diff --git a/llvm/include/llvm/CodeGen/CallingConvLower.h b/llvm/include/llvm/CodeGen/CallingConvLower.h
--- a/llvm/include/llvm/CodeGen/CallingConvLower.h
+++ b/llvm/include/llvm/CodeGen/CallingConvLower.h
@@ -30,6 +30,13 @@
 /// CCValAssign - Represent assignment of one arg/retval to a location.
 class CCValAssign {
 public:
+  /// The kind of the location the value is assigned to.
+  enum class LocKind : unsigned {
+    Register, /// The value is assigned to a register.
+    Memory,   /// The value is assigned to memory.
+    Pending,  /// The location (register or memory) has not yet been decided.
+  };
+
   enum LocInfo {
     Full,      // The value fills the full location.
     SExt,      // The value is sign extended in the location.
@@ -52,14 +59,22 @@
   };
 
 private:
+  // A union discriminated by the kind of the location.
+  union {
+    // When Kind == Register: the register that the value is assigned to.
+    Register RegNo;
+    // When Kind == Memory: the memory offset at which the value resides.
+    unsigned Offset;
+    // When Kind == Pending: additional information about this pending location.
+    // The exact interpretation of this field is target-dependent.
+    unsigned ExtraInfo;
+  };
+
   /// ValNo - This is the value number being assigned (e.g. an argument number).
   unsigned ValNo;
 
-  /// Loc is either a stack offset or a register number.
-  unsigned Loc;
-
-  /// isMem - True if this is a memory loc, false if it is a register loc.
-  unsigned isMem : 1;
+  /// The kind of the location.
+  LocKind Kind : 2;
 
   /// isCustom - True if this arg/retval requires special handling.
   unsigned isCustom : 1;
@@ -72,82 +87,79 @@
 
   /// LocVT - The type of the location being assigned to.
   MVT LocVT;
-public:
 
-  static CCValAssign getReg(unsigned ValNo, MVT ValVT,
-                            unsigned RegNo, MVT LocVT,
-                            LocInfo HTP) {
-    CCValAssign Ret;
-    Ret.ValNo = ValNo;
-    Ret.Loc = RegNo;
-    Ret.isMem = false;
-    Ret.isCustom = false;
-    Ret.HTP = HTP;
-    Ret.ValVT = ValVT;
-    Ret.LocVT = LocVT;
+  CCValAssign(LocKind Kind, LocInfo HTP, unsigned ValNo, MVT ValVT, MVT LocVT,
+              bool IsCustom)
+      : ValNo(ValNo), Kind(Kind), isCustom(IsCustom), HTP(HTP), ValVT(ValVT),
+        LocVT(LocVT) {}
+
+public:
+  static CCValAssign getReg(unsigned ValNo, MVT ValVT, unsigned RegNo,
+                            MVT LocVT, LocInfo HTP, bool IsCustom = false) {
+    CCValAssign Ret(LocKind::Register, HTP, ValNo, ValVT, LocVT, IsCustom);
+    Ret.RegNo = RegNo;
     return Ret;
   }
 
-  static CCValAssign getCustomReg(unsigned ValNo, MVT ValVT,
-                                  unsigned RegNo, MVT LocVT,
-                                  LocInfo HTP) {
-    CCValAssign Ret;
-    Ret = getReg(ValNo, ValVT, RegNo, LocVT, HTP);
-    Ret.isCustom = true;
-    return Ret;
+  static CCValAssign getCustomReg(unsigned ValNo, MVT ValVT, unsigned RegNo,
+                                  MVT LocVT, LocInfo HTP) {
+    return getReg(ValNo, ValVT, RegNo, LocVT, HTP, /*IsCustom=*/true);
   }
 
