[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/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);