Index: lib/CodeGen/StackProtector.cpp
===================================================================
--- lib/CodeGen/StackProtector.cpp
+++ lib/CodeGen/StackProtector.cpp
@@ -422,7 +422,6 @@
       CallInst *Call = B.CreateCall(GuardCheck, {Guard});
       llvm::Function *Function = cast<llvm::Function>(GuardCheck);
       Call->setAttributes(Function->getAttributes());
-      Call->setCallingConv(Function->getCallingConv());
     } else {
       // Generate the epilogue with inline instrumentation.
       // If we do not support SelectionDAG based tail calls, generate IR level
Index: lib/IR/Instructions.cpp
===================================================================
--- lib/IR/Instructions.cpp
+++ lib/IR/Instructions.cpp
@@ -281,6 +281,13 @@
 //                        CallInst Implementation
 //===----------------------------------------------------------------------===//
 
+template <class CallTy>
+static void tryCopyCallingConvention(CallTy *To, Value const *From) {
+  // ensure Calling Convention consistency if possible
+  if (Function const *F = dyn_cast<Function const>(From->stripPointerCasts()))
+    To->setCallingConv(F->getCallingConv());
+}
+
 void CallInst::init(FunctionType *FTy, Value *Func, ArrayRef<Value *> Args,
                     ArrayRef<OperandBundleDef> Bundles, const Twine &NameStr) {
   this->FTy = FTy;
@@ -306,6 +313,7 @@
   assert(It + 1 == op_end() && "Should add up!");
 
   setName(NameStr);
+  tryCopyCallingConvention(this, Func);
 }
 
 void CallInst::init(Value *Func, const Twine &NameStr) {
@@ -317,6 +325,7 @@
   assert(FTy->getNumParams() == 0 && "Calling a function with bad signature");
 
   setName(NameStr);
+  tryCopyCallingConvention(this, Func);
 }
 
 CallInst::CallInst(Value *Func, const Twine &Name,
@@ -652,9 +661,6 @@
     Result = CallInst::Create(FreeFunc, PtrCast, Bundles, "");
   }
   Result->setTailCall();
-  if (Function *F = dyn_cast<Function>(FreeFunc))
-    Result->setCallingConv(F->getCallingConv());
-
   return Result;
 }
 
@@ -718,6 +724,7 @@
   assert(It + 3 == op_end() && "Should add up!");
 
   setName(NameStr);
+  tryCopyCallingConvention(this, Fn);
 }
 
 InvokeInst::InvokeInst(const InvokeInst &II)
Index: lib/Target/AMDGPU/AMDGPULibCalls.cpp
===================================================================
--- lib/Target/AMDGPU/AMDGPULibCalls.cpp
+++ lib/Target/AMDGPU/AMDGPULibCalls.cpp
@@ -220,8 +220,6 @@
 CallInst *CreateCallEx(IRB &B, Value *Callee, Value *Arg, const Twine &Name="")
 {
   CallInst *R = B.CreateCall(Callee, Arg, Name);
-  if (Function* F = dyn_cast<Function>(Callee))
-    R->setCallingConv(F->getCallingConv());
   return R;
 }
 
@@ -229,8 +227,6 @@
 CallInst *CreateCallEx2(IRB &B, Value *Callee, Value *Arg1, Value *Arg2,
                         const Twine &Name="") {
   CallInst *R = B.CreateCall(Callee, {Arg1, Arg2}, Name);
-  if (Function* F = dyn_cast<Function>(Callee))
-    R->setCallingConv(F->getCallingConv());
   return R;
 }
 
Index: lib/Transforms/Utils/BuildLibCalls.cpp
===================================================================
--- lib/Transforms/Utils/BuildLibCalls.cpp
+++ lib/Transforms/Utils/BuildLibCalls.cpp
@@ -727,9 +727,6 @@
                                             B.getInt8PtrTy());
   inferLibFuncAttributes(*M->getFunction("strlen"), *TLI);
   CallInst *CI = B.CreateCall(StrLen, castToCStr(Ptr, B), "strlen");
-  if (const Function *F = dyn_cast<Function>(StrLen->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
-
   return CI;
 }
 
@@ -746,8 +743,6 @@
   inferLibFuncAttributes(*M->getFunction("strchr"), *TLI);
   CallInst *CI = B.CreateCall(
       StrChr, {castToCStr(Ptr, B), ConstantInt::get(I32Ty, C)}, "strchr");
-  if (const Function *F = dyn_cast<Function>(StrChr->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
   return CI;
 }
 
@@ -764,10 +759,6 @@
   inferLibFuncAttributes(*M->getFunction("strncmp"), *TLI);
   CallInst *CI = B.CreateCall(
       StrNCmp, {castToCStr(Ptr1, B), castToCStr(Ptr2, B), Len}, "strncmp");
-
-  if (const Function *F = dyn_cast<Function>(StrNCmp->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
-
   return CI;
 }
 
