Revert "[opaque pointer types] Add a FunctionCallee wrapper type, and use it."

This reverts commit f47d6b38c7a61d50db4566b02719de05492dcef1 (r352791).

Seems to run into compilation failures with GCC (but not clang, where
I tested it). Reverting while I investigate.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@352800 91177308-0d34-0410-b5e6-96231b3b80d8

lib/IR/Module.cpp

@@ -140,8 +140,8 @@ void Module::getOperandBundleTags(SmallVectorImpl<StringRef> &Result) const {
 // it.  This is nice because it allows most passes to get away with not handling
 // the symbol table directly for this common task.
 //
-FunctionCallee Module::getOrInsertFunction(StringRef Name, FunctionType *Ty,
-                                           AttributeList AttributeList) {
+Constant *Module::getOrInsertFunction(StringRef Name, FunctionType *Ty,
+                                      AttributeList AttributeList) {
   // See if we have a definition for the specified function already.
   GlobalValue *F = getNamedValue(Name);
   if (!F) {
@@ -151,20 +151,21 @@ FunctionCallee Module::getOrInsertFunction(StringRef Name, FunctionType *Ty,
     if (!New->isIntrinsic())       // Intrinsics get attrs set on construction
       New->setAttributes(AttributeList);
     FunctionList.push_back(New);
-    return {Ty, New}; // Return the new prototype.
+    return New;                    // Return the new prototype.
   }
 
   // If the function exists but has the wrong type, return a bitcast to the
   // right type.
   auto *PTy = PointerType::get(Ty, F->getAddressSpace());
   if (F->getType() != PTy)
-    return {Ty, ConstantExpr::getBitCast(F, PTy)};
+    return ConstantExpr::getBitCast(F, PTy);
 
   // Otherwise, we just found the existing function or a prototype.
-  return {Ty, F};
+  return F;
 }
 
-FunctionCallee Module::getOrInsertFunction(StringRef Name, FunctionType *Ty) {
+Constant *Module::getOrInsertFunction(StringRef Name,
+                                      FunctionType *Ty) {
   return getOrInsertFunction(Name, Ty, AttributeList());
 }