diff --git a/include/llvm/Analysis/ConstantFolding.h b/include/llvm/Analysis/ConstantFolding.h
index 479731e..43a2df0 100644
--- a/include/llvm/Analysis/ConstantFolding.h
+++ b/include/llvm/Analysis/ConstantFolding.h
@@ -22,7 +22,7 @@
 namespace llvm {
 class APInt;
 template <typename T> class ArrayRef;
-class CallSite;
+class CallBase;
 class Constant;
 class ConstantExpr;
 class ConstantVector;
@@ -30,7 +30,6 @@
 class Function;
 class GlobalValue;
 class Instruction;
-class ImmutableCallSite;
 class TargetLibraryInfo;
 class Type;
 
@@ -138,11 +137,11 @@
 
 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
 /// the specified function.
-bool canConstantFoldCallTo(ImmutableCallSite CS, const Function *F);
+bool canConstantFoldCallTo(const CallBase *Call, const Function *F);
 
 /// ConstantFoldCall - Attempt to constant fold a call to the specified function
 /// with the specified arguments, returning null if unsuccessful.
-Constant *ConstantFoldCall(ImmutableCallSite CS, Function *F,
+Constant *ConstantFoldCall(const CallBase *Call, Function *F,
                            ArrayRef<Constant *> Operands,
                            const TargetLibraryInfo *TLI = nullptr);
 
@@ -154,7 +153,7 @@
 
 /// Check whether the given call has no side-effects.
 /// Specifically checks for math routimes which sometimes set errno.
-bool isMathLibCallNoop(CallSite CS, const TargetLibraryInfo *TLI);
+bool isMathLibCallNoop(const CallBase *Call, const TargetLibraryInfo *TLI);
 }
 
 #endif
diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp
index 69e1dda..3b4e603 100644
--- a/lib/Analysis/ConstantFolding.cpp
+++ b/lib/Analysis/ConstantFolding.cpp
@@ -1024,9 +1024,9 @@
   case Instruction::FCmp: llvm_unreachable("Invalid for compares");
   case Instruction::Call:
     if (auto *F = dyn_cast<Function>(Ops.back())) {
-      ImmutableCallSite CS(cast<CallInst>(InstOrCE));
-      if (canConstantFoldCallTo(CS, F))
-        return ConstantFoldCall(CS, F, Ops.slice(0, Ops.size() - 1), TLI);
+      const auto *Call = cast<CallBase>(InstOrCE);
+      if (canConstantFoldCallTo(Call, F))
+        return ConstantFoldCall(Call, F, Ops.slice(0, Ops.size() - 1), TLI);
     }
     return nullptr;
   case Instruction::Select:
@@ -1366,8 +1366,8 @@
 //  Constant Folding for Calls
 //
 
-bool llvm::canConstantFoldCallTo(ImmutableCallSite CS, const Function *F) {
-  if (CS.isNoBuiltin() || CS.isStrictFP())
+bool llvm::canConstantFoldCallTo(const CallBase *Call, const Function *F) {
+  if (Call->isNoBuiltin() || Call->isStrictFP())
     return false;
   switch (F->getIntrinsicID()) {
   case Intrinsic::fabs:
@@ -1643,7 +1643,7 @@
 Constant *ConstantFoldScalarCall(StringRef Name, unsigned IntrinsicID, Type *Ty,
                                  ArrayRef<Constant *> Operands,
                                  const TargetLibraryInfo *TLI,
-                                 ImmutableCallSite CS) {
+                                 const CallBase *Call) {
   if (Operands.size() == 1) {
     if (IntrinsicID == Intrinsic::is_constant) {
       // We know we have a "Constant" argument. But we want to only
@@ -1671,9 +1671,10 @@
       if (IntrinsicID == Intrinsic::launder_invariant_group ||
           IntrinsicID == Intrinsic::strip_invariant_group) {
         // If instruction is not yet put in a basic block (e.g. when cloning
-        // a function during inlining), CS caller may not be available.
-        // So check CS's BB first before querying CS.getCaller.
-        const Function *Caller = CS.getParent() ? CS.getCaller() : nullptr;
+        // a function during inlining), Call's caller may not be available.
+        // So check Call's BB first before querying Call->getCaller.
+        const Function *Caller =
+            Call->getParent() ? Call->getCaller() : nullptr;
         if (Caller &&
             !NullPointerIsDefined(
                 Caller, Operands[0]->getType()->getPointerAddressSpace())) {
@@ -2215,7 +2216,7 @@
                                  VectorType *VTy, ArrayRef<Constant *> Operands,
                                  const DataLayout &DL,
                                  const TargetLibraryInfo *TLI,
-                                 ImmutableCallSite CS) {
+                                 const CallBase *Call) {
   SmallVector<Constant *, 4> Result(VTy->getNumElements());
   SmallVector<Constant *, 4> Lane(Operands.size());
   Type *Ty = VTy->getElementType();
@@ -2278,7 +2279,8 @@
     }
 