-  static CCValAssign getMem(unsigned ValNo, MVT ValVT,
-                            unsigned Offset, MVT LocVT,
-                            LocInfo HTP) {
-    CCValAssign Ret;
-    Ret.ValNo = ValNo;
-    Ret.Loc = Offset;
-    Ret.isMem = true;
-    Ret.isCustom = false;
-    Ret.HTP = HTP;
-    Ret.ValVT = ValVT;
-    Ret.LocVT = LocVT;
+  static CCValAssign getMem(unsigned ValNo, MVT ValVT, unsigned Offset,
+                            MVT LocVT, LocInfo HTP, bool IsCustom = false) {
+    CCValAssign Ret(LocKind::Memory, HTP, ValNo, ValVT, LocVT, IsCustom);
+    Ret.Offset = Offset;
     return Ret;
   }
 
-  static CCValAssign getCustomMem(unsigned ValNo, MVT ValVT,
-                                  unsigned Offset, MVT LocVT,
-                                  LocInfo HTP) {
-    CCValAssign Ret;
-    Ret = getMem(ValNo, ValVT, Offset, LocVT, HTP);
-    Ret.isCustom = true;
-    return Ret;
+  static CCValAssign getCustomMem(unsigned ValNo, MVT ValVT, unsigned Offset,
+                                  MVT LocVT, LocInfo HTP) {
+    return getMem(ValNo, ValVT, Offset, LocVT, HTP, /*IsCustom=*/true);
   }
 
-  // There is no need to differentiate between a pending CCValAssign and other
-  // kinds, as they are stored in a different list.
   static CCValAssign getPending(unsigned ValNo, MVT ValVT, MVT LocVT,
                                 LocInfo HTP, unsigned ExtraInfo = 0) {
-    return getReg(ValNo, ValVT, ExtraInfo, LocVT, HTP);
+    CCValAssign Ret(LocKind::Pending, HTP, ValNo, ValVT, LocVT, false);
+    Ret.ExtraInfo = ExtraInfo;
+    return Ret;
   }
 
   void convertToReg(unsigned RegNo) {
-    Loc = RegNo;
-    isMem = false;
+    Kind = LocKind::Register;
+    this->RegNo = RegNo;
   }
 
   void convertToMem(unsigned Offset) {
-    Loc = Offset;
-    isMem = true;
+    Kind = LocKind::Memory;
+    this->Offset = Offset;
   }
 
   unsigned getValNo() const { return ValNo; }
   MVT getValVT() const { return ValVT; }
 
-  bool isRegLoc() const { return !isMem; }
-  bool isMemLoc() const { return isMem; }
+  LocKind getLocKind() const { return Kind; }
+  bool isRegLoc() const { return Kind == LocKind::Register; }
+  bool isMemLoc() const { return Kind == LocKind::Memory; }
+  bool isPendingLoc() const { return Kind == LocKind::Pending; }
 
   bool needsCustom() const { return isCustom; }
 
-  Register getLocReg() const { assert(isRegLoc()); return Loc; }
-  unsigned getLocMemOffset() const { assert(isMemLoc()); return Loc; }
-  unsigned getExtraInfo() const { return Loc; }
+  Register getLocReg() const {
+    assert(isRegLoc());
+    return RegNo;
+  }
+
+  unsigned getLocMemOffset() const {
+    assert(isMemLoc());
+    return Offset;
+  }
+
+  unsigned getExtraInfo() const {
+    assert(isPendingLoc());
+    return ExtraInfo;
+  }
+
   MVT getLocVT() const { return LocVT; }
 
   LocInfo getLocInfo() const { return HTP; }
diff --git a/llvm/lib/CodeGen/CallingConvLower.cpp b/llvm/lib/CodeGen/CallingConvLower.cpp
--- a/llvm/lib/CodeGen/CallingConvLower.cpp
+++ b/llvm/lib/CodeGen/CallingConvLower.cpp
@@ -231,7 +231,7 @@
   // when i64 and f64 are both passed in GPRs.
   StackOffset = SavedStackOffset;
   MaxStackArgAlign = SavedMaxStackArgAlign;
-  Locs.resize(NumLocs);
+  Locs.truncate(NumLocs);
 }
 
 void CCState::analyzeMustTailForwardedRegisters(
@@ -270,19 +270,20 @@
   CCState CCInfo2(CallerCC, false, MF, RVLocs2, C);
   CCInfo2.AnalyzeCallResult(Ins, CallerFn);
 
