[BranchFolding] Replace MachineBlockFrequencyInfo with MBFIWrapper. NFC.

[haicheng]

Summary

Another part of enabling BranchFolding in MBP.

BranchFolding changes the CFG and stores the updated MachineBlockFrequencyInfo inside the MBFIWrapper. This patch allows other passes that call BranchFolding use the updated MachineBlockFrequencyInfo without recalculation.

Besides cutting and pasting, I added two more print functions for the debugging purpose.

[haicheng]

Cleanup the code.

[haicheng]

Fix a bug.

[mssimpso]

lib/CodeGen/BranchFolding.h

29

Do you need to take this class out of the BranchFolder scope or would a forward declaration work?

[haicheng]

lib/CodeGen/BranchFolding.h

29

Forward declaration works. At first I just wanted to type less letters when this class is used outside of BranchFolder :)

[haicheng]

Address Matt's comment. Thank you.

[mcrosier]

LGTM.

lib/CodeGen/BranchFolding.h

namespace llvm {
   class MachineBlockFrequencyInfo;
   class MachineBranchProbabilityInfo;
   class MachineFunction;
   class MachineModuleInfo;
   class RegScavenger;
   class TargetInstrInfo;
   class TargetRegisterInfo;
 
+  /// \brief This class keeps track of branch frequencies of newly created
+  /// blocks and tail-merged blocks.
+  class MBFIWrapper {
+  public:
+    MBFIWrapper(const MachineBlockFrequencyInfo &I) : MBFI(I) {}
+    BlockFrequency getBlockFreq(const MachineBasicBlock *MBB) const;
+    void setBlockFreq(const MachineBasicBlock *MBB, BlockFrequency F);
+    raw_ostream &printBlockFreq(raw_ostream &OS,
+                                const MachineBasicBlock *MBB) const;
+    raw_ostream &printBlockFreq(raw_ostream &OS,
+                                const BlockFrequency Freq) const;
+
+  private:
+    const MachineBlockFrequencyInfo &MBFI;
+    DenseMap<const MachineBasicBlock *, BlockFrequency> MergedBBFreq;
+  };
+
   class LLVM_LIBRARY_VISIBILITY BranchFolder {
   public:
     explicit BranchFolder(bool defaultEnableTailMerge, bool CommonHoist,
-                          const MachineBlockFrequencyInfo &MBFI,
+                          MBFIWrapper &MBFI,
                           const MachineBranchProbabilityInfo &MBPI);
 
     bool OptimizeFunction(MachineFunction &MF,
                           const TargetInstrInfo *tii,
                           const TargetRegisterInfo *tri,
                           MachineModuleInfo *mmi);
   private:
     class MergePotentialsElt {
private:
 
     bool EnableTailMerge;
     bool EnableHoistCommonCode;
     const TargetInstrInfo *TII;
     const TargetRegisterInfo *TRI;
     MachineModuleInfo *MMI;
     RegScavenger *RS;
 
-    /// \brief This class keeps track of branch frequencies of newly created
-    /// blocks and tail-merged blocks.
-    class MBFIWrapper {
-    public:
-      MBFIWrapper(const MachineBlockFrequencyInfo &I) : MBFI(I) {}
-      BlockFrequency getBlockFreq(const MachineBasicBlock *MBB) const;
-      void setBlockFreq(const MachineBasicBlock *MBB, BlockFrequency F);
-
-    private:
-      const MachineBlockFrequencyInfo &MBFI;
-      DenseMap<const MachineBasicBlock *, BlockFrequency> MergedBBFreq;
-    };
-
-    MBFIWrapper MBBFreqInfo;
+    MBFIWrapper &MBBFreqInfo;
     const MachineBranchProbabilityInfo &MBPI;
 
     bool TailMergeBlocks(MachineFunction &MF);
     bool TryTailMergeBlocks(MachineBasicBlock* SuccBB,
                        MachineBasicBlock* PredBB);
     void setCommonTailEdgeWeights(MachineBasicBlock &TailMBB);
     void MaintainLiveIns(MachineBasicBlock *CurMBB,
                          MachineBasicBlock *NewMBB);

lib/CodeGen/BranchFolding.cpp

bool BranchFolderPass::runOnMachineFunction(MachineFunction &MF) {
   if (skipFunction(*MF.getFunction()))
     return false;
 
   TargetPassConfig *PassConfig = &getAnalysis<TargetPassConfig>();
   // TailMerge can create jump into if branches that make CFG irreducible for
   // HW that requires structurized CFG.
   bool EnableTailMerge = !MF.getTarget().requiresStructuredCFG() &&
                          PassConfig->getEnableTailMerge();
-  BranchFolder Folder(EnableTailMerge, /*CommonHoist=*/true,
-                      getAnalysis<MachineBlockFrequencyInfo>(),
+  MBFIWrapper MBBFreqInfo(getAnalysis<MachineBlockFrequencyInfo>());
+  BranchFolder Folder(EnableTailMerge, /*CommonHoist=*/true, MBBFreqInfo,
                       getAnalysis<MachineBranchProbabilityInfo>());
   return Folder.OptimizeFunction(MF, MF.getSubtarget().getInstrInfo(),
                                  MF.getSubtarget().getRegisterInfo(),
                                  getAnalysisIfAvailable<MachineModuleInfo>());
 }
 
