[CallGraph] Given -print-callgraph a stable printing order.

[sanjoy]

Summary

Since FunctionMap maps Function* (pointers) the order in which the
traversal happens can differ from run to run, causing spurious FileCheck
failures. Have CallGraph::print sort the CallGraphNodes by name before
printing them.

llvm/trunk/lib/Analysis/IPA/CallGraph.cpp

 void CallGraph::print(raw_ostream &OS) const {
   OS << "CallGraph Root is: ";
   if (Function *F = Root->getFunction())
     OS << F->getName() << "\n";
   else {
     OS << "<<null function: 0x" << Root << ">>\n";
   }
 
-  for (CallGraph::const_iterator I = begin(), E = end(); I != E; ++I)
-    I->second->print(OS);
+  // Print in a deterministic order by sorting CallGraphNodes by name.  We do
+  // this here to avoid slowing down the non-printing fast path.
+
+  SmallVector<CallGraphNode *, 16> Nodes;
+  Nodes.reserve(FunctionMap.size());
+
+  for (auto I = begin(), E = end(); I != E; ++I)
+    Nodes.push_back(I->second);
+
+  std::sort(Nodes.begin(), Nodes.end(),
+            [](CallGraphNode *LHS, CallGraphNode *RHS) {
+    if (Function *LF = LHS->getFunction())
+      if (Function *RF = RHS->getFunction())
+        return LF->getName() < RF->getName();
+
+    return RHS->getFunction() != nullptr;
+  });
+
+  for (CallGraphNode *CN : Nodes)
+    CN->print(OS);
 }
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 void CallGraph::dump() const { print(dbgs()); }
 #endif
 
 // removeFunctionFromModule - Unlink the function from this module, returning
 // it.  Because this removes the function from the module, the call graph node

llvm/trunk/test/Analysis/CallGraph/non-leaf-intrinsics.ll

entry:
   tail call void (i64, i32, i8*, i32, ...) @llvm.experimental.patchpoint.void(i64 1, i32 15, i8* %c, i32 0, i16 65535, i16 -1, i32 65536, i32 2000000000, i32 2147483647, i32 -1, i32 4294967295, i32 4294967296, i64 2147483648, i64 4294967295, i64 4294967296, i64 -1)
   ret void
 }
 
 
 ; CHECK: Call graph node <<null function>>
 ; CHECK:  CS<0x0> calls function 'f'
 
-; CHECK: Call graph node for function: 'calls_statepoint'
-; CHECK-NEXT:  CS<[[addr_0:[^>]+]]> calls external node
-
 ; CHECK: Call graph node for function: 'calls_patchpoint'
 ; CHECK-NEXT:  CS<[[addr_1:[^>]+]]> calls external node
+
+; CHECK: Call graph node for function: 'calls_statepoint'
+; CHECK-NEXT:  CS<[[addr_0:[^>]+]]> calls external node