[CallGraph] Teach the CallGraph about non-leaf intrinsics.

Summary:
Currently intrinsics don't affect the creation of the call graph.
This is not accurate with respect to statepoint and patchpoint
intrinsics -- these do call (or invoke) LLVM level functions.

This change fixes this inconsistency by adding a call to the external
node for call sites that call these non-leaf intrinsics.  This coupled
with the fact that these intrinsics also escape the function pointer
they call gives us a conservatively correct call graph.

Reviewers: reames, chandlerc, atrick, pgavlin

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10526

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240039 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/CallGraph.h

@@ -56,6 +56,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/Function.h"
+#include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/Pass.h"
 #include <map>
@@ -229,7 +230,8 @@ public:
   /// \brief Adds a function to the list of functions called by this one.
   void addCalledFunction(CallSite CS, CallGraphNode *M) {
     assert(!CS.getInstruction() || !CS.getCalledFunction() ||
-           !CS.getCalledFunction()->isIntrinsic());
+           !CS.getCalledFunction()->isIntrinsic() ||
+           !Intrinsic::isLeaf(CS.getCalledFunction()->getIntrinsicID()));
     CalledFunctions.emplace_back(CS.getInstruction(), M);
     M->AddRef();
   }

include/llvm/IR/Intrinsics.h

@@ -52,6 +52,11 @@ namespace Intrinsic {
   /// Returns true if the intrinsic can be overloaded.
   bool isOverloaded(ID id);
 
+  /// Returns true if the intrinsic is a leaf, i.e. it does not make any calls
+  /// itself.  Most intrinsics are leafs, the exceptions being the patchpoint
+  /// and statepoint intrinsics. These call (or invoke) their "target" argument.
+  bool isLeaf(ID id);
+
   /// Return the attributes for an intrinsic.
   AttributeSet getAttributes(LLVMContext &C, ID id);