     // Use the regular scalar folding to simplify this column.
-    Constant *Folded = ConstantFoldScalarCall(Name, IntrinsicID, Ty, Lane, TLI, CS);
+    Constant *Folded =
+        ConstantFoldScalarCall(Name, IntrinsicID, Ty, Lane, TLI, Call);
     if (!Folded)
       return nullptr;
     Result[I] = Folded;
@@ -2289,11 +2291,10 @@
 
 } // end anonymous namespace
 
-Constant *
-llvm::ConstantFoldCall(ImmutableCallSite CS, Function *F,
-                       ArrayRef<Constant *> Operands,
-                       const TargetLibraryInfo *TLI) {
-  if (CS.isNoBuiltin() || CS.isStrictFP())
+Constant *llvm::ConstantFoldCall(const CallBase *Call, Function *F,
+                                 ArrayRef<Constant *> Operands,
+                                 const TargetLibraryInfo *TLI) {
+  if (Call->isNoBuiltin() || Call->isStrictFP())
     return nullptr;
   if (!F->hasName())
     return nullptr;
@@ -2303,17 +2304,19 @@
 
   if (auto *VTy = dyn_cast<VectorType>(Ty))
     return ConstantFoldVectorCall(Name, F->getIntrinsicID(), VTy, Operands,
-                                  F->getParent()->getDataLayout(), TLI, CS);
+                                  F->getParent()->getDataLayout(), TLI, Call);
 
-  return ConstantFoldScalarCall(Name, F->getIntrinsicID(), Ty, Operands, TLI, CS);
+  return ConstantFoldScalarCall(Name, F->getIntrinsicID(), Ty, Operands, TLI,
+                                Call);
 }
 
-bool llvm::isMathLibCallNoop(CallSite CS, const TargetLibraryInfo *TLI) {
+bool llvm::isMathLibCallNoop(const CallBase *Call,
+                             const TargetLibraryInfo *TLI) {
   // FIXME: Refactor this code; this duplicates logic in LibCallsShrinkWrap
   // (and to some extent ConstantFoldScalarCall).
-  if (CS.isNoBuiltin() || CS.isStrictFP())
+  if (Call->isNoBuiltin() || Call->isStrictFP())
     return false;
-  Function *F = CS.getCalledFunction();
+  Function *F = Call->getCalledFunction();
   if (!F)
     return false;
 
@@ -2321,8 +2324,8 @@
   if (!TLI || !TLI->getLibFunc(*F, Func))
     return false;
 
-  if (CS.getNumArgOperands() == 1) {
-    if (ConstantFP *OpC = dyn_cast<ConstantFP>(CS.getArgOperand(0))) {
+  if (Call->getNumArgOperands() == 1) {
+    if (ConstantFP *OpC = dyn_cast<ConstantFP>(Call->getArgOperand(0))) {
       const APFloat &Op = OpC->getValueAPF();
       switch (Func) {
       case LibFunc_logl:
@@ -2420,9 +2423,9 @@
     }
   }
 
