Introduce ImmutableCallSite, useful for contexts where no mutation

is necessary. Inherits from new templated baseclass CallSiteBase<>
which is highly customizable. Base CallSite on it too, in a configuration
that allows full mutation.
Adapt some call sites in analyses to employ ImmutableCallSite.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100100 91177308-0d34-0410-b5e6-96231b3b80d8

lib/VMCore/Function.cpp

@@ -408,7 +408,7 @@ bool Function::hasAddressTaken(const User* *PutOffender) const {
     const User *U = *I;
     if (!isa<CallInst>(U) && !isa<InvokeInst>(U))
       return PutOffender ? (*PutOffender = U, true) : true;
-    CallSite CS(const_cast<Instruction*>(static_cast<const Instruction*>(U)));
+    ImmutableCallSite CS(cast<Instruction>(U));
     if (!CS.isCallee(I))
       return PutOffender ? (*PutOffender = U, true) : true;
   }