Added BlockFrequencyInfo::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.

llvm-svn: 194654

1 files changed, 103 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/BlockFrequencyInfo.cpp b/llvm/lib/Analysis/BlockFrequencyInfo.cpp
index 541404d91b5..62f3ab16ca7 100644
--- a/llvm/lib/Analysis/BlockFrequencyInfo.cpp
+++ b/llvm/lib/Analysis/BlockFrequencyInfo.cpp
@@ -17,9 +17,92 @@
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/Passes.h"
 #include "llvm/InitializePasses.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/GraphWriter.h"
 
 using namespace llvm;
 
+#ifndef NDEBUG
+enum GVDAGType {
+  GVDT_None,
+  GVDT_Fraction,
+  GVDT_Integer
+};
+
+static cl::opt<GVDAGType>
+ViewBlockFreqPropagationDAG("view-block-freq-propagation-dags", cl::Hidden,
+          cl::desc("Pop up a window to show a dag displaying how block "
+                   "frequencies propagation through the CFG."),
+          cl::values(
+            clEnumValN(GVDT_None, "none",
+                       "do not display graphs."),
+            clEnumValN(GVDT_Fraction, "fraction", "display a graph using the "
+                       "fractional block frequency representation."),
+            clEnumValN(GVDT_Integer, "integer", "display a graph using the raw "
+                       "integer fractional block frequency representation."),
+            clEnumValEnd));
+
+namespace llvm {
+
+template <>
+struct GraphTraits<BlockFrequencyInfo *> {
+  typedef const BasicBlock NodeType;
+  typedef succ_const_iterator ChildIteratorType;
+  typedef Function::const_iterator nodes_iterator;
+
+  static inline const NodeType *getEntryNode(const BlockFrequencyInfo *G) {
+    return G->getFunction()->begin();
+  }
+  static ChildIteratorType child_begin(const NodeType *N) {
+    return succ_begin(N);
+  }
+  static ChildIteratorType child_end(const NodeType *N) {
+    return succ_end(N);
+  }
+  static nodes_iterator nodes_begin(const BlockFrequencyInfo *G) {
+    return G->getFunction()->begin();
+  }
+  static nodes_iterator nodes_end(const BlockFrequencyInfo *G) {
+    return G->getFunction()->end();
+  }
+};
+
+template<>
+struct DOTGraphTraits<BlockFrequencyInfo*> : public DefaultDOTGraphTraits {
+  explicit DOTGraphTraits(bool isSimple=false) :
+    DefaultDOTGraphTraits(isSimple) {}
+
+  static std::string getGraphName(const BlockFrequencyInfo *G) {
+    return G->getFunction()->getName();
+  }
+
+  std::string getNodeLabel(const BasicBlock *Node,
+                           const BlockFrequencyInfo *Graph) {
+    std::string Result;
+    raw_string_ostream OS(Result);
+
+    OS << Node->getName().str() << ":";
+    switch (ViewBlockFreqPropagationDAG) {
+    case GVDT_Fraction:
+      Graph->getBlockFreq(Node).print(OS);
+      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;
+  }
+};
+
+} // end namespace llvm
+#endif
+
 INITIALIZE_PASS_BEGIN(BlockFrequencyInfo, "block-freq",
                       "Block Frequency Analysis", true, true)
 INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfo)
@@ -46,6 +129,10 @@ void BlockFrequencyInfo::getAnalysisUsage(AnalysisUsage &AU) const {
 bool BlockFrequencyInfo::runOnFunction(Function &F) {
   BranchProbabilityInfo &BPI = getAnalysis<BranchProbabilityInfo>();
   BFI->doFunction(&F, &BPI);
+#ifndef NDEBUG
+  if (ViewBlockFreqPropagationDAG != GVDT_None)
+    view();
+#endif
   return false;
 }
 
@@ -56,3 +143,19 @@ void BlockFrequencyInfo::print(raw_ostream &O, const Module *) const {
 BlockFrequency BlockFrequencyInfo::getBlockFreq(const BasicBlock *BB) const {
   return BFI->getBlockFreq(BB);
 }
+
+/// Pop up a ghostview window with the current block frequency propagation
+/// rendered using dot.
+void BlockFrequencyInfo::view() const {
+// This code is only for debugging.
+#ifndef NDEBUG
+  ViewGraph(const_cast<BlockFrequencyInfo *>(this), "BlockFrequencyDAGs");
+#else
+  errs() << "BlockFrequencyInfo::view is only available in debug builds on "
+            "systems with Graphviz or gv!\n";
+#endif // NDEBUG
+}
+
+const Function *BlockFrequencyInfo::getFunction() const {
+  return BFI->Fn;
+}