Added MachineBlockFrequencyInfo::view for displaying the block frequency propagation graph via graphviz.

This is useful for debugging issues in the BlockFrequency implementation
since one can easily visualize where probability mass and other errors
occur in the propagation.

This is the MI version of r194654.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196183 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/MachineBlockFrequencyInfo.h

@@ -1,4 +1,4 @@
-//====----- MachineBlockFrequencyInfo.h - MachineBlock Frequency Analysis ----====//
+//====-- MachineBlockFrequencyInfo.h - MBB Frequency Analysis -*- C++ -*--====//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -49,6 +49,9 @@ public:
   /// the other block frequencies. We do this to avoid using of floating points.
   ///
   BlockFrequency getBlockFreq(const MachineBasicBlock *MBB) const;
+
+  MachineFunction *getFunction() const;
+  void view() const;
 };
 
 }