[PATCH] D21596: [MBFI] add edge label with branch probability info

[David Li via llvm-commits]

davidxl created this revision.
davidxl added reviewers: danielcdh, silvas.
davidxl added a subscriber: llvm-commits.

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.

http://reviews.llvm.org/D21596

Files:
  lib/CodeGen/MachineBlockFrequencyInfo.cpp

Index: lib/CodeGen/MachineBlockFrequencyInfo.cpp
===================================================================
--- lib/CodeGen/MachineBlockFrequencyInfo.cpp
+++ lib/CodeGen/MachineBlockFrequencyInfo.cpp
@@ -20,7 +20,9 @@
 #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;
 
@@ -80,6 +82,7 @@
   explicit DOTGraphTraits(bool isSimple = false)
       : DefaultDOTGraphTraits(isSimple) {}
 
+  typedef MachineBasicBlock::const_succ_iterator EdgeIter;
   static std::string getGraphName(const MachineBlockFrequencyInfo *G) {
     return G->getFunction()->getName();
   }
@@ -104,6 +107,21 @@
 
     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


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