Index: llvm/trunk/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
===================================================================
--- llvm/trunk/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
+++ llvm/trunk/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
@@ -2638,13 +2638,15 @@
     return MatchOperand_NoMatch;
 
   bool IsKnown;
-  auto MRSMapper = AArch64SysReg::MRSMapper(STI.getFeatureBits());
-  uint32_t MRSReg = MRSMapper.fromString(Tok.getString(), IsKnown);
+  auto MRSMapper = AArch64SysReg::MRSMapper();
+  uint32_t MRSReg = MRSMapper.fromString(Tok.getString(), STI.getFeatureBits(),
+                                         IsKnown);
   assert(IsKnown == (MRSReg != -1U) &&
          "register should be -1 if and only if it's unknown");
 
-  auto MSRMapper = AArch64SysReg::MSRMapper(STI.getFeatureBits());
-  uint32_t MSRReg = MSRMapper.fromString(Tok.getString(), IsKnown);
+  auto MSRMapper = AArch64SysReg::MSRMapper();
+  uint32_t MSRReg = MSRMapper.fromString(Tok.getString(), STI.getFeatureBits(),
+                                         IsKnown);
   assert(IsKnown == (MSRReg != -1U) &&
          "register should be -1 if and only if it's unknown");
 
Index: llvm/trunk/lib/Target/AArch64/InstPrinter/AArch64InstPrinter.cpp
===================================================================
--- llvm/trunk/lib/Target/AArch64/InstPrinter/AArch64InstPrinter.cpp
+++ llvm/trunk/lib/Target/AArch64/InstPrinter/AArch64InstPrinter.cpp
@@ -1276,8 +1276,8 @@
                                                 raw_ostream &O) {
   unsigned Val = MI->getOperand(OpNo).getImm();
 
-  auto Mapper = AArch64SysReg::MRSMapper(getAvailableFeatures());
-  std::string Name = Mapper.toString(Val);
+  auto Mapper = AArch64SysReg::MRSMapper();
+  std::string Name = Mapper.toString(Val, getAvailableFeatures());
 
   O << StringRef(Name).upper();
 }
@@ -1286,8 +1286,8 @@
                                                 raw_ostream &O) {
   unsigned Val = MI->getOperand(OpNo).getImm();
 
-  auto Mapper = AArch64SysReg::MSRMapper(getAvailableFeatures());
-  std::string Name = Mapper.toString(Val);
+  auto Mapper = AArch64SysReg::MSRMapper();
+  std::string Name = Mapper.toString(Val, getAvailableFeatures());
 
   O << StringRef(Name).upper();
 }
Index: llvm/trunk/lib/Target/AArch64/Utils/AArch64BaseInfo.h
===================================================================
--- llvm/trunk/lib/Target/AArch64/Utils/AArch64BaseInfo.h
+++ llvm/trunk/lib/Target/AArch64/Utils/AArch64BaseInfo.h
@@ -1139,21 +1139,20 @@
 
     const AArch64NamedImmMapper::Mapping *InstMappings;
     size_t NumInstMappings;
-    uint64_t FeatureBits;
 
-    SysRegMapper(uint64_t FeatureBits) : FeatureBits(FeatureBits) { }
-    uint32_t fromString(StringRef Name, bool &Valid) const;
-    std::string toString(uint32_t Bits) const;
+    SysRegMapper() { }
+    uint32_t fromString(StringRef Name, uint64_t FeatureBits, bool &Valid) const;
+    std::string toString(uint32_t Bits, uint64_t FeatureBits) const;
   };
 
   struct MSRMapper : SysRegMapper {
     static const AArch64NamedImmMapper::Mapping MSRMappings[];
-    MSRMapper(uint64_t FeatureBits);
+    MSRMapper();
   };
 
   struct MRSMapper : SysRegMapper {
     static const AArch64NamedImmMapper::Mapping MRSMappings[];
-    MRSMapper(uint64_t FeatureBits);
+    MRSMapper();
   };
 
   uint32_t ParseGenericRegister(StringRef Name, bool &Valid);
Index: llvm/trunk/lib/Target/AArch64/Utils/AArch64BaseInfo.cpp
===================================================================
--- llvm/trunk/lib/Target/AArch64/Utils/AArch64BaseInfo.cpp
+++ llvm/trunk/lib/Target/AArch64/Utils/AArch64BaseInfo.cpp
@@ -245,8 +245,7 @@
   {"ich_elsr_el2", ICH_ELSR_EL2}
 };
 
-AArch64SysReg::MRSMapper::MRSMapper(uint64_t FeatureBits)
-  : SysRegMapper(FeatureBits) {
+AArch64SysReg::MRSMapper::MRSMapper() {
     InstMappings = &MRSMappings[0];
     NumInstMappings = llvm::array_lengthof(MRSMappings);
 }
@@ -269,8 +268,7 @@
   {"icc_sgi0r_el1", ICC_SGI0R_EL1}
 };
 
-AArch64SysReg::MSRMapper::MSRMapper(uint64_t FeatureBits)
-  : SysRegMapper(FeatureBits) {
+AArch64SysReg::MSRMapper::MSRMapper() {
     InstMappings = &MSRMappings[0];
     NumInstMappings = llvm::array_lengthof(MSRMappings);
 }
@@ -761,7 +759,8 @@
 };
 
 uint32_t
-AArch64SysReg::SysRegMapper::fromString(StringRef Name, bool &Valid) const {
+AArch64SysReg::SysRegMapper::fromString(StringRef Name, uint64_t FeatureBits, 
+                                        bool &Valid) const {
   std::string NameLower = Name.lower();
 
   // First search the registers shared by all
@@ -814,7 +813,7 @@
 }
 
 std::string
-AArch64SysReg::SysRegMapper::toString(uint32_t Bits) const {
+AArch64SysReg::SysRegMapper::toString(uint32_t Bits, uint64_t FeatureBits) const {
   // First search the registers shared by all
   for (unsigned i = 0; i < array_lengthof(SysRegMappings); ++i) {
     if (SysRegMappings[i].Value == Bits) {