 BranchFolder::BranchFolder(bool defaultEnableTailMerge, bool CommonHoist,
-                           const MachineBlockFrequencyInfo &FreqInfo,
+                           MBFIWrapper &FreqInfo,
                            const MachineBranchProbabilityInfo &ProbInfo)
     : EnableHoistCommonCode(CommonHoist), MBBFreqInfo(FreqInfo),
       MBPI(ProbInfo) {
   switch (FlagEnableTailMerge) {
   case cl::BOU_UNSET: EnableTailMerge = defaultEnableTailMerge; break;
   case cl::BOU_TRUE: EnableTailMerge = true; break;
   case cl::BOU_FALSE: EnableTailMerge = false; break;
   }
BranchFolder::MergePotentialsElt::operator<(const MergePotentialsElt &o) const {
   // an object with itself.
 #ifndef _GLIBCXX_DEBUG
   llvm_unreachable("Predecessor appears twice");
 #else
   return false;
 #endif
 }
 
-BlockFrequency
-BranchFolder::MBFIWrapper::getBlockFreq(const MachineBasicBlock *MBB) const {
+BlockFrequency MBFIWrapper::getBlockFreq(const MachineBasicBlock *MBB) const {
   auto I = MergedBBFreq.find(MBB);
 
   if (I != MergedBBFreq.end())
     return I->second;
 
   return MBFI.getBlockFreq(MBB);
 }
 
-void BranchFolder::MBFIWrapper::setBlockFreq(const MachineBasicBlock *MBB,
-                                             BlockFrequency F) {
+void MBFIWrapper::setBlockFreq(const MachineBasicBlock *MBB, BlockFrequency F) {
   MergedBBFreq[MBB] = F;
 }
 
+raw_ostream &MBFIWrapper::printBlockFreq(raw_ostream &OS,
+                                         const MachineBasicBlock *MBB) const {
+  return MBFI.printBlockFreq(OS, MBB);
+}
+
+raw_ostream &MBFIWrapper::printBlockFreq(raw_ostream &OS,
+                                         const BlockFrequency Freq) const {
+  return MBFI.printBlockFreq(OS, Freq);
+}
+
 /// CountTerminators - Count the number of terminators in the given
 /// block and set I to the position of the first non-terminator, if there
 /// is one, or MBB->end() otherwise.
 static unsigned CountTerminators(MachineBasicBlock *MBB,
                                  MachineBasicBlock::iterator &I) {
   I = MBB->end();
   unsigned NumTerms = 0;
   for (;;) {

lib/CodeGen/IfConversion.cpp

class IfConverter : public MachineFunctionPass {
     /// BBAnalysis - Results of if-conversion feasibility analysis indexed by
     /// basic block number.
     std::vector<BBInfo> BBAnalysis;
     TargetSchedModel SchedModel;
 
     const TargetLoweringBase *TLI;
     const TargetInstrInfo *TII;
     const TargetRegisterInfo *TRI;
-    const MachineBlockFrequencyInfo *MBFI;
     const MachineBranchProbabilityInfo *MBPI;
     MachineRegisterInfo *MRI;
 
     LivePhysRegs Redefs;
     LivePhysRegs DontKill;
 
     bool PreRegAlloc;
     bool MadeChange;
bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
   if (skipFunction(*MF.getFunction()) ||
       (PredicateFtor && !PredicateFtor(*MF.getFunction())))
     return false;
 
   const TargetSubtargetInfo &ST = MF.getSubtarget();
   TLI = ST.getTargetLowering();
   TII = ST.getInstrInfo();
   TRI = ST.getRegisterInfo();
-  MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
+  MBFIWrapper MBFI(getAnalysis<MachineBlockFrequencyInfo>());
   MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
   MRI = &MF.getRegInfo();
   SchedModel.init(ST.getSchedModel(), &ST, TII);
 
   if (!TII) return false;
 
   PreRegAlloc = MRI->isSSA();
 
   bool BFChange = false;
   if (!PreRegAlloc) {
     // Tail merge tend to expose more if-conversion opportunities.
-    BranchFolder BF(true, false, *MBFI, *MBPI);
+    BranchFolder BF(true, false, MBFI, *MBPI);
     BFChange = BF.OptimizeFunction(MF, TII, ST.getRegisterInfo(),
                                    getAnalysisIfAvailable<MachineModuleInfo>());
   }
 
   DEBUG(dbgs() << "\nIfcvt: function (" << ++FnNum <<  ") \'"
                << MF.getName() << "\'");
 
   if (FnNum < IfCvtFnStart || (IfCvtFnStop != -1 && FnNum > IfCvtFnStop)) {
if (!Change)
       break;
     MadeChange |= Change;
   }
 
   Tokens.clear();
   BBAnalysis.clear();
 
   if (MadeChange && IfCvtBranchFold) {
-    BranchFolder BF(false, false, *MBFI, *MBPI);
+    BranchFolder BF(false, false, MBFI, *MBPI);
     BF.OptimizeFunction(MF, TII, MF.getSubtarget().getRegisterInfo(),
                         getAnalysisIfAvailable<MachineModuleInfo>());
   }
 
   MadeChange |= BFChange;
   return MadeChange;
 }