Index: llvm/trunk/include/llvm/CodeGen/LazyMachineBlockFrequencyInfo.h
===================================================================
--- llvm/trunk/include/llvm/CodeGen/LazyMachineBlockFrequencyInfo.h
+++ llvm/trunk/include/llvm/CodeGen/LazyMachineBlockFrequencyInfo.h
@@ -17,9 +17,9 @@
 #ifndef LLVM_ANALYSIS_LAZYMACHINEBLOCKFREQUENCYINFO_H
 #define LLVM_ANALYSIS_LAZYMACHINEBLOCKFREQUENCYINFO_H
 
-#include "llvm/Analysis/LazyBlockFrequencyInfo.h"
 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
+#include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 
 namespace llvm {
@@ -28,30 +28,30 @@
 /// computed when the analysis pass is executed but rather when the BFI result
 /// is explicitly requested by the analysis client.
 ///
-/// There are some additional requirements for any client pass that wants to use
-/// the analysis:
-///
-/// 1. The pass needs to initialize dependent passes with:
-///
-///   INITIALIZE_PASS_DEPENDENCY(LazyMachineBFIPass)
-///
-/// 2. Similarly, getAnalysisUsage should call:
-///
-///   LazyMachineBlockFrequencyInfoPass::getLazyMachineBFIAnalysisUsage(AU)
-///
-/// 3. The computed MachineBFI should be requested with
-///    getAnalysis<LazyMachineBlockFrequencyInfoPass>().getBFI() before
-///    MachineLoopInfo could be invalidated for example by changing the CFG.
+/// This works by checking querying if MBFI is available and otherwise
+/// generating MBFI on the fly.  In this case the passes required for (LI, DT)
+/// are also queried before being computed on the fly.
 ///
 /// Note that it is expected that we wouldn't need this functionality for the
 /// new PM since with the new PM, analyses are executed on demand.
 
 class LazyMachineBlockFrequencyInfoPass : public MachineFunctionPass {
 private:
-  /// \brief Machine BPI is an immutable pass, no need to use it lazily.
-  LazyBlockFrequencyInfo<MachineFunction, MachineBranchProbabilityInfo,
-                         MachineLoopInfo, MachineBlockFrequencyInfo>
-      LMBFI;
+  /// If generated on the fly this own the instance.
+  mutable std::unique_ptr<MachineBlockFrequencyInfo> OwnedMBFI;
+
+  /// If generated on the fly this own the instance.
+  mutable std::unique_ptr<MachineLoopInfo> OwnedMLI;
+
+  /// If generated on the fly this own the instance.
+  mutable std::unique_ptr<MachineDominatorTree> OwnedMDT;
+
+  /// The function.
+  MachineFunction *MF = nullptr;
+
+  /// \brief Calculate MBFI and all other analyses that's not available and
+  /// required by BFI.
+  MachineBlockFrequencyInfo &calculateIfNotAvailable() const;
 
 public:
   static char ID;
@@ -59,25 +59,18 @@
   LazyMachineBlockFrequencyInfoPass();
 
   /// \brief Compute and return the block frequencies.
-  MachineBlockFrequencyInfo &getBFI() { return LMBFI.getCalculated(); }
+  MachineBlockFrequencyInfo &getBFI() { return calculateIfNotAvailable(); }
 
   /// \brief Compute and return the block frequencies.
   const MachineBlockFrequencyInfo &getBFI() const {
-    return LMBFI.getCalculated();
+    return calculateIfNotAvailable();
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override;
 
-  /// Helper for client passes to set up the analysis usage on behalf of this
-  /// pass.
-  static void getLazyMachineBFIAnalysisUsage(AnalysisUsage &AU);
-
   bool runOnMachineFunction(MachineFunction &F) override;
   void releaseMemory() override;
   void print(raw_ostream &OS, const Module *M) const override;
 };
-
-/// \brief Helper for client passes to initialize dependent passes for LMBFI.
-void initializeLazyMachineBFIPassPass(PassRegistry &Registry);
 }
 #endif
Index: llvm/trunk/lib/CodeGen/LazyMachineBlockFrequencyInfo.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/LazyMachineBlockFrequencyInfo.cpp
+++ llvm/trunk/lib/CodeGen/LazyMachineBlockFrequencyInfo.cpp
@@ -37,38 +37,61 @@
 
 void LazyMachineBlockFrequencyInfoPass::print(raw_ostream &OS,
                                               const Module *M) const {
-  LMBFI.getCalculated().print(OS, M);
+  getBFI().print(OS, M);
 }
 
