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