-  if (RVLocs1.size() != RVLocs2.size())
-    return false;
-  for (unsigned I = 0, E = RVLocs1.size(); I != E; ++I) {
-    const CCValAssign &Loc1 = RVLocs1[I];
-    const CCValAssign &Loc2 = RVLocs2[I];
-
-    if ( // Must both be in registers, or both in memory
-        Loc1.isRegLoc() != Loc2.isRegLoc() ||
-        // Must fill the same part of their locations
+  auto AreCompatible = [](const CCValAssign &Loc1, const CCValAssign &Loc2) {
+    assert(!Loc1.isPendingLoc() && !Loc2.isPendingLoc() &&
+           "The location must have been decided by now");
+    if (Loc1.getLocKind() != Loc2.getLocKind() ||
         Loc1.getLocInfo() != Loc2.getLocInfo() ||
-        // Memory offset/register number must be the same
-        Loc1.getExtraInfo() != Loc2.getExtraInfo())
+        Loc1.needsCustom() != Loc2.needsCustom())
       return false;
-  }
-  return true;
+    if (Loc1.isRegLoc())
+      return Loc1.getLocReg() == Loc2.getLocReg();
+    if (Loc1.isMemLoc())
+      return Loc1.getLocMemOffset() == Loc2.getLocMemOffset();
+    llvm_unreachable("Unknown location kind");
+  };
+
+  return std::equal(RVLocs1.begin(), RVLocs1.end(), RVLocs2.begin(),
+                    RVLocs2.end(), AreCompatible);
 }
diff --git a/llvm/lib/Target/Sparc/SparcISelLowering.cpp b/llvm/lib/Target/Sparc/SparcISelLowering.cpp
--- a/llvm/lib/Target/Sparc/SparcISelLowering.cpp
+++ b/llvm/lib/Target/Sparc/SparcISelLowering.cpp
@@ -1138,7 +1138,7 @@
 static void fixupVariableFloatArgs(SmallVectorImpl<CCValAssign> &ArgLocs,
                                    ArrayRef<ISD::OutputArg> Outs) {
   for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
-    const CCValAssign &VA = ArgLocs[i];
+    CCValAssign &VA = ArgLocs[i];
     MVT ValTy = VA.getLocVT();
     // FIXME: What about f32 arguments? C promotes them to f64 when calling
     // varargs functions.
@@ -1149,7 +1149,6 @@
       continue;
 
     // This floating point argument should be reassigned.
-    CCValAssign NewVA;
 
     // Determine the offset into the argument array.
     Register firstReg = (ValTy == MVT::f64) ? SP::D0 : SP::Q0;
@@ -1162,21 +1161,20 @@
       unsigned IReg = SP::I0 + Offset/8;
       if (ValTy == MVT::f64)
         // Full register, just bitconvert into i64.
-        NewVA = CCValAssign::getReg(VA.getValNo(), VA.getValVT(),
-                                    IReg, MVT::i64, CCValAssign::BCvt);
+        VA = CCValAssign::getReg(VA.getValNo(), VA.getValVT(), IReg, MVT::i64,
+                                 CCValAssign::BCvt);
       else {
         assert(ValTy == MVT::f128 && "Unexpected type!");
         // Full register, just bitconvert into i128 -- We will lower this into
         // two i64s in LowerCall_64.
-        NewVA = CCValAssign::getCustomReg(VA.getValNo(), VA.getValVT(),
-                                          IReg, MVT::i128, CCValAssign::BCvt);
+        VA = CCValAssign::getCustomReg(VA.getValNo(), VA.getValVT(), IReg,
+                                       MVT::i128, CCValAssign::BCvt);
       }
     } else {
       // This needs to go to memory, we're out of integer registers.
-      NewVA = CCValAssign::getMem(VA.getValNo(), VA.getValVT(),
-                                  Offset, VA.getLocVT(), VA.getLocInfo());
+      VA = CCValAssign::getMem(VA.getValNo(), VA.getValVT(), Offset,
+                               VA.getLocVT(), VA.getLocInfo());
     }
-    ArgLocs[i] = NewVA;
   }
 }