Add a hidden command line option to display edge bundle graphs as they are
calculated.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122912 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/EdgeBundles.cpp b/lib/CodeGen/EdgeBundles.cpp
index d7e73d1..aed8bc9 100644
--- a/lib/CodeGen/EdgeBundles.cpp
+++ b/lib/CodeGen/EdgeBundles.cpp
@@ -15,10 +15,15 @@
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/Passes.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/GraphWriter.h"
 
 using namespace llvm;
 
+static cl::opt<bool>
+ViewEdgeBundles("view-edge-bundles", cl::Hidden,
+                cl::desc("Pop up a window to show edge bundle graphs"));
+
 char EdgeBundles::ID = 0;
 
 INITIALIZE_PASS(EdgeBundles, "edge-bundles", "Bundle Machine CFG Edges",
@@ -46,6 +51,8 @@
       EC.join(OutE, 2 * (*SI)->getNumber());
   }
   EC.compress();
+  if (ViewEdgeBundles)
+    view();
   return false;
 }