[CallSite removal] Migrate all Alias Analysis APIs to use the newly
minted `CallBase` class instead of the `CallSite` wrapper.

This moves the largest interwoven collection of APIs that traffic in
`CallSite`s. While a handful of these could have been migrated with
a minorly more shallow migration by converting from a `CallSite` to
a `CallBase`, it hardly seemed worth it. Most of the APIs needed to
migrate together because of the complex interplay of AA APIs and the
fact that converting from a `CallBase` to a `CallSite` isn't free in its
current implementation.

Out of tree users of these APIs can fairly reliably migrate with some
combination of `.getInstruction()` on the `CallSite` instance and
casting the resulting pointer. The most generic form will look like `CS`
-> `cast_or_null<CallBase>(CS.getInstruction())` but in most cases there
is a more elegant migration. Hopefully, this migrates enough APIs for
users to fully move from `CallSite` to the base class. All of the
in-tree users were easily migrated in that fashion.

Thanks for the review from Saleem!

Differential Revision: https://reviews.llvm.org/D55641

llvm-svn: 350503
diff --git a/llvm/lib/Analysis/ObjCARCAliasAnalysis.cpp b/llvm/lib/Analysis/ObjCARCAliasAnalysis.cpp
index 096ea66..95ae1a6 100644
--- a/llvm/lib/Analysis/ObjCARCAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/ObjCARCAliasAnalysis.cpp
@@ -106,12 +106,12 @@
   return AAResultBase::getModRefBehavior(F);
 }
 
-ModRefInfo ObjCARCAAResult::getModRefInfo(ImmutableCallSite CS,
+ModRefInfo ObjCARCAAResult::getModRefInfo(const CallBase *Call,
                                           const MemoryLocation &Loc) {
   if (!EnableARCOpts)
-    return AAResultBase::getModRefInfo(CS, Loc);
+    return AAResultBase::getModRefInfo(Call, Loc);
 
-  switch (GetBasicARCInstKind(CS.getInstruction())) {
+  switch (GetBasicARCInstKind(Call)) {
   case ARCInstKind::Retain:
   case ARCInstKind::RetainRV:
   case ARCInstKind::Autorelease:
@@ -128,7 +128,7 @@
     break;
   }
 
-  return AAResultBase::getModRefInfo(CS, Loc);
+  return AAResultBase::getModRefInfo(Call, Loc);
 }
 
 ObjCARCAAResult ObjCARCAA::run(Function &F, FunctionAnalysisManager &AM) {