Create a wrapper pass for BranchProbabilityInfo so that branch probability analysis can be done without requiring a pass.

[congh]

Summary

This patch is similar to the one adding a wrapper to BlockFrequencyInfo. The patch creates a wrapper pass for BranchProbabilityInfo. This is useful when we want to do branch probability analysis conditionally (e.g. only in PGO mode) but don't want to add one more pass dependence.

[congh]

This patch is already in the trunk, which was accepted by dexonsmith in email.

include/llvm/Analysis/BranchProbabilityInfo.h

 #include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/BranchProbability.h"
 
 namespace llvm {
 class LoopInfo;
 class raw_ostream;
 
-/// \brief Analysis pass providing branch probability information.
+/// \brief Analysis providing branch probability information.
 ///
-/// This is a function analysis pass which provides information on the relative
+/// This is a function analysis which provides information on the relative
 /// probabilities of each "edge" in the function's CFG where such an edge is
 /// defined by a pair (PredBlock and an index in the successors). The
 /// probability of an edge from one block is always relative to the
 /// probabilities of other edges from the block. The probabilites of all edges
 /// from a block sum to exactly one (100%).
 /// We use a pair (PredBlock and an index in the successors) to uniquely
 /// identify an edge, since we can have multiple edges from Src to Dst.
 /// As an example, we can have a switch which jumps to Dst with value 0 and
 /// value 10.
-class BranchProbabilityInfo : public FunctionPass {
+class BranchProbabilityInfo {
 public:
-  static char ID;
-
-  BranchProbabilityInfo() : FunctionPass(ID) {
-    initializeBranchProbabilityInfoPass(*PassRegistry::getPassRegistry());
-  }
-
-  void getAnalysisUsage(AnalysisUsage &AU) const override;
-  bool runOnFunction(Function &F) override;
+  void releaseMemory();
 
-  void releaseMemory() override;
-
-  void print(raw_ostream &OS, const Module *M = nullptr) const override;
+  void print(raw_ostream &OS) const;
 
   /// \brief Get an edge's probability, relative to other out-edges of the Src.
   ///
   /// This routine provides access to the fractional probability between zero
   /// (0%) and one (100%) of this edge executing, relative to other edges
   /// leaving the 'Src' block. The returned probability is never zero, and can
   /// only be one if the source block has only one successor.
   BranchProbability getEdgeProbability(const BasicBlock *Src,
public:
   /// weights are calculated carefully before using!
   void setEdgeWeight(const BasicBlock *Src, unsigned IndexInSuccessors,
                      uint32_t Weight);
 
   static uint32_t getBranchWeightStackProtector(bool IsLikely) {
     return IsLikely ? (1u << 20) - 1 : 1;
   }
 
+  void calculate(Function &F, const LoopInfo& LI);
+
 private:
   // Since we allow duplicate edges from one basic block to another, we use
   // a pair (PredBlock and an index in the successors) to specify an edge.
   typedef std::pair<const BasicBlock *, unsigned> Edge;
 
   // Default weight value. Used when we don't have information about the edge.
   // TODO: DEFAULT_WEIGHT makes sense during static predication, when none of
   // the successors have a weight yet. But it doesn't make sense when providing
private:
 
   /// \brief Get sum of the block successors' weights.
   uint32_t getSumForBlock(const BasicBlock *BB) const;
 
   bool calcUnreachableHeuristics(BasicBlock *BB);
   bool calcMetadataWeights(BasicBlock *BB);
   bool calcColdCallHeuristics(BasicBlock *BB);
   bool calcPointerHeuristics(BasicBlock *BB);
-  bool calcLoopBranchHeuristics(BasicBlock *BB);
+  bool calcLoopBranchHeuristics(BasicBlock *BB, const LoopInfo &LI);
   bool calcZeroHeuristics(BasicBlock *BB);
   bool calcFloatingPointHeuristics(BasicBlock *BB);
   bool calcInvokeHeuristics(BasicBlock *BB);
 };
 
