diff --git a/llvm/lib/DebugInfo/DWARF/DWARFGdbIndex.cpp b/llvm/lib/DebugInfo/DWARF/DWARFGdbIndex.cpp
--- a/llvm/lib/DebugInfo/DWARF/DWARFGdbIndex.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFGdbIndex.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/DebugInfo/DWARF/DWARFGdbIndex.h"
+#include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/DataExtractor.h"
@@ -166,19 +167,20 @@
   // for both a string and a CU vector.
   uint32_t SymTableSize = (ConstantPoolOffset - SymbolTableOffset) / 8;
   SymbolTable.reserve(SymTableSize);
-  uint32_t CuVectorsTotal = 0;
+  DenseSet<uint32_t> CUIndeces;
   for (uint32_t i = 0; i < SymTableSize; ++i) {
     uint32_t NameOffset = Data.getU32(&Offset);
     uint32_t CuVecOffset = Data.getU32(&Offset);
     SymbolTable.push_back({NameOffset, CuVecOffset});
     if (NameOffset || CuVecOffset)
-      ++CuVectorsTotal;
+      CUIndeces.insert(CuVecOffset);
   }
 
   // The constant pool. CU vectors are stored first, followed by strings.
   // The first value is the number of CU indices in the vector. Each subsequent
   // value is the index and symbol attributes of a CU in the CU list.
-  for (uint32_t i = 0; i < CuVectorsTotal; ++i) {
+  for (uint32_t I = 0, CuVectorsTotal = CUIndeces.size(); I < CuVectorsTotal;
+       ++I) {
     ConstantPoolVectors.emplace_back(0, SmallVector<uint32_t, 0>());
     auto &Vec = ConstantPoolVectors.back();
     Vec.first = Offset - ConstantPoolOffset;