 void LazyMachineBlockFrequencyInfoPass::getAnalysisUsage(
     AnalysisUsage &AU) const {
   AU.addRequired<MachineBranchProbabilityInfo>();
-  AU.addRequired<MachineLoopInfo>();
   AU.setPreservesAll();
   MachineFunctionPass::getAnalysisUsage(AU);
 }
 
 void LazyMachineBlockFrequencyInfoPass::releaseMemory() {
-  LMBFI.releaseMemory();
+  OwnedMBFI.reset();
+  OwnedMLI.reset();
+  OwnedMDT.reset();
+}
+
+MachineBlockFrequencyInfo &
+LazyMachineBlockFrequencyInfoPass::calculateIfNotAvailable() const {
+  auto *MBFI = getAnalysisIfAvailable<MachineBlockFrequencyInfo>();
+  if (MBFI) {
+    DEBUG(dbgs() << "MachineBlockFrequencyInfo is available\n");
+    return *MBFI;
+  }
+
+  auto &MBPI = getAnalysis<MachineBranchProbabilityInfo>();
+  auto *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
+  auto *MDT = getAnalysisIfAvailable<MachineDominatorTree>();
+  DEBUG(dbgs() << "Building MachineBlockFrequencyInfo on the fly\n");
+  DEBUG(if (MLI) dbgs() << "LoopInfo is available\n");
+
+  if (!MLI) {
+    DEBUG(dbgs() << "Building LoopInfo on the fly\n");
+    // First create a dominator tree.
+    DEBUG(if (MDT) dbgs() << "DominatorTree is available\n");
+
+    if (!MDT) {
+      DEBUG(dbgs() << "Building DominatorTree on the fly\n");
+      OwnedMDT = make_unique<MachineDominatorTree>();
+      OwnedMDT->getBase().recalculate(*MF);
+      MDT = OwnedMDT.get();
+    }
+
+    // Generate LoopInfo from it.
+    OwnedMLI = make_unique<MachineLoopInfo>();
+    OwnedMLI->getBase().analyze(MDT->getBase());
+    MLI = OwnedMLI.get();
+  }
+
+  OwnedMBFI = make_unique<MachineBlockFrequencyInfo>();
+  OwnedMBFI->calculate(*MF, MBPI, *MLI);
+  return *OwnedMBFI.get();
 }
 
 bool LazyMachineBlockFrequencyInfoPass::runOnMachineFunction(
-    MachineFunction &MF) {
-  auto &BPIPass = getAnalysis<MachineBranchProbabilityInfo>();
-  auto &LI = getAnalysis<MachineLoopInfo>();
-  LMBFI.setAnalysis(&MF, &BPIPass, &LI);
+    MachineFunction &F) {
+  MF = &F;
   return false;
 }
-
-void LazyMachineBlockFrequencyInfoPass::getLazyMachineBFIAnalysisUsage(
-    AnalysisUsage &AU) {
-  AU.addRequired<LazyMachineBlockFrequencyInfoPass>();
-  AU.addRequired<MachineBranchProbabilityInfo>();
-  AU.addRequired<MachineLoopInfo>();
-}
-
-void llvm::initializeLazyMachineBFIPassPass(PassRegistry &Registry) {
-  INITIALIZE_PASS_DEPENDENCY(LazyMachineBlockFrequencyInfoPass);
-  INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo);
-  INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo);
-}
Index: llvm/trunk/lib/CodeGen/MachineOptimizationRemarkEmitter.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/MachineOptimizationRemarkEmitter.cpp
+++ llvm/trunk/lib/CodeGen/MachineOptimizationRemarkEmitter.cpp
@@ -74,7 +74,7 @@
 
 void MachineOptimizationRemarkEmitterPass::getAnalysisUsage(
     AnalysisUsage &AU) const {
-  LazyMachineBlockFrequencyInfoPass::getLazyMachineBFIAnalysisUsage(AU);
+  AU.addRequired<LazyMachineBlockFrequencyInfoPass>();
   AU.setPreservesAll();
   MachineFunctionPass::getAnalysisUsage(AU);
 }
@@ -85,6 +85,6 @@
 
 INITIALIZE_PASS_BEGIN(MachineOptimizationRemarkEmitterPass, ORE_NAME, ore_name,
                       false, true)
-INITIALIZE_PASS_DEPENDENCY(LazyMachineBFIPass)
+INITIALIZE_PASS_DEPENDENCY(LazyMachineBlockFrequencyInfoPass)
 INITIALIZE_PASS_END(MachineOptimizationRemarkEmitterPass, ORE_NAME, ore_name,
                     false, true)