+/// \brief Legacy analysis pass which computes \c BranchProbabilityInfo.
+class BranchProbabilityInfoWrapperPass : public FunctionPass {
+  BranchProbabilityInfo BPI;
+
+public:
+  static char ID;
+
+  BranchProbabilityInfoWrapperPass() : FunctionPass(ID) {
+    initializeBranchProbabilityInfoWrapperPassPass(
+        *PassRegistry::getPassRegistry());
+  }
+
+  BranchProbabilityInfo &getBPI() { return BPI; }
+  const BranchProbabilityInfo &getBPI() const { return BPI; }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override;
+  bool runOnFunction(Function &F) override;
+  void releaseMemory() override;
+  void print(raw_ostream &OS, const Module *M = nullptr) const override;
+};
+
 }
 
 #endif

include/llvm/InitializePasses.h

 void initializeAlignmentFromAssumptionsPass(PassRegistry&);
 void initializeBarrierNoopPass(PassRegistry&);
 void initializeBasicAliasAnalysisPass(PassRegistry&);
 void initializeCallGraphWrapperPassPass(PassRegistry &);
 void initializeBlockExtractorPassPass(PassRegistry&);
 void initializeBlockFrequencyInfoWrapperPassPass(PassRegistry&);
 void initializeBoundsCheckingPass(PassRegistry&);
 void initializeBranchFolderPassPass(PassRegistry&);
-void initializeBranchProbabilityInfoPass(PassRegistry&);
+void initializeBranchProbabilityInfoWrapperPassPass(PassRegistry&);
 void initializeBreakCriticalEdgesPass(PassRegistry&);
 void initializeCallGraphPrinterPass(PassRegistry&);
 void initializeCallGraphViewerPass(PassRegistry&);
 void initializeCFGOnlyPrinterPass(PassRegistry&);
 void initializeCFGOnlyViewerPass(PassRegistry&);
 void initializeCFGPrinterPass(PassRegistry&);
 void initializeCFGSimplifyPassPass(PassRegistry&);
 void initializeCFLAliasAnalysisPass(PassRegistry&);

lib/Analysis/Analysis.cpp

void llvm::initializeAnalysis(PassRegistry &Registry) {
   initializeAliasAnalysisAnalysisGroup(Registry);
   initializeAliasAnalysisCounterPass(Registry);
   initializeAAEvalPass(Registry);
   initializeAliasDebuggerPass(Registry);
   initializeAliasSetPrinterPass(Registry);
   initializeNoAAPass(Registry);
   initializeBasicAliasAnalysisPass(Registry);
   initializeBlockFrequencyInfoWrapperPassPass(Registry);
-  initializeBranchProbabilityInfoPass(Registry);
+  initializeBranchProbabilityInfoWrapperPassPass(Registry);
   initializeCostModelAnalysisPass(Registry);
   initializeCFGViewerPass(Registry);
   initializeCFGPrinterPass(Registry);
   initializeCFGOnlyViewerPass(Registry);
   initializeCFGOnlyPrinterPass(Registry);
   initializeCFLAliasAnalysisPass(Registry);
   initializeDependenceAnalysisPass(Registry);
   initializeDelinearizationPass(Registry);

lib/Analysis/BlockFrequencyInfo.cpp

 void BlockFrequencyInfo::print(raw_ostream &OS) const {
   if (BFI)
     BFI->print(OS);
 }
 
 
 INITIALIZE_PASS_BEGIN(BlockFrequencyInfoWrapperPass, "block-freq",
                       "Block Frequency Analysis", true, true)
-INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfo)
+INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfoWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
 INITIALIZE_PASS_END(BlockFrequencyInfoWrapperPass, "block-freq",
                     "Block Frequency Analysis", true, true)
 
 char BlockFrequencyInfoWrapperPass::ID = 0;
 
 
 BlockFrequencyInfoWrapperPass::BlockFrequencyInfoWrapperPass()
     : FunctionPass(ID) {
   initializeBlockFrequencyInfoWrapperPassPass(*PassRegistry::getPassRegistry());
 }
 
