LLVM  10.0.0svn
MachineSSAUpdater.h
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1 //===- MachineSSAUpdater.h - Unstructured SSA Update Tool -------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file declares the MachineSSAUpdater class.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_CODEGEN_MACHINESSAUPDATER_H
14 #define LLVM_CODEGEN_MACHINESSAUPDATER_H
15 
16 namespace llvm {
17 
18 class MachineBasicBlock;
19 class MachineFunction;
20 class MachineInstr;
21 class MachineOperand;
22 class MachineRegisterInfo;
23 class TargetInstrInfo;
24 class TargetRegisterClass;
25 template<typename T> class SmallVectorImpl;
26 template<typename T> class SSAUpdaterTraits;
27 
28 /// MachineSSAUpdater - This class updates SSA form for a set of virtual
29 /// registers defined in multiple blocks. This is used when code duplication
30 /// or another unstructured transformation wants to rewrite a set of uses of one
31 /// vreg with uses of a set of vregs.
34 
35 private:
36  /// AvailableVals - This keeps track of which value to use on a per-block
37  /// basis. When we insert PHI nodes, we keep track of them here.
38  //typedef DenseMap<MachineBasicBlock*, unsigned > AvailableValsTy;
39  void *AV = nullptr;
40 
41  /// VR - Current virtual register whose uses are being updated.
42  unsigned VR;
43 
44  /// VRC - Register class of the current virtual register.
45  const TargetRegisterClass *VRC;
46 
47  /// InsertedPHIs - If this is non-null, the MachineSSAUpdater adds all PHI
48  /// nodes that it creates to the vector.
49  SmallVectorImpl<MachineInstr*> *InsertedPHIs;
50 
51  const TargetInstrInfo *TII;
53 
54 public:
55  /// MachineSSAUpdater constructor. If InsertedPHIs is specified, it will be
56  /// filled in with all PHI Nodes created by rewriting.
58  SmallVectorImpl<MachineInstr*> *NewPHI = nullptr);
59  MachineSSAUpdater(const MachineSSAUpdater &) = delete;
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.
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.
98 
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);
105 
106 private:
107  unsigned GetValueAtEndOfBlockInternal(MachineBasicBlock *BB);
108 };
109 
110 } // end namespace llvm
111 
112 #endif // LLVM_CODEGEN_MACHINESSAUPDATER_H
This class represents lattice values for constants.
Definition: AllocatorList.h:23
void RewriteUse(MachineOperand &U)
RewriteUse - Rewrite a use of the symbolic value.
MachineSSAUpdater - This class updates SSA form for a set of virtual registers defined in multiple bl...
unsigned GetValueAtEndOfBlock(MachineBasicBlock *BB)
GetValueAtEndOfBlock - Construct SSA form, materializing a value that is live at the end of the speci...
const HexagonInstrInfo * TII
MachineSSAUpdater(MachineFunction &MF, SmallVectorImpl< MachineInstr *> *NewPHI=nullptr)
MachineSSAUpdater constructor.
void Initialize(unsigned V)
Initialize - Reset this object to get ready for a new set of SSA updates.
MachineSSAUpdater & operator=(const MachineSSAUpdater &)=delete
TargetInstrInfo - Interface to description of machine instruction set.
unsigned const MachineRegisterInfo * MRI
MachineOperand class - Representation of each machine instruction operand.
MachineRegisterInfo - Keep track of information for virtual and physical registers, including vreg register classes, use/def chains for registers, etc.
bool HasValueForBlock(MachineBasicBlock *BB) const
HasValueForBlock - Return true if the MachineSSAUpdater already has a value for the specified block...
unsigned GetValueInMiddleOfBlock(MachineBasicBlock *BB)
GetValueInMiddleOfBlock - Construct SSA form, materializing a value that is live in the middle of the...
void AddAvailableValue(MachineBasicBlock *BB, unsigned V)
AddAvailableValue - Indicate that a rewritten value is available at the end of the specified block wi...