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, 84 insertions, 0 deletions

diff --git a/lib/CodeGen/BranchFolding.h b/lib/CodeGen/BranchFolding.h
new file mode 100644
index 0000000000..9763e3339a
--- /dev/null
+++ b/lib/CodeGen/BranchFolding.h
@@ -0,0 +1,84 @@
+//===-- BranchFolding.h - Fold machine code branch instructions --*- C++ -*===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_BRANCHFOLDING_HPP
+#define LLVM_CODEGEN_BRANCHFOLDING_HPP
+
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include <vector>
+
+namespace llvm {
+  class MachineFunction;
+  class MachineModuleInfo;
+  class RegScavenger;
+  class TargetInstrInfo;
+  class TargetRegisterInfo;
+
+  class BranchFolder {
+  public:
+    explicit BranchFolder(bool defaultEnableTailMerge);
+
+    bool OptimizeFunction(MachineFunction &MF,
+                          const TargetInstrInfo *tii,
+                          const TargetRegisterInfo *tri,
+                          MachineModuleInfo *mmi);
+  private:
+    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;
+
+    bool EnableTailMerge;
+    const TargetInstrInfo *TII;
+    const TargetRegisterInfo *TRI;
+    MachineModuleInfo *MMI;
+    RegScavenger *RS;
+
+    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);
+
+    bool OptimizeBranches(MachineFunction &MF);
+    bool 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);
+  };
+
+
+  /// BranchFolderPass - Wrap branch folder in a machine function pass.
+  class BranchFolderPass : public MachineFunctionPass,
+                           public BranchFolder {
+  public:
+    static char ID;
+    explicit BranchFolderPass(bool defaultEnableTailMerge)
+      :  MachineFunctionPass(&ID), BranchFolder(defaultEnableTailMerge) {}
+
+    virtual bool runOnMachineFunction(MachineFunction &MF);
+    virtual const char *getPassName() const { return "Control Flow Optimizer"; }
+  };
+}
+
+#endif /* LLVM_CODEGEN_BRANCHFOLDING_HPP */