7 +41,9 @@
       F << "@(" << std::hex << It->second << ")";
     });
 
-  return F.str();
+  auto S = F.str();
+  CachedNames[FuncId] = S;
+  return S;
 }
 
 std::string FuncIdConversionHelper::FileLineAndColumn(int32_t FuncId) const {