diff --git a/llvm/lib/Analysis/StackSafetyAnalysis.cpp b/llvm/lib/Analysis/StackSafetyAnalysis.cpp
--- a/llvm/lib/Analysis/StackSafetyAnalysis.cpp
+++ b/llvm/lib/Analysis/StackSafetyAnalysis.cpp
@@ -10,7 +10,6 @@
 
 #include "llvm/Analysis/StackSafetyAnalysis.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
-#include "llvm/IR/CallSite.h"
 #include "llvm/IR/InstIterator.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/InitializePasses.h"
@@ -340,7 +339,7 @@
 
       case Instruction::Call:
       case Instruction::Invoke: {
-        ImmutableCallSite CS(I);
+        const auto &CB = cast<CallBase>(*I);
 
         if (I->isLifetimeStartOrEnd())
           break;
@@ -354,7 +353,7 @@
         // Do not follow aliases, otherwise we could inadvertently follow
         // dso_preemptable aliases or aliases with interposable linkage.
         const GlobalValue *Callee =
-            dyn_cast<GlobalValue>(CS.getCalledValue()->stripPointerCasts());
+            dyn_cast<GlobalValue>(CB.getCalledValue()->stripPointerCasts());
         if (!Callee) {
           US.updateRange(UnknownRange);
           return false;
@@ -362,8 +361,8 @@
 
         assert(isa<Function>(Callee) || isa<GlobalAlias>(Callee));
 
-        ImmutableCallSite::arg_iterator B = CS.arg_begin(), E = CS.arg_end();
-        for (ImmutableCallSite::arg_iterator A = B; A != E; ++A) {
+        auto B = CB.arg_begin(), E = CB.arg_end();
+        for (auto A = B; A != E; ++A) {
           if (A->get() == V) {
             ConstantRange Offset = offsetFromAlloca(UI, Ptr);
             US.Calls.emplace_back(Callee, A - B, Offset);
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -31,7 +31,6 @@
 #include "llvm/Config/llvm-config.h"
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/BasicBlock.h"
-#include "llvm/IR/CallSite.h"
 #include "llvm/IR/Comdat.h"
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/Constants.h"
@@ -374,7 +373,7 @@
   void writeModuleConstants();
   bool pushValueAndType(const Value *V, unsigned InstID,
                         SmallVectorImpl<unsigned> &Vals);
-  void writeOperandBundles(ImmutableCallSite CS, unsigned InstID);
+  void writeOperandBundles(const CallBase &CB, unsigned InstID);
   void pushValue(const Value *V, unsigned InstID,
                  SmallVectorImpl<unsigned> &Vals);
   void pushValueSigned(const Value *V, unsigned InstID,
@@ -2583,10 +2582,10 @@
   return false;
 }
 
-void ModuleBitcodeWriter::writeOperandBundles(ImmutableCallSite CS,
+void ModuleBitcodeWriter::writeOperandBundles(const CallBase &CS,
                                               unsigned InstID) {
   SmallVector<unsigned, 64> Record;
-  LLVMContext &C = CS.getInstruction()->getContext();
+  LLVMContext &C = CS.getContext();
 
   for (unsigned i = 0, e = CS.getNumOperandBundles(); i != e; ++i) {
     const auto &Bundle = CS.getOperandBundleAt(i);
@@ -2778,7 +2777,7 @@
     FunctionType *FTy = II->getFunctionType();
 
     if (II->hasOperandBundles())
-      writeOperandBundles(II, InstID);
+      writeOperandBundles(*II, InstID);
 
     Code = bitc::FUNC_CODE_INST_INVOKE;
 
@@ -2854,7 +2853,7 @@
     FunctionType *FTy = CBI->getFunctionType();
 
     if (CBI->hasOperandBundles())
-      writeOperandBundles(CBI, InstID);
+      writeOperandBundles(*CBI, InstID);
 
     Code = bitc::FUNC_CODE_INST_CALLBR;
 
@@ -3011,7 +3010,7 @@
     FunctionType *FTy = CI.getFunctionType();
 
     if (CI.hasOperandBundles())
-      writeOperandBundles(&CI, InstID);
+      writeOperandBundles(CI, InstID);
 
     Code = bitc::FUNC_CODE_INST_CALL;
 
diff --git a/llvm/lib/Transforms/ObjCARC/DependencyAnalysis.cpp b/llvm/lib/Transforms/ObjCARC/DependencyAnalysis.cpp
--- a/llvm/lib/Transforms/ObjCARC/DependencyAnalysis.cpp
+++ b/llvm/lib/Transforms/ObjCARC/DependencyAnalysis.cpp
@@ -95,10 +95,9 @@
     // of any other dynamic reference-counted pointers.
     if (!IsPotentialRetainableObjPtr(ICI->getOperand(1), *PA.getAA()))
       return false;
-  } else if (auto CS = ImmutableCallSite(Inst)) {
+  } else if (const auto *CS = dyn_cast<CallBase>(Inst)) {
     // For calls, just check the arguments (and not the callee operand).
-    for (ImmutableCallSite::arg_iterator OI = CS.arg_begin(),
-         OE = CS.arg_end(); OI != OE; ++OI) {
+    for (auto OI = CS->arg_begin(), OE = CS->arg_end(); OI != OE; ++OI) {
       const Value *Op = *OI;
       if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) &&
           PA.related(Ptr, Op, DL))
diff --git a/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp b/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp
--- a/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp
+++ b/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp
@@ -115,8 +115,7 @@
 /// return value. We do this late so we do not disrupt the dataflow analysis in
 /// ObjCARCOpt.
 bool ObjCARCContract::optimizeRetainCall(Function &F, Instruction *Retain) {
-  ImmutableCallSite CS(GetArgRCIdentityRoot(Retain));
-  const Instruction *Call = CS.getInstruction();
+  const auto *Call = dyn_cast<CallBase>(GetArgRCIdentityRoot(Retain));
   if (!Call)
     return false;
   if (Call->getParent() != Retain->getParent())