diff --git a/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index 0e1e50e5293..6a9bfc34d22 100644
--- a/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -72,17 +72,21 @@ ARMBaseRegisterInfo::getCallPreservedMask(CallingConv::ID) const {
 }
 
 const uint32_t*
-ARMBaseRegisterInfo::getThisReturnPreservedMask(CallingConv::ID) const {
-  return (STI.isTargetIOS() && !STI.isAAPCS_ABI())
-    ? CSR_iOS_ThisReturn_RegMask : CSR_AAPCS_ThisReturn_RegMask;
-  // This should return NULL in the case of any calling convention that does
-  // not use the same register for an i32 first argument and an i32 return
-  // value
+ARMBaseRegisterInfo::getNoPreservedMask() const {
+  return CSR_NoRegs_RegMask;
 }
 
 const uint32_t*
-ARMBaseRegisterInfo::getNoPreservedMask() const {
-  return CSR_NoRegs_RegMask;
+ARMBaseRegisterInfo::getThisReturnPreservedMask(CallingConv::ID) const {
+  // This should return a register mask that is the same as that returned by
+  // getCallPreservedMask but that additionally preserves the register used for
+  // the first i32 argument (which must also be the register used to return a
+  // single i32 return value)
+  //
+  // In case that the calling convention does not use the same register for
+  // both, the function should return NULL (does not currently apply)
+  return (STI.isTargetIOS() && !STI.isAAPCS_ABI())
+    ? CSR_iOS_ThisReturn_RegMask : CSR_AAPCS_ThisReturn_RegMask;
 }
 
 BitVector ARMBaseRegisterInfo::
diff --git a/lib/Target/ARM/ARMBaseRegisterInfo.h b/lib/Target/ARM/ARMBaseRegisterInfo.h
index be3f1368f69..cdaad053f9f 100644
--- a/lib/Target/ARM/ARMBaseRegisterInfo.h
+++ b/lib/Target/ARM/ARMBaseRegisterInfo.h
@@ -96,14 +96,14 @@ public:
   const uint32_t *getCallPreservedMask(CallingConv::ID) const;
   const uint32_t *getNoPreservedMask() const;
 
-  // getThisReturnPreservedMask - Returns a call preserved mask specific to the
-  // case that 'returned' is  an i32 first argument if the calling convention
-  // is one that can (partially) model this attribute with a preserved mask
-  // (i.e. it is a calling convention that uses the same register for the first
-  // i32 argument and an i32 return value)
-  //
-  // Should return NULL in the case that the calling convention does not have
-  // this property
+  /// getThisReturnPreservedMask - Returns a call preserved mask specific to the
+  /// case that 'returned' is on an i32 first argument if the calling convention
+  /// is one that can (partially) model this attribute with a preserved mask
+  /// (i.e. it is a calling convention that uses the same register for the first
+  /// i32 argument and an i32 return value)
+  ///
+  /// Should return NULL in the case that the calling convention does not have
+  /// this property
   const uint32_t *getThisReturnPreservedMask(CallingConv::ID) const;
   
   BitVector getReservedRegs(const MachineFunction &MF) const;