Index: llvm/trunk/include/llvm/MC/MCRegisterInfo.h
===================================================================
--- llvm/trunk/include/llvm/MC/MCRegisterInfo.h
+++ llvm/trunk/include/llvm/MC/MCRegisterInfo.h
@@ -271,6 +271,16 @@
     NumSubRegIndices = NumIndices;
     SubRegIdxRanges = SubIdxRanges;
     RegEncodingTable = RET;
+
+    // Initialize DWARF register mapping variables
+    EHL2DwarfRegs = nullptr;
+    EHL2DwarfRegsSize = 0;
+    L2DwarfRegs = nullptr;
+    L2DwarfRegsSize = 0;
+    EHDwarf2LRegs = nullptr;
+    EHDwarf2LRegsSize = 0;
+    Dwarf2LRegs = nullptr;
+    Dwarf2LRegsSize = 0;
   }
 
   /// \brief Used to initialize LLVM register to Dwarf
Index: llvm/trunk/lib/MC/MCRegisterInfo.cpp
===================================================================
--- llvm/trunk/lib/MC/MCRegisterInfo.cpp
+++ llvm/trunk/lib/MC/MCRegisterInfo.cpp
@@ -62,6 +62,8 @@
   const DwarfLLVMRegPair *M = isEH ? EHL2DwarfRegs : L2DwarfRegs;
   unsigned Size = isEH ? EHL2DwarfRegsSize : L2DwarfRegsSize;
 
+  if (!M)
+    return -1;
   DwarfLLVMRegPair Key = { RegNum, 0 };
   const DwarfLLVMRegPair *I = std::lower_bound(M, M+Size, Key);
   if (I == M+Size || I->FromReg != RegNum)
@@ -73,6 +75,8 @@
   const DwarfLLVMRegPair *M = isEH ? EHDwarf2LRegs : Dwarf2LRegs;
   unsigned Size = isEH ? EHDwarf2LRegsSize : Dwarf2LRegsSize;
 
+  if (!M)
+    return -1;
   DwarfLLVMRegPair Key = { RegNum, 0 };
   const DwarfLLVMRegPair *I = std::lower_bound(M, M+Size, Key);
   assert(I != M+Size && I->FromReg == RegNum && "Invalid RegNum");