[MBFI] add edge label with branch probability info

[davidxl]

Summary

This patch improves the dot cfg dump for BFI with edges labeled with branch probability info. This gives a more complete picture of profiling of a function. It also helps to identify bugs in BFI. This of course can be done under an option, but I think it is better to always show the information as it does not clutter the graph in any way. See http://reviews.llvm.org/F2090394 as an example of BFI graph with BP info.

[silvas]

Nice! Thanks for the screenshot. LGTM

lib/CodeGen/MachineBlockFrequencyInfo.cpp

 #include "llvm/Analysis/BlockFrequencyInfoImpl.h"
 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/Format.h"
 #include "llvm/Support/GraphWriter.h"
+#include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
 
 #define DEBUG_TYPE "block-freq"
 
 #ifndef NDEBUG
 enum GVDAGType { GVDT_None, GVDT_Fraction, GVDT_Integer };
 

 };
 
 template <>
 struct DOTGraphTraits<MachineBlockFrequencyInfo *>
     : public DefaultDOTGraphTraits {
   explicit DOTGraphTraits(bool isSimple = false)
       : DefaultDOTGraphTraits(isSimple) {}
 
+  typedef MachineBasicBlock::const_succ_iterator EdgeIter;
   static std::string getGraphName(const MachineBlockFrequencyInfo *G) {
     return G->getFunction()->getName();
   }
 
   std::string getNodeLabel(const MachineBasicBlock *Node,
                            const MachineBlockFrequencyInfo *Graph) {
     std::string Result;
     raw_string_ostream OS(Result);
 
     OS << Node->getName().str() << ":";
     switch (ViewMachineBlockFreqPropagationDAG) {
     case GVDT_Fraction:
       Graph->printBlockFreq(OS, Node);
       break;
     case GVDT_Integer:
       OS << Graph->getBlockFreq(Node).getFrequency();
       break;
     case GVDT_None:
       llvm_unreachable("If we are not supposed to render a graph we should "
                        "never reach this point.");
     }
 
     return Result;
   }
+  static std::string getEdgeAttributes(const MachineBasicBlock *Node,
+                                       EdgeIter EI,
+                                       const MachineBlockFrequencyInfo *MBFI) {
+    MachineBranchProbabilityInfo &MBPI =
+        MBFI->getAnalysis<MachineBranchProbabilityInfo>();
+    BranchProbability BP = MBPI.getEdgeProbability(Node, EI);
+    uint32_t N = BP.getNumerator();
+    uint32_t D = BP.getDenominator();
+    double Percent = 100.0 * N / D;
+    std::string Str;
+    raw_string_ostream OS(Str);
+    OS << format("label=\"%.1f%%\"", Percent);
+    OS.flush();
+    return Str;
+  }
 };
 
 } // end namespace llvm
 #endif
 
 INITIALIZE_PASS_BEGIN(MachineBlockFrequencyInfo, "machine-block-freq",
                       "Machine Block Frequency Analysis", true, true)
 INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)