Run branch folding if if-converter make some transformations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80994 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 63 insertions, 84 deletions

diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp
index dd51d5f6f6..f9abeacbdb 100644
--- a/lib/CodeGen/BranchFolding.cpp
+++ b/lib/CodeGen/BranchFolding.cpp
@@ -17,6 +17,7 @@
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "branchfolding"
+#include "BranchFolding.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
@@ -46,64 +47,28 @@ TailMergeThreshold("tail-merge-threshold",
           cl::desc("Max number of predecessors to consider tail merging"),
           cl::init(150), cl::Hidden);
 
-namespace {
-  struct VISIBILITY_HIDDEN BranchFolder : public MachineFunctionPass {
-    static char ID;
-    explicit BranchFolder(bool defaultEnableTailMerge) : 
-      MachineFunctionPass(&ID) {
-      switch (FlagEnableTailMerge) {
-        case cl::BOU_UNSET: EnableTailMerge = defaultEnableTailMerge; break;
-        case cl::BOU_TRUE: EnableTailMerge = true; break;
-        case cl::BOU_FALSE: EnableTailMerge = false; break;
-      }
-    }
 
-    virtual bool runOnMachineFunction(MachineFunction &MF);
-    virtual const char *getPassName() const { return "Control Flow Optimizer"; }
-    const TargetInstrInfo *TII;
-    MachineModuleInfo *MMI;
-    bool MadeChange;
-  private:
-    // Tail Merging.
-    bool EnableTailMerge;
-    bool TailMergeBlocks(MachineFunction &MF);
-    bool TryMergeBlocks(MachineBasicBlock* SuccBB,
-                        MachineBasicBlock* PredBB);
-    void ReplaceTailWithBranchTo(MachineBasicBlock::iterator OldInst,
-                                 MachineBasicBlock *NewDest);
-    MachineBasicBlock *SplitMBBAt(MachineBasicBlock &CurMBB,
-                                  MachineBasicBlock::iterator BBI1);
-    unsigned ComputeSameTails(unsigned CurHash, unsigned minCommonTailLength);
-    void RemoveBlocksWithHash(unsigned CurHash, MachineBasicBlock* SuccBB,
-                                                MachineBasicBlock* PredBB);
-    unsigned CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
-                                       unsigned maxCommonTailLength);
-
-    typedef std::pair<unsigned,MachineBasicBlock*> MergePotentialsElt;
-    typedef std::vector<MergePotentialsElt>::iterator MPIterator;
-    std::vector<MergePotentialsElt> MergePotentials;
-
-    typedef std::pair<MPIterator, MachineBasicBlock::iterator> SameTailElt;
-    std::vector<SameTailElt> SameTails;
-
-    const TargetRegisterInfo *RegInfo;
-    RegScavenger *RS;
-    // Branch optzn.
-    bool OptimizeBranches(MachineFunction &MF);
-    void OptimizeBlock(MachineBasicBlock *MBB);
-    void RemoveDeadBlock(MachineBasicBlock *MBB);
-    bool OptimizeImpDefsBlock(MachineBasicBlock *MBB);
-    
-    bool CanFallThrough(MachineBasicBlock *CurBB);
-    bool CanFallThrough(MachineBasicBlock *CurBB, bool BranchUnAnalyzable,
-                        MachineBasicBlock *TBB, MachineBasicBlock *FBB,
-                        const SmallVectorImpl<MachineOperand> &Cond);
-  };
-  char BranchFolder::ID = 0;
-}
+char BranchFolderPass::ID = 0;
 
 FunctionPass *llvm::createBranchFoldingPass(bool DefaultEnableTailMerge) { 
-  return new BranchFolder(DefaultEnableTailMerge);
+  return new BranchFolderPass(DefaultEnableTailMerge);
+}
+
+bool BranchFolderPass::runOnMachineFunction(MachineFunction &MF) {
+  return OptimizeFunction(MF,
+                          MF.getTarget().getInstrInfo(),
+                          MF.getTarget().getRegisterInfo(),
+                          getAnalysisIfAvailable<MachineModuleInfo>());
+}
+
+
+
+BranchFolder::BranchFolder(bool defaultEnableTailMerge) {
+  switch (FlagEnableTailMerge) {
+  case cl::BOU_UNSET: EnableTailMerge = defaultEnableTailMerge; break;
+  case cl::BOU_TRUE: EnableTailMerge = true; break;
+  case cl::BOU_FALSE: EnableTailMerge = false; break;
+  }
 }
 
