[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

lib/IR/Function.cpp

@@ -846,6 +846,18 @@ bool Intrinsic::isOverloaded(ID id) {
 #undef GET_INTRINSIC_OVERLOAD_TABLE
 }
 
+bool Intrinsic::isLeaf(ID id) {
+  switch (id) {
+  default:
+    return true;
+
+  case Intrinsic::experimental_gc_statepoint:
+  case Intrinsic::experimental_patchpoint_void:
+  case Intrinsic::experimental_patchpoint_i64:
+    return false;
+  }
+}
+
 /// This defines the "Intrinsic::getAttributes(ID id)" method.
 #define GET_INTRINSIC_ATTRIBUTES
 #include "llvm/IR/Intrinsics.gen"