LLVM  3.7.0
MachineSSAUpdater.h
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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.
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;
56 public:
57  /// MachineSSAUpdater constructor. If InsertedPHIs is specified, it will be
58  /// filled in with all PHI Nodes created by rewriting.
60  SmallVectorImpl<MachineInstr*> *InsertedPHIs = nullptr);
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.
97  ///
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&) = delete;
111  MachineSSAUpdater(const MachineSSAUpdater&) = delete;
112 };
113 
114 } // End llvm namespace
115 
116 #endif
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...
This file defines the MallocAllocator and BumpPtrAllocator interfaces.
unsigned GetValueAtEndOfBlock(MachineBasicBlock *BB)
GetValueAtEndOfBlock - Construct SSA form, materializing a value that is live at the end of the speci...
const HexagonInstrInfo * TII
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APInt.h:33
bool HasValueForBlock(MachineBasicBlock *BB) const
HasValueForBlock - Return true if the MachineSSAUpdater already has a value for the specified block...
void Initialize(unsigned V)
Initialize - Reset this object to get ready for a new set of SSA updates.
TargetInstrInfo - Interface to description of machine instruction set.
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.
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...
MachineSSAUpdater(MachineFunction &MF, SmallVectorImpl< MachineInstr * > *InsertedPHIs=nullptr)
MachineSSAUpdater constructor.