@@ -782,8 +773,6 @@
   inferLibFuncAttributes(*M->getFunction(Name), *TLI);
   CallInst *CI =
       B.CreateCall(StrCpy, {castToCStr(Dst, B), castToCStr(Src, B)}, Name);
-  if (const Function *F = dyn_cast<Function>(StrCpy->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
   return CI;
 }
 
@@ -799,8 +788,6 @@
   inferLibFuncAttributes(*M->getFunction(Name), *TLI);
   CallInst *CI = B.CreateCall(
       StrNCpy, {castToCStr(Dst, B), castToCStr(Src, B), Len}, "strncpy");
-  if (const Function *F = dyn_cast<Function>(StrNCpy->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
   return CI;
 }
 
@@ -822,8 +809,6 @@
   Dst = castToCStr(Dst, B);
   Src = castToCStr(Src, B);
   CallInst *CI = B.CreateCall(MemCpy, {Dst, Src, Len, ObjSize});
-  if (const Function *F = dyn_cast<Function>(MemCpy->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
   return CI;
 }
 
@@ -839,10 +824,6 @@
                                          DL.getIntPtrType(Context));
   inferLibFuncAttributes(*M->getFunction("memchr"), *TLI);
   CallInst *CI = B.CreateCall(MemChr, {castToCStr(Ptr, B), Val, Len}, "memchr");
-
-  if (const Function *F = dyn_cast<Function>(MemChr->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
-
   return CI;
 }
 
@@ -859,10 +840,6 @@
   inferLibFuncAttributes(*M->getFunction("memcmp"), *TLI);
   CallInst *CI = B.CreateCall(
       MemCmp, {castToCStr(Ptr1, B), castToCStr(Ptr2, B), Len}, "memcmp");
-
-  if (const Function *F = dyn_cast<Function>(MemCmp->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
-
   return CI;
 }
 
@@ -897,9 +874,6 @@
   CI->setAttributes(Attrs.removeAttribute(B.getContext(),
                                           AttributeList::FunctionIndex,
                                           Attribute::Speculatable));
-  if (const Function *F = dyn_cast<Function>(Callee->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
-
   return CI;
 }
 
@@ -913,9 +887,6 @@
                                          Op2->getType());
   CallInst *CI = B.CreateCall(Callee, {Op1, Op2}, Name);
   CI->setAttributes(Attrs);
-  if (const Function *F = dyn_cast<Function>(Callee->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
-
   return CI;
 }
 
@@ -933,9 +904,6 @@
                               /*isSigned*/true,
                               "chari"),
                               "putchar");
-
-  if (const Function *F = dyn_cast<Function>(PutChar->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
   return CI;
 }
 
@@ -949,8 +917,6 @@
       M->getOrInsertFunction("puts", B.getInt32Ty(), B.getInt8PtrTy());
   inferLibFuncAttributes(*M->getFunction("puts"), *TLI);
   CallInst *CI = B.CreateCall(PutS, castToCStr(Str, B), "puts");
-  if (const Function *F = dyn_cast<Function>(PutS->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
   return CI;
 }
 
@@ -967,9 +933,6 @@
   Char = B.CreateIntCast(Char, B.getInt32Ty(), /*isSigned*/true,
                          "chari");
   CallInst *CI = B.CreateCall(F, {Char, File}, "fputc");
-
-  if (const Function *Fn = dyn_cast<Function>(F->stripPointerCasts()))
-    CI->setCallingConv(Fn->getCallingConv());
   return CI;
 }
 
@@ -985,9 +948,6 @@
   if (File->getType()->isPointerTy())
     inferLibFuncAttributes(*M->getFunction(FPutsName), *TLI);
   CallInst *CI = B.CreateCall(F, {castToCStr(Str, B), File}, "fputs");
-
-  if (const Function *Fn = dyn_cast<Function>(F->stripPointerCasts()))
-    CI->setCallingConv(Fn->getCallingConv());
   return CI;
 }
 
@@ -1008,8 +968,5 @@
   CallInst *CI =
       B.CreateCall(F, {castToCStr(Ptr, B), Size,
                        ConstantInt::get(DL.getIntPtrType(Context), 1), File});
-
-  if (const Function *Fn = dyn_cast<Function>(F->stripPointerCasts()))
-    CI->setCallingConv(Fn->getCallingConv());
   return CI;
 }
Index: lib/Transforms/Utils/SimplifyLibCalls.cpp
===================================================================
--- lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -844,9 +844,6 @@
                                          PtrType, PtrType);
   CallInst *CI = B.CreateCall(Calloc, { Num, Size }, "calloc");
 
-  if (const auto *F = dyn_cast<Function>(Calloc->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
-
   return CI;
 }
 
@@ -1280,8 +1277,6 @@
           M->getOrInsertFunction(TLI->getName(LdExp), Op->getType(),
                                  Op->getType(), B.getInt32Ty());
       CallInst *CI = B.CreateCall(NewCallee, {One, LdExpArg});
-      if (const Function *F = dyn_cast<Function>(Callee->stripPointerCasts()))
-        CI->setCallingConv(F->getCallingConv());
 
       return CI;
     }