diff --git a/llvm/lib/CodeGen/IntrinsicLowering.cpp b/llvm/lib/CodeGen/IntrinsicLowering.cpp
index 4a66083..aebc8fa5 100644
--- a/llvm/lib/CodeGen/IntrinsicLowering.cpp
+++ b/llvm/lib/CodeGen/IntrinsicLowering.cpp
@@ -23,6 +23,39 @@
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 
+template <class ArgIt>
+static void EnsureFunctionExists(Module &M, const char *Name,
+                                 ArgIt ArgBegin, ArgIt ArgEnd,
+                                 Type *RetTy) {
+  // Insert a correctly-typed definition now.
+  std::vector<Type *> ParamTys;
+  for (ArgIt I = ArgBegin; I != ArgEnd; ++I)
+    ParamTys.push_back(I->getType());
+  M.getOrInsertFunction(Name, FunctionType::get(RetTy, ParamTys, false));
+}
+
+static void EnsureFPIntrinsicsExist(Module &M, Function &Fn,
+                                    const char *FName,
+                                    const char *DName, const char *LDName) {
+  // Insert definitions for all the floating point types.
+  switch((int)Fn.arg_begin()->getType()->getTypeID()) {
+  case Type::FloatTyID:
+    EnsureFunctionExists(M, FName, Fn.arg_begin(), Fn.arg_end(),
+                         Type::getFloatTy(M.getContext()));
+    break;
+  case Type::DoubleTyID:
+    EnsureFunctionExists(M, DName, Fn.arg_begin(), Fn.arg_end(),
+                         Type::getDoubleTy(M.getContext()));
+    break;
+  case Type::X86_FP80TyID:
+  case Type::FP128TyID:
+  case Type::PPC_FP128TyID:
+    EnsureFunctionExists(M, LDName, Fn.arg_begin(), Fn.arg_end(),
+                         Fn.arg_begin()->getType());
+    break;
+  }
+}
+
 /// This function is used when we want to lower an intrinsic call to a call of
 /// an external function. This handles hard cases such as when there was already
 /// a prototype for the external function, but that prototype doesn't match the
@@ -38,8 +71,8 @@
   std::vector<Type *> ParamTys;
   for (ArgIt I = ArgBegin; I != ArgEnd; ++I)
     ParamTys.push_back((*I)->getType());
-  FunctionCallee FCache =
-      M->getOrInsertFunction(NewFn, FunctionType::get(RetTy, ParamTys, false));
+  Constant* FCache = M->getOrInsertFunction(NewFn,
+                                  FunctionType::get(RetTy, ParamTys, false));
 
   IRBuilder<> Builder(CI->getParent(), CI->getIterator());
   SmallVector<Value *, 8> Args(ArgBegin, ArgEnd);
@@ -58,6 +91,75 @@
 #  define setjmp_undefined_for_msvc
 #endif
 
+void IntrinsicLowering::AddPrototypes(Module &M) {
+  LLVMContext &Context = M.getContext();
+  for (auto &F : M)
+    if (F.isDeclaration() && !F.use_empty())
+      switch (F.getIntrinsicID()) {
+      default: break;
+      case Intrinsic::setjmp:
+        EnsureFunctionExists(M, "setjmp", F.arg_begin(), F.arg_end(),
+                             Type::getInt32Ty(M.getContext()));
+        break;
+      case Intrinsic::longjmp:
+        EnsureFunctionExists(M, "longjmp", F.arg_begin(), F.arg_end(),
+                             Type::getVoidTy(M.getContext()));
+        break;
+      case Intrinsic::siglongjmp:
+        EnsureFunctionExists(M, "abort", F.arg_end(), F.arg_end(),
+                             Type::getVoidTy(M.getContext()));
+        break;
+      case Intrinsic::memcpy:
+        M.getOrInsertFunction("memcpy",
+          Type::getInt8PtrTy(Context),
+                              Type::getInt8PtrTy(Context),
+                              Type::getInt8PtrTy(Context),
+                              DL.getIntPtrType(Context));
+        break;
+      case Intrinsic::memmove:
+        M.getOrInsertFunction("memmove",
+          Type::getInt8PtrTy(Context),
+                              Type::getInt8PtrTy(Context),
+                              Type::getInt8PtrTy(Context),
+                              DL.getIntPtrType(Context));
+        break;
+      case Intrinsic::memset:
+        M.getOrInsertFunction("memset",
+          Type::getInt8PtrTy(Context),
+                              Type::getInt8PtrTy(Context),
+                              Type::getInt32Ty(M.getContext()),
+                              DL.getIntPtrType(Context));
+        break;
+      case Intrinsic::sqrt:
+        EnsureFPIntrinsicsExist(M, F, "sqrtf", "sqrt", "sqrtl");
+        break;
+      case Intrinsic::sin:
+        EnsureFPIntrinsicsExist(M, F, "sinf", "sin", "sinl");
+        break;
+      case Intrinsic::cos:
+        EnsureFPIntrinsicsExist(M, F, "cosf", "cos", "cosl");
+        break;
+      case Intrinsic::pow:
+        EnsureFPIntrinsicsExist(M, F, "powf", "pow", "powl");
+        break;
+      case Intrinsic::log:
+        EnsureFPIntrinsicsExist(M, F, "logf", "log", "logl");
+        break;
+      case Intrinsic::log2:
+        EnsureFPIntrinsicsExist(M, F, "log2f", "log2", "log2l");
+        break;
+      case Intrinsic::log10:
+        EnsureFPIntrinsicsExist(M, F, "log10f", "log10", "log10l");
+        break;
+      case Intrinsic::exp:
+        EnsureFPIntrinsicsExist(M, F, "expf", "exp", "expl");
+        break;
+      case Intrinsic::exp2:
+        EnsureFPIntrinsicsExist(M, F, "exp2f", "exp2", "exp2l");
+        break;
+      }
+}
+
 /// Emit the code to lower bswap of V before the specified instruction IP.
 static Value *LowerBSWAP(LLVMContext &Context, Value *V, Instruction *IP) {
   assert(V->getType()->isIntOrIntVectorTy() && "Can't bswap a non-integer type!");