 /// RemoveDeadBlock - Remove the specified dead machine basic block from the
@@ -149,7 +114,7 @@ bool BranchFolder::OptimizeImpDefsBlock(MachineBasicBlock *MBB) {
       break;
     unsigned Reg = I->getOperand(0).getReg();
     ImpDefRegs.insert(Reg);
-    for (const unsigned *SubRegs = RegInfo->getSubRegisters(Reg);
+    for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
          unsigned SubReg = *SubRegs; ++SubRegs)
       ImpDefRegs.insert(SubReg);
     ++I;
@@ -183,32 +148,37 @@ bool BranchFolder::OptimizeImpDefsBlock(MachineBasicBlock *MBB) {
   return true;
 }
 
-bool BranchFolder::runOnMachineFunction(MachineFunction &MF) {
-  TII = MF.getTarget().getInstrInfo();
-  if (!TII) return false;
+/// OptimizeFunction - Perhaps branch folding, tail merging and other
+/// CFG optimizations on the given function.
+bool BranchFolder::OptimizeFunction(MachineFunction &MF,
+                                    const TargetInstrInfo *tii,
+                                    const TargetRegisterInfo *tri,
+                                    MachineModuleInfo *mmi) {
+  if (!tii) return false;
+
+  TII = tii;
+  TRI = tri;
+  MMI = mmi;
 
-  RegInfo = MF.getTarget().getRegisterInfo();
+  RS = TRI->requiresRegisterScavenging(MF) ? new RegScavenger() : NULL;
 
   // Fix CFG.  The later algorithms expect it to be right.
-  bool EverMadeChange = false;
+  bool MadeChange = false;
   for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; I++) {
     MachineBasicBlock *MBB = I, *TBB = 0, *FBB = 0;
     SmallVector<MachineOperand, 4> Cond;
     if (!TII->AnalyzeBranch(*MBB, TBB, FBB, Cond, true))
-      EverMadeChange |= MBB->CorrectExtraCFGEdges(TBB, FBB, !Cond.empty());
-    EverMadeChange |= OptimizeImpDefsBlock(MBB);
+      MadeChange |= MBB->CorrectExtraCFGEdges(TBB, FBB, !Cond.empty());
+    MadeChange |= OptimizeImpDefsBlock(MBB);
   }
 
-  RS = RegInfo->requiresRegisterScavenging(MF) ? new RegScavenger() : NULL;
-
-  MMI = getAnalysisIfAvailable<MachineModuleInfo>();
 
   bool MadeChangeThisIteration = true;
   while (MadeChangeThisIteration) {
     MadeChangeThisIteration = false;
     MadeChangeThisIteration |= TailMergeBlocks(MF);
     MadeChangeThisIteration |= OptimizeBranches(MF);
-    EverMadeChange |= MadeChangeThisIteration;
+    MadeChange |= MadeChangeThisIteration;
   }
 
   // See if any jump tables have become mergable or dead as the code generator
@@ -225,8 +195,12 @@ bool BranchFolder::runOnMachineFunction(MachineFunction &MF) {
 
     // Scan the jump tables, seeing if there are any duplicates.  Note that this
     // is N^2, which should be fixed someday.
-    for (unsigned i = 1, e = JTs.size(); i != e; ++i)
-      JTMapping.push_back(JTI->getJumpTableIndex(JTs[i].MBBs));
+    for (unsigned i = 1, e = JTs.size(); i != e; ++i) {
+      if (JTs[i].MBBs.empty())
+        JTMapping.push_back(i);
+      else
+        JTMapping.push_back(JTI->getJumpTableIndex(JTs[i].MBBs));
+    }
     
     // If a jump table was merge with another one, walk the function rewriting
     // references to jump tables to reference the new JT ID's.  Keep track of
@@ -253,12 +227,12 @@ bool BranchFolder::runOnMachineFunction(MachineFunction &MF) {
     for (unsigned i = 0, e = JTIsLive.size(); i != e; ++i)
       if (!JTIsLive.test(i)) {
         JTI->RemoveJumpTable(i);
-        EverMadeChange = true;
+        MadeChange = true;
       }
   }
-  
+
   delete RS;
-  return EverMadeChange;
+  return MadeChange;
 }
 