 BlockFrequencyInfoWrapperPass::~BlockFrequencyInfoWrapperPass() {}
 
 void BlockFrequencyInfoWrapperPass::print(raw_ostream &OS,
                                           const Module *) const {
   BFI.print(OS);
 }
 
 void BlockFrequencyInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
-  AU.addRequired<BranchProbabilityInfo>();
+  AU.addRequired<BranchProbabilityInfoWrapperPass>();
   AU.addRequired<LoopInfoWrapperPass>();
   AU.setPreservesAll();
 }
 
 void BlockFrequencyInfoWrapperPass::releaseMemory() { BFI.releaseMemory(); }
 
 bool BlockFrequencyInfoWrapperPass::runOnFunction(Function &F) {
-  BranchProbabilityInfo &BPI = getAnalysis<BranchProbabilityInfo>();
+  BranchProbabilityInfo &BPI =
+      getAnalysis<BranchProbabilityInfoWrapperPass>().getBPI();
   LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
   BFI.calculate(F, BPI, LI);
   return false;
 }

lib/Analysis/BranchProbabilityInfo.cpp

 #include "llvm/IR/Metadata.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
 
 #define DEBUG_TYPE "branch-prob"
 
-INITIALIZE_PASS_BEGIN(BranchProbabilityInfo, "branch-prob",
+INITIALIZE_PASS_BEGIN(BranchProbabilityInfoWrapperPass, "branch-prob",
                       "Branch Probability Analysis", false, true)
 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
-INITIALIZE_PASS_END(BranchProbabilityInfo, "branch-prob",
+INITIALIZE_PASS_END(BranchProbabilityInfoWrapperPass, "branch-prob",
                     "Branch Probability Analysis", false, true)
 
-char BranchProbabilityInfo::ID = 0;
+char BranchProbabilityInfoWrapperPass::ID = 0;
 
 // Weights are for internal use only. They are used by heuristics to help to
 // estimate edges' probability. Example:
 //
 // Using "Loop Branch Heuristics" we predict weights of edges for the
 // block BB2.
 //         ...
 //          |
bool BranchProbabilityInfo::calcPointerHeuristics(BasicBlock *BB) {
 
   setEdgeWeight(BB, TakenIdx, PH_TAKEN_WEIGHT);
   setEdgeWeight(BB, NonTakenIdx, PH_NONTAKEN_WEIGHT);
   return true;
 }
 
 // Calculate Edge Weights using "Loop Branch Heuristics". Predict backedges
 // as taken, exiting edges as not-taken.
-bool BranchProbabilityInfo::calcLoopBranchHeuristics(BasicBlock *BB) {
-  Loop *L = LI->getLoopFor(BB);
+bool BranchProbabilityInfo::calcLoopBranchHeuristics(BasicBlock *BB,
+                                                     const LoopInfo &LI) {
+  Loop *L = LI.getLoopFor(BB);
   if (!L)
     return false;
 
   SmallVector<unsigned, 8> BackEdges;
   SmallVector<unsigned, 8> ExitingEdges;
   SmallVector<unsigned, 8> InEdges; // Edges from header to the loop.
 
   for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) {
bool BranchProbabilityInfo::calcInvokeHeuristics(BasicBlock *BB) {
   if (!II)
     return false;
 
   setEdgeWeight(BB, 0/*Index for Normal*/, IH_TAKEN_WEIGHT);
   setEdgeWeight(BB, 1/*Index for Unwind*/, IH_NONTAKEN_WEIGHT);
   return true;
 }
 
