Allow derived DOTViewers to choose the functions to illustrate

Instead of always showing/printing all functions, a class derived from
the DOTViewer class can overwrite the set of functions that will be
processed.

This will be used (and tested) by Polly's scop viewers, but other users
can be imagined as well.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243881 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/DOTGraphTraitsPass.h

@@ -36,7 +36,18 @@ class DOTGraphTraitsViewer : public FunctionPass {
   DOTGraphTraitsViewer(StringRef GraphName, char &ID)
       : FunctionPass(ID), Name(GraphName) {}
 
+  /// @brief Return true if this function should be processed.
+  ///
+  /// An implementation of this class my override this function to indicate that
+  /// only certain functions should be viewed.
+  virtual bool processFunction(Function &F) {
+    return true;
+  }
+
   bool runOnFunction(Function &F) override {
+    if (!processFunction(F))
+      return false;
+
     GraphT Graph = AnalysisGraphTraitsT::getGraph(&getAnalysis<AnalysisT>());
     std::string GraphName = DOTGraphTraits<GraphT>::getGraphName(Graph);
     std::string Title = GraphName + " for '" + F.getName().str() + "' function";
@@ -63,7 +74,18 @@ class DOTGraphTraitsPrinter : public FunctionPass {
   DOTGraphTraitsPrinter(StringRef GraphName, char &ID)
       : FunctionPass(ID), Name(GraphName) {}
 
+  /// @brief Return true if this function should be processed.
+  ///
+  /// An implementation of this class my override this function to indicate that
+  /// only certain functions should be printed.
+  virtual bool processFunction(Function &F) {
+    return true;
+  }
+
   bool runOnFunction(Function &F) override {
+    if (!processFunction(F))
+      return false;
+
     GraphT Graph = AnalysisGraphTraitsT::getGraph(&getAnalysis<AnalysisT>());
     std::string Filename = Name + "." + F.getName().str() + ".dot";
     std::error_code EC;