src/llvm/include/llvm/CodeGen/MachineSSAUpdater.h

   1 //===-- MachineSSAUpdater.h - Unstructured SSA Update Tool ------*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file declares the MachineSSAUpdater class.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_CODEGEN_MACHINESSAUPDATER_H
  15 #define LLVM_CODEGEN_MACHINESSAUPDATER_H
  16
  17 #include "llvm/Support/Allocator.h"
  18 #include "llvm/Support/Compiler.h"
  19
  20 namespace llvm {
  21   class MachineBasicBlock;
  22   class MachineFunction;
  23   class MachineInstr;
  24   class MachineOperand;
  25   class MachineRegisterInfo;
  26   class TargetInstrInfo;
  27   class TargetRegisterClass;
  28   template<typename T> class SmallVectorImpl;
  29   template<typename T> class SSAUpdaterTraits;
  30
  31 /// MachineSSAUpdater - This class updates SSA form for a set of virtual
  32 /// registers defined in multiple blocks.  This is used when code duplication
  33 /// or another unstructured transformation wants to rewrite a set of uses of one
  34 /// vreg with uses of a set of vregs.
  35 class MachineSSAUpdater {
  36   friend class SSAUpdaterTraits<MachineSSAUpdater>;
  37
  38 private:
  39   /// AvailableVals - This keeps track of which value to use on a per-block
  40   /// basis.  When we insert PHI nodes, we keep track of them here.
  41   //typedef DenseMap<MachineBasicBlock*, unsigned > AvailableValsTy;
  42   void *AV;
  43
  44   /// VR - Current virtual register whose uses are being updated.
  45   unsigned VR;
  46
  47   /// VRC - Register class of the current virtual register.
  48   const TargetRegisterClass *VRC;
  49
  50   /// InsertedPHIs - If this is non-null, the MachineSSAUpdater adds all PHI
  51   /// nodes that it creates to the vector.
  52   SmallVectorImpl<MachineInstr*> *InsertedPHIs;
  53
  54   const TargetInstrInfo *TII;
  55   MachineRegisterInfo *MRI;
  56 public:
  57   /// MachineSSAUpdater constructor.  If InsertedPHIs is specified, it will be
  58   /// filled in with all PHI Nodes created by rewriting.
  59   explicit MachineSSAUpdater(MachineFunction &MF,
  60                         SmallVectorImpl<MachineInstr*> *InsertedPHIs = nullptr);
  61   ~MachineSSAUpdater();
  62
  63   /// Initialize - Reset this object to get ready for a new set of SSA
  64   /// updates.
  65   void Initialize(unsigned V);
  66
  67   /// AddAvailableValue - Indicate that a rewritten value is available at the
  68   /// end of the specified block with the specified value.
  69   void AddAvailableValue(MachineBasicBlock *BB, unsigned V);
  70
  71   /// HasValueForBlock - Return true if the MachineSSAUpdater already has a
  72   /// value for the specified block.
  73   bool HasValueForBlock(MachineBasicBlock *BB) const;
  74
  75   /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
  76   /// live at the end of the specified block.
  77   unsigned GetValueAtEndOfBlock(MachineBasicBlock *BB);
  78
  79   /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
  80   /// is live in the middle of the specified block.
  81   ///
  82   /// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
  83   /// important case: if there is a definition of the rewritten value after the
  84   /// 'use' in BB.  Consider code like this:
  85   ///
  86   ///      X1 = ...
  87   ///   SomeBB:
  88   ///      use(X)
  89   ///      X2 = ...
  90   ///      br Cond, SomeBB, OutBB
  91   ///
  92   /// In this case, there are two values (X1 and X2) added to the AvailableVals
  93   /// set by the client of the rewriter, and those values are both live out of
  94   /// their respective blocks.  However, the use of X happens in the *middle* of
  95   /// a block.  Because of this, we need to insert a new PHI node in SomeBB to
  96   /// merge the appropriate values, and this value isn't live out of the block.
  97   ///
  98   unsigned GetValueInMiddleOfBlock(MachineBasicBlock *BB);
  99
 100   /// RewriteUse - Rewrite a use of the symbolic value.  This handles PHI nodes,
 101   /// which use their value in the corresponding predecessor.  Note that this
 102   /// will not work if the use is supposed to be rewritten to a value defined in
 103   /// the same block as the use, but above it.  Any 'AddAvailableValue's added
 104   /// for the use's block will be considered to be below it.
 105   void RewriteUse(MachineOperand &U);
 106
 107 private:
 108   unsigned GetValueAtEndOfBlockInternal(MachineBasicBlock *BB);
 109
 110   void operator=(const MachineSSAUpdater&) LLVM_DELETED_FUNCTION;
 111   MachineSSAUpdater(const MachineSSAUpdater&) LLVM_DELETED_FUNCTION;
 112 };
 113
 114 } // End llvm namespace
 115
 116 #endif