-void BranchProbabilityInfo::getAnalysisUsage(AnalysisUsage &AU) const {
-  AU.addRequired<LoopInfoWrapperPass>();
-  AU.setPreservesAll();
-}
-
-bool BranchProbabilityInfo::runOnFunction(Function &F) {
-  DEBUG(dbgs() << "---- Branch Probability Info : " << F.getName()
-               << " ----\n\n");
-  LastF = &F; // Store the last function we ran on for printing.
-  LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
-  assert(PostDominatedByUnreachable.empty());
-  assert(PostDominatedByColdCall.empty());
-
-  // Walk the basic blocks in post-order so that we can build up state about
-  // the successors of a block iteratively.
-  for (auto BB : post_order(&F.getEntryBlock())) {
-    DEBUG(dbgs() << "Computing probabilities for " << BB->getName() << "\n");
-    if (calcUnreachableHeuristics(BB))
-      continue;
-    if (calcMetadataWeights(BB))
-      continue;
-    if (calcColdCallHeuristics(BB))
-      continue;
-    if (calcLoopBranchHeuristics(BB))
-      continue;
-    if (calcPointerHeuristics(BB))
-      continue;
-    if (calcZeroHeuristics(BB))
-      continue;
-    if (calcFloatingPointHeuristics(BB))
-      continue;
-    calcInvokeHeuristics(BB);
-  }
-
-  PostDominatedByUnreachable.clear();
-  PostDominatedByColdCall.clear();
-  return false;
-}
-
 void BranchProbabilityInfo::releaseMemory() {
   Weights.clear();
 }
 
-void BranchProbabilityInfo::print(raw_ostream &OS, const Module *) const {
+void BranchProbabilityInfo::print(raw_ostream &OS) const {
   OS << "---- Branch Probabilities ----\n";
   // We print the probabilities from the last function the analysis ran over,
   // or the function it is currently running over.
   assert(LastF && "Cannot print prior to running over a function");
   for (Function::const_iterator BI = LastF->begin(), BE = LastF->end();
        BI != BE; ++BI) {
     for (succ_const_iterator SI = succ_begin(BI), SE = succ_end(BI);
          SI != SE; ++SI) {
BranchProbabilityInfo::printEdgeProbability(raw_ostream &OS,
 
   const BranchProbability Prob = getEdgeProbability(Src, Dst);
   OS << "edge " << Src->getName() << " -> " << Dst->getName()
      << " probability is " << Prob
      << (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n");
 
   return OS;
 }
+
+void BranchProbabilityInfo::calculate(Function &F, const LoopInfo& LI) {
+  DEBUG(dbgs() << "---- Branch Probability Info : " << F.getName()
+               << " ----\n\n");
+  LastF = &F; // Store the last function we ran on for printing.
+  assert(PostDominatedByUnreachable.empty());
+  assert(PostDominatedByColdCall.empty());
+
+  // Walk the basic blocks in post-order so that we can build up state about
+  // the successors of a block iteratively.
+  for (auto BB : post_order(&F.getEntryBlock())) {
+    DEBUG(dbgs() << "Computing probabilities for " << BB->getName() << "\n");
+    if (calcUnreachableHeuristics(BB))
+      continue;
+    if (calcMetadataWeights(BB))
+      continue;
+    if (calcColdCallHeuristics(BB))
+      continue;
+    if (calcLoopBranchHeuristics(BB, LI))
+      continue;
+    if (calcPointerHeuristics(BB))
+      continue;
+    if (calcZeroHeuristics(BB))
+      continue;
+    if (calcFloatingPointHeuristics(BB))
+      continue;
+    calcInvokeHeuristics(BB);
+  }
+
+  PostDominatedByUnreachable.clear();
+  PostDominatedByColdCall.clear();
+}
+
+void BranchProbabilityInfoWrapperPass::getAnalysisUsage(
+    AnalysisUsage &AU) const {
+  AU.addRequired<LoopInfoWrapperPass>();
+  AU.setPreservesAll();
+}
+
+bool BranchProbabilityInfoWrapperPass::runOnFunction(Function &F) {
+  const LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+  BPI.calculate(F, LI);
+  return false;
+}
+
+void BranchProbabilityInfoWrapperPass::releaseMemory() { BPI.releaseMemory(); }
+
+void BranchProbabilityInfoWrapperPass::print(raw_ostream &OS,
+                                             const Module *) const {
+  BPI.print(OS);
+}

lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

SelectionDAGISel::SelectionDAGISel(TargetMachine &tm,
   FuncInfo(new FunctionLoweringInfo()),
   CurDAG(new SelectionDAG(tm, OL)),
   SDB(new SelectionDAGBuilder(*CurDAG, *FuncInfo, OL)),
   GFI(),
   OptLevel(OL),
   DAGSize(0) {
     initializeGCModuleInfoPass(*PassRegistry::getPassRegistry());
     initializeAliasAnalysisAnalysisGroup(*PassRegistry::getPassRegistry());
-    initializeBranchProbabilityInfoPass(*PassRegistry::getPassRegistry());
+    initializeBranchProbabilityInfoWrapperPassPass(
+        *PassRegistry::getPassRegistry());
     initializeTargetLibraryInfoWrapperPassPass(
         *PassRegistry::getPassRegistry());
   }
 
