diff --git a/lib/Target/X86/X86CallingConv.td b/lib/Target/X86/X86CallingConv.td
index 487e39f..56863d9 100644
--- a/lib/Target/X86/X86CallingConv.td
+++ b/lib/Target/X86/X86CallingConv.td
@@ -379,3 +379,35 @@
   // Pass in STG registers: Base, Sp, Hp, R1
   CCIfType<[i32], CCAssignToReg<[EBX, EBP, EDI, ESI]>>
 ]>;
+
+//===----------------------------------------------------------------------===//
+// X86 Root Argument Calling Conventions
+//===----------------------------------------------------------------------===//
+
+// This is the root argument convention for the X86-32 backend.
+def CC_X86_32 : CallingConv<[
+  CCIfCC<"CallingConv::X86_FastCall", CCDelegateTo<CC_X86_32_FastCall>>,
+  CCIfCC<"CallingConv::X86_ThisCall", CCDelegateTo<CC_X86_32_ThisCall>>,
+  CCIfCC<"CallingConv::Fast", CCDelegateTo<CC_X86_32_FastCC>>,
+  CCIfCC<"CallingConv::GHC", CCDelegateTo<CC_X86_32_GHC>>,
+
+  // Otherwise, drop to normal X86-32 CC
+  CCDelegateTo<CC_X86_32_C>
+]>;
+
+// This is the root argument convention for the X86-64 backend.
+def CC_X86_64 : CallingConv<[
+  CCIfCC<"CallingConv::GHC", CCDelegateTo<CC_X86_64_GHC>>,
+
+  // Mingw64 and native Win64 use Win64 CC
+  CCIfSubtarget<"isTargetWin64()", CCDelegateTo<CC_X86_Win64_C>>,
+
+  // Otherwise, drop to normal X86-64 CC
+  CCDelegateTo<CC_X86_64_C>
+]>;
+
+// This is the argument convention used for the entire X86 backend.
+def CC_X86 : CallingConv<[
+  CCIfSubtarget<"is64Bit()", CCDelegateTo<CC_X86_64>>,
+  CCDelegateTo<CC_X86_32>
+]>;
diff --git a/lib/Target/X86/X86FastISel.cpp b/lib/Target/X86/X86FastISel.cpp
index cbbc2fd..962ead1 100644
--- a/lib/Target/X86/X86FastISel.cpp
+++ b/lib/Target/X86/X86FastISel.cpp
@@ -114,8 +114,6 @@
   bool X86VisitIntrinsicCall(const IntrinsicInst &I);
   bool X86SelectCall(const Instruction *I);
 
-  CCAssignFn *CCAssignFnForCall(CallingConv::ID CC, bool isTailCall = false);
-
   const X86InstrInfo *getInstrInfo() const {
     return getTargetMachine()->getInstrInfo();
   }
@@ -163,31 +161,6 @@
 
 #include "X86GenCallingConv.inc"
 
-/// CCAssignFnForCall - Selects the correct CCAssignFn for a given calling
-/// convention.
-CCAssignFn *X86FastISel::CCAssignFnForCall(CallingConv::ID CC,
-                                           bool isTaillCall) {
-  if (Subtarget->is64Bit()) {
-    if (CC == CallingConv::GHC)
-      return CC_X86_64_GHC;
-    else if (Subtarget->isTargetWin64())
-      return CC_X86_Win64_C;
-    else
-      return CC_X86_64_C;
-  }
-
-  if (CC == CallingConv::X86_FastCall)
-    return CC_X86_32_FastCall;
-  else if (CC == CallingConv::X86_ThisCall)
-    return CC_X86_32_ThisCall;
-  else if (CC == CallingConv::Fast)
-    return CC_X86_32_FastCC;
-  else if (CC == CallingConv::GHC)
-    return CC_X86_32_GHC;
-  else
-    return CC_X86_32_C;
-}
-
 /// X86FastEmitLoad - Emit a machine instruction to load a value of type VT.
 /// The address is either pre-computed, i.e. Ptr, or a GlobalAddress, i.e. GV.
 /// Return true and the result register by reference if it is possible.
@@ -1548,7 +1521,7 @@
     CCInfo.AllocateStack(32, 8); 
   }
 
-  CCInfo.AnalyzeCallOperands(ArgVTs, ArgFlags, CCAssignFnForCall(CC));
+  CCInfo.AnalyzeCallOperands(ArgVTs, ArgFlags, CC_X86);
 
   // Get a count of how many bytes are to be pushed on the stack.
   unsigned NumBytes = CCInfo.getNextStackOffset();
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index d8ec6a3..69589d2 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1457,30 +1457,6 @@
   return Ins[0].Flags.isSRet();
 }
 
-/// CCAssignFnForNode - Selects the correct CCAssignFn for a the
-/// given CallingConvention value.
-CCAssignFn *X86TargetLowering::CCAssignFnForNode(CallingConv::ID CC) const {
-  if (Subtarget->is64Bit()) {
-    if (CC == CallingConv::GHC)
-      return CC_X86_64_GHC;
-    else if (Subtarget->isTargetWin64())
-      return CC_X86_Win64_C;
-    else
-      return CC_X86_64_C;
-  }
-
-  if (CC == CallingConv::X86_FastCall)
-    return CC_X86_32_FastCall;
-  else if (CC == CallingConv::X86_ThisCall)
-    return CC_X86_32_ThisCall;
-  else if (CC == CallingConv::Fast)
-    return CC_X86_32_FastCC;
-  else if (CC == CallingConv::GHC)
-    return CC_X86_32_GHC;
-  else
-    return CC_X86_32_C;
-}
-
 /// CreateCopyOfByValArgument - Make a copy of an aggregate at address specified
 /// by "Src" to address "Dst" with size and alignment information specified by
 /// the specific parameter attribute. The copy will be passed as a byval
@@ -1576,7 +1552,7 @@
   SmallVector<CCValAssign, 16> ArgLocs;
   CCState CCInfo(CallConv, isVarArg, getTargetMachine(),
                  ArgLocs, *DAG.getContext());
-  CCInfo.AnalyzeFormalArguments(Ins, CCAssignFnForNode(CallConv));
+  CCInfo.AnalyzeFormalArguments(Ins, CC_X86);
 
   unsigned LastVal = ~0U;
   SDValue ArgValue;
@@ -1895,7 +1871,7 @@
   SmallVector<CCValAssign, 16> ArgLocs;
   CCState CCInfo(CallConv, isVarArg, getTargetMachine(),
                  ArgLocs, *DAG.getContext());
-  CCInfo.AnalyzeCallOperands(Outs, CCAssignFnForNode(CallConv));
+  CCInfo.AnalyzeCallOperands(Outs, CC_X86);
 
   // Get a count of how many bytes are to be pushed on the stack.
   unsigned NumBytes = CCInfo.getNextStackOffset();
@@ -2478,7 +2454,7 @@
     SmallVector<CCValAssign, 16> ArgLocs;
     CCState CCInfo(CalleeCC, isVarArg, getTargetMachine(),
                    ArgLocs, *DAG.getContext());
-    CCInfo.AnalyzeCallOperands(Outs, CCAssignFnForNode(CalleeCC));
+    CCInfo.AnalyzeCallOperands(Outs, CC_X86);
     if (CCInfo.getNextStackOffset()) {
       MachineFunction &MF = DAG.getMachineFunction();
       if (MF.getInfo<X86MachineFunctionInfo>()->getBytesToPopOnReturn())
diff --git a/lib/Target/X86/X86ISelLowering.h b/lib/Target/X86/X86ISelLowering.h
index 287853f..bc79719 100644
--- a/lib/Target/X86/X86ISelLowering.h
+++ b/lib/Target/X86/X86ISelLowering.h
@@ -717,7 +717,6 @@
                                 SDValue Chain, bool IsTailCall, bool Is64Bit,
                                 int FPDiff, DebugLoc dl) const;
 
-    CCAssignFn *CCAssignFnForNode(CallingConv::ID CallConv) const;
     unsigned GetAlignedArgumentStackSize(unsigned StackSize,
                                          SelectionDAG &DAG) const;