Change Function::getIntrinsicID() to return an Intrinsic::ID. NFC.

Now that Intrinsic::ID is a typed enum, we can forward declare it and so return it from this method.

This updates all users which were either using an unsigned to store it, or had a now unnecessary cast.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237810 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -2382,7 +2382,7 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
       Intrinsic::ID IID  = Intrinsic::not_intrinsic;
       Value *ScalarArg = nullptr;
       if (CI && (FI = CI->getCalledFunction())) {
-        IID = (Intrinsic::ID) FI->getIntrinsicID();
+        IID = FI->getIntrinsicID();
       }
       std::vector<Value *> OpVecs;
       for (int j = 0, e = CI->getNumArgOperands(); j < e; ++j) {