 SelectionDAGISel::~SelectionDAGISel() {
   delete SDB;
   delete CurDAG;
   delete FuncInfo;
 }
 
 void SelectionDAGISel::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<AliasAnalysis>();
   AU.addPreserved<AliasAnalysis>();
   AU.addRequired<GCModuleInfo>();
   AU.addPreserved<GCModuleInfo>();
   AU.addRequired<TargetLibraryInfoWrapperPass>();
   if (UseMBPI && OptLevel != CodeGenOpt::None)
-    AU.addRequired<BranchProbabilityInfo>();
+    AU.addRequired<BranchProbabilityInfoWrapperPass>();
   MachineFunctionPass::getAnalysisUsage(AU);
 }
 
 /// SplitCriticalSideEffectEdges - Look for critical edges with a PHI value that
 /// may trap on it.  In this case we have to split the edge so that the path
 /// through the predecessor block that doesn't go to the phi block doesn't
 /// execute the possibly trapping instruction.
 ///
bool SelectionDAGISel::runOnMachineFunction(MachineFunction &mf) {
   DEBUG(dbgs() << "\n\n\n=== " << Fn.getName() << "\n");
 
   SplitCriticalSideEffectEdges(const_cast<Function&>(Fn), AA);
 
   CurDAG->init(*MF);
   FuncInfo->set(Fn, *MF, CurDAG);
 
   if (UseMBPI && OptLevel != CodeGenOpt::None)
-    FuncInfo->BPI = &getAnalysis<BranchProbabilityInfo>();
+    FuncInfo->BPI = &getAnalysis<BranchProbabilityInfoWrapperPass>().getBPI();
   else
     FuncInfo->BPI = nullptr;
 
   SDB->init(GFI, *AA, LibInfo);
 
   MF->setHasInlineAsm(false);
 
   SelectAllBasicBlocks(Fn);

lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp

initializeInductiveRangeCheckEliminationPass(
         *PassRegistry::getPassRegistry());
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.addRequired<LoopInfoWrapperPass>();
     AU.addRequiredID(LoopSimplifyID);
     AU.addRequiredID(LCSSAID);
     AU.addRequired<ScalarEvolution>();
-    AU.addRequired<BranchProbabilityInfo>();
+    AU.addRequired<BranchProbabilityInfoWrapperPass>();
   }
 
   bool runOnLoop(Loop *L, LPPassManager &LPM) override;
 };
 
 char InductiveRangeCheckElimination::ID = 0;
 }
 
if (!Preheader) {
     DEBUG(dbgs() << "irce: loop has no preheader, leaving\n");
     return false;
   }
 
   LLVMContext &Context = Preheader->getContext();
   InductiveRangeCheck::AllocatorTy IRCAlloc;
   SmallVector<InductiveRangeCheck *, 16> RangeChecks;
   ScalarEvolution &SE = getAnalysis<ScalarEvolution>();
-  BranchProbabilityInfo &BPI = getAnalysis<BranchProbabilityInfo>();
+  BranchProbabilityInfo &BPI =
+      getAnalysis<BranchProbabilityInfoWrapperPass>().getBPI();
 
   for (auto BBI : L->getBlocks())
     if (BranchInst *TBI = dyn_cast<BranchInst>(BBI->getTerminator()))
       if (InductiveRangeCheck *IRC =
           InductiveRangeCheck::create(IRCAlloc, TBI, L, SE, BPI))
         RangeChecks.push_back(IRC);
 
   if (RangeChecks.empty())