 //===----------------------------------------------------------------------===//
@@ -398,9 +372,9 @@ MachineBasicBlock *BranchFolder::SplitMBBAt(MachineBasicBlock &CurMBB,
     RS->enterBasicBlock(&CurMBB);
     if (!CurMBB.empty())
       RS->forward(prior(CurMBB.end()));
-    BitVector RegsLiveAtExit(RegInfo->getNumRegs());
+    BitVector RegsLiveAtExit(TRI->getNumRegs());
     RS->getRegsUsed(RegsLiveAtExit, false);
-    for (unsigned int i=0, e=RegInfo->getNumRegs(); i!=e; i++)
+    for (unsigned int i=0, e=TRI->getNumRegs(); i!=e; i++)
       if (RegsLiveAtExit[i])
         NewMBB->addLiveIn(i);
   }
@@ -593,11 +567,12 @@ unsigned BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
 
 bool BranchFolder::TryMergeBlocks(MachineBasicBlock *SuccBB,
                                   MachineBasicBlock* PredBB) {
+  bool MadeChange = false;
+
   // It doesn't make sense to save a single instruction since tail merging
   // will add a jump.
   // FIXME: Ask the target to provide the threshold?
   unsigned minCommonTailLength = (SuccBB ? 1 : 2) + 1;
-  MadeChange = false;
   
   DEBUG(errs() << "\nTryMergeBlocks " << MergePotentials.size() << '\n');
 
@@ -668,7 +643,7 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
 
   if (!EnableTailMerge) return false;
  
-  MadeChange = false;
+  bool MadeChange = false;
 
   // First find blocks with no successors.
   MergePotentials.clear();
@@ -779,14 +754,14 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
 //===----------------------------------------------------------------------===//
 
 bool BranchFolder::OptimizeBranches(MachineFunction &MF) {
-  MadeChange = false;
+  bool MadeChange = false;
   
   // Make sure blocks are numbered in order
   MF.RenumberBlocks();
 
   for (MachineFunction::iterator I = ++MF.begin(), E = MF.end(); I != E; ) {
     MachineBasicBlock *MBB = I++;
-    OptimizeBlock(MBB);
+    MadeChange |= OptimizeBlock(MBB);
     
     // If it is dead, remove it.
     if (MBB->pred_empty()) {
@@ -880,7 +855,9 @@ static bool IsBetterFallthrough(MachineBasicBlock *MBB1,
 
 /// OptimizeBlock - Analyze and optimize control flow related to the specified
 /// block.  This is never called on the entry block.
-void BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
+bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
+  bool MadeChange = false;
+
   MachineFunction::iterator FallThrough = MBB;
   ++FallThrough;
   
@@ -889,7 +866,7 @@ void BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
   // points to this block.
   if (MBB->empty() && !MBB->isLandingPad()) {
     // Dead block?  Leave for cleanup later.
-    if (MBB->pred_empty()) return;
+    if (MBB->pred_empty()) return MadeChange;
     
     if (FallThrough == MBB->getParent()->end()) {
       // TODO: Simplify preds to not branch here if possible!
@@ -906,7 +883,7 @@ void BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
         ReplaceMBBInJumpTables(MBB, FallThrough);
       MadeChange = true;
     }
-    return;
+    return MadeChange;
   }
 
   // Check to see if we can simplify the terminator of the block before this
@@ -1020,7 +997,7 @@ void BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
           MBB->moveAfter(--MBB->getParent()->end());
           MadeChange = true;
           ++NumBranchOpts;
-          return;
+          return MadeChange;
         }
       }
     }
@@ -1122,7 +1099,7 @@ void BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
           if (DidChange) {
             ++NumBranchOpts;
             MadeChange = true;
-            if (!HasBranchToSelf) return;
+            if (!HasBranchToSelf) return MadeChange;
           }
         }
       }
@@ -1203,8 +1180,10 @@ void BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
           PrevBB.isSuccessor(FallThrough)) {
         MBB->moveAfter(--MBB->getParent()->end());
         MadeChange = true;
-        return;
+        return MadeChange;
       }
     }
   }
+
+  return MadeChange;
 }