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

1 files changed, 107 insertions, 0 deletions

diff --git a/lib/CodeGen/MachineBlockFrequencyInfo.cpp b/lib/CodeGen/MachineBlockFrequencyInfo.cpp
index e269d24e1d..f3d7c80cef 100644
--- a/lib/CodeGen/MachineBlockFrequencyInfo.cpp
+++ b/lib/CodeGen/MachineBlockFrequencyInfo.cpp
@@ -16,9 +16,93 @@
 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/InitializePasses.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>
+ViewMachineBlockFreqPropagationDAG("view-machine-block-freq-propagation-dags",
+                                   cl::Hidden,
+          cl::desc("Pop up a window to show a dag displaying how machine block "
+                   "frequencies propgate 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<MachineBlockFrequencyInfo *> {
+  typedef const MachineBasicBlock NodeType;
+  typedef MachineBasicBlock::const_succ_iterator ChildIteratorType;
+  typedef MachineFunction::const_iterator nodes_iterator;
+
+  static inline const NodeType *getEntryNode(const MachineBlockFrequencyInfo *G) {
+    return G->getFunction()->begin();
+  }
+  static ChildIteratorType child_begin(const NodeType *N) {
+    return N->succ_begin();
+  }
+  static ChildIteratorType child_end(const NodeType *N) {
+    return N->succ_end();
+  }
+  static nodes_iterator nodes_begin(const MachineBlockFrequencyInfo *G) {
+    return G->getFunction()->begin();
+  }
+  static nodes_iterator nodes_end(const MachineBlockFrequencyInfo *G) {
+    return G->getFunction()->end();
+  }
+};
+
+template<>
+struct DOTGraphTraits<MachineBlockFrequencyInfo*> : public DefaultDOTGraphTraits {
+  explicit DOTGraphTraits(bool isSimple=false) :
+    DefaultDOTGraphTraits(isSimple) {}
+
+  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->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(MachineBlockFrequencyInfo, "machine-block-freq",
                       "Machine Block Frequency Analysis", true, true)
 INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
@@ -47,10 +131,33 @@ void MachineBlockFrequencyInfo::getAnalysisUsage(AnalysisUsage &AU) const {
 bool MachineBlockFrequencyInfo::runOnMachineFunction(MachineFunction &F) {
   MachineBranchProbabilityInfo &MBPI = getAnalysis<MachineBranchProbabilityInfo>();
   MBFI->doFunction(&F, &MBPI);
+#ifndef NDEBUG
+  if (ViewMachineBlockFreqPropagationDAG != GVDT_None) {
+    view();
+  }
+#endif
   return false;
 }
 
+/// Pop up a ghostview window with the current block frequency propagation
+/// rendered using dot.
+void MachineBlockFrequencyInfo::view() const {
+// This code is only for debugging.
+#ifndef NDEBUG
+  ViewGraph(const_cast<MachineBlockFrequencyInfo *>(this),
+            "MachineBlockFrequencyDAGs");
+#else
+  errs() << "BlockFrequencyInfo::view is only available in debug builds on "
+            "systems with Graphviz or gv!\n";
+#endif // NDEBUG
+}
+
 BlockFrequency MachineBlockFrequencyInfo::
 getBlockFreq(const MachineBasicBlock *MBB) const {
   return MBFI->getBlockFreq(MBB);
 }
+
+MachineFunction *MachineBlockFrequencyInfo::getFunction() const {
+  return MBFI->Fn;
+}
+