diff --git a/lib/Target/PowerPC/PPCISelLowering.cpp b/lib/Target/PowerPC/PPCISelLowering.cpp
index 2a4fb02..a11d624 100644
--- a/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -1572,7 +1572,7 @@
 
   EVT PtrVT = DAG.getTargetLoweringInfo().getPointerTy();
   // Potential tail calls could cause overwriting of argument stack slots.
-  bool isImmutable = !(PerformTailCallOpt && (CallConv==CallingConv::Fast));
+  bool isImmutable = !(GuaranteedTailCallOpt && (CallConv==CallingConv::Fast));
   unsigned PtrByteSize = 4;
 
   // Assign locations to all of the incoming arguments.
@@ -1773,7 +1773,7 @@
   EVT PtrVT = DAG.getTargetLoweringInfo().getPointerTy();
   bool isPPC64 = PtrVT == MVT::i64;
   // Potential tail calls could cause overwriting of argument stack slots.
-  bool isImmutable = !(PerformTailCallOpt && (CallConv==CallingConv::Fast));
+  bool isImmutable = !(GuaranteedTailCallOpt && (CallConv==CallingConv::Fast));
   unsigned PtrByteSize = isPPC64 ? 8 : 4;
 
   unsigned ArgOffset = PPCFrameInfo::getLinkageSize(isPPC64, true);
@@ -2164,7 +2164,7 @@
                       PPCFrameInfo::getMinCallFrameSize(isPPC64, true));
 
   // Tail call needs the stack to be aligned.
-  if (CC==CallingConv::Fast && PerformTailCallOpt) {
+  if (CC==CallingConv::Fast && GuaranteedTailCallOpt) {
     unsigned TargetAlign = DAG.getMachineFunction().getTarget().getFrameInfo()->
       getStackAlignment();
     unsigned AlignMask = TargetAlign-1;
@@ -2200,7 +2200,7 @@
                                                      bool isVarArg,
                                       const SmallVectorImpl<ISD::InputArg> &Ins,
                                                      SelectionDAG& DAG) const {
-  if (!PerformTailCallOpt)
+  if (!GuaranteedTailCallOpt)
     return false;
 
   // Variable argument functions are not supported.
@@ -2604,7 +2604,7 @@
   // the stack. Account for this here so these bytes can be pushed back on in
   // PPCRegisterInfo::eliminateCallFramePseudoInstr.
   int BytesCalleePops =
-    (CallConv==CallingConv::Fast && PerformTailCallOpt) ? NumBytes : 0;
+    (CallConv==CallingConv::Fast && GuaranteedTailCallOpt) ? NumBytes : 0;
 
   if (InFlag.getNode())
     Ops.push_back(InFlag);
@@ -2720,7 +2720,7 @@
   // and restoring the callers stack pointer in this functions epilog. This is
   // done because by tail calling the called function might overwrite the value
   // in this function's (MF) stack pointer stack slot 0(SP).
-  if (PerformTailCallOpt && CallConv==CallingConv::Fast)
+  if (GuaranteedTailCallOpt && CallConv==CallingConv::Fast)
     MF.getInfo<PPCFunctionInfo>()->setHasFastCall();
   
   // Count how many bytes are to be pushed on the stack, including the linkage
@@ -2923,7 +2923,7 @@
   // and restoring the callers stack pointer in this functions epilog. This is
   // done because by tail calling the called function might overwrite the value
   // in this function's (MF) stack pointer stack slot 0(SP).
-  if (PerformTailCallOpt && CallConv==CallingConv::Fast)
+  if (GuaranteedTailCallOpt && CallConv==CallingConv::Fast)
     MF.getInfo<PPCFunctionInfo>()->setHasFastCall();
 
   unsigned nAltivecParamsAtEnd = 0;
diff --git a/lib/Target/PowerPC/PPCRegisterInfo.cpp b/lib/Target/PowerPC/PPCRegisterInfo.cpp
index 0c3c8eb..ad2cdcf 100644
--- a/lib/Target/PowerPC/PPCRegisterInfo.cpp
+++ b/lib/Target/PowerPC/PPCRegisterInfo.cpp
@@ -406,7 +406,7 @@
 static bool needsFP(const MachineFunction &MF) {
   const MachineFrameInfo *MFI = MF.getFrameInfo();
   return NoFramePointerElim || MFI->hasVarSizedObjects() ||
-    (PerformTailCallOpt && MF.getInfo<PPCFunctionInfo>()->hasFastCall());
+    (GuaranteedTailCallOpt && MF.getInfo<PPCFunctionInfo>()->hasFastCall());
 }
 
 static bool spillsCR(const MachineFunction &MF) {
@@ -486,7 +486,7 @@
 void PPCRegisterInfo::
 eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
                               MachineBasicBlock::iterator I) const {
-  if (PerformTailCallOpt && I->getOpcode() == PPC::ADJCALLSTACKUP) {
+  if (GuaranteedTailCallOpt && I->getOpcode() == PPC::ADJCALLSTACKUP) {
     // Add (actually subtract) back the amount the callee popped on return.
     if (int CalleeAmt =  I->getOperand(1).getImm()) {
       bool is64Bit = Subtarget.isPPC64();
@@ -1050,7 +1050,7 @@
 
   // Reserve stack space to move the linkage area to in case of a tail call.
   int TCSPDelta = 0;
-  if (PerformTailCallOpt && (TCSPDelta = FI->getTailCallSPDelta()) < 0) {
+  if (GuaranteedTailCallOpt && (TCSPDelta = FI->getTailCallSPDelta()) < 0) {
     MF.getFrameInfo()->CreateFixedObject(-1 * TCSPDelta, TCSPDelta,
                                          true, false);
   }
@@ -1160,7 +1160,7 @@
 
   // Take into account stack space reserved for tail calls.
   int TCSPDelta = 0;
-  if (PerformTailCallOpt && (TCSPDelta = PFI->getTailCallSPDelta()) < 0) {
+  if (GuaranteedTailCallOpt && (TCSPDelta = PFI->getTailCallSPDelta()) < 0) {
     LowerBound = TCSPDelta;
   }
 
@@ -1575,7 +1575,7 @@
     // The loaded (or persistent) stack pointer value is offset by the 'stwu'
     // on entry to the function.  Add this offset back now.
     if (!isPPC64) {
-      // If this function contained a fastcc call and PerformTailCallOpt is
+      // If this function contained a fastcc call and GuaranteedTailCallOpt is
       // enabled (=> hasFastCall()==true) the fastcc call might contain a tail
       // call which invalidates the stack pointer value in SP(0). So we use the
       // value of R31 in this case.
@@ -1654,7 +1654,7 @@
 
   // Callee pop calling convention. Pop parameter/linkage area. Used for tail
   // call optimization
-  if (PerformTailCallOpt && RetOpcode == PPC::BLR &&
+  if (GuaranteedTailCallOpt && RetOpcode == PPC::BLR &&
       MF.getFunction()->getCallingConv() == CallingConv::Fast) {
      PPCFunctionInfo *FI = MF.getInfo<PPCFunctionInfo>();
      unsigned CallerAllocatedAmt = FI->getMinReservedArea();
diff --git a/lib/Target/TargetMachine.cpp b/lib/Target/TargetMachine.cpp
index 8d99044..88871e3 100644
--- a/lib/Target/TargetMachine.cpp
+++ b/lib/Target/TargetMachine.cpp
@@ -40,7 +40,7 @@
   bool UnwindTablesMandatory;
   Reloc::Model RelocationModel;
   CodeModel::Model CMModel;
-  bool PerformTailCallOpt;
+  bool GuaranteedTailCallOpt;
   unsigned StackAlignment;
   bool RealignStack;
   bool DisableJumpTables;
@@ -173,9 +173,9 @@
                "Large code model"),
     clEnumValEnd));
 static cl::opt<bool, true>
-EnablePerformTailCallOpt("tailcallopt",
+EnableGuaranteedTailCallOpt("tailcallopt",
   cl::desc("Turn fastcc calls into tail calls by (potentially) changing ABI."),
-  cl::location(PerformTailCallOpt),
+  cl::location(GuaranteedTailCallOpt),
   cl::init(false));
 static cl::opt<unsigned, true>
 OverrideStackAlignment("stack-alignment",
diff --git a/lib/Target/X86/X86FastISel.cpp b/lib/Target/X86/X86FastISel.cpp
index d466ce0..392b96d 100644
--- a/lib/Target/X86/X86FastISel.cpp
+++ b/lib/Target/X86/X86FastISel.cpp
@@ -1247,7 +1247,7 @@
 
   // fastcc with -tailcallopt is intended to provide a guaranteed
   // tail call optimization. Fastisel doesn't know how to do that.
-  if (CC == CallingConv::Fast && PerformTailCallOpt)
+  if (CC == CallingConv::Fast && GuaranteedTailCallOpt)
     return false;
 
   // Let SDISel handle vararg functions.
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index b268e4b..331bac6 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1391,7 +1391,7 @@
   case CallingConv::X86_FastCall:
     return !Subtarget->is64Bit();
   case CallingConv::Fast:
-    return PerformTailCallOpt;
+    return GuaranteedTailCallOpt;
   }
 }
 
@@ -1441,7 +1441,7 @@
 /// FuncIsMadeTailCallSafe - Return true if the function is being made into
 /// a tailcall target by changing its ABI.
 static bool FuncIsMadeTailCallSafe(CallingConv::ID CC) {
-  return PerformTailCallOpt && CC == CallingConv::Fast;
+  return GuaranteedTailCallOpt && CC == CallingConv::Fast;
 }
 
 SDValue
@@ -1797,7 +1797,7 @@
 
     // Sibcalls are automatically detected tailcalls which do not require
     // ABI changes.
-    if (!PerformTailCallOpt && isTailCall)
+    if (!GuaranteedTailCallOpt && isTailCall)
       IsSibcall = true;
 
     if (isTailCall)
@@ -1819,7 +1819,7 @@
     // This is a sibcall. The memory operands are available in caller's
     // own caller's stack.
     NumBytes = 0;
-  else if (PerformTailCallOpt && CallConv == CallingConv::Fast)
+  else if (GuaranteedTailCallOpt && CallConv == CallingConv::Fast)
     NumBytes = GetAlignedArgumentStackSize(NumBytes, DAG);
 
   int FPDiff = 0;
@@ -1986,7 +1986,7 @@
     int FI = 0;
     // Do not flag preceeding copytoreg stuff together with the following stuff.
     InFlag = SDValue();
-    if (PerformTailCallOpt) {
+    if (GuaranteedTailCallOpt) {
       for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
         CCValAssign &VA = ArgLocs[i];
         if (VA.isRegLoc())
@@ -2311,7 +2311,7 @@
 
   // If -tailcallopt is specified, make fastcc functions tail-callable.
   const Function *CallerF = DAG.getMachineFunction().getFunction();
-  if (PerformTailCallOpt) {
+  if (GuaranteedTailCallOpt) {
     if (CalleeCC == CallingConv::Fast &&
         CallerF->getCallingConv() == CalleeCC)
       return true;