-  if (CS.getNumArgOperands() == 2) {
-    ConstantFP *Op0C = dyn_cast<ConstantFP>(CS.getArgOperand(0));
-    ConstantFP *Op1C = dyn_cast<ConstantFP>(CS.getArgOperand(1));
+  if (Call->getNumArgOperands() == 2) {
+    ConstantFP *Op0C = dyn_cast<ConstantFP>(Call->getArgOperand(0));
+    ConstantFP *Op1C = dyn_cast<ConstantFP>(Call->getArgOperand(1));
     if (Op0C && Op1C) {
       const APFloat &Op0 = Op0C->getValueAPF();
       const APFloat &Op1 = Op1C->getValueAPF();
diff --git a/lib/Analysis/InlineCost.cpp b/lib/Analysis/InlineCost.cpp
index 0e20739..574a1b6 100644
--- a/lib/Analysis/InlineCost.cpp
+++ b/lib/Analysis/InlineCost.cpp
@@ -1177,7 +1177,7 @@
   // because we have to continually rebuild the argument list even when no
   // simplifications can be performed. Until that is fixed with remapping
   // inside of instsimplify, directly constant fold calls here.
-  if (!canConstantFoldCallTo(CS, F))
+  if (!canConstantFoldCallTo(cast<CallBase>(CS.getInstruction()), F))
     return false;
 
   // Try to re-map the arguments to constants.
@@ -1193,7 +1193,8 @@
 
     ConstantArgs.push_back(C);
   }
-  if (Constant *C = ConstantFoldCall(CS, F, ConstantArgs)) {
+  if (Constant *C = ConstantFoldCall(cast<CallBase>(CS.getInstruction()), F,
+                                     ConstantArgs)) {
     SimplifiedValues[CS.getInstruction()] = C;
     return true;
   }
diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index c83d62f..5145e27 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -5166,7 +5166,7 @@
     if (Value *Ret = simplifyIntrinsic(F, ArgBegin, ArgEnd, Q))
       return Ret;
 
-  if (!canConstantFoldCallTo(CS, F))
+  if (!canConstantFoldCallTo(cast<CallBase>(CS.getInstruction()), F))
     return nullptr;
 
   SmallVector<Constant *, 4> ConstantArgs;
@@ -5178,7 +5178,8 @@
     ConstantArgs.push_back(C);
   }
 
-  return ConstantFoldCall(CS, F, ConstantArgs, Q.TLI);
+  return ConstantFoldCall(cast<CallBase>(CS.getInstruction()), F, ConstantArgs,
+                          Q.TLI);
 }
 
 Value *llvm::SimplifyCall(ImmutableCallSite CS, Value *V,
diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index 39d294f..e75a5db 100644
--- a/lib/Transforms/Scalar/SCCP.cpp
+++ b/lib/Transforms/Scalar/SCCP.cpp
@@ -1243,7 +1243,7 @@
     // Otherwise, if we have a single return value case, and if the function is
     // a declaration, maybe we can constant fold it.
     if (F && F->isDeclaration() && !I->getType()->isStructTy() &&
-        canConstantFoldCallTo(CS, F)) {
+        canConstantFoldCallTo(cast<CallBase>(CS.getInstruction()), F)) {
       SmallVector<Constant*, 8> Operands;
       for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
            AI != E; ++AI) {
@@ -1264,7 +1264,8 @@
 
       // If we can constant fold this, mark the result of the call as a
       // constant.
-      if (Constant *C = ConstantFoldCall(CS, F, Operands, TLI)) {
+      if (Constant *C = ConstantFoldCall(cast<CallBase>(CS.getInstruction()), F,
+                                         Operands, TLI)) {
         // call -> undef.
         if (isa<UndefValue>(C))
           return;
diff --git a/lib/Transforms/Utils/Evaluator.cpp b/lib/Transforms/Utils/Evaluator.cpp
index 4a8ec43..fb8cb3d 100644
--- a/lib/Transforms/Utils/Evaluator.cpp
+++ b/lib/Transforms/Utils/Evaluator.cpp
@@ -540,7 +540,8 @@
 
       if (Callee->isDeclaration()) {
         // If this is a function we can constant fold, do it.
-        if (Constant *C = ConstantFoldCall(CS, Callee, Formals, TLI)) {
+        if (Constant *C = ConstantFoldCall(cast<CallBase>(CS.getInstruction()),
+                                           Callee, Formals, TLI)) {
           InstResult = castCallResultIfNeeded(CS.getCalledValue(), C);
           if (!InstResult)
             return false;
diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index b7e6966..f10bc65 100644
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -415,8 +415,8 @@
     if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0)))
       return C->isNullValue() || isa<UndefValue>(C);
 
-  if (CallSite CS = CallSite(I))
-    if (isMathLibCallNoop(CS, TLI))
+  if (auto *Call = dyn_cast<CallBase>(I))
+    if (isMathLibCallNoop(Call, TLI))
